Science.gov

Sample records for group size cohesion

  1. Network cohesion, group size and neocortex size in female-bonded Old World primates.

    PubMed

    Lehmann, Julia; Dunbar, R I M

    2009-12-22

    Most primates are intensely social and spend a large amount of time servicing social relationships. In this study, we use social network analysis to examine the relationship between primate group size, total brain size, neocortex ratio and several social network metrics concerned with network cohesion. Using female grooming networks from a number of Old World monkey species, we found that neocortex size was a better predictor of network characteristics than endocranial volumes. We further found that when we controlled for group size, neocortex ratio was negatively correlated with network density, connectivity, relative clan size and proportional clan membership, while there was no effect of neocortex ratio on change in connectivity following the removal of the most central female in the network. Thus, in species with larger neocortex ratios, females generally live in more fragmented networks, belong to smaller grooming clans and are members of relatively fewer clans despite living in a closely bonded group. However, even though groups are more fragmented to begin with among species with larger neocortices, the removal of the most central individual does cause groups to fall apart, suggesting that social complexity may ultimately involve the management of highly fragmented social groups while at the same time maintaining overall social cohesion. These results emphasize a need for more detailed brain data on a wider sample of primate species.

  2. Relational diversity and neighbourhood cohesion. Unpacking variety, balance and in-group size.

    PubMed

    Koopmans, Ruud; Schaeffer, Merlin

    2015-09-01

    Ethnic diversity is typically measured by the well-known Hirschman-Herfindahl Index. This paper discusses the merits of an alternative approach, which is in our view better suited to tease out why and how ethnic diversity matters. The approach consists of two elements. First, all existing diversity indices are non-relational. From the viewpoint of theoretical accounts that attribute negative diversity effects to in-group favoritism and out-group threat, it should however matter whether, given a certain level of overall diversity, an individual belongs to a minority group or to the dominant majority. We therefore decompose diversity by distinguishing the in-group share from the diversity of ethnic out-groups. Second, we show how generalized entropy measures can be used to test which of diversity's two basic dimensions matters most: the variety of groups, or the unequal distribution (balance) of the population over groups. These measures allow us to test different theoretical explanations against each other, because they imply different expectations regarding the effects of in-group size, out-group variety, and out-group balance. We apply these ideas in an analysis of various social cohesion measures across 55 German localities and show that both in-group size and out-group diversity matter. For the native majority as well as for persons of immigration background, the variety component of diversity seems to be more decisive than has formerly been acknowledged. These findings provide little support for group threat and in-group favoritism as the decisive mechanisms behind negative diversity effects, and are most in line with the predictions of theories that emphasize coordination problems, asymmetric preferences, and network closure.

  3. Density and group size influence shoal cohesion, but not coordination in zebrafish (Danio rerio).

    PubMed

    Shelton, Delia S; Price, Brittany C; Ocasio, Karen M; Martins, Emília P

    2015-02-01

    The formations made by gregarious animals can range from loose aggregates to highly synchronized and ordered structures. For very large, coordinated groups, both physical and social environments are important for determining the physical arrangement of individuals in the group. Here we tested whether physical and social factors are also important in determining the structure of small, loosely coordinated groups of zebrafish. We found that even though our fish were not crowded and did not use most of the available space, the distance between individual fish was explained primarily by the amount of available space (i.e., density). Zebrafish in a larger space spread out more and the total dimensions of the shoal were an additive function also of group size. We, however, did not find any impact of social or physical environment on the orientation of individual fish or shoal. Thus, both physical and social factors were important for shoal spatial arrangements, but not individual orientation and shoal alignment.

  4. [Group cohesion: a concept analysis].

    PubMed

    Lin, Yen-Ru; Chen, Yu-Jung; Tzeng, Wen-Chii; Chou, Kuei-Ru

    2007-10-01

    Group cohesion is considered an essential condition for achieving a successful treatment team. High cohesion groups more readily reach their goals, with group members also feeling more secure about their functions and contributions. In clinical practice, nurses use group teaching and group therapy to help patient and family members gain knowledge and skills related to illness treatment and recuperation. Effective group leadership helps minimize non-productive time and manpower and enhance interpersonal interaction. A further advantage of group cohesion is that the more effective administration of nursing programs that results can raise the profession level of staffs and reduce turnover. Walker and Avant (1995) employ concept analysis to use defining attributes in order to apply the same definition and communication to the same profession. The purpose of this paper was to apply this methodology to an analysis of group cohesion. Steps used include a review of the literature on conceptual definitions of group cohesion, a determination of defining attributes, model construction, identification of borderline, contrary, and related cases, and identification of antecedents and consequences and empirical tools. It is hoped that this analysis can help nursing staff to gain a better understanding of the concept of group cohesion and to apply such to clinical practice and nursing administration.

  5. Unit-level voluntary turnover rates and customer service quality: implications of group cohesiveness, newcomer concentration, and size.

    PubMed

    Hausknecht, John P; Trevor, Charlie O; Howard, Michael J

    2009-07-01

    Despite substantial growth in the service industry and emerging work on turnover consequences, little research examines how unit-level turnover rates affect essential customer-related outcomes. The authors propose an operational disruption framework to explain why voluntary turnover impairs customers' service quality perceptions. On the basis of a sample of 75 work units and data from 5,631 employee surveys, 59,602 customer surveys, and organizational records, results indicate that unit-level voluntary turnover rates are negatively related to service quality perceptions. The authors also examine potential boundary conditions related to the disruption framework. Of 3 moderators studied (group cohesiveness, group size, and newcomer concentration), results show that turnover's negative effects on service quality are more pronounced in larger units and in those with a greater concentration of newcomers.

  6. Group Cohesion in Experiential Growth Groups

    ERIC Educational Resources Information Center

    Steen, Sam; Vasserman-Stokes, Elaina; Vannatta, Rachel

    2014-01-01

    This article explores the effect of web-based journaling on changes in group cohesion within experiential growth groups. Master's students were divided into 2 groups. Both used a web-based platform to journal after each session; however, only 1 of the groups was able to read each other's journals. Quantitative data collected before and…

  7. Group Cohesion in Experiential Growth Groups

    ERIC Educational Resources Information Center

    Steen, Sam; Vasserman-Stokes, Elaina; Vannatta, Rachel

    2014-01-01

    This article explores the effect of web-based journaling on changes in group cohesion within experiential growth groups. Master's students were divided into 2 groups. Both used a web-based platform to journal after each session; however, only 1 of the groups was able to read each other's journals. Quantitative data collected before and…

  8. Living in forest fragments reduces group cohesion in diademed sifakas (Propithecus diadema) in eastern Madagascar by reducing food patch size.

    PubMed

    Irwin, Mitchell T

    2007-04-01

    Forest fragmentation is thought to threaten primate populations, yet the mechanisms by which this occurs remain largely unknown. However, fragmentation is known to cause dietary shifts in several primate species, and links between food resource distribution and within-group spatial dynamics are well documented. Thus, fragmentation has the potential to indirectly affect spatial dynamics, and these changes may present additional stresses to fragmented populations. I present the results from a 12-month study of Propithecus diadema at Tsinjoarivo, eastern Madagascar, including two groups in fragments and two in continuous forest. Instantaneous data on activity and spatial position were collected during all-day focal animal follows. Fragment groups had much lower cohesion, being more likely to have no neighbor within 5 and 10 m. For continuous forest groups, cohesion was highest in the rainy season (when food patches are large) and lowest in winter (when the animals rely on small-crowned mistletoes), and the chance of having no neighbor within 5 m was positively correlated with mistletoe consumption. Thus their decreased cohesion in fragment groups is inferred to result from their increased reliance on mistletoes and other small resources, which causes them to spread out among multiple patches. This scenario is consistent with the reduced body mass of subordinate individuals (males and immatures) in fragments, and suggests the occurrence of steeper within-group fitness gradients. Further research is necessary to determine whether these patterns apply to other primates; however, since fragmentation tends to cause the loss of the largest trees, many primates in fragments may lose their largest food resources and undergo similar behavioral shifts.

  9. Sustaining exercise participation through group cohesion.

    PubMed

    Estabrooks, P A

    2000-04-01

    The general hypothesis to be examined by this article is that increased group cohesion leads to an increase in adherence to an exercise program over time. Although preliminary research is promising, there is a need for further research aimed at examining the model of group development in exercise classes, the impact of group cohesion on both group and individual exercise behavior, and the measurement of group cohesion.

  10. An Assessment of Work Group Cohesion and Productivity.

    DTIC Science & Technology

    1986-09-01

    Perspective. MS thesis. Administrative Science Department, Naval Postgraduate School, Monterey CA, June 1983 (AD-A128047). Cartwright , Dorwin and Alvin...work group. The size of a group may have a moderating influence on those variables that affect cohesion ( Cartwright and Zander, 1968). If group size has...industrial work groups (Seashore, 1954). Cartwright and Zander, in their review of studies relating similarities and group cohesion, stated that dis

  11. "-ing" Project: Encouraging Cohesion in Small Groups

    ERIC Educational Resources Information Center

    McBride, M. Chad

    2006-01-01

    Group cohesiveness is a topic addressed in most small group communication texts and courses and is often defined as the degree of attraction members feel towards one another, the degree of loyalty within a group, or the "groupness" felt among members. Further, groups which are cohesive tend to be happier and more productive. When working on…

  12. Group Cohesiveness, Deviation, Stress, and Conformity

    DTIC Science & Technology

    1993-08-11

    assessed pre- and post- conformity pressure (see Appendix VIII). Components of group influences , Offer of Reward for Conformity (ORC), and Threat of...Cohesiveness Pressures to Uniformity Studies . . . . Evidence Supporting a Group Cohesiveness- Conformity Relationship . . . . . . Evidence Supporting a...Response and Conformity Pressure . . . . Stress and ORC and TPN . . . . . . . . TPN and Space Crews . . . . . . . . . . Summary of Group

  13. Inventory of Individually Perceived Group Cohesiveness (IIPGC).

    ERIC Educational Resources Information Center

    Johnson, David L.

    The Inventory of Individually Perceived Group Cohesiveness (IIPGC) is a self-report measure of an individual's perception of group cohesiveness, which is defined as the perceived degree, extent, or strength of mutual attention given by the membership to processes of cooperation, control, and task communication. The IIPGC provides a reliable…

  14. Group cohesion: Relationships with work team culture.

    PubMed

    Sánchez, José C; Yurrebaso, Amaia

    2009-02-01

    The aim of this study was to examine the relationships between group cohesion and the perceived culture and desired culture of work teams. Two separate studies were carried out with a time interval of one year. The first study had a sample of 50 work teams belonging to different organizations and the second study had a sample of 75 work teams. We used Lindell's index of agreement to estimate the culture and cohesion variables. Multiple and hierarchical regression analysis in both studies confirmed our initial hypothesis, showing that perceived and desired culture were positively related to group cohesion, and that culture gap had a negative association with cohesion. To a lesser extent, control variables such as job tenure and gender had a positive relationship with cohesion. The implications of these results are discussed along with the importance of considering the group level as analysis.

  15. Alliance and group cohesion in relationship education.

    PubMed

    Owen, Jesse; Antle, Becky; Barbee, Anita

    2013-09-01

    Relationship education programs have been shown as an effective way to increase relationship functioning. There is less known about how process factors, such as alliance with the leader or group dynamics, affect outcomes in these interventions. We examined group cohesion and alliance with the leader in a relationship education program tailored for individuals. Specifically, we examined whether participants' ratings (n = 126) of the group cohesion and alliance with the leader were associated with changes in relationship adjustment, relationship confidence, and communication quality from pre- to postintervention. The results demonstrated that participants' perceptions of the cohesion among the members in their relationship education group, but not the leader-participant alliance, made a significant contribution to the changes in participants' relationship functioning. These results suggest that the group dynamics among the members in the group are important ingredients in relationship education. Implications for relationship programs are provided. © FPI, Inc.

  16. The Effect of Feedback on Group Cohesiveness.

    ERIC Educational Resources Information Center

    Mears, Peter M.

    The effect of feedback on group cohesiveness (measured in terms of group and task attractiveness) for a person who is performing a simple, highly repetitive task was studied. One hundred business administration students, randomly assigned to five member groups, completed a series of trials having the goal of determining the number commonly held by…

  17. Behavioural Contagion Explains Group Cohesion in a Social Crustacean

    PubMed Central

    Broly, Pierre; Deneubourg, Jean-Louis

    2015-01-01

    In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living. The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment. In this view, social aggregation in terrestrial isopods represents an interesting model due to its recurrence both in the field and in the laboratory. In this study, and under a perturbation context, we experimentally tested the stability of groups of woodlice according to group size and time spent in group. Our results indicate that the response to the disturbance of groups decreases with increases in these two variables. Models neglecting social effects cannot reproduce experimental data, attesting that cohesion of aggregation in terrestrial isopods is partly governed by a social effect. In particular, models involving calmed and excited individuals and a social transition between these two behavioural states more accurately reproduced our experimental data. Therefore, we concluded that group cohesion (and collective response to stimulus) in terrestrial isopods is governed by a transitory resting state under the influence of density of conspecifics and time spent in group. Lastly, we discuss the nature of direct or indirect interactions possibly implicated. PMID:26067565

  18. Behavioural Contagion Explains Group Cohesion in a Social Crustacean.

    PubMed

    Broly, Pierre; Deneubourg, Jean-Louis

    2015-06-01

    In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living. The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment. In this view, social aggregation in terrestrial isopods represents an interesting model due to its recurrence both in the field and in the laboratory. In this study, and under a perturbation context, we experimentally tested the stability of groups of woodlice according to group size and time spent in group. Our results indicate that the response to the disturbance of groups decreases with increases in these two variables. Models neglecting social effects cannot reproduce experimental data, attesting that cohesion of aggregation in terrestrial isopods is partly governed by a social effect. In particular, models involving calmed and excited individuals and a social transition between these two behavioural states more accurately reproduced our experimental data. Therefore, we concluded that group cohesion (and collective response to stimulus) in terrestrial isopods is governed by a transitory resting state under the influence of density of conspecifics and time spent in group. Lastly, we discuss the nature of direct or indirect interactions possibly implicated.

  19. Groupthink: one peril of group cohesiveness.

    PubMed

    Rosenblum, E H

    1982-04-01

    A group's aim is to make well-conceived, well-understood, well-accepted and realistic decisions to reach their agreed-upon goals. This aim applies equally to their own goals and those occasionally imposed by outsiders such as hospital administration, accreditation committees and the federal government. Effective groupwork requires group cohesion with its components of trust, risk taking, mutual support, and group esteem. With constant vigilance the group can maintain its positive dynamics, so that the unhealthy state of groupthink does not undermine its existence.

  20. Facilitating Group Cohesion among Adolescents through Challenge Course Experiences.

    ERIC Educational Resources Information Center

    Glass, J. Scott; Benshoff, James M.

    2002-01-01

    A study examined the effects of participation in a low-element challenge course on younger adolescents' perceptions of group cohesion. Pre- and post-tests of group cohesion were administered to 167 North Carolina adolescents aged 11-14. Participants perceived an increase in group cohesion after the daylong program, regardless of their age, race,…

  1. Working with Group-Tasks and Group Cohesiveness

    ERIC Educational Resources Information Center

    Anwar, Khoirul

    2016-01-01

    This study aimed at exploring the connection between the use of group task and group cohesiveness. This study is very important because the nature of the learner's success is largely determined by the values of cooperation, interaction, and understanding of the learning objectives together. Subjects of this study are 28 students on the course…

  2. Effective particle sizes of cohesive sediment in north Mississippi streams

    USDA-ARS?s Scientific Manuscript database

    Knowledge of the size of cohesive sediment particles transported in streams is important information for predicting how the sediment and contaminants the sediment may be carrying will be transported by the flow. Cohesive sediments (less than 0.062 mm in diameter) generally are not transported in th...

  3. Leadership Status Congruency and Cohesion in Outdoor Expedition Groups

    ERIC Educational Resources Information Center

    Eys, Mark A.; Ritchie, Stephen; Little, Jim; Slade, Heather; Oddson, Bruce

    2008-01-01

    The purpose of the present study was to examine the relationship between status congruency and group cohesion in outdoor expedition groups in an educational setting. Specifically, three aspects of status congruency were assessed in relation to group cohesion in four adventure canoe groups. The groups participated in 2-week expeditions in the…

  4. Introducing Semantic Cohesion Analysis: A Study of Group Talk.

    ERIC Educational Resources Information Center

    Friedlander, Myrna L.; And Others

    1985-01-01

    Cohesive talk was observed over time and across psychotherapy groups led by self-disclosing or nondisclosing therapists. Despite individual therapist differences, the nondisclosing groups showed more cohesive interactions throughout therapy. No differences were observed in clients' perceptions of therapists or their attraction to the group.…

  5. Exploring Group Cohesion in a Higher Education Field Experience

    ERIC Educational Resources Information Center

    Malcarne, Brian Keith

    2012-01-01

    The purpose of this study was to gain understanding into the experience of group cohesion for university students participating in an academic field experience. A mixed methods approach was used following a two-phase, sequential research design to help provide a more complete explanation of how group cohesion was impacted by the field experience.…

  6. Relationship between group cohesion and anxiety in soccer.

    PubMed

    Borrego, Carla Chicau; Cid, Luis; Silva, Carlos

    2012-10-01

    Group cohesion in sport is a widely spread theme today. Research has found cohesion to be influenced by several individual and group components. Among the cognitive variables that relate to cohesion we found competitive anxiety. The purpose of this study was to examine the relation between task cohesion (ATG-T, and GI-T) and competitive state anxiety (A-state), and also if there would be a relation between cohesion and self-confidence. Participants were 366 football players of both genders male and female, aged between 15 to 23 years old, from Portugal's championships. Cohesion was measured using the Portuguese version of the Group Environment Questionnaire, and to assess competitive anxiety, we used the Portuguese version of the Competition State Anxiety Inventory 2. Our results show that female athletes report experiencing more cognitive anxiety and less self-confidence than male athletes. Only cognitive anxiety relates in a significantly negative way with the perception of cohesion (GI-T e ATG-T) in the total number of participants and in male athletes. Relatively to the somatic anxiety, it only relates negatively with the perception of the integration of the group in the total number of participants and in the male gender.

  7. Characteristics of work groups and their relationship with social and task cohesion in student teams.

    PubMed

    Forrester, William R; Tashchian, Armen

    2004-08-01

    Results of an exploratory study of relationships between work-group characteristics and the social and task cohesion of 18 business students engaged in team class projects. Regression analysis of scores on workload sharing, team spirit, task flexibility, and team cohesiveness for scales of the Work Group Characteristics Inventory indicated sharing of the workload was significantly associated with both task and social cohesion; team spirit with task cohesion but not social cohesion; and task flexibility with social cohesion but not task cohesion.

  8. The role of biophysical cohesion on subaqueous bed form size

    PubMed Central

    Schindler, Robert J.; Hope, Julie A.; Malarkey, Jonathan; Baas, Jaco H.; Peakall, Jeffrey; Manning, Andrew J.; Ye, Leiping; Simmons, Steve; Paterson, David M.; Aspden, Rebecca J.; Bass, Sarah J.; Davies, Alan G.; Lichtman, Ian D.; Thorne, Peter D.

    2016-01-01

    Abstract Biologically active, fine‐grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud‐sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross‐stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record. PMID:27011393

  9. Root Cohesion Controls on Shallow Landslide Size, Shape and Location

    NASA Astrophysics Data System (ADS)

    Douglas, M.; Bellugi, D. G.; Perron, J.; Coe, J. A.; Schmidt, K. M.

    2013-12-01

    Many environmental factors, including ground cover, local hydrology, and recent weather events interact to cause shallow landslides and determine landslide characteristics. Vegetation is of particular interest, because changes in vegetation density, age, and composition are expected consequences of human land use and climate change. These changes alter effective cohesion due to root reinforcement, which is known to impact landslide abundance, but the effects of root cohesion on landslide size, shape and location have not been quantified. The Elliott State Forest, a 376 km2 managed forest in Douglas County, Oregon, provides an ideal venue to study these effects. There, a single storm in November 1996 triggered 154 shallow landslides, which were subsequently mapped using aerial images onto laser altimetry data, in an area with a range of vegetation ages but relatively uniform soil properties, topography, and lithology. We used aerial imagery to categorize areas with different land use histories into 3 vegetation classes, ranging from clear-cuts to forest with mature trees over 100 years old. Each mapped landslide was then assigned to a class, and its size, shape and location was recorded. Our results show that, in addition to the expected decrease in landslide abundance in more-vegetated areas (which could be influenced by a bias against detecting landslides under trees), landslides in those areas were also larger and more elongated in the down-slope direction. Although landslides in all three classes generally occurred at locations with similar drainage area and slope, we observed that slides with a larger ratio of drainage area to slope were slightly more abundant in areas with lower vegetation cover. To investigate the causes of these variations, we used a new shallow landslide model calibrated for the Oregon Coast Range to predict the size, shape and location of landslides triggered by the 1996 storm under a range of root cohesion values in a subset of the study

  10. Some Measures of Interpersonal Attraction and Group Cohesiveness.

    ERIC Educational Resources Information Center

    Aiken, Lewis R.

    1992-01-01

    The computation and determination of the statistical significance of three coefficients of interpersonal attractiveness or cohesiveness in task-oriented or social groups are described. The approach is based on ratings made by each member of a group of all other group members. Experience using the technique is reviewed. (SLD)

  11. The Role of Communication and Cohesion in Reducing Social Loafing in Group Projects

    ERIC Educational Resources Information Center

    Lam, Chris

    2015-01-01

    This study examines previously untested variables that influence social loafing in professional and technical communication group projects by determining the influence of communication quality and task cohesion on social loafing. A set-up factors model, which included group size, peer review, project scope, and method of team formation, was also…

  12. The Role of Communication and Cohesion in Reducing Social Loafing in Group Projects

    ERIC Educational Resources Information Center

    Lam, Chris

    2015-01-01

    This study examines previously untested variables that influence social loafing in professional and technical communication group projects by determining the influence of communication quality and task cohesion on social loafing. A set-up factors model, which included group size, peer review, project scope, and method of team formation, was also…

  13. Groupthink: One Peril of Group Cohesiveness.

    ERIC Educational Resources Information Center

    Rosenblum, Estelle H.

    1982-01-01

    This article briefly discusses some important elements of group effectiveness, then outlines characteristics of groupthink, provides examples of situations in which it occurs, and recommends actions in each case for preventing or lessening it. (Author/CT)

  14. Groupthink: One Peril of Group Cohesiveness.

    ERIC Educational Resources Information Center

    Rosenblum, Estelle H.

    1982-01-01

    This article briefly discusses some important elements of group effectiveness, then outlines characteristics of groupthink, provides examples of situations in which it occurs, and recommends actions in each case for preventing or lessening it. (Author/CT)

  15. Examining the Relationship between Emotional Intelligence and Group Cohesion

    ERIC Educational Resources Information Center

    Moore, Amanda; Mamiseishvili, Ketevan

    2012-01-01

    Collaborative learning experiences increase student learning, but what happens when students fail to collaborate? The authors investigated the relationship between emotional intelligence and group cohesion by studying 44 undergraduate teams who were completing semester-long projects in their business classes at a small private university in the…

  16. Examining the Relationship between Emotional Intelligence and Group Cohesion

    ERIC Educational Resources Information Center

    Moore, Amanda; Mamiseishvili, Ketevan

    2012-01-01

    Collaborative learning experiences increase student learning, but what happens when students fail to collaborate? The authors investigated the relationship between emotional intelligence and group cohesion by studying 44 undergraduate teams who were completing semester-long projects in their business classes at a small private university in the…

  17. Dynamic Task Performance, Cohesion, and Communications in Human Groups.

    PubMed

    Giraldo, Luis Felipe; Passino, Kevin M

    2016-10-01

    In the study of the behavior of human groups, it has been observed that there is a strong interaction between the cohesiveness of the group, its performance when the group has to solve a task, and the patterns of communication between the members of the group. Developing mathematical and computational tools for the analysis and design of task-solving groups that are not only cohesive but also perform well is of importance in social sciences, organizational management, and engineering. In this paper, we model a human group as a dynamical system whose behavior is driven by a task optimization process and the interaction between subsystems that represent the members of the group interconnected according to a given communication network. These interactions are described as attractions and repulsions among members. We show that the dynamics characterized by the proposed mathematical model are qualitatively consistent with those observed in real-human groups, where the key aspect is that the attraction patterns in the group and the commitment to solve the task are not static but change over time. Through a theoretical analysis of the system we provide conditions on the parameters that allow the group to have cohesive behaviors, and Monte Carlo simulations are used to study group dynamics for different sets of parameters, communication topologies, and tasks to solve.

  18. Groupthink: Effects of Cohesiveness and Problem-Solving Procedures on Group Decision Making.

    ERIC Educational Resources Information Center

    Callaway, Michael R.; Esser, James K.

    1984-01-01

    Tested Janis' groupthink formulation with 126 students by manipulating group cohesiveness and adequacy of decision procedures in a factorial design. Results showed highest quality decisions were produced by groups of intermediate cohesiveness. Highly cohesive groups without adequate decision procedures (the groupthink condition) tended to make the…

  19. Groupthink: Effects of Cohesiveness and Problem-Solving Procedures on Group Decision Making.

    ERIC Educational Resources Information Center

    Callaway, Michael R.; Esser, James K.

    1984-01-01

    Tested Janis' groupthink formulation with 126 students by manipulating group cohesiveness and adequacy of decision procedures in a factorial design. Results showed highest quality decisions were produced by groups of intermediate cohesiveness. Highly cohesive groups without adequate decision procedures (the groupthink condition) tended to make the…

  20. Dynamic Relationships of Therapist Alliance and Group Cohesion in Transdiagnostic Group CBT for Anxiety Disorders

    PubMed Central

    Norton, Peter J.; Kazantzis, Nikolaos

    2015-01-01

    Objective Little is known about the temporal variability of the alliance-symptom change and cohesion-symptom change relationships over the course of group therapy. These questions were examined in a sample of 373 clients receiving a transdiagnostic cognitive behavior therapy (tCBT), which culled the principle research-supported mechanisms of change for anxiety disorders. Method We examined relationships between the client versions of the Working Alliance Inventory and Group Cohesion Scale in predicting subsequent symptom change, as assessed by the state scale of the State-Trait Anxiety Inventory. Results Alliance and cohesion were significant predictors of next session anxiety scores. The alliance was consistently associated with anxiety symptoms (rs = −.152 to −.198, ps < .05), but cohesion only showed significant relationships with anxiety symptoms at sessions 8 and 10 (Session 8, r = −.233, p = .020, and 10, r = −.236, p = .027). Alliance-anxiety relations remained constant, whereas cohesion-anxiety relations substantially increased from earlier to later sessions. Discussion Differences that were obtained in the relation of alliance and cohesion with anxiety symptoms suggests that these processes have different roles within group tCBT. If replicated, the present findings would suggest that the dynamic relationships between alliance and cohesion and symptoms within group CBT for anxiety disorders have been an important omission in process-outcome studies. PMID:26689305

  1. Dynamic relationships of therapist alliance and group cohesion in transdiagnostic group CBT for anxiety disorders.

    PubMed

    Norton, Peter J; Kazantzis, Nikolaos

    2016-02-01

    Little is known about the temporal variability of the alliance-symptom change and cohesion-symptom change relationships over the course of group therapy. These questions were examined in a sample of 373 clients receiving a transdiagnostic cognitive behavior therapy (tCBT), which culled the principle research-supported mechanisms of change for anxiety disorders. The authors examined relationships between the client versions of the Working Alliance Inventory and Group Cohesion Scale in predicting subsequent symptom change, as assessed by the state scale of the State-Trait Anxiety Inventory. Alliance and cohesion were significant predictors of next session anxiety scores. The alliance was consistently associated with anxiety symptoms (rs = -.152 to -.198, ps < .05), but cohesion only showed significant relationships with anxiety symptoms at Sessions 8 and 10 (Session 8, r = -.233, p = .020, and 10, r = -.236, p = .027). Alliance-anxiety relations remained constant, whereas cohesion-anxiety relations substantially increased from earlier to later sessions. Differences that were obtained in the relation of alliance and cohesion with anxiety symptoms suggests that these processes have different roles within group tCBT. If replicated, the present findings would suggest that the dynamic relationships between alliance and cohesion and symptoms within group CBT for anxiety disorders have been an important omission in process-outcome studies. (c) 2016 APA, all rights reserved).

  2. Internal character dictates transition dynamics between isolation and cohesive grouping

    NASA Astrophysics Data System (ADS)

    Manrique, Pedro D.; Hui, Pak Ming; Johnson, Neil F.

    2015-12-01

    We show that accounting for internal character among interacting heterogeneous entities generates rich transition behavior between isolation and cohesive dynamical grouping. Our analytical and numerical calculations reveal different critical points arising for different character-dependent grouping mechanisms. These critical points move in opposite directions as the population's diversity decreases. Our analytical theory may help explain why a particular class of universality is so common in the real world, despite the fundamental differences in the underlying entities. It also correctly predicts the nonmonotonic temporal variation in connectivity observed recently in one such system.

  3. Internal character dictates transition dynamics between isolation and cohesive grouping.

    PubMed

    Manrique, Pedro D; Hui, Pak Ming; Johnson, Neil F

    2015-12-01

    We show that accounting for internal character among interacting heterogeneous entities generates rich transition behavior between isolation and cohesive dynamical grouping. Our analytical and numerical calculations reveal different critical points arising for different character-dependent grouping mechanisms. These critical points move in opposite directions as the population's diversity decreases. Our analytical theory may help explain why a particular class of universality is so common in the real world, despite the fundamental differences in the underlying entities. It also correctly predicts the nonmonotonic temporal variation in connectivity observed recently in one such system.

  4. Particle Size and Structural Arrangement of Suspended Cohesive Sediments

    NASA Astrophysics Data System (ADS)

    Tan, X.; Zhang, G.; Reed, A. H.; Furukawa, Y.

    2012-12-01

    Coastal environments are often characterized by high concentrations of cohesive sediments influenced by the loaded organic matter (particularly extracellular polymeric substances (EPS)), salt, and hydrodynamic disturbance. The size and structural variation of suspended cohesive sediments due to flocculation and/or disaggregation is of key importance for understanding a variety of sediment transport processes (e.g., settling, breakage, survivability) in littoral environments and the geotechnical/geophysical properties of the bottom bed. To obtain a comprehensive understanding of sediment floc behavior and correlate the clay-EPS-ion interaction mechanisms with their structures, a series of sediment samples were synthesized in laboratory using four pure clays (i.e., kaolinite, illite, Ca-montmorillonite, and Na-montmorillonite), three EPS (cationic, neutral, and anionic) at different concentrations, and saltwater of different salinity under different hydrodynamic conditions. Particle size analysis of the pure clays, clay-EPS, and clay-salt flocs under three hydrodynamic conditions demonstrated for the first time in the laboratory that pure clays and clay-EPS mixtures exhibit lognormal, multimodal (i.e., 2-4 levels consisting of primary particle, flocculi, microfloc, and macrofloc) particle size distributions (PSDs) within the size range of ~0.1 to ~500 μm. The presence of EPS causes the formation of macroflocs (>200 μm) and can significantly increase the mean particle size by several orders of magnitude through flocculation, assisted by electrostatic forces, ion-dipole, van der Waals forces, and other mechanisms. The change in size of the pure clay flocs in saltwater showed different trends: Due to the clays' different properties and interaction mechanisms with EPS, their PSDs and size changes are also different in different flow conditions: the hydrodynamic turbulence may promote the flocculation of Ca-montmorillonite, but break kaolinite and Na

  5. Developing cohesion in court-mandated group treatment of male spouse abusers.

    PubMed

    Robbins, Reuben N

    2003-07-01

    Cohesion in group treatment of spouse abusers plays an important and often overlooked role. Involuntary abuser groups can benefit from cohesion, but due to their unique structure, cohesion may develop differently than in voluntary psychotherapy groups. Initially, abuser groups may develop premature levels of cohesion that can make group members unwilling to express conflict, develop intimacy, and take responsibility for their actions. Understanding the abuser personality and the unique characteristics of involuntary abuser groups can shed light on why cohesion develops the way it does and the importance it plays in abuser groups. Developing effective interventions that target premature cohesion can help the group members express conflict, develop intimacy, and take responsibility for their actions, thus bringing about therapeutic levels of cohesion.

  6. A Longitudinal Field Investigation of the Impact of Group Composition on Group Performance and Cohesion.

    ERIC Educational Resources Information Center

    Terborg, James R.; And Others

    In a longitudinal field experiment, 42 groups were assembled on the factors of individual ability and attitude similarity resulting in a 2 x 2 crossed ANOVA design. These groups then worked on six projects which spanned a three-month time period. For each project, measures of group performance and group cohesion were taken. Analyses showed that…

  7. Group cohesion in cognitive-behavioral group therapy for social phobia.

    PubMed

    Taube-Schiff, Marlene; Suvak, Michael K; Antony, Martin M; Bieling, Peter J; McCabe, Randi E

    2007-04-01

    Cognitive-behavior therapy (CBT) for Social Phobia is effective in both group and individual formats. However, the impact of group processes on treatment efficacy remains relatively unexplored. In this study we examined group cohesion ratings made by individuals at the midpoint and endpoint of CBT groups for social phobia. Symptom measures were also completed at the beginning and end of treatment. We found that cohesion ratings significantly increased over the course of the group and were associated with improvement over time in social anxiety symptoms, as well as improvement on measures of general anxiety, depression, and functional impairment. In conclusion, findings are consistent with the idea that changes in group cohesion are related to social anxiety symptom reduction and, therefore, speak to the importance of nonspecific therapeutic factors in treatment outcome.

  8. Components of Group Cohesion: Intermember Attraction, Instrumental Value, and Risk Taking.

    ERIC Educational Resources Information Center

    Stokes, Joseph Powell

    1983-01-01

    Explored the nature of cohesion in groups formed to affect personal change. Members (N=227) of eight therapy groups completed the Three Factor Group Questionnaire. Results suggested risk-taking, attraction to individual group members, and the instrumental value of the group were all related to group cohesion. (Author/JAC)

  9. Group Climate, Cohesion, Alliance, and Empathy in Group Psychotherapy: Multilevel Structural Equation Models

    ERIC Educational Resources Information Center

    Johnson, Jennifer E.; Burlingame, Gary M.; Olsen, Joseph A.; Davies, D. Robert; Gleave, Robert L.

    2005-01-01

    This study examined the definitional and statistical overlap among 4 key group therapeutic relationship constructs--group climate, cohesion, alliance, and empathy--across member-member, member-group, and member-leader relationships. Three multilevel structural equation models were tested using self-report measures completed by 662 participants…

  10. Leader Behaviors, Group Cohesion, and Participation in a Walking Group Program.

    PubMed

    Izumi, Betty T; Schulz, Amy J; Mentz, Graciela; Israel, Barbara A; Sand, Sharon L; Reyes, Angela G; Hoston, Bernadine; Richardson, Dawn; Gamboa, Cindy; Rowe, Zachary; Diaz, Goya

    2015-07-01

    Less than half of all U.S. adults meet the 2008 Physical Activity Guidelines. Leader behaviors and group cohesion have been associated with increased participation or adherence in sports team and exercise class settings. Physical activity interventions in community settings that encompass these factors may enhance intervention adherence. The purpose of this study is to examine the impact of Community Health Promoter leader behaviors and group cohesion on participation in a walking group intervention among racially/ethnically diverse adults in low to moderate-income communities in Detroit, Michigan. Data for the current study were drawn from the Walk Your Heart to Health (WYHH) data set. WYHH was a multisite cluster RCT with a lagged intervention and outcome measurements at baseline and 4, 8, and 32 weeks. Pooled survey data from both intervention arms were used for the current study. Data were analyzed between August 2013 and October 2014. A total of 603 non-Hispanic black, non-Hispanic white, and Hispanic adults across five cohorts that began the 32-week WYHH intervention between March 2009 and October 2011. The intervention was a 32-week walking group program hosted by community- and faith-based organizations and facilitated by Community Health Promoters. Walking groups met three times per week for 90 minutes per session. To promote participation in or adherence to WYHH, Community Health Promoters used evidence-based strategies to facilitate group cohesion. Group members assumed increasing leadership responsibility for facilitating sessions over time. Participation in WYHH as measured by consistency of attendance. Community Health Promoter leader behaviors were positively associated with participation in WYHH. Social but not task cohesion was significantly associated with consistent participation. Social cohesion may mediate the relationship between leader behaviors and walking group participation. Providing leaders with training to build socially cohesive groups

  11. Effects of an Explicit Group Contract on SelfDisclosure and Group Cohesiveness

    ERIC Educational Resources Information Center

    Ribner, Neil G.

    1974-01-01

    Effects of a group eontract specifically calling for self-disclosure was investigated. Frequency and depth of self disclosure were increased but level of intimacy of topics discussed was not. Group cohesiveness was enhanced by the contract but it decreased members' mutual liking. (Author/EAK)

  12. Effects of a Low-Element Challenge Course on Abstinence Self-Efficacy and Group Cohesion

    ERIC Educational Resources Information Center

    Clem, Jamie M.; Smith, Thomas E.; Richards, Kristin V.

    2012-01-01

    Substance abuse researchers identify self-efficacy and group cohesion as important components in alcohol and other drug-dependency treatment. Objectives: The purpose of this single-group, pretest-posttest study is to explore the therapeutic value of a challenge course intervention on the self-efficacy and group cohesion of nine chemically…

  13. Comparison of Group Cohesion, Class Participation, and Exam Performance in Live and Online Classes

    ERIC Educational Resources Information Center

    Galyon, Charles E.; Heaton, Eleanore C. T.; Best, Tiffany L.; Williams, Robert L.

    2016-01-01

    Though class participation and group cohesion have shown some potential to promote student performance in conventional classrooms, their efficacy has not yet been demonstrated in an online-class setting. Group cohesion, defined as member attraction to and self-identification with a group, is thought to promote positive interdependence and the…

  14. Comparison of Group Cohesion, Class Participation, and Exam Performance in Live and Online Classes

    ERIC Educational Resources Information Center

    Galyon, Charles E.; Heaton, Eleanore C. T.; Best, Tiffany L.; Williams, Robert L.

    2016-01-01

    Though class participation and group cohesion have shown some potential to promote student performance in conventional classrooms, their efficacy has not yet been demonstrated in an online-class setting. Group cohesion, defined as member attraction to and self-identification with a group, is thought to promote positive interdependence and the…

  15. Cohesion and outcome in short-term psychodynamic groups for complicated grief.

    PubMed

    Kipnes, Dianne R; Piper, William E; Joyce, Anthony S

    2002-10-01

    This study used two measures of cohesion for the process analysis of 12 short-term, time-limited groups for complicated grief. The measures had similar theoretical definitions but differed in terms of rater source (member vs. observer), measurement score (mean of items vs. global rating), and rating unit (individual vs. group). We examined the relationship between the measures, assessed the development of cohesion over the life of the group, and evaluated each measure's relationship to outcome. A principal components analysis with each measure yielded one cohesion component, which supported a unidimensional model; however, the two cohesion components were independent of each other, which supported a multidimensional model. Repeated measures analyses indicated that observer-rated cohesion developed in a quadratic manner (v pattern) across sessions, while member-rated cohesion developed in a linear manner. The object focus (the group, other members, the therapist) of the members' ratings determined whether cohesion increased or decreased across sessions. No significant relationships between cohesion and outcome were identified. Implications of the findings for the understanding of group cohesion are considered.

  16. Influence of Sport Education on Group Cohesion in University Physical Education

    ERIC Educational Resources Information Center

    Jenkins, Jayne M.; Alderman, Brandon L.

    2011-01-01

    The Sport Education ("SE") curricular model incorporated within university physical education Basic Instruction Program (BIP) may increase group cohesion. This study's purpose was to identify student perceptions of a BIP course taught within "SE," and investigate group cohesion in differing activity content. Participants…

  17. Influence of Sport Education on Group Cohesion in University Physical Education

    ERIC Educational Resources Information Center

    Jenkins, Jayne M.; Alderman, Brandon L.

    2011-01-01

    The Sport Education ("SE") curricular model incorporated within university physical education Basic Instruction Program (BIP) may increase group cohesion. This study's purpose was to identify student perceptions of a BIP course taught within "SE," and investigate group cohesion in differing activity content. Participants…

  18. INFLUENCE OF CLASSROOM GROUP COHESIVENESS ON LEARNING AND ADHERENCE TO STANDARDS.

    ERIC Educational Resources Information Center

    LOTT, ALBERT J.; LOTT, BERNICE E.

    RESULTS INDICATE THAT THE DEGREE OF LIKING AMONG ELEMENTARY SCHOOL CHILDREN (DEGREE OF GROUP COHESIVENESS) HAS A SIGNIFICANT INFLUENCE ON ASPECTS OF PUPIL BEHAVIOR. IN THE THEORETICAL FRAMEWORK OF REINFORCEMENT LEARNING THEORY, INVESTIGATION OF RELATIONSHIPS BETWEEN COHESIVENESS (A GROUP VARIABLE) AND INDIVIDUAL BEHAVIOR CAN LEAD BOTH TO A BETTER…

  19. Group cohesion and starting status in successful and less successful elite volleyball teams.

    PubMed

    Spink, K S

    1992-08-01

    The main purpose of this study was to examine the relationship between members' perceptions of group cohesion and starting status in elite volleyball teams. The results of the study revealed that the form of the cohesion-starting status relationship was moderated by the variable of success. The results for less successful teams revealed that differences did emerge between specific measures of cohesion endorsed by starters and non-starters. No such differences in cohesion emerged when the starters and non-starters on successful teams were compared. These results provide initial support for the suggestion that the most successful teams are the ones where the perceptions of cohesiveness by starters and non-starters are similar. A secondary purpose of the study was to determine whether those teams that were the most successful and similar in their members' perceptions of cohesiveness, were also the teams whose members have the most positive outcome expectancy. The results supported this prediction.

  20. Family Cohesion and Its Relationship to Psychological Distress among Latino Groups

    ERIC Educational Resources Information Center

    Rivera, Fernando I.; Guarnaccia, Peter J.; Mulvaney-Day, Norah; Lin, Julia Y.; Torres, Maria; Alegria, Margarita

    2008-01-01

    This article presents analyses of a representative sample of U.S. Latinos (N = 2,540) to investigate whether family cohesion moderates the effects of cultural conflict on psychological distress. The results for the aggregated Latino group suggest a significant association between family cohesion and lower psychological distress, and the…

  1. Family Cohesion and Its Relationship to Psychological Distress among Latino Groups

    ERIC Educational Resources Information Center

    Rivera, Fernando I.; Guarnaccia, Peter J.; Mulvaney-Day, Norah; Lin, Julia Y.; Torres, Maria; Alegria, Margarita

    2008-01-01

    This article presents analyses of a representative sample of U.S. Latinos (N = 2,540) to investigate whether family cohesion moderates the effects of cultural conflict on psychological distress. The results for the aggregated Latino group suggest a significant association between family cohesion and lower psychological distress, and the…

  2. Interdependence and organizational citizenship behavior: exploring the mediating effect of group cohesion in multilevel analysis.

    PubMed

    Chen, Chun-Hsi Vivian; Tang, Ya-Yun; Wang, Shih-Jon

    2009-12-01

    The authors investigated the mechanism of group cohesion in the relationship between (a) task interdependence and goal interdependence and (b) individuals' organizational citizenship behavior (OCB). The authors adopted a multilevel perspective to facilitate understanding of the complex relations among variables. They collected data from 53 supervisors and 270 employees from R&D departments in Taiwan. The authors found that group cohesion fully mediated the effects of task interdependence and goal interdependence on employees' OCB. In addition, task interdependence had a greater effect on group cohesion than did goal interdependence. The authors discuss implications and suggestions for future research.

  3. Cohesion and performance in groups: a meta-analytic clarification of construct relations.

    PubMed

    Beal, Daniel J; Cohen, Robin R; Burke, Michael J; McLendon, Christy L

    2003-12-01

    Previous meta-analytic examinations of group cohesion and performance have focused primarily on contextual factors. This study examined issues relevant to applied researchers by providing a more detailed analysis of the criterion domain. In addition, the authors reinvestigated the role of components of cohesion using more modern meta-analytic methods and in light of different types of performance criteria. The results of the authors' meta-analyses revealed stronger correlations between cohesion and performance when performance was defined as behavior (as opposed to outcome), when it was assessed with efficiency measures (as opposed to effectiveness measures), and as patterns of team workflow became more intensive. In addition, and in contrast to B. Mullen and C. Copper's (1994) meta-analysis, the 3 main components of cohesion were independently related to the various performance domains. Implications for organizations and future research on cohesion and performance are discussed.

  4. Family Cohesion and its Relationship to Psychological Distress among Latino Groups.

    PubMed

    Rivera, Fernando I; Guarnaccia, Peter J; Mulvaney-Day, Norah; Lin, Julia Y; Torres, Maria; Alegria, Margarita

    2008-01-01

    This paper presents analyses of a representative sample of US Latinos (N=2540) to investigate whether family cohesion moderates the effects of cultural conflict on psychological distress. The results for the aggregated Latino group suggests a significant association between family cohesion and lower psychological distress and the combination of strong family cohesion with presence of family cultural conflict was associated with higher psychological distress. However, this association differed by Latino groups. We found no association for Puerto Ricans, Cuban results were similar to the aggregate group, family cultural conflict in Mexicans was associated with higher psychological distress, while family cohesion in Other Latinos was associated with higher psychological distress. Implications of these findings are discussed to unravel the differences in family dynamics across Latino subethnic groups.

  5. Psychosocial mediators of group cohesion on physical activity intention of older adults.

    PubMed

    Caperchione, Cristina; Mummery, Kerry

    2007-01-01

    Considerable evidence has indicated that group-based physical activity may be a promising approach to reducing and preventing age-related illness. However, this research has not examined the mechanisms by which cohesion may impact on behaviour. The purpose of the present research was to utilise the theory of planned behaviour to investigate the mechanism by which group cohesion may affect physical activity intention. Participants were recruited from an existing physical activity intervention studying the effects of group cohesion on physical activity behaviour. The outcomes of this intervention are reported elsewhere. This paper presents data from a sub-sample of the intervention population (N=74) that examined the mediating relationships between the theory of planned behaviour and group cohesion on physical activity intention. Analyses showed that attitude and perceived behavioural control mediated the relationship between specific group cohesion concepts and physical activity intention. The direct measure of subjective norm failed to display a mediating relationship. The mediating relationships displayed between attitude and perceived behavioural control and physical activity intention provide insight into potential mechanisms by which group cohesion may affect behaviour.

  6. Symptom fluctuations, self-esteem, and cohesion during group cognitive behaviour therapy for early psychosis.

    PubMed

    Lecomte, Tania; Leclerc, Claude; Wykes, Til

    2017-07-14

    Group cohesion has been linked to positive changes in self-esteem and in symptoms during group psychotherapy in people with psychosis. These changes may be linked to changes in symptoms as fluctuations in self-esteem have been linked to symptom fluctuations. We aimed to determine the relationship between these three factors - group cohesion, self-esteem, and symptoms - during group cognitive behaviour therapy for psychosis (GCBTp). We hypothesized that group cohesion would precede changes in symptoms and self-esteem and that improvements in self-esteem would precede improvements in symptoms. This is an uncontrolled longitudinal study recruiting from a convenience sample within two early psychosis clinics. Sixty-six individuals from first episode of psychosis treatment programmes participated in this study and received 24 sessions of a validated GCBTp protocol. Participants answered a brief questionnaire at the end of each session, measuring their group cohesion, self-esteem, and perception of their symptoms as worse, same, or better than usual. Orthogonal polynomial contrasts for time effects were estimated with a mixed model for repeated measures with a random cluster effect and revealed a quartic trend regarding changes in symptoms over the 24 sessions. Self-esteem, symptoms, and group cohesion were strongly linked during a given session. Also, self-esteem changes predicted changes in symptoms up to two sessions later, and symptoms changes predicted self-esteem changes at the next session. Group cohesion preceded improvements in both self-esteem and symptoms; self-esteem also predicted improvements in group cohesion. These results suggest that self-esteem and symptoms influence each other during therapy, with improvements in one leading to improvements in the other. Group cohesion also appears to be an essential prerequisite to positive changes in self-esteem and symptoms during GCBTp. This study emphasizes the interrelation between self-esteem improvements and

  7. Moderating effects of group status, cohesion, and ethnic composition on socialization of aggression in children's peer groups.

    PubMed

    Shi, Bing; Xie, Hongling

    2014-09-01

    We explored the effects of 3 group features (i.e., status, cohesion, and ethnic composition) on socialization processes of aggression in early adolescents' natural peer social groups. Gender differences in these effects were also determined. A total of 245 seventh-grade individuals belonging to 65 peer groups were included in the analyses. All 3 group features moderated the strength of group socialization on physical aggression with the exception of group status on girls' physical aggression. Stronger socialization of physical aggression occurred in higher status, more cohesive, or ethnically more homogeneous groups. In contrast, only group cohesion moderated the strength of group socialization on social aggression among girls. These findings suggest that somewhat different processes may be involved in peer group influences on different forms of aggression. Future intervention and prevention efforts for adolescent aggression should consider peer group membership and group features simultaneously.

  8. Great Expectations: How Role Expectations and Role Experiences Relate to Perceptions of Group Cohesion.

    PubMed

    Benson, Alex J; Eys, Mark A; Irving, P Gregory

    2016-04-01

    Many athletes experience a discrepancy between the roles they expect to fulfill and the roles they eventually occupy. Drawing from met expectations theory, we applied response surface methodology to examine how role expectations, in relation to role experiences, influence perceptions of group cohesion among Canadian Interuniversity Sport athletes (N = 153). On the basis of data from two time points, as athletes approached and exceeded their role contribution expectations, they reported higher perceptions of task cohesion. Furthermore, as athletes approached and exceeded their social involvement expectations, they reported higher perceptions of social cohesion. These response surface patterns-pertaining to task and social cohesion-were driven by the positive influence of role experiences. On the basis of the interplay between athletes' role experiences and their perception of the group environment, efforts to improve team dynamics may benefit from focusing on improving the quality of role experiences, in conjunction with developing realistic role expectations.

  9. Enhancing Small Group Cohesion and Effectiveness in Long Range Reconnaissance Teams

    DTIC Science & Technology

    1987-06-01

    Relations Compatibility Orientation - Behavior ( FIRO - B ) Small grnup cohesion Small group effectiveness M0 Aftr ACT (0Cowdus , powerso adeW N ne••e em lom...reconnaissance field exercise. After the exercise, the teams were administered the Fundamental Interpersonal Relations Orientation - Behavior ( FIRO - B ...compatibility, as dsessed by the FIRO - B , may be an important mediator of both team cohesion and per𔃽rmance. Moreover, the FIRO - B may offer a cost-effective means

  10. Relations of attachment styles and group cohesion in premier league female volleyball players.

    PubMed

    Tiryaki, M Sefik; Cepikkurt, Fatma

    2007-02-01

    The relations of attachment styles with group cohesion were monitored for premier league female volleyball teams. 74 volleyball players from 8 teams responded to the Relationship Scales Questionnaire and Group Environment Questionnaire. Pearson correlations indicated significant association of attachment styles with group cohesion. Specifically, a significant negative correlation was found between female volleyball players' individual attraction to the group-social subscale and fearful attachment style. In addition, there was a significant positive correlation for scores on the group integration-social and secure and preoccupied attachment subscales and a significant negative correlation for scores on the group integration-task subscale and preoccupied attachment style. In conclusion, attachment styles might be considered important in predicting group cohesion

  11. Therapeutic alliance and cohesion variables as predictors of outcome in short-term group psychotherapy.

    PubMed

    Joyce, Anthony S; Piper, William E; Ogrodniczuk, John S

    2007-07-01

    The current study explored the relative ability of aggregate therapeutic alliance and cohesion variables to predict short-term group therapy outcome. Data were collected from a comparative trial of two forms of time-limited group psychotherapy for complicated grief (Piper, McCallum, Joyce, Rosie, & Ogrodniczuk, 2001). The therapeutic alliance and elements of the cohesion construct were measured from the perspectives of each patient and the group therapist at intervals during the groups; scores were aggregated across assessments. Hierarchical multiple regression analyses, adjusting for the effects of treatment approach (interpretive vs. supportive) and specific group membership, demonstrated that the patient-rated alliance was a consistent predictor of outcome. Two cohesion measures, reflecting other participants' (therapist, other members) views of the patient's "fit" with the group, also accounted for variation in outcome. Implications of the findings for research and clinical practice, and the limitations of the measurement approach taken in this study, are considered.

  12. Group cohesion in foraging meerkats: follow the moving 'vocal hot spot'.

    PubMed

    Gall, Gabriella E C; Manser, Marta B

    2017-04-01

    Group coordination, when 'on the move' or when visibility is low, is a challenge faced by many social living animals. While some animals manage to maintain cohesion solely through visual contact, the mechanism of group cohesion through other modes of communication, a necessity when visual contact is reduced, is not yet understood. Meerkats (Suricata suricatta), a small, social carnivore, forage as a cohesive group while moving continuously. While foraging, they frequently emit 'close calls', soft close-range contact calls. Variations in their call rates based on their local environment, coupled with individual movement, produce a dynamic acoustic landscape with a moving 'vocal hotspot' of the highest calling activity. We investigated whether meerkats follow such a vocal hotspot by playing back close calls of multiple individuals to foraging meerkats from the front and back edge of the group simultaneously. These two artificially induced vocal hotspots caused the group to spatially elongate and split into two subgroups. We conclude that meerkats use the emergent dynamic call pattern of the group to adjust their movement direction and maintain cohesion. Our study describes a highly flexible mechanism for the maintenance of group cohesion through vocal communication, for mobile species in habitats with low visibility and where movement decisions need to be adjusted continuously to changing environmental conditions.

  13. Group cohesion in foraging meerkats: follow the moving ‘vocal hot spot’

    PubMed Central

    Manser, Marta B.

    2017-01-01

    Group coordination, when ‘on the move’ or when visibility is low, is a challenge faced by many social living animals. While some animals manage to maintain cohesion solely through visual contact, the mechanism of group cohesion through other modes of communication, a necessity when visual contact is reduced, is not yet understood. Meerkats (Suricata suricatta), a small, social carnivore, forage as a cohesive group while moving continuously. While foraging, they frequently emit ‘close calls’, soft close-range contact calls. Variations in their call rates based on their local environment, coupled with individual movement, produce a dynamic acoustic landscape with a moving ‘vocal hotspot’ of the highest calling activity. We investigated whether meerkats follow such a vocal hotspot by playing back close calls of multiple individuals to foraging meerkats from the front and back edge of the group simultaneously. These two artificially induced vocal hotspots caused the group to spatially elongate and split into two subgroups. We conclude that meerkats use the emergent dynamic call pattern of the group to adjust their movement direction and maintain cohesion. Our study describes a highly flexible mechanism for the maintenance of group cohesion through vocal communication, for mobile species in habitats with low visibility and where movement decisions need to be adjusted continuously to changing environmental conditions. PMID:28484628

  14. Group cohesion and social support in exercise classes: results from a danish intervention study.

    PubMed

    Christensen, Ulla; Schmidt, Lone; Budtz-Jørgensen, Esben; Avlund, Kirsten

    2006-10-01

    This study examines the formation of group cohesion and social support in exercise classes among former sedentary adults, participating in a Danish community-based intervention. Furthermore, the aim is to analyze the impact of this process on exercise activity among the participants. A multimethod approach was used, analyzing both survey data and 18 personal interviews collected among 87 participants who completed the intervention project. Analysis was performed according to the grounded theory method. The formation of group cohesion was conditioned by the social composition of the group, the teaching ability by the instructors, and the activity by itself. The cohesive group was characterized by an attitude of mutual support toward exercise activities. This mutual support facilitated development of self-efficacy beliefs among the participants improving their mastery expectation regarding exercise. Manipulating group dynamics may be a promising intervention tool in the promotion of leisure-time physical activity.

  15. Swarming behaviour associated with group cohesion in tree-dwelling bats.

    PubMed

    Naďo, Ladislav; Kaňuch, Peter

    2015-11-01

    Group living of social species increases the individual survival rate and enhances optimal exploitation of resources within their environment. Groups of cryptic tree-dwelling bats perform frequent roost switching on relatively long distances, whereas groups are temporarily disintegrated during foraging that precedes moving into new roost. In this study, we attempted to elucidate a mechanism in which group members can select new roost from a large set of potential roosting sites without disintegration of the whole group. Exploring the activity at the front of the tree hollows, recorded by automatic infrared monitors, we found that the swarming activity of Leisler's bats was performed during the whole night and was concentrated before the civil twilight at occupied roosts. A generalized linear model revealed significant positive association between the group size and swarming activity while season had negative but smaller effect. As bats swarmed the whole night also at sites that were less occupied or even unoccupied, we suggest that members of a bat colony selected new roost from a potentially larger set of available roosting sites. Thus, we propose a possible signalling role of swarming as a threshold behaviour that ensures group cohesion during roost switching.

  16. The Relationship between Organizational Citizenship Behavior, Group Cohesiveness and Workplace Deviance Behavior of Turkish Teachers

    ERIC Educational Resources Information Center

    Apaydin, Çigdem; Sirin, Hüseyin

    2016-01-01

    This study aims to develop a structural model for organizational citizenship behavior, group cohesiveness and workplace deviance behavior. The study group consists of 639 Turkish teachers working in primary and secondary public schools. In the study, the "Organizational Citizenship Behavior Scale" and the "Group Cohesiveness…

  17. Effect of a Collective Project on Group Cohesion.

    ERIC Educational Resources Information Center

    Shipley, Robert H.

    Immediately before their second group therapy session, 10 newly formed inpatient therapy groups were randomly assigned to complete either collective or individual art projects. The members of a group in the collective-project condition completed a single art project as a group. Each member of a group assigned to the individual project condition…

  18. Moderating Effects of Group Status, Cohesion, and Ethnic Composition on Socialization of Aggression in Children's Peer Groups

    ERIC Educational Resources Information Center

    Shi, Bing; Xie, Hongling

    2014-01-01

    We explored the effects of 3 group features (i.e., status, cohesion, and ethnic composition) on socialization processes of aggression in early adolescents' natural peer social groups. Gender differences in these effects were also determined. A total of 245 seventh-grade individuals belonging to 65 peer groups were included in the analyses. All 3…

  19. Moderating Effects of Group Status, Cohesion, and Ethnic Composition on Socialization of Aggression in Children's Peer Groups

    ERIC Educational Resources Information Center

    Shi, Bing; Xie, Hongling

    2014-01-01

    We explored the effects of 3 group features (i.e., status, cohesion, and ethnic composition) on socialization processes of aggression in early adolescents' natural peer social groups. Gender differences in these effects were also determined. A total of 245 seventh-grade individuals belonging to 65 peer groups were included in the analyses. All 3…

  20. Workplace drinking climate, stress, and problem indicators: assessing the influence of teamwork (group cohesion).

    PubMed

    Bennett, J B; Lehman, W E

    1998-09-01

    While job-related alcohol use may be associated with problems for drinkers, less is known about the effects of employee drinking on co-workers. We hypothesized that either exposure to co-worker drinking or the presence of a drinking climate would positively correlate with reports of stress and other problems. Following previous research, we also predicted that work group cohesion (or team orientation) would buffer against such problems. Two random samples of municipal employees (Ns = 909 and 1,068) completed anonymous surveys. These assessed individual drinking, co-worker drinking, task-oriented group cohesion, the direct reports of negative consequences due to co-worker substance use, and five problem indicators: job stress, job withdrawal, health problems, and performance (work accidents and absences). In each sample, drinking climate correlated with stress and withdrawal more so than did reports of individual drinking. Drinking climate and individual job stress were negatively associated with cohesion. ANCOVA results indicated that drinking climate combined with low cohesion resulted in increased vulnerability for all five problems. Moreover, cohesion appeared to attenuate the negative impact of exposure to drinking norms. As many as 40% of employees report at least one negative consequence associated with co-worker substance use (alcohol and drugs). Because teamwork may buffer negative effects of drinking climate on co-workers, workplace prevention efforts might be enhanced through a focus on the social environment. These efforts would include team-building and discussions of the impact of co-worker drinking on employee productivity.

  1. Improving participation rates for women of color in health research: the role of group cohesion.

    PubMed

    Smith-Ray, Renae L; Mama, Scherezade; Reese-Smith, Jacqueline Y; Estabrooks, Paul A; Lee, Rebecca E

    2012-02-01

    Adherence to physical activity and dietary interventions is a common challenge. Interventions that use group cohesion strategies show promise for increasing adherence, but have not been tested among women of color. The purpose of this study was to determine whether dimensions of group cohesion mediate the association between intervention condition and attendance within a community physical activity program for women of color. African American and Hispanic or Latina women (N = 310) completed measurements at baseline and post-intervention and participated in a social cohesion intervention to improve physical activity and dietary habits. Women were assigned to a physical activity or fruit and vegetable intervention group. Social and task cohesion was measured using the Physical Activity Group Environment Questionnaire (PAGE-Q). Attendance was recorded at each of six intervention sessions. Women were generally middle-age (M age = 46.4 years, SD = 9.1) and obese (M BMI = 34.4 kg/m2, SD = 7.7). The estimate of the mediated effect was significant for all group cohesion constructs, indicating both task constructs-attraction to the group's task (SE = 0.096, CI: -0.599 to -0.221) and group integration around the task (SE = 0.060, CI: -0.092 to -0.328)-and social constructs-attraction to the group's social aspects (SE = 0.046, CI: -0.546 to -0.366) and group integration around social aspects (SE = 0.046, CI: -0.546 to -0.366)-significantly mediated the association between group assignment and attendance. Both task and social constructs are important to improve attendance in health promotion interventions for women of color.

  2. The Relation between Sociometric Choices and Group Cohesion

    DTIC Science & Technology

    2006-11-01

    informal group (Jennings, 1977; Secord & Backman , 1964). In sociometry, interpersonal relations are measured by asking group members to express their...on the research question or design. 2 The sociometric "test" reveals the group (affect) structure (Secord & Backman , 1964) and identifies possible... assessments . The matrix approach enables the calculation of personal choice status by using the formula CSx = Y•Cx / (n - 1) where CS,, is the choice

  3. The Relationship of Group Cohesion to Group Performance: A Research Integration Attempt

    DTIC Science & Technology

    1988-07-01

    display the data. The median effect size (product-moment correlation coefficient ) for the data. The median effect size (product-moment correlation ... coefficient ) for the 14 codable studies was .36, and the unweighted mean r was .42. When study effect sizes were weighted by the number of groups involved, the

  4. Psychological Sense of Community and Group Cohesion on Wilderness Trips

    ERIC Educational Resources Information Center

    Breunig, Mary; O'Connell, Tim; Todd, Sharon; Young, Anderson; Anderson, Lynn; Anderson, Dale

    2008-01-01

    A primary purpose of many wilderness trip programs is the development of positive interpersonal relationships and group experiences that lead to enhanced sense of community among group members. Although there is anecdotal evidence to support the development of sense of community on wilderness trips, there is little empirical evidence to support…

  5. Psychological Sense of Community and Group Cohesion on Wilderness Trips

    ERIC Educational Resources Information Center

    Breunig, Mary; O'Connell, Tim; Todd, Sharon; Young, Anderson; Anderson, Lynn; Anderson, Dale

    2008-01-01

    A primary purpose of many wilderness trip programs is the development of positive interpersonal relationships and group experiences that lead to enhanced sense of community among group members. Although there is anecdotal evidence to support the development of sense of community on wilderness trips, there is little empirical evidence to support…

  6. Influence of group cohesion on maternal well-being among participants in a support/education group program for single mothers.

    PubMed

    Lipman, Ellen L; Waymouth, Marjorie; Gammon, Tara; Carter, Patricia; Secord, Margaret; Leung, Olivia; Mills, Brenda; Hicks, Frances

    2007-10-01

    Single mothers are at increased risk of psychosocial disadvantage, social isolation and physical and mental health difficulties. The authors present (1) the results of group cohesion assessments completed by mothers participating in a trial of community-based support/education groups, and (2) assessments of the association between group cohesion ratings and intervention outcomes of maternal self-evaluations of well-being (mood, self-esteem, and social support) and parenting. Mothers participating in groups completed the Group Atmosphere Scale, a measure of group cohesion, post-group. Overall, most participants provided strong ratings of group cohesion. Significant associations were found between group cohesion and specific positive outcomes. This suggests a positive association between group cohesion and mood, self-esteem, social support, and parenting, in this trial.

  7. Experimental investigation of lumpy cohesive loose materials with the object of determining the size of the outlet opening of bunkers

    NASA Astrophysics Data System (ADS)

    Lifshits, Yu. F.

    1981-04-01

    The article examines the determination of the shear characteristics of polydisperse loose materials containing both a cohesive fine fraction and large particles in connection with the problem of calculating the size of the bunker opening.

  8. Improving Participation Rates for Women of Color in Health Research: The Role of Group Cohesion

    PubMed Central

    Mama, Scherezade; Reese-Smith, Jacqueline Y.; Estabrooks, Paul A.; Lee, Rebecca E.

    2015-01-01

    Adherence to physical activity and dietary interventions is a common challenge. Interventions that use group cohesion strategies show promise for increasing adherence, but have not been tested among women of color. The purpose of this study was to determine whether dimensions of group cohesion mediate the association between intervention condition and attendance within a community physical activity program for women of color. African American and Hispanic or Latina women (N=310) completed measurements at baseline and post-intervention and participated in a social cohesion intervention to improve physical activity and dietary habits. Women were assigned to a physical activity or fruit and vegetable intervention group. Social and task cohesion was measured using the Physical Activity Group Environment Questionnaire (PAGE-Q). Attendance was recorded at each of six intervention sessions. Women were generally middle-age (M age = 46.4 years, SD=9.1) and obese (M BMI = 34.4 kg/m2, SD=7.7). The estimate of the mediated effect was significant for all group cohesion constructs, indicating both task constructs—attraction to the group’s task (SE=0.096, CI: −0.599 to −0.221) and group integration around the task (SE=0.060, CI: −0.092 to −0.328)—and social constructs—attraction to the group’s social aspects (SE=0.046, CI: −0.546 to −0.366) and group integration around social aspects (SE=0.046, CI: −0.546 to −0.366)—significantly mediated the association between group assignment and attendance. Both task and social constructs are important to improve attendance in health promotion interventions for women of color. PMID:21826476

  9. The effects of group music therapy on mood states and cohesiveness in adult oncology patients.

    PubMed

    Waldon, E G

    2001-01-01

    The purpose of the current investigation was to examine the efficacy of a music therapy protocol on mood states and levels of group cohesiveness in adult oncology patients. Eleven oncology patients in 2 groups (ages 30 to 84 years) took part in the study over a 10-week period of time (10 participants completed the study). During that period, participants took part in 8 music therapy sessions consisting of 2 types of interventions: (a) 4 "music making" sessions (where the mechanism for change included the process of making music) and (b) 4 "music responding" sessions (where the mechanism included the process of responding to music). The two types of music therapy sessions and their effectiveness on improving mood states and group cohesiveness were examined. The Profile of Mood States-Short Form (POMS-SF) was used to assess changes in participants' mood states. A content analysis, attendance records, and a questionnaire were used to assess levels of group cohesiveness. Results showed significant improvement in mood state scores (from presession levels to postsessions levels) after involvement in all music therapy sessions. Similar significant findings were found within each of the "music making" and "music responding" conditions but no differences were found when comparisons were made between those conditions. No statistically significant effects were found with respect to group cohesiveness measures. Study implications and future research directions are discussed.

  10. A prospective study of group cohesiveness in therapeutic horticulture for clinical depression.

    PubMed

    Gonzalez, Marianne Thorsen; Hartig, Terry; Patil, Grete Grindal; Martinsen, Egil W; Kirkevold, Marit

    2011-04-01

    This study aimed to assess changes in psychological distress and social participation in adults diagnosed with clinical depression during and after participating in a therapeutic horticulture programme, and to investigate if the changes covaried with levels of group cohesiveness during the intervention. An intervention with a single-group design was repeated with different samples in successive years (pooled n = 46). In each year, five groups of 3-7 participants went through the intervention. Data were collected before, twice during, and immediately after a 12-week therapeutic horticulture programme, as well as at 3-months' follow up. Mental health assessments included the Beck Depression Inventory, the State Subscale of Spielberger State-Trait Anxiety Inventory, the Positive Affect Scale from the Positive and Negative Affect Scale, the Perceived Stress Scale, and the Therapeutic Factors Inventory-Cohesiveness Scale. The analysis of the pooled data confirmed significant beneficial change in all mental health variables during the intervention. Change from baseline in depression severity persisted at 3-months' follow up. Increased social activity after the intervention was reported for 38% of the participants. The groups quickly established strong cohesiveness, and this continued to increase during the intervention. The average level of group cohesiveness correlated positively, but not significantly, with change in all mental health outcome variables.

  11. [A measure of team cohesion in sport. Spanish adaptation of Group Environment Questionnaire (GEQ)].

    PubMed

    Iturbide, Luis María; Elosua, Paula; Yanes, Félix

    2010-08-01

    The aim of this work was to adapt the Group Environment Questionnaire (GEQ) to Spanish. Judgmental procedures were used to assess the linguistic and cultural equivalence of the versions. Psychometric procedures were used in the operational phase of the study. The normative sample comprised 924 sportsmen/sportswomen from 75 teams. The GEQ scale showed suitable indexes of internal consistency and a bidimensional structure based on two factors of the cohesion model, the Task component and the Social component. In addition, a positive relation between team-performance and the Task component of team cohesion was observed. Overall, the results supported the Spanish version of the GEQ.

  12. Group Cohesion and Social Support in Exercise Classes: Results from a Danish Intervention Study

    ERIC Educational Resources Information Center

    Christensen, Ulla; Schmidt, Lone; Budtz-Jorgensen, Esben; Avlund, Kirsten

    2006-01-01

    This study examines the formation of group cohesion and social support in exercise classes among former sedentary adults, participating in a Danish community-based intervention. Furthermore, the aim is to analyze the impact of this process on exercise activity among the participants. A multimethod approach was used, analyzing both survey data and…

  13. Group Cohesion, Collective Efficacy, and Motivational Climate As Predictors of Conductor Support in Music Ensembles

    ERIC Educational Resources Information Center

    Matthews, Wendy K.; Kitsantas, Anastasia

    2007-01-01

    In the present study, we examined whether collective efficacy, group cohesion (task and social), and perceived motivational climate (task-involving and ego-involving orientations) in a music ensemble predict instrumentalists' perceived conductor support. Ninety-one (N = 91) skilled high school instrumentalists participated in the study. To assess…

  14. Group Cohesion and Social Support in Exercise Classes: Results from a Danish Intervention Study

    ERIC Educational Resources Information Center

    Christensen, Ulla; Schmidt, Lone; Budtz-Jorgensen, Esben; Avlund, Kirsten

    2006-01-01

    This study examines the formation of group cohesion and social support in exercise classes among former sedentary adults, participating in a Danish community-based intervention. Furthermore, the aim is to analyze the impact of this process on exercise activity among the participants. A multimethod approach was used, analyzing both survey data and…

  15. Team cohesiveness, team size and team performance in team-based learning teams.

    PubMed

    Thompson, Britta M; Haidet, Paul; Borges, Nicole J; Carchedi, Lisa R; Roman, Brenda J B; Townsend, Mark H; Butler, Agata P; Swanson, David B; Anderson, Michael P; Levine, Ruth E

    2015-04-01

    The purpose of this study was to explore the relationships among variables associated with teams in team-based learning (TBL) settings and team outcomes. We administered the National Board of Medical Examiners (NBME) Psychiatry Subject Test first to individuals and then to teams of Year three students at four medical schools that used TBL in their psychiatry core clerkships. Team cohesion was analysed using the Team Performance Scale (TPS). Bivariate correlation and linear regression analysis were used to analyse the relationships among team-level variables (mean individual TPS scores for each team, mean individual NBME scores of teams, team size, rotation and gender make-up) and team NBME test scores. A hierarchical linear model was used to test the effects of individual TPS and individual NBME test scores within each team, as well as the effects of the team-level variables of team size, team rotation and gender on team NBME test scores. Individual NBME test and TPS scores were nested within teams and treated as subsampling units. Individual NBME test scores and individual TPS scores were positively and statistically significantly (p < 0.01) associated with team NBME test scores, when team rotation, team size and gender make-up were controlled for. Higher team NBME test scores were associated with teams rotating later in the year and larger teams (p < 0.01). Gender make-up was not significantly associated. The results of an NBME Psychiatry Subject Test administered to TBL teams at four medical schools suggest that larger teams on later rotations score higher on a team NBME test. Individual NBME test scores and team cohesion were positively and significantly associated with team NBME test scores. These results suggest the need for additional studies focusing on team outcomes, team cohesion, team size, rotation and other factors as they relate to the effective and efficient performance of TBL teams in health science education. © 2015 John Wiley & Sons Ltd.

  16. [Social participation processes, task-oriented participation and learning as antecedents of group cohesion. A longitudinal perspective].

    PubMed

    Picazo Lahiguera, Carmen; Zornoza Abad, Ana; Peiró Silla, José M

    2009-05-01

    The aim of this paper is to analyze the effect of changes in social participation and task- and learning-oriented processes on the development of cohesion (social and task-focused) in new groups. Cohesion has been considered one of the most important constructs in small groups, and its influence on team performance and efficacy has been highlighted. However, there are few papers that analyze the processes and the variables that precede the construct and that affect its evolution. Results of the longitudinal study show the importance of changes in participation processes on the development of task cohesion and social cohesion.

  17. The benefits of pass-fail grading on stress, mood, and group cohesion in medical students.

    PubMed

    Rohe, Daniel E; Barrier, Patricia A; Clark, Matthew M; Cook, David A; Vickers, Kristin S; Decker, Paul A

    2006-11-01

    To objectively measure the effect of a pass-fail grading system on stress, mood, group cohesion, and test anxiety in medical students. Beginning with the class of 2006, the Mayo Medical School, Rochester, Minn, changed the grading system for first-year courses from a 5-interval grading system to a pass-fail grading system. Students in the previous class of 2005, who were graded using a 5-interval system during their first year of medical school, were compared with students in the class of 2006. Using a prospective study design, the 2 groups were compared at the end of both the first year and the second year of medical school on the Perceived Stress Scale, Profile of Mood States, Perceived Cohesion Scale, Test Anxiety Inventory, and (after year 2) the United States Medical Licensing Examination Step 1. Data collection occurred in 2002 and 2003 with the class of 2005 and in 2003 and 2004 with the class of 2006. Students graded with the pass-fail system had less perceived stress (median, 15.0 vs 21.0; P-.01) and greater group cohesion (median, 34.5 vs 30.0; P=.02) at the end of their second year of coursework than their 5-interval graded peers. The pass-fail group had better mood (median, 46.5) than the graded group (median, 64.0), but this difference was not statistically significant (P=.07). No significant differences were found between the 2 groups in test-taking anxiety or in United States Medical Licensing Examination Step 1 board scores. Pass-fail grading may reduce stress and increase group cohesion in medical students compared with traditional 5-interval grading.

  18. System size effects on the mechanical response of cohesive-frictional granular ensembles

    NASA Astrophysics Data System (ADS)

    Singh, Saurabh; Kandasami, Ramesh Kannan; Mahendran, Rupesh Kumar; Murthy, Tejas

    2017-06-01

    Shear resistance in granular ensembles is a result of interparticle interaction and friction. However, even the presence of small amounts of cohesion between the particles changes the landscape of the mechanical response considerably. Very often such cohesive frictional (c-ϕ) granular ensembles are encountered in nature as well as while handling and storage of granular materials in the pharmaceutical, construction and mining industries. Modeling of these c-ϕ materials, especially in engineering applications have relied on the oft-made assumption of a "continua" and have utilized the popular tenets of continuum plasticity theory. We present an experimental investigation on the fundamental mechanics of c-ϕ materials specifically; we investigate if there exists a system size effect and any additional length scales beyond the continuum length scale on their mechanical response. For this purpose, we conduct a series of 1-D compression (UC) tests on cylindrical specimens reconstituted in the laboratory with a range of model particle-binder combinations such as sandcement, sand-epoxy, and glass ballotini-epoxy mixtures. Specimens are reconstituted to various diameters ranging from 10 mm to 150 mm (with an aspect ratio of 2) to a predefined packing fraction. In addition to the effect of the type of binder (cement, epoxy) and system size, the mean particle size is also varied from 0.5 to 2.5 mm. The peak strength of these materials is significant as it signals the initiation of the cohesive-bond breaking and onset of mobilization of the inter particle frictional resistance. For these model systems, the peak strength is a strong function of the system size of the ensemble as well as the mean particle size. This intriguing observation is counter to the traditional notion of a continuum plastic typical granular ensemble. Microstructure studies in a computed-tomograph have revealed the existence of a web patterned `entangled-chain' like structure, we argue that this ushers

  19. Scaling of Traction Forces with the Size of Cohesive Cell Colonies

    PubMed Central

    Mertz, Aaron F.; Banerjee, Shiladitya; Che, Yonglu; German, Guy K.; Xu, Ye; Hyland, Callen; Marchetti, M. Cristina; Horsley, Valerie; Dufresne, Eric R.

    2014-01-01

    To understand how the mechanical properties of tissues emerge from interactions of multiple cells, we measure traction stresses of cohesive colonies of 1–27 cells adherent to soft substrates. We find that traction stresses are generally localized at the periphery of the colony and the total traction force scales with the colony radius. For large colony sizes, the scaling appears to approach linear, suggesting the emergence of an apparent surface tension of the order of 10−3 N/m. A simple model of the cell colony as a contractile elastic medium coupled to the substrate captures the spatial distribution of traction forces and the scaling of traction forces with the colony size. PMID:23003091

  20. Composition, concentration and deprivation: exploring their association with social cohesion among different ethnic groups in the UK.

    PubMed

    Bécares, Laia; Stafford, Mai; Laurence, James; Nazroo, James

    2011-01-01

    Although studies in the US have shown an association between the ethnic residential composition of an area and reports of decreased social cohesion among its residents, this association is not clear in the UK, and particularly for ethnic minority groups. The current study analyses a merged dataset from the 2005 and 2007 Citizenship Survey to assess the evidence for an association between social cohesion and ethnic residential concentration, composition and area deprivation across different ethnic groups in the UK. Results of the multilevel regression models show that, after adjusting for area deprivation, increased levels of social cohesion are found in areas of greater ethnic residential heterogeneity. Although different patterns emerge across ethnic groups and the measure of social cohesion used, findings consistently show that it is area deprivation, and not ethnic residential heterogeneity, which erodes social cohesion in the UK.

  1. Grooming network cohesion and the role of individuals in a captive chimpanzee group.

    PubMed

    Kanngiesser, Patricia; Sueur, Cédric; Riedl, Katrin; Grossmann, Johannes; Call, Josep

    2011-08-01

    Social network analysis offers new tools to study the social structure of primate groups. We used social network analysis to investigate the cohesiveness of a grooming network in a captive chimpanzee group (N = 17) and the role that individuals may play in it. Using data from a year-long observation, we constructed an unweighted social network of preferred grooming interactions by retaining only those dyads that groomed above the group mean. This choice of criterion was validated by the finding that the properties of the unweighted network correlated with the properties of a weighted network (i.e. a network representing the frequency of grooming interactions) constructed from the same data. To investigate group cohesion, we tested the resilience of the unweighted grooming network to the removal of central individuals (i.e. individuals with high betweenness centrality). The network fragmented more after the removal of individuals with high betweenness centrality than after the removal of random individuals. Central individuals played a pivotal role in maintaining the network's cohesiveness, and we suggest that this may be a typical property of affiliative networks like grooming networks. We found that the grooming network correlated with kinship and age, and that individuals with higher social status occupied more central positions in the network. Overall, the grooming network showed a heterogeneous structure, yet did not exhibit scale-free properties similar to many other primate networks. We discuss our results in light of recent findings on animal social networks and chimpanzee grooming.

  2. Predicting Group Performance Using Cohesion and Social Network Density: A Comparative Analysis

    DTIC Science & Technology

    2007-03-01

    with the teamwork-performance relationship (Evans & Dion, 1991; Klein & Mulvey , 1995; Oliver, Harman, Hoover, Hayes, & Pandhi, 2000), other empirical...group cohesion and its relation to performance (Beal, et al., 2003; Evans & Dion, 1991; Gully, et al., 1995; Klein & Mulvey , 1995; Mullen & Copper...Copper, 1994; Oliver, et al., 2000), other empirical studies have had varied results ( Klein & Mulvey , 1995; Stogdill, 1972). One of the papers suggests

  3. Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups.

    PubMed

    Bousquet, Christophe A H; Sumpter, David J T; Manser, Marta B

    2011-05-22

    Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route.

  4. Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups

    PubMed Central

    Bousquet, Christophe A. H.; Sumpter, David J. T.; Manser, Marta B.

    2011-01-01

    Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route. PMID:21047853

  5. Improving Decision Speed, Accuracy and Group Cohesion through Early Information Gathering in House-Hunting Ants

    PubMed Central

    Stroeymeyt, Nathalie; Giurfa, Martin; Franks, Nigel R.

    2010-01-01

    Background Successful collective decision-making depends on groups of animals being able to make accurate choices while maintaining group cohesion. However, increasing accuracy and/or cohesion usually decreases decision speed and vice-versa. Such trade-offs are widespread in animal decision-making and result in various decision-making strategies that emphasize either speed or accuracy, depending on the context. Speed-accuracy trade-offs have been the object of many theoretical investigations, but these studies did not consider the possible effects of previous experience and/or knowledge of individuals on such trade-offs. In this study, we investigated how previous knowledge of their environment may affect emigration speed, nest choice and colony cohesion in emigrations of the house-hunting ant Temnothorax albipennis, a collective decision-making process subject to a classical speed-accuracy trade-off. Methodology/Principal Findings Colonies allowed to explore a high quality nest site for one week before they were forced to emigrate found that nest and accepted it faster than emigrating naïve colonies. This resulted in increased speed in single choice emigrations and higher colony cohesion in binary choice emigrations. Additionally, colonies allowed to explore both high and low quality nest sites for one week prior to emigration remained more cohesive, made more accurate decisions and emigrated faster than emigrating naïve colonies. Conclusions/Significance These results show that colonies gather and store information about available nest sites while their nest is still intact, and later retrieve and use this information when they need to emigrate. This improves colony performance. Early gathering of information for later use is therefore an effective strategy allowing T. albipennis colonies to improve simultaneously all aspects of the decision-making process – i.e. speed, accuracy and cohesion – and partly circumvent the speed-accuracy trade-off classically

  6. Respect the technique: Status-based respect increases minority group social cohesion with majority groups, while also increasing minority collective action tendencies.

    PubMed

    Glasford, Demis E; Johnston, Brian

    2017-05-08

    The present work explores the implications of respect for social change. Social change can be achieved via improved attitudes between minority and majority groups (i.e., social cohesion) or via action taken by minority groups (i.e., collective action). Recent work suggests that the social cohesion route to social change, in particular an emphasis on commonality, may be incompatible with the collective action route to social change. We suggest that social-cohesion strategies rooted in status-based respect may allow for social cohesion and collective action. We experimentally investigated the relative effects of a majority group communicating status-based respect and commonality, as compared to a control, on minority group members' social cohesion with the majority group and willingness to engage in collective action. Status-based respect increased positive attitudes toward a majority group, relative to commonality and control, but was also associated with increased collective action tendencies. Implications for social change are discussed.

  7. Both information and social cohesion determine collective decisions in animal groups

    PubMed Central

    Miller, Noam; Garnier, Simon; Hartnett, Andrew T.; Couzin, Iain D.

    2013-01-01

    During consensus decision making, individuals in groups balance personal information (based on their own past experiences) with social information (based on the behavior of other individuals), allowing the group to reach a single collective choice. Previous studies of consensus decision making processes have focused on the informational aspects of behavioral choice, assuming that individuals make choices based solely on their likelihood of being beneficial (e.g., rewarded). However, decisions by both humans and nonhuman animals systematically violate such expectations. Furthermore, the typical experimental paradigm of assessing binary decisions, those between two mutually exclusive options, confounds two aspects common to most group decisions: minimizing uncertainty (through the use of personal and social information) and maintaining group cohesion (for example, to reduce predation risk). Here we experimentally disassociate cohesion-based decisions from information-based decisions using a three-choice paradigm and demonstrate that both factors are crucial to understanding the collective decision making of schooling fish. In addition, we demonstrate how multiple informational dimensions (here color and stripe orientation) are integrated within groups to achieve consensus, even though no individual is explicitly aware of, or has a unique preference for, the consensus option. Balancing of personal information and social cues by individuals in key frontal positions in the group is shown to be essential for such group-level capabilities. Our results demonstrate the importance of integrating informational with other social considerations when explaining the collective capabilities of group-living animals. PMID:23440218

  8. Both information and social cohesion determine collective decisions in animal groups.

    PubMed

    Miller, Noam; Garnier, Simon; Hartnett, Andrew T; Couzin, Iain D

    2013-03-26

    During consensus decision making, individuals in groups balance personal information (based on their own past experiences) with social information (based on the behavior of other individuals), allowing the group to reach a single collective choice. Previous studies of consensus decision making processes have focused on the informational aspects of behavioral choice, assuming that individuals make choices based solely on their likelihood of being beneficial (e.g., rewarded). However, decisions by both humans and nonhuman animals systematically violate such expectations. Furthermore, the typical experimental paradigm of assessing binary decisions, those between two mutually exclusive options, confounds two aspects common to most group decisions: minimizing uncertainty (through the use of personal and social information) and maintaining group cohesion (for example, to reduce predation risk). Here we experimentally disassociate cohesion-based decisions from information-based decisions using a three-choice paradigm and demonstrate that both factors are crucial to understanding the collective decision making of schooling fish. In addition, we demonstrate how multiple informational dimensions (here color and stripe orientation) are integrated within groups to achieve consensus, even though no individual is explicitly aware of, or has a unique preference for, the consensus option. Balancing of personal information and social cues by individuals in key frontal positions in the group is shown to be essential for such group-level capabilities. Our results demonstrate the importance of integrating informational with other social considerations when explaining the collective capabilities of group-living animals.

  9. Group heterogeneity increases the risks of large group size: a longitudinal study of productivity in research groups.

    PubMed

    Cummings, Jonathon N; Kiesler, Sara; Bosagh Zadeh, Reza; Balakrishnan, Aruna D

    2013-06-01

    Heterogeneous groups are valuable, but differences among members can weaken group identification. Weak group identification may be especially problematic in larger groups, which, in contrast with smaller groups, require more attention to motivating members and coordinating their tasks. We hypothesized that as groups increase in size, productivity would decrease with greater heterogeneity. We studied the longitudinal productivity of 549 research groups varying in disciplinary heterogeneity, institutional heterogeneity, and size. We examined their publication and citation productivity before their projects started and 5 to 9 years later. Larger groups were more productive than smaller groups, but their marginal productivity declined as their heterogeneity increased, either because their members belonged to more disciplines or to more institutions. These results provide evidence that group heterogeneity moderates the effects of group size, and they suggest that desirable diversity in groups may be better leveraged in smaller, more cohesive units.

  10. Homing and group cohesion in Atlantic cod Gadus morhua revealed by tagging experiments.

    PubMed

    Tamdrari, H; Brêthes, J-C; Castonguay, M; Duplisea, D E

    2012-07-01

    Homing behaviour and group cohesion in Atlantic cod Gadus morhua from the northern Gulf of St Lawrence were studied based on tagging-recapture data from two periods, the 1980s and a recent period from 1996 to 2008. Two or more tags from a single tagging experiment were frequently recovered together in subsequent years. The null hypothesis was tested that the frequency of matching tag recoveries occurred by chance only through random mixing of tagged G. morhua before their recapture by the commercial fishery. The alternative hypothesis was that non-random, positive association (group cohesion) existed among tagged individuals that persisted through time and during migrations. Results show that the G. morhua population exhibits a homing behaviour, with temporal stability across seasons and years: 50% of recaptured fish in the recent period were caught <34 km from their mark site, even 3 years after release. In the 1980s, G. morhua were located at <10 km from their release site 1 year after tagging during summer and at <16 km during spring and autumn combined. Despite the increasing distance between the mark and recapture sites over time, the difference was not significant. In addition, occurrences of two or more tagged fish from the same release event that were caught together indicated a non-random association among individual fish for periods of one to several years and through migrations over several hundred kilometres. Hence G. morhua showed group cohesion in addition to site fidelity. These two interacting behaviours may be fundamental for the rebuilding and conservation of depleted fish stocks. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

  11. Social Ecology and Group Cohesion in Pilot Whales and Their Responses to Playback of Anthropogenic and Natural Sounds

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Social ecology and group cohesion in pilot whales and their...N000141410410 LONG-TERM GOALS This project investigates the social ecology and cohesion of long-finned pilot whales as part of a broad multi...rules on individual and collective foraging success, to understand the ecological importance of different collective foraging strategies. At the

  12. Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species

    NASA Astrophysics Data System (ADS)

    van Oosterom, L.; Montgomery, J. C.; Jeffs, A. G.; Radford, C. A.

    2016-01-01

    Soundscapes provide a new tool for the study of fish communities. Bigeyes (Pempheris adspersa) are nocturnal planktivorous reef fish, feed in loose shoals and are soniferous. These vocalisations have been suggested to be contact calls to maintain group cohesion, however direct evidence for this is absent, despite the fact that contact calls are well documented for many other vertebrates, including marine mammals. For fish, direct evidence for group cohesion signals is restricted to the use of visual and hydrodynamic cues. In support of adding vocalisation as a contributing cue, our laboratory experiments show that bigeyes significantly increased group cohesion when exposed to recordings of ambient reef sound at higher sound levels while also decreasing vocalisations. These patterns of behaviour are consistent with acoustic masking. When exposed to playback of conspecific vocalisations, the group cohesion and vocalisation rates of bigeyes both significantly increased. These results provide the first direct experimental support for the hypotheses that vocalisations are used as contact calls to maintain group cohesion in fishes, making fish the evolutionarily oldest vertebrate group in which this phenomenon has been observed, and adding a new dimension to the interpretation of nocturnal reef soundscapes.

  13. Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species

    PubMed Central

    van Oosterom, L.; Montgomery, J. C.; Jeffs, A. G.; Radford, C. A.

    2016-01-01

    Soundscapes provide a new tool for the study of fish communities. Bigeyes (Pempheris adspersa) are nocturnal planktivorous reef fish, feed in loose shoals and are soniferous. These vocalisations have been suggested to be contact calls to maintain group cohesion, however direct evidence for this is absent, despite the fact that contact calls are well documented for many other vertebrates, including marine mammals. For fish, direct evidence for group cohesion signals is restricted to the use of visual and hydrodynamic cues. In support of adding vocalisation as a contributing cue, our laboratory experiments show that bigeyes significantly increased group cohesion when exposed to recordings of ambient reef sound at higher sound levels while also decreasing vocalisations. These patterns of behaviour are consistent with acoustic masking. When exposed to playback of conspecific vocalisations, the group cohesion and vocalisation rates of bigeyes both significantly increased. These results provide the first direct experimental support for the hypotheses that vocalisations are used as contact calls to maintain group cohesion in fishes, making fish the evolutionarily oldest vertebrate group in which this phenomenon has been observed, and adding a new dimension to the interpretation of nocturnal reef soundscapes. PMID:26750559

  14. Predictors of Evidence-Based Practice Implementation, Job Satisfaction, and Group Cohesion Among Regional Fellowship Program Participants.

    PubMed

    Kim, Son Chae; Stichler, Jaynelle F; Ecoff, Laurie; Brown, Caroline E; Gallo, Ana-Maria; Davidson, Judy E

    2016-10-01

    A regional, collaborative evidence-based practice (EBP) fellowship program utilizing institution-matched mentors was offered to a targeted group of nurses from multiple local hospitals to implement unit-based EBP projects. The Advancing Research and Clinical Practice through Close Collaboration (ARCC) model postulates that strong EBP beliefs result in high EBP implementation, which in turn causes high job satisfaction and group cohesion among nurses. This study examined the relationships among EBP beliefs, EBP implementation, job satisfaction, group cohesion, and group attractiveness among the fellowship program participants. A total of 175 participants from three annual cohorts between 2012 and 2014 completed the questionnaires at the beginning of each annual session. The questionnaires included the EBP beliefs, EBP implementation, job satisfaction, group cohesion, and group attractiveness scales. There were positive correlations between EBP beliefs and EBP implementation (r = 0.47; p <.001), as well as EBP implementation and job satisfaction (r = 0.17; p = .029). However, no statistically significant correlations were found between EBP implementation and group cohesion, or group attractiveness. Hierarchical multiple regression models showed that EBP beliefs was a significant predictor of both EBP implementation (β = 0.33; p <.001) and job satisfaction (β = 0.25; p = .011). However, EBP implementation was not a significant predictor of job satisfaction, group cohesion, or group attractiveness. In multivariate analyses where demographic variables were taken into account, although EBP beliefs predicted job satisfaction, no significant relationship was found between EBP implementation and job satisfaction or group cohesion. Further studies are needed to confirm these unexpected study findings. © 2016 Sigma Theta Tau International.

  15. The Role of Preceptorship and Group Cohesion on Newly Licensed Registered Nurses' Satisfaction and Intent to Stay.

    PubMed

    Bontrager, Sarah; Hart, Patricia L; Mareno, Nicole

    2016-03-01

    Thirteen percent of newly licensed registered nurses (NLRNs) vacate their first job after 1 year, and 37% report that they feel ready to change jobs. Turnover can lead to consistent and detrimental nursing shortages in nursing units, as well as increased costs for health care systems. A descriptive, prospective, cross-sectional design was used to understand how preceptor role effectiveness and group cohesion affect NLRNs' satisfaction and intent to stay. NLRNs reported high levels of perceived preceptor role effectiveness, group cohesion, and job satisfaction, with only moderate levels of intent to stay. Statistically significant relationships were found among preceptor role effectiveness, job satisfaction, and intent to stay, as well as among group cohesion, job satisfaction, and intent to stay. Preceptor role effectiveness and group cohesion are predictors of NLRNs' level of job satisfaction. Job satisfaction is a predictor of NLRNs' intent to stay. Effective preceptors and positive group cohesion are factors that are important to NLRNs' job satisfaction and intent to stay. Copyright 2016, SLACK Incorporated.

  16. The Role of Adolescent Friendship Group Integration and Cohesion in Weapon-Related Violent Crime as a Young Adult.

    PubMed

    Mundt, Marlon P; Antonaccio, Olena P; French, Michael T; Zakletskaia, Larissa I

    2017-01-16

    Weapon-related violent crime is a serious, complex, and multifaceted public health problem. The present study uses data from Waves I and III of Add Health (n = 10,482, 54% female) to examine how friendship group integration and cohesion in adolescence (ages 12-19) is associated with weapon-related criminal activity as a young adult (ages 18-26). Results indicate that greater cohesion in friendship groups is associated with significantly lower weapon-related criminal activity in young adulthood. In addition, for adolescent girls, a greater number of close friendship ties-an indicator of friendship group integration-is associated with less weapon-related criminal activity in young adulthood. These findings suggest that school-based initiatives to facilitate inclusive and cohesive adolescent peer communities may be an effective strategy to curb weapon-related criminal activity in young adulthood.

  17. Policing effectiveness depends on relatedness and group size.

    PubMed

    Walter, Bartosz; Brunner, Elisabeth; Heinze, Jürgen

    2011-03-01

    Cohesion of social groups requires the suppression of individual selfishness. Indeed, worker egg laying in insect societies is usually suppressed or punished through aggression and egg removal. The effectiveness of such "policing" is expected to increase with decreasing relatedness, as inclusive fitness of group members is more strongly affected by selfish worker reproduction when group members are less closely related to each other. As inclusive fitness is also influenced by the costs and benefits of helping, the effectiveness of policing should decrease with increasing colony size, because the costs for the whole colony from selfish worker reproduction are proportionally reduced in large groups. Here, we show that policing effectiveness in colonies of the ant Temnothorax unifasciatus is low in large groups and high in small groups when relatedness is high. When we experimentally decreased the relatedness in groups, the policing effectiveness reached the same high level as in small, highly related groups, irrespective of group size. Therefore, our results indicate that policing effectiveness is simultaneously shaped by relatedness and group size, that is, an ecological factor. This may have major implications for testing policing across species of animals.

  18. Mediating Effects of Group Cohesion on Physical Activity and Diet in Women of Color: Health Is Power

    PubMed Central

    Lee, Rebecca E.; O’Connor, Daniel P.; Smith-Ray, Renae; Mama, Scherezade K.; Medina, Ashley V.; Reese-Smith, Jacqueline Y.; Banda, Jorge A.; Layne, Charles S.; Brosnan, Marcella; Cubbin, Catherine; McMillan, Tracy; Estabrooks, Paul A.

    2015-01-01

    Purpose To determine the effects and mediating factors of a physical activity (PA) or vegetable and fruit (VF) group cohesion intervention. Design Longitudinal design. Setting Harris County and Travis County, Texas. Participants Community-dwelling African-American and Hispanic or Latina women. Intervention Three hundred ten women were randomized to a PA (n = 204) or VF (n = 106) intervention group. Women met in groups six times over the course of 6 months and were exposed to a group cohesion intervention to promote walking or to increase VF consumption. Measures Women completed the International PA Questionnaire, National Cancer Institute VF and fat screeners, PA Group Environment Questionnaire, and 7-day accelerometer protocol at baseline and post-intervention. Analyses The direct and mediated effects of the intervention on outcomes were evaluated using a mediational chain model, controlling for baseline values and covariates using path analysis. Results Women were middle aged (mean = 44.4 years) and overweight or obese (mean body mass index = 34.0 kg/m2). PA increased and fat consumption decreased for both groups, whereas VF consumption increased for women in VF group only (all p <.05). Increased task cohesion led to hypothesized increases in psychosocial factors in the PA group but not to behavioral changes. Conclusions Group cohesion interventions may have psychological and physical health benefits for African-American and Hispanic or Latina women, but refinement of measures and intervention delivery is needed to determine whether hypothesized mediational pathways are valid. PMID:22375580

  19. Floc morphology and size distributions of cohesive sediment in steady-state flow.

    PubMed

    Stone, M; Krishnappan, B G

    2003-06-01

    Fractal dimensions of particle populations of cohesive sediment were examined during deposition experiments in an annular flume at four conditions of steady-state flow (0.058, 0.123, 0.212 and 0.323Pa). Light microscopy and an image analysis system were used to determine area, longest axis and perimeter of suspended solids. Four fractal dimensions (D, D(1), D(2), D(k)) were calculated from the slopes of regression lines of the relevant variables on double log plots. The fractal dimension D, which relates the projected area (A) to the perimeter (P) of the particle (P proportional, variant A(D/2)), increased from 1.25+/-0.005 at a shear stress of 0.058Pa to a maximum of 1.36+/-0.003 at 0.121Pa then decreased to 1.34+/-0.001 at 0.323Pa. The change in D indicated that particle boundaries became more convoluted and the shape of larger particles was more irregular at higher levels of shear stress. At the highest shear stress, the observed decrease in D resulted from floc breakage due to increased particle collisions. The fractal dimension D(1), which relates the longest axis (l) to the perimeter of the particle (P proportional to l(D1)), increased from 1.00+/-0.006 at a shear stress of 0.058Pa to a maximum of 1.25+/-0.003 at 0.325Pa. The fractal dimension D(2), which relates the longest axis with the projected area of the particle (A proportional to l(D(2)), increased from 1.35+/-0.014 at a shear stress of 0.058Pa to a maximum of 1.81+/-0.005 at 0.323Pa. The observed increases in D(1) and D(2) indicate that particles became more elongated with increasing shear stress. Values of the fractal dimension D(k), resulting from the Korcak's empirical law for particle population, decreased from 3.68+/-0.002 at a shear stress of 0.058Pa to 1.33+/-0.001 at 0.323Pa and indicate that the particle size distribution changed from a population of similar sized particles at low shear to larger flocculated particles at higher levels of shear. The results show that small particle clusters

  20. Competition in human groups-Impact on group cohesion, perceived stress and outcome satisfaction.

    PubMed

    Boos, Margarete; Franiel, Xaver; Belz, Michael

    2015-11-01

    This study on competition in human groups was performed within the context of the competitive outcome interdependence concept: the degree to which personal outcomes among group members are affected by the consequences of task performance of others, e.g. when one group member gains a high reward for a task, this lowers the available reward for other group members. Our computer-based multi-participant game empirically assessed how competitive versus neutral conditions influenced the reward-maximising behaviour of 200 undergraduate students functioning in ten-person groups - each playing two games (1 neutral and 1 competitive), their perceived pay satisfaction as well as perceived stress levels and sense of calmness within the games' task to search for coins. Participants were represented by black dots moving on a virtual playground. Results showed that competition led to reward-maximising but fellow group member disadvantaging behaviour, and all participants experienced lower pay satisfaction, higher stress levels and less calmness. We conclude that short-term behavioural consequences of positive individual competitive behaviour were gained at the above-mentioned potential long-term negative costs for all group members. This implies group paradigms aimed at sustainability should avoid introducing competitive factors that at best result in short-lived gains and at worst cause widespread dissatisfaction, stress and a pervasive lack of calmness.

  1. Group cohesion and between session homework activities predict self-reported cognitive-behavioral skill use amongst participants of SMART Recovery groups.

    PubMed

    Kelly, Peter J; Deane, Frank P; Baker, Amanda L

    2015-04-01

    SMART Recovery groups are cognitive-behaviorally oriented mutual support groups for individuals with addictions. The aim of the study was to assess the extent to which the quality of group facilitation, group cohesion and the use of between session homework activities contribute to self-rated use of cognitive-behavioral skills amongst group participants. Participants attending SMART Recovery groups in Australia completed a cross sectional survey (N=124). The survey included measures of cognitive and behavioral skill utilization, group cohesion, quality of group facilitation and a rating of how frequently participants leave group meetings with an achievable between session homework plan. On average, participants had been attending SMART Recovery meetings for 9 months. Participants were most likely to attend SMART Recovery for problematic alcohol use. Regression analyses indicated that group cohesion significantly predicted use of cognitive restructuring, but that only provision of homework at the end of each group session predicted self-reported behavioral activation. Both group cohesion and leaving a group with an achievable homework plan predicted participant use of cognitive behavioral skills. The concrete actions associated with homework activities may facilitate behavioral activation. There is a need for longitudinal research to examine the relationship between the utilization of cognitive and behavioral skills and participant outcomes (e.g. substance use, mental health) for people attending SMART Recovery groups.

  2. Interteaching: Discussion Group Size and Course Performance

    ERIC Educational Resources Information Center

    Truelove, Jacob C.; Saville, Bryan K.; Van Patten, Ryan

    2013-01-01

    Researchers have yet to examine whether discussion group size affects student performance in an interteaching-based course. In the current study, we addressed this question by manipulating discussion group size (smaller groups of 2 students vs. larger groups of 4 students) across 2 sections of an undergraduate psychology course. We found no…

  3. The Distribution of Instructional Time and Its Effect on Group Cohesion in the Foreign Language Classroom: A Comparison of Intensive and Standard Format Courses

    ERIC Educational Resources Information Center

    Hinger, Barbara

    2006-01-01

    This paper argues for the influence of the distribution of instructional time on group cohesion in the foreign language classroom and postulates that concentrating classroom time enhances group cohesion. To test the hypothesis, a comparative classroom study of two groups of Spanish learners in their second year of learning, one following an…

  4. Teamwork Orientation, Group Cohesiveness, and Student Learning: A Study of the Use of Teams in Online Distance Education

    ERIC Educational Resources Information Center

    Williams, Ethlyn A.; Duray, Rebecca; Reddy, Venkateshwar

    2006-01-01

    This research examines computer-supported collaborative learning. Master's of business administration (MBA) students in an online program were surveyed to examine the extent to which an orientation toward teamwork and the development of group cohesiveness affect overall student learning and the learning that results specifically from team…

  5. The group matters: an explorative study of group cohesion and quality of life in cancer patients participating in physical exercise intervention during treatment.

    PubMed

    Midtgaard, J; Rorth, M; Stelter, R; Adamsen, L

    2006-03-01

    A series of studies have shown that physical activity improves cancer patients functional capacity and quality of life (QOL). Few of these studies have included physical exercise carried out in a group setting. However, patient's experience with the in-group processes remains unexplored. This study investigated group cohesion and changes in QOL in 55 cancer patients undergoing chemotherapy who participated in a 9 h weekly group exercise programme for 6 weeks. The study used a method triangulation component design. Seven qualitative group interviews were conducted post-intervention. QOL (SF-36; EORTC QLQ-C30) was assessed at baseline and after Week 6. The interviews revealed that group cohesion was an interim goal aimed to maximize peak performance potential by patients. Group cohesion was characterized by a special 'esprit de corps' and enabled the group members to feel like sport teams. The programme made purposeful togetherness possible while allowing the patients an opportunity to let their illness fade into the background. Questionnaire data showed significant improvements in mental health, social and emotional functioning. This study identified a conceptualization of group cohesion that forms a valuable basis for a larger randomized controlled trial to conclude whether the observed changes are a result of this specific intervention.

  6. Understanding Animal Group-Size Distributions

    PubMed Central

    Griesser, Michael; Ma, Qi; Webber, Simone; Bowgen, Katharine; Sumpter, David J. T.

    2011-01-01

    One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus) to investigate the factors determining group-size distribution. Over a wide range of conditions, we observed that animal group sizes followed a single parameter distribution known as the logarithmic distribution. This single parameter is the mean group size experienced by a randomly chosen individual (including the individual itself). For sparrows, the experienced mean group size, and hence the distribution, was affected by four factors: morning temperature, place, behavior and the degree of food spillage. Our results further indicate that the sparrows regulate the mean group size they experience, either by groups splitting more or merging less when local densities are high. We suggest that the mean experienced group size provides a simple but general tool for assessing the ecology and evolution of grouping. PMID:21912596

  7. Scaling in animal group-size distributions

    PubMed Central

    Bonabeau, Eric; Dagorn, Laurent; Fréon, Pierre

    1999-01-01

    An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes. PMID:10200286

  8. Two ways related to performance in elite sport: the path of self-confidence and competitive anxiety and the path of group cohesion and group goal-clarity.

    PubMed

    Kjørmo, Odd; Halvari, Hallgeir

    2002-06-01

    A model tested among 136 Norwegian Olympic-level athletes yielded two paths related to performance. The first path indicated that self-confidence, modeled as an antecedent of competitive anxiety, is negatively correlated with anxiety. Competitive anxiety in turn is negatively correlated with performance. The second path indicated that group cohesion is positively correlated with group goal-clarity, which in turn is positively correlated with performance. Competitive anxiety mediates the relation between self-confidence and performance, whereas group goal-clarity mediates the relation between group cohesion and performance. Results from multiple regression analyses supported the model in the total sample and among individual sport athletes organized in training groups (n = 100). Among team sport athletes (n = 36), personality and group measures are more strongly intercorrelated than among individual sport athletes, and the relation with performance is more complex for the former group. The interaction of self-confidence and competitive anxiety is related to performance among team sport athletes.

  9. Group cohesion and organizational commitment: protective factors for nurse residents' job satisfaction, compassion fatigue, compassion satisfaction, and burnout.

    PubMed

    Li, Angela; Early, Sean F; Mahrer, Nicole E; Klaristenfeld, Jessica L; Gold, Jeffrey I

    2014-01-01

    Stress can have detrimental effects on nurse residents' levels of job satisfaction, compassion, fatigue, and burnout. This can lead to high turnover rates and poor quality of care among novice nurses. Therefore, it is critical to identify protective factors to prevent the onset of negative nurse outcomes (compassion fatigue, burnout, and job dissatisfaction) and to promote positive nurse outcomes (job satisfaction, compassion satisfaction). This study aimed to determine whether factors such as group cohesion and organizational commitment would be protective and moderate the association between stress exposure and posttraumatic stress symptoms and other negative nurse outcomes, thus facilitating positive outcomes. Findings showed that group cohesion was effective in moderating the negative effects of current stress exposure and posttraumatic stress symptoms on negative nurse outcomes, specifically on increased compassion fatigue and burnout, and reduced compassion satisfaction. In addition, organizational commitment was determined to promote positive nurse outcomes such as job satisfaction and compassion satisfaction. The study findings are promising, as retention of quality nurses is a significant problem for hospitals. Nurse managers and hospital administrators should be aware of the benefits of group cohesion and organizational commitment and strive to make the promotion of these factors a priority. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. The Role of Conformity in Relation to Cohesiveness and Intimacy in Day-Hospital Groups of Patients with Schizophrenia

    PubMed Central

    Park, Il Ho; Park, Sun Young; Choi, Sulkee; Lee, Soo Young

    2017-01-01

    Objective Conformity is defined as the act of adjusting one's behavior to match the social responses of others. Patients with schizophrenia often adjust their maladaptive behaviors by conforming in group treatment settings. This study aimed to examine whether the opinions of group members influence conformity of patients with schizophrenia who attend day-hospital programs. Methods Nineteen patients with schizophrenia from four different day-hospital programs and 23 healthy controls from four different social clubs completed the homographic meaning choice task under conditions of prior exposure to the pseudo-opinions of their group members, strangers, and unknown information sources. Group influences on conformity were observed when the level of group cohesiveness was high and the level of intimacy was low across participant groups. Results Controls did not exhibit a significant effect of group influence on conformity, whereas patients were significantly influenced by their group members when making conformity-based decisions despite significantly lower intimacy and cohesiveness levels. Conclusion These findings suggest that unlike controls, patients with schizophrenia tend to respond with conformity when influenced by the opinions of their affiliated group. In patients with schizophrenia group conformity may be used to select a more accurate decision and to enhance feelings of affiliation among them. PMID:28845174

  11. Treatment compliance among patients with personality disorders receiving group psychotherapy: what are the roles of interpersonal distress and cohesion?

    PubMed

    Ogrodniczuk, John S; Piper, William E; Joyce, Anthony S

    2006-01-01

    It is often assumed that patients with personality disorders have worse compliance in psychotherapy (i.e., attend fewer sessions) than patients without personality disorders. Such an assumption can have negative consequences for the treatment of patients with personality disorders. It also denies the presence of variability in session attendance among patients with personality disorders. Research that attempts to identify the factors that are associated with variability in session attendance among patients with personality disorders is needed. The present study examined the role of interpersonal distress as a predictor of session attendance for patients with personality disorders (n = 72) in two different forms of group psychotherapy (interpretive, supportive). The study also investigated whether patients' cohesion to their group mediated the effect of interpersonal distress on attendance. Findings indicated that interpersonal distress had a strong, direct association with attendance in supportive group therapy, but minimal association in interpretive group therapy. High levels of interpersonal distress were associated with higher attendance in supportive therapy. Furthermore, cohesion to the group accounted for about two-thirds of the effect of interpersonal distress on attendance in supportive group therapy, thus providing compelling evidence for its role as a mediator. Possible explanations and clinical implications of these findings are discussed.

  12. Cohesion Group Approach for Evolutionary Analysis of TyrA, a Protein Family with Wide-Ranging Substrate Specificities

    PubMed Central

    Bonner, Carol A.; Disz, Terrence; Hwang, Kaitlyn; Song, Jian; Vonstein, Veronika; Overbeek, Ross; Jensen, Roy A.

    2008-01-01

    Summary: Many enzymes and other proteins are difficult subjects for bioinformatic analysis because they exhibit variant catalytic, structural, regulatory, and fusion mode features within a protein family whose sequences are not highly conserved. However, such features reflect dynamic and interesting scenarios of evolutionary importance. The value of experimental data obtained from individual organisms is instantly magnified to the extent that given features of the experimental organism can be projected upon related organisms. But how can one decide how far along the similarity scale it is reasonable to go before such inferences become doubtful? How can a credible picture of evolutionary events be deduced within the vertical trace of inheritance in combination with intervening events of lateral gene transfer (LGT)? We present a comprehensive analysis of a dehydrogenase protein family (TyrA) as a prototype example of how these goals can be accomplished through the use of cohesion group analysis. With this approach, the full collection of homologs is sorted into groups by a method that eliminates bias caused by an uneven representation of sequences from organisms whose phylogenetic spacing is not optimal. Each sufficiently populated cohesion group is phylogenetically coherent and defined by an overall congruence with a distinct section of the 16S rRNA gene tree. Exceptions that occasionally are found implicate a clearly defined LGT scenario whereby the recipient lineage is apparent and the donor lineage of the gene transferred is localized to those organisms that define the cohesion group. Systematic procedures to manage and organize otherwise overwhelming amounts of data are demonstrated. PMID:18322033

  13. Cohesion group approach for evolutionary analysis of TyrA, a protein family with wide-ranging substrate specificities.

    PubMed

    Bonner, Carol A; Disz, Terrence; Hwang, Kaitlyn; Song, Jian; Vonstein, Veronika; Overbeek, Ross; Jensen, Roy A

    2008-03-01

    Many enzymes and other proteins are difficult subjects for bioinformatic analysis because they exhibit variant catalytic, structural, regulatory, and fusion mode features within a protein family whose sequences are not highly conserved. However, such features reflect dynamic and interesting scenarios of evolutionary importance. The value of experimental data obtained from individual organisms is instantly magnified to the extent that given features of the experimental organism can be projected upon related organisms. But how can one decide how far along the similarity scale it is reasonable to go before such inferences become doubtful? How can a credible picture of evolutionary events be deduced within the vertical trace of inheritance in combination with intervening events of lateral gene transfer (LGT)? We present a comprehensive analysis of a dehydrogenase protein family (TyrA) as a prototype example of how these goals can be accomplished through the use of cohesion group analysis. With this approach, the full collection of homologs is sorted into groups by a method that eliminates bias caused by an uneven representation of sequences from organisms whose phylogenetic spacing is not optimal. Each sufficiently populated cohesion group is phylogenetically coherent and defined by an overall congruence with a distinct section of the 16S rRNA gene tree. Exceptions that occasionally are found implicate a clearly defined LGT scenario whereby the recipient lineage is apparent and the donor lineage of the gene transferred is localized to those organisms that define the cohesion group. Systematic procedures to manage and organize otherwise overwhelming amounts of data are demonstrated.

  14. The use of group dynamics strategies to enhance cohesion in a lifestyle intervention program for obese children

    PubMed Central

    Martin, Luc J; Burke, Shauna M; Shapiro, Sheree; Carron, Albert V; Irwin, Jennifer D; Petrella, Robert; Prapavessis, Harry; Shoemaker, Kevin

    2009-01-01

    Background Most research pertaining to childhood obesity has assessed the effectiveness of preventative interventions, while relatively little has been done to advance knowledge in the treatment of obesity. Thus, a 4-week family- and group-based intervention utilizing group dynamics strategies designed to increase cohesion was implemented to influence the lifestyles and physical activity levels of obese children. Methods/Design This paper provides an overview of the rationale for and implementation of the intervention for obese children and their families. Objectives of the intervention included the modification of health behaviors and cohesion levels through the use of group dynamics strategies. To date, a total of 15 children (7 boys and 8 girls, mean age = 10.5) and their families have completed the intervention (during the month of August 2008). Physiological and psychological outcomes were assessed throughout the 4-week intervention and at 3-, 6-, and 12-month follow-up periods. Discussion It is believed that the information provided will help researchers and health professionals develop similar obesity treatment interventions through the use of evidence-based group dynamics strategies. There is also a need for continued research in this area, and it is our hope that the Children's Health and Activity Modification Program (C.H.A.M.P.) will provide a strong base from which others may build. PMID:19646259

  15. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  16. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  17. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  18. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  19. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General Provisions...

  20. A universal approximation to grain size from images of non-cohesive sediment

    USGS Publications Warehouse

    Buscombe, D.; Rubin, D.M.; Warrick, J.A.

    2010-01-01

    The two-dimensional spectral decomposition of an image of sediment provides a direct statistical estimate, grid-by-number style, of the mean of all intermediate axes of all single particles within the image. We develop and test this new method which, unlike existing techniques, requires neither image processing algorithms for detection and measurement of individual grains, nor calibration. The only information required of the operator is the spatial resolution of the image. The method is tested with images of bed sediment from nine different sedimentary environments (five beaches, three rivers, and one continental shelf), across the range 0.1 mm to 150 mm, taken in air and underwater. Each population was photographed using a different camera and lighting conditions. We term it a “universal approximation” because it has produced accurate estimates for all populations we have tested it with, without calibration. We use three approaches (theory, computational experiments, and physical experiments) to both understand and explore the sensitivities and limits of this new method. Based on 443 samples, the root-mean-squared (RMS) error between size estimates from the new method and known mean grain size (obtained from point counts on the image) was found to be ±≈16%, with a 95% probability of estimates within ±31% of the true mean grain size (measured in a linear scale). The RMS error reduces to ≈11%, with a 95% probability of estimates within ±20% of the true mean grain size if point counts from a few images are used to correct bias for a specific population of sediment images. It thus appears it is transferable between sedimentary populations with different grain size, but factors such as particle shape and packing may introduce bias which may need to be calibrated for. For the first time, an attempt has been made to mathematically relate the spatial distribution of pixel intensity within the image of sediment to the grain size.

  1. Comparison of 12-step groups to mutual help alternatives for AUD in a large, national study: Differences in membership characteristics and group participation, cohesion, and satisfaction.

    PubMed

    Zemore, Sarah E; Kaskutas, Lee Ann; Mericle, Amy; Hemberg, Jordana

    2017-02-01

    Many studies suggest that participation in 12-step groups contributes to better recovery outcomes, but people often object to such groups and most do not sustain regular involvement. Yet, research on alternatives to 12-step groups is very sparse. The present study aimed to extend the knowledge base on mutual help group alternatives for those with an alcohol use disorder (AUD), sampling from large, active, abstinence-focused groups including Women for Sobriety (WFS), LifeRing, and SMART Recovery (SMART). This paper presents a cross-sectional analysis of this longitudinal study, using baseline data to describe the profile and participation characteristics of attendees of these groups in comparison to 12-step members. Data from participants 18 and over with a lifetime AUD (N=651) were collected using Web-based surveys. Members of alternative 12-step groups were recruited in collaboration with group directors, who helped publicize the study by emailing meeting conveners and attendees and posting announcements on social media. A comparison group of current (past-30-day) 12-step attendees was recruited from an online meeting hub for recovering persons. Interested parties were directed to a Webpage where they were screened, and eligible participants completed an online survey assessing demographic and clinical variables; in-person and online mutual help involvement; and group satisfaction and cohesion. Analyses involved comparing those identifying WFS, SMART, and LifeRing as their primary group to 12-step members on the above characteristics. Compared to 12-step members, members of the mutual help alternatives were less religious and generally higher on education and income. WFS and LifeRing members were also older, more likely to be married, and lower on lifetime drug and psychiatric severity; meanwhile, LifeRing and SMART members were less likely to endorse the most stringent abstinence goal. Finally, despite lower levels of in-person meeting attendance, members of all

  2. Cohesion Group Approach for Evolutionary Analysis of Aspartokinase, an Enzyme That Feeds a Branched Network of Many Biochemical Pathways

    PubMed Central

    Lo, Chien-Chi; Bonner, Carol A.; Xie, Gary; D'Souza, Mark; Jensen, Roy A.

    2009-01-01

    Summary: Aspartokinase (Ask) exists within a variable network that supports the synthesis of 9 amino acids and a number of other important metabolites. Lysine, isoleucine, aromatic amino acids, and dipicolinate may arise from the ASK network or from alternative pathways. Ask proteins were subjected to cohesion group analysis, a methodology that sorts a given protein assemblage into groups in which evolutionary continuity is assured. Two subhomology divisions, ASKα and ASKβ, have been recognized. The ASKα subhomology division is the most ancient, being widely distributed throughout the Archaea and Eukarya and in some Bacteria. Within an indel region of about 75 amino acids near the N terminus, ASKβ sequences differ from ASKα sequences by the possession of a proposed ancient deletion. ASKβ sequences are present in most Bacteria and usually exhibit an in-frame internal translational start site that can generate a small Ask subunit that is identical to the C-terminal portion of the larger subunit of a heterodimeric unit. Particularly novel are ask genes embedded in gene contexts that imply specialization for ectoine (osmotic agent) or aromatic amino acids. The cohesion group approach is well suited for the easy recognition of relatively recent lateral gene transfer (LGT) events, and many examples of these are described. Given the current density of genome representation for Proteobacteria, it is possible to reconstruct more ancient landmark LGT events. Thus, a plausible scenario in which the three well-studied and iconic Ask homologs of Escherichia coli are not within the vertical genealogy of Gammaproteobacteria, but rather originated via LGT from a Bacteroidetes donor, is supported. PMID:19946135

  3. Cohesion group approach for evolutionary analysis of aspartokinase, an enzyme that feeds a branched network of many biochemical pathways.

    PubMed

    Lo, Chien-Chi; Bonner, Carol A; Xie, Gary; D'Souza, Mark; Jensen, Roy A

    2009-12-01

    Aspartokinase (Ask) exists within a variable network that supports the synthesis of 9 amino acids and a number of other important metabolites. Lysine, isoleucine, aromatic amino acids, and dipicolinate may arise from the ASK network or from alternative pathways. Ask proteins were subjected to cohesion group analysis, a methodology that sorts a given protein assemblage into groups in which evolutionary continuity is assured. Two subhomology divisions, ASK(alpha) and ASK(beta), have been recognized. The ASK(alpha) subhomology division is the most ancient, being widely distributed throughout the Archaea and Eukarya and in some Bacteria. Within an indel region of about 75 amino acids near the N terminus, ASK(beta) sequences differ from ASK(alpha) sequences by the possession of a proposed ancient deletion. ASK(beta) sequences are present in most Bacteria and usually exhibit an in-frame internal translational start site that can generate a small Ask subunit that is identical to the C-terminal portion of the larger subunit of a heterodimeric unit. Particularly novel are ask genes embedded in gene contexts that imply specialization for ectoine (osmotic agent) or aromatic amino acids. The cohesion group approach is well suited for the easy recognition of relatively recent lateral gene transfer (LGT) events, and many examples of these are described. Given the current density of genome representation for Proteobacteria, it is possible to reconstruct more ancient landmark LGT events. Thus, a plausible scenario in which the three well-studied and iconic Ask homologs of Escherichia coli are not within the vertical genealogy of Gammaproteobacteria, but rather originated via LGT from a Bacteroidetes donor, is supported.

  4. The Impact of Homogeneity on Intra-Group Cohesion: A Macro-Level Comparison of Minority Communities in a Western Diaspora

    ERIC Educational Resources Information Center

    Deffa, Oromiya-Jalata

    2016-01-01

    Contrary to earlier studies dealing with the cultural identity development of diasporic minorities, this paper assesses the impact of homogeneity on intra-group cohesion and ethnic orientation. To this end, Oromo-Americans, an ethnic group originally located within the national borders of Ethiopia, will be compared to Armenian-Americans,…

  5. The Impact of Homogeneity on Intra-Group Cohesion: A Macro-Level Comparison of Minority Communities in a Western Diaspora

    ERIC Educational Resources Information Center

    Deffa, Oromiya-Jalata

    2016-01-01

    Contrary to earlier studies dealing with the cultural identity development of diasporic minorities, this paper assesses the impact of homogeneity on intra-group cohesion and ethnic orientation. To this end, Oromo-Americans, an ethnic group originally located within the national borders of Ethiopia, will be compared to Armenian-Americans,…

  6. The Discursive Construction of Group Cohesion in Problem-Based Learning Tutorials

    ERIC Educational Resources Information Center

    Hendry, Gillian; Wiggins, Sally; Anderson, Tony

    2016-01-01

    Research has shown that educators may be reluctant to implement group work in their teaching due to concerns about students partaking in off-task behaviours. However, such off-task interactions have been shown to promote motivation, trust, and rapport-building. This paper details a study in which student groups were video recorded as they engaged…

  7. The Discursive Construction of Group Cohesion in Problem-Based Learning Tutorials

    ERIC Educational Resources Information Center

    Hendry, Gillian; Wiggins, Sally; Anderson, Tony

    2016-01-01

    Research has shown that educators may be reluctant to implement group work in their teaching due to concerns about students partaking in off-task behaviours. However, such off-task interactions have been shown to promote motivation, trust, and rapport-building. This paper details a study in which student groups were video recorded as they engaged…

  8. Cohesion predicts success in junior ice hockey.

    PubMed

    Salminen, S; Luhtanen, P

    1998-10-01

    This study examined the relationship between cohesion measured by the Group Environment Questionnaire and success measured by winning percentage with over 200 junior ice hockey players. The cohesion explained 29% of the variance of the success. Scores on task cohesion were better predictors of success than social cohesion.

  9. Predicting the size- and shape-dependent cohesive energy and order-disorder transition temperature of Co-Pt nanoparticles by embedded-atom-method potential.

    PubMed

    Liu, Chenze; Qi, Weihong; Ouyang, Bin; Wang, Xing; Huang, Baiyun

    2013-02-01

    The cohesive energy (CE) of CoPt nanoparticles (NPs) with different sizes and shapes have been calculated by embedded-atom-method (EAM) potential. It is shown that CE of NPs with order or disorder structures decreases with the decrease of particle size, while the shape effects become obvious only at small size. The CE difference per atom between order and disorder structures decreases with the decrease of particle size, indicating that the possibility of order-disorder transition in small size becomes larger compared with these in large size. Significantly, the CE difference varies in proportion to order-disorder transition temperature (T(c)), which suggests that one can predict order-disorder transition of NPs by calculation the cohesive energy. The present calculated T(c) of CoPt NPs is consistent with recent experiments, simulation and theoretical predictions, and the method can also be applied to study the order-disorder transition of FePt, FePd, and so on.

  10. Examining the Effects of Campus Climate, Ethnic Group Cohesion, and Cross-Cultural Interaction on Filipino American Students' Sense of Belonging in College

    ERIC Educational Resources Information Center

    Maramba, Dina C.; Museus, Samuel D.

    2013-01-01

    The purpose of this study is to explore how campus climate, ethnic group cohesion and cross cultural interaction influence Filipino American college students' sense of belonging in college. Specifically, we examine the impact of three environmental and behavioral factors on students' sense of belonging: 1) campus racial climate, 2) ethnic group…

  11. Lexical Cohesion in Students' Argumentative Essay among a Select Group of Filipino College Students

    ERIC Educational Resources Information Center

    Alarcon, Josephine B.

    2013-01-01

    This study analyzed the lexical devices used by undergraduate students in their argumentative text using Halliday and Hasan (1976) and Halliday's (2004) taxonomy. One hundred forty-eight argumentative essays were analyzed. The essays underwent interrating by three independent raters using a 20-point rubric and were grouped according to rating.…

  12. Comparative Model Tests of SDP and CFA Pile Groups in Non-Cohesive Soil

    NASA Astrophysics Data System (ADS)

    Krasiński, Adam; Kusio, Tomasz

    2015-02-01

    The research topic relates to the subject of deep foundations supported on continuous flight auger (CFA) piles and screw displacement piles (SDP). The authors have decided to conduct model tests of foundations supported on the group of piles mentioned above and also the tests of the same piles working as a single. The tests are ongoing in Geotechnical Laboratory of Gdaňsk University of Technology. The description of test procedure, interpretation and analysis of the preliminary testing series results are presented in the paper.

  13. Behavioural ecology and group cohesion of juvenile western lowland gorillas (Gorilla g. gorilla) during rehabilitation in the Batéké Plateaux National Park, Gabon.

    PubMed

    Le Flohic, Guillaume; Motsch, Peggy; DeNys, Hélène; Childs, Simon; Courage, Amos; King, Tony

    2015-01-01

    Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing

  14. Behavioural Ecology and Group Cohesion of Juvenile Western Lowland Gorillas (Gorilla g. gorilla) during Rehabilitation in the Batéké Plateaux National Park, Gabon

    PubMed Central

    Le Flohic, Guillaume; Motsch, Peggy; DeNys, Hélène; Childs, Simon; Courage, Amos; King, Tony

    2015-01-01

    Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing

  15. Item wording and internal consistency of a measure of cohesion: the group environment questionnaire.

    PubMed

    Eys, Mark A; Carron, Albert V; Bray, Steven R; Brawley, Lawrence R

    2007-06-01

    A common practice for counteracting response acquiescence in psychological measures has been to employ both negatively and positively worded items. However, previous research has highlighted that the reliability of measures can be affected by this practice (Spector, 1992). The purpose of the present study was to examine the effect that the presence of negatively worded items has on the internal reliability of the Group Environment Questionnaire (GEQ). Two samples (N = 276) were utilized, and participants were asked to complete the GEQ (original and revised) on separate occasions. Results demonstrated that the revised questionnaire (containing all positively worded items) had significantly higher Cronbach alpha values for three of the four dimensions of the GEQ. Implications, alternatives, and future directions are discussed.

  16. 48 CFR 1602.170-13 - Similarly sized subscriber groups.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... MANAGEMENT FEDERAL EMPLOYEES HEALTH BENEFITS ACQUISITION REGULATION GENERAL DEFINITIONS OF WORDS AND TERMS Definitions of FEHBP Terms 1602.170-13 Similarly sized subscriber groups. (a) Similarly sized...

  17. An Engineering Solution for Solving Mesh Size Effects in the Simulation of Delamination with Cohesive Zone Models

    NASA Technical Reports Server (NTRS)

    Turon, A.; Davila, C. G.; Camanho, P. P.; Costa, J.

    2007-01-01

    This paper presents a methodology to determine the parameters to be used in the constitutive equations of Cohesive Zone Models employed in the simulation of delamination in composite materials by means of decohesion finite elements. A closed-form expression is developed to define the stiffness of the cohesive layer. A novel procedure that allows the use of coarser meshes of decohesion elements in large-scale computations is also proposed. The procedure ensures that the energy dissipated by the fracture process is computed correctly. It is shown that coarse-meshed models defined using the approach proposed here yield the same results as the models with finer meshes normally used for the simulation of fracture processes.

  18. Developing Team Cohesion: A Quasi-Field Experiment

    DTIC Science & Technology

    2004-03-01

    the extent of motivation to accomplishing the organization’s goals and Group Characteristics Group Processes Cohesion Social Task...Workload Sharing Cohesion Social (Bonding) Task Effectiveness Spirit Pride Environment Stressful activities Social activities Individual...n Task Cohesion Social Cohesion Affective Horizontal Bonding Figure 3. Growth of cohesion over time for seven week familiarity period and one week

  19. Does Group Size Matter for Behavior in Online Trust Dilemmas?

    PubMed Central

    Artinger, Sabrina; Vulkan, Nir

    2016-01-01

    How does group size influence behavior in online trust dilemmas? We investigate cooperation in groups of 4 to 100 players. While overall levels of cooperation are stable across group sizes, we find significant gender differences: women increase cooperation with group size and cooperate significantly more than men in large groups. These results are robust when controlling for risk aversion, age, and other individual differences. They highlight the importance of studying behavior and gender differences in large groups. PMID:27898667

  20. Optimal group size in a highly social mammal.

    PubMed

    Markham, A Catherine; Gesquiere, Laurence R; Alberts, Susan C; Altmann, Jeanne

    2015-12-01

    Group size is an important trait of social animals, affecting how individuals allocate time and use space, and influencing both an individual's fitness and the collective, cooperative behaviors of the group as a whole. Here we tested predictions motivated by the ecological constraints model of group size, examining the effects of group size on ranging patterns and adult female glucocorticoid (stress hormone) concentrations in five social groups of wild baboons (Papio cynocephalus) over an 11-y period. Strikingly, we found evidence that intermediate-sized groups have energetically optimal space-use strategies; both large and small groups experience ranging disadvantages, in contrast to the commonly reported positive linear relationship between group size and home range area and daily travel distance, which depict a disadvantage only in large groups. Specifically, we observed a U-shaped relationship between group size and home range area, average daily distance traveled, evenness of space use within the home range, and glucocorticoid concentrations. We propose that a likely explanation for these U-shaped patterns is that large, socially dominant groups are constrained by within-group competition, whereas small, socially subordinate groups are constrained by between-group competition and predation pressures. Overall, our results provide testable hypotheses for evaluating group-size constraints in other group-living species, in which the costs of intra- and intergroup competition vary as a function of group size.

  1. Music listening in families and peer groups: benefits for young people's social cohesion and emotional well-being across four cultures.

    PubMed

    Boer, Diana; Abubakar, Amina

    2014-01-01

    Families are central to the social and emotional development of youth, and most families engage in musical activities together, such as listening to music or talking about their favorite songs. However, empirical evidence of the positive effects of musical family rituals on social cohesion and emotional well-being is scarce. Furthermore, the role of culture in the shaping of musical family rituals and their psychological benefits has been neglected entirely. This paper investigates musical rituals in families and in peer groups (as an important secondary socialization context) in two traditional/collectivistic and two secular/individualistic cultures, and across two developmental stages (adolescence vs. young adulthood). Based on cross-sectional data from 760 young people in Kenya, the Philippines, New Zealand, and Germany, our study revealed that across cultures music listening in families and in peer groups contributes to family and peer cohesion, respectively. Furthermore, the direct contribution of music in peer groups on well-being appears across cultural contexts, whereas musical family rituals affect emotional well-being in more traditional/collectivistic contexts. Developmental analyses show that musical family rituals are consistently and strongly related to family cohesion across developmental stages, whereas musical rituals in peer groups appear more dependent on the developmental stage (in interaction with culture). Contributing to developmental as well as cross-cultural psychology, this research elucidated musical rituals and their positive effects on the emotional and social development of young people across cultures. The implications for future research and family interventions are discussed.

  2. Music listening in families and peer groups: benefits for young people's social cohesion and emotional well-being across four cultures

    PubMed Central

    Boer, Diana; Abubakar, Amina

    2014-01-01

    Families are central to the social and emotional development of youth, and most families engage in musical activities together, such as listening to music or talking about their favorite songs. However, empirical evidence of the positive effects of musical family rituals on social cohesion and emotional well-being is scarce. Furthermore, the role of culture in the shaping of musical family rituals and their psychological benefits has been neglected entirely. This paper investigates musical rituals in families and in peer groups (as an important secondary socialization context) in two traditional/collectivistic and two secular/individualistic cultures, and across two developmental stages (adolescence vs. young adulthood). Based on cross-sectional data from 760 young people in Kenya, the Philippines, New Zealand, and Germany, our study revealed that across cultures music listening in families and in peer groups contributes to family and peer cohesion, respectively. Furthermore, the direct contribution of music in peer groups on well-being appears across cultural contexts, whereas musical family rituals affect emotional well-being in more traditional/collectivistic contexts. Developmental analyses show that musical family rituals are consistently and strongly related to family cohesion across developmental stages, whereas musical rituals in peer groups appear more dependent on the developmental stage (in interaction with culture). Contributing to developmental as well as cross-cultural psychology, this research elucidated musical rituals and their positive effects on the emotional and social development of young people across cultures. The implications for future research and family interventions are discussed. PMID:24847296

  3. Evaluation of the Parameters Affecting the Cohesion of Fine Grained Soil

    NASA Astrophysics Data System (ADS)

    Vondráčková, Terezie; Kmec, Ján; Čejka, Jiří; Bartuška, Ladislav; Stopka, Ondrej

    2016-10-01

    Cohesion of the soils is one of the most important parameters which soil is evaluated in terms of its suitability for building foundations. Safety of construction is in fact dependent on the strength of soil, respectively shear strength. Fine-grained soil represents very specific group, in which is distinguished an effective and total cohesion of soils. The water in the soil thus drastically affects its cohesion contrary to gravel and sandy soils. The publication compares the tabular values of the effective and total cohesion and define the influence of water, grain size and consistency of her behaviour.

  4. Antimicrobial strength increases with group size: implications for social evolution.

    PubMed

    Turnbull, Christine; Hoggard, Stephen; Gillings, Michael; Palmer, Chris; Stow, Adam; Beattie, Doug; Briscoe, David; Smith, Shannon; Wilson, Peter; Beattie, Andrew

    2011-04-23

    We hypothesize that aggregations of animals are likely to attract pathogenic micro-organisms and that this is especially the case for semisocial and eusocial insects where selection ultimately led to group sizes in the thousands or even millions, attracting the epithet 'superorganism'. Here, we analyse antimicrobial strength, per individual, in eight thrips species (Insecta: Thysanoptera) that present increasing innate group sizes and show that species with the largest group size (100-700) had the strongest antimicrobials, those with smaller groups (10-80) had lower antimicrobial activity, while solitary species showed none. Species with large innate group sizes showed strong antimicrobial activity while the semisocial species showed no activity until group size increased sufficiently to make activity detectable. The eusocial species behaved in a similar way, with detectable activity appearing once group size exceeded 120. These analyses show that antimicrobial strength is determined by innate group size. This suggests that the evolution of sociality that, by definition, increases group size, may have had particular requirements for defences against microbial pathogens. Thus, increase in group size, accompanied by increased antibiotic strength, may have been a critical factor determining the 'point of no return', early in the evolution of social insects, beyond which the evolution of social anatomical and morphological traits was irreversible. Our data suggest that traits that increase group size in general are accompanied by increased antimicrobial strength and that this was critical for transitions from solitary to social and eusocial organization.

  5. Variability in group size and the evolution of collective action.

    PubMed

    Peña, Jorge; Nöldeke, Georg

    2016-01-21

    Models of the evolution of collective action typically assume that interactions occur in groups of identical size. In contrast, social interactions between animals occur in groups of widely dispersed size. This paper models collective action problems as two-strategy multiplayer games and studies the effect of variability in group size on the evolution of cooperative behavior under the replicator dynamics. The analysis identifies elementary conditions on the payoff structure of the game implying that the evolution of cooperative behavior is promoted or inhibited when the group size experienced by a focal player is more or less variable. Similar but more stringent conditions are applicable when the confounding effect of size-biased sampling, which causes the group-size distribution experienced by a focal player to differ from the statistical distribution of group sizes, is taken into account.

  6. Assessing eye orbits as predictors of Neandertal group size.

    PubMed

    Traynor, Sarah; Gurtov, Alia N; Senjem, Jess Hutton; Hawks, John

    2015-08-01

    The objective is to investigate the hypothesis that Neandertal eye orbits can predict group size and social cognition as presented by Pearce et al. (Proc R Soc B Biol Sci 280 (2013) 20130168). We performed a linear regression of known orbital aperture diameter (OAD), neocortex ratio, and group size among 18 extant diurnal primate species. Our data were derived from Kirk (J Hum Evol 51 (2006) 159-170) and Dunbar (J Hum Evol 22 (1992), 469-493; J Hum Evol 28 (1995) 287-296). There is a positive correlation between OAD and group size; a positive correlation between neocortex and group size; and a positive correlation between OAD and neocortex size. The strength of the collinearity between OAD and neocortex ratio accounts for any significance of OAD in a model. The model that best accounts for variation in group size is one that includes only neocortex ratio; including OAD does not strengthen the model. OAD accounts for 29 percent of the variation in group size. Larger orbits are correlated with larger group sizes in primates, although not significantly when controlling for neocortex ratio. Moreover, the amount of variation in group size that can be explained by OAD is negligible. The larger orbits of Neandertals compared to the average modern human population do not permit any interpretation of cognitive ability related to group size. © 2015 Wiley Periodicals, Inc.

  7. Group Size and Attitudes toward the Simulation Experience.

    ERIC Educational Resources Information Center

    Gentry, James W.

    1980-01-01

    A study to determine whether a relationship existed between team size and various attitudinal and performance variables in simulation games played by undergraduate business students indicated that group size had no impact on the group's performance, but that it was strongly related to the amount of dissension in the group. (LLS)

  8. Understanding and Teaching Cohesion Comprehension.

    ERIC Educational Resources Information Center

    Irwin, Judith W., Ed.

    Concerned with improving student comprehension of text, this book focuses particularly on teaching students how sentences tie together. Articles in the three sections are grouped as follows: Part 1, What Is Cohesion Comprehension? contains "Cohesion, Coherence, and Comprehension" (Alden J. Moe and Judith W. Irwin); "Identifying…

  9. Understanding and Teaching Cohesion Comprehension.

    ERIC Educational Resources Information Center

    Irwin, Judith W., Ed.

    Concerned with improving student comprehension of text, this book focuses particularly on teaching students how sentences tie together. Articles in the three sections are grouped as follows: Part 1, What Is Cohesion Comprehension? contains "Cohesion, Coherence, and Comprehension" (Alden J. Moe and Judith W. Irwin); "Identifying…

  10. Understanding improved dissolution of indomethacin through the use of cohesive poorly water-soluble aluminium hydroxide: effects of concentration and particle size distribution.

    PubMed

    Tay, Tracy; Allahham, Ayman; Morton, David A V; Stewart, Peter J

    2011-10-01

    The objective of this study was to explore the effects of concentration and particle size distribution of an added poorly water-soluble inorganic salt, aluminium hydroxide, on the dissolution of a poorly water-soluble drug, indomethacin (IMC), from lactose interactive mixtures. Dissolution was studied using the United States Pharmacopeia paddle method in buffer pH 5.0 and the data most aptly fitted a bi-exponential dissolution model which represented dissolution occurring from dispersed and agglomerated particles. The dispersion of IMC mixtures was measured in dissolution media under non-sink conditions by laser diffraction. The dissolution of IMC increased as a function of the concentration of aluminium hydroxide (5-20%) added to the mixtures. Increasing the proportion of larger particles of the cohesive aluminium hydroxide increased the dissolution rate of IMC. The enhanced dissolution was attributed to increases in both the dissolution rate constant and initial concentration of dispersed particles. Mechanistically, the aluminium hydroxide was found to facilitate the detachment of IMC particles from the carrier surface, forming a complex interactive mixture that more readily deagglomerated than the cohesive drug agglomerates. The outcomes of this work would therefore allow more careful control and selection of the excipient specifications in producing solid dosage formulations with improved dissolution of poorly water-soluble drugs. Copyright © 2011 Wiley-Liss, Inc.

  11. Modeling group size and scalar stress by logistic regression from an archaeological perspective.

    PubMed

    Alberti, Gianmarco

    2014-01-01

    Johnson's scalar stress theory, describing the mechanics of (and the remedies to) the increase in in-group conflictuality that parallels the increase in groups' size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout). Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson's theory and on Dunbar's findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a) confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b) allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c) allows locating a critical scalar stress threshold at community size 127 (95% CI: 122-132), while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147-170). The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion.

  12. Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo

    DOE PAGES

    Santana, Juan A.; Krogel, Jaron T.; Kent, Paul R. C.; ...

    2016-05-03

    We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3 and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local and semi-local Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local and semi-local DFT approximations themore » deviation is 3.06 and 0.94 eV, respectively. For lattice constants, the mean absolute deviation in DMC, local and semi-local DFT approximations, are 0.017(1), 0.07 and 0.05 , respectively. In conclusion, DMC is highly accurate method, outperforming the local and semi-local DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.« less

  13. Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo

    SciTech Connect

    Santana, Juan A.; Krogel, Jaron T.; Kent, Paul R. C.; Reboredo, Fernando A.

    2016-05-03

    We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3 and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local and semi-local Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local and semi-local DFT approximations the deviation is 3.06 and 0.94 eV, respectively. For lattice constants, the mean absolute deviation in DMC, local and semi-local DFT approximations, are 0.017(1), 0.07 and 0.05 , respectively. In conclusion, DMC is highly accurate method, outperforming the local and semi-local DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.

  14. Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Santana, Juan A.; Krogel, Jaron T.; Kent, Paul R. C.; Reboredo, Fernando A.

    2016-05-01

    We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3, and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local, semi-local, and hybrid Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local, semi-local, and hybrid DFT approximations, the deviation is 3.06, 0.94, and 1.23 eV, respectively. For lattice constants, the mean absolute deviations in DMC, local, semi-local, and hybrid DFT approximations are 0.017(1), 0.07, 0.05, and 0.04 Å, respectively. DMC is a highly accurate method, outperforming the DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.

  15. Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo

    SciTech Connect

    Santana, Juan A.; Krogel, Jaron T.; Kent, Paul R. C.; Reboredo, Fernando A.

    2016-05-03

    We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3 and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local and semi-local Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local and semi-local DFT approximations the deviation is 3.06 and 0.94 eV, respectively. For lattice constants, the mean absolute deviation in DMC, local and semi-local DFT approximations, are 0.017(1), 0.07 and 0.05 , respectively. In conclusion, DMC is highly accurate method, outperforming the local and semi-local DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.

  16. Classroom contexts: connections between class size and within class grouping.

    PubMed

    Blatchford, P; Baines, E; Kutnick, P; Martin, C

    2001-06-01

    There has been a vigorous debate for many years about the educational effects of class size differences, but even if differences have an impact on pupils' academic progress this still leaves unanswered important questions about what mediates the effect. This paper is informed by a classroom contextual perspective, and examines associations between class size and within class groupings (in terms of size and number of groups, adult presence in groups, and type of interaction between grouping members). Age differences in these relationships are also explored. The quantitative study is based on analysis of 3157 groupings, from 672 Reception, Year 2 and Year 5 classes in 331 schools. The qualitative study was based on 12 classes in 8 case study schools, and questionnaire responses completed by over 100 class teachers. Links between size of class and within class groupings were examined on the basis of a 'grouping mapping survey', in which teachers at a given time in the school day provided information on group size and number, adult presence, and type of interaction between pupils, and complementary qualitative analyses of data from teacher-completed questionnaires, and interviews. The number of groups in a class increased with the size of the class. Over all three year groups, small classes had on average just over three groups, while large classes approached six groups. The size of groups in the class decreased with size of class. In class sizes over 25, pupils were more likely to be in a large group of 7-10, while in classes under 25 they were more likely to be in whole class groupings. Qualitative analyses showed that teachers felt that groups of 7-10 pupils had negative educational effects, for example, in terms of the quality and quantity of teaching and children's concentration and contribution in groups. Results suggest that the effects of class size can be best seen as through the size and number of groups, which will then have implications for learning

  17. Modeling Group Size and Scalar Stress by Logistic Regression from an Archaeological Perspective

    PubMed Central

    Alberti, Gianmarco

    2014-01-01

    Johnson’s scalar stress theory, describing the mechanics of (and the remedies to) the increase in in-group conflictuality that parallels the increase in groups’ size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout). Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson’s theory and on Dunbar’s findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a) confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b) allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c) allows locating a critical scalar stress threshold at community size 127 (95% CI: 122–132), while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147–170). The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion. PMID:24626241

  18. The Sample Size Needed for the Trimmed "t" Test when One Group Size Is Fixed

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2009-01-01

    The sample size determination is an important issue for planning research. However, limitations in size have seldom been discussed in the literature. Thus, how to allocate participants into different treatment groups to achieve the desired power is a practical issue that still needs to be addressed when one group size is fixed. The authors focused…

  19. Majority, Minority, and Parity: Effects of Gender and Group Size on Perceived Group Variability

    ERIC Educational Resources Information Center

    Voci, Alberto; Hewstone, Miles; Crisp, Richard J.; Rubin, Mark

    2008-01-01

    We investigated the effects of gender and group size on perceptions of group variability, using groups of students taking different majors that varied in the proportion of men and women (female-majority, parity, and male-majority). We found that both group size and gender had consistent effects on perceived out-group variability, even when…

  20. Effects of Group Size on Students Mathematics Achievement in Small Group Settings

    ERIC Educational Resources Information Center

    Enu, Justice; Danso, Paul Amoah; Awortwe, Peter K.

    2015-01-01

    An ideal group size is hard to obtain in small group settings; hence there are groups with more members than others. The purpose of the study was to find out whether group size has any effects on students' mathematics achievement in small group settings. Two third year classes of the 2011/2012 academic year were selected from two schools in the…

  1. Fluctuating survival selection explains variation in avian group size

    USGS Publications Warehouse

    Brown, Charles B.; Brown, Mary Bomberger; Roche, Erin A.; O'brien, Valerie A; Page, Catherine E.

    2016-01-01

    Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

  2. Fluctuating survival selection explains variation in avian group size

    PubMed Central

    Brown, Charles R.; Brown, Mary Bomberger; Roche, Erin A.; O’Brien, Valerie A.; Page, Catherine E.

    2016-01-01

    Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population. PMID:27091998

  3. The Marine Corps Basic Training Experience: Stresses, Leadership, and Group Cohesion as Predictors of Attitudes, Health, and Performance.

    DTIC Science & Technology

    1982-11-01

    Development. Graduating recruits typically report increased self- esteem and increased social skills as a result of BT. Scales to measure these...statement is particularly true for improved self-esteem and social skills and commitment to maintaining a high level of personal performance (Table 5...DEVELOPMENT DURING BASIC TRAINING IN STUDY 2’ EFFECT Group A B SIZE NL(.lTII 1 .STR𔃻hSL3i Role Ambiguity Social Skills -. 19 .22 S /’S/1LI Ll 51tk

  4. Epidemiological effects of group size variation in social species

    PubMed Central

    Caillaud, Damien; Craft, Meggan E.; Meyers, Lauren Ancel

    2013-01-01

    Contact patterns in group-structured populations determine the course of infectious disease outbreaks. Network-based models have revealed important connections between group-level contact patterns and the dynamics of epidemics, but these models typically ignore heterogeneities in within-group composition. Here, we analyse a flexible mathematical model of disease transmission in a hierarchically structured wildlife population, and find that increased variation in group size reduces the epidemic threshold, making social animal populations susceptible to a broader range of pathogens. Variation in group size also increases the likelihood of an epidemic for mildly transmissible diseases, but can reduce the likelihood and expected size of an epidemic for highly transmissible diseases. Further, we introduce the concept of epidemiological effective group size, which we define to be the group size of a hypothetical population containing groups of identical size that has the same epidemic threshold as an observed population. Using data from the Serengeti Lion Project, we find that pride-living Serengeti lions are epidemiologically comparable to a homogeneous population with up to 20 per cent larger prides. PMID:23576784

  5. Boundaries around Group Interaction: The Effect of Size and Status.

    ERIC Educational Resources Information Center

    Knowles, Eric S.

    The stimulus value of group boundaries was investigated in a field experiment. It was hypothesized that the size of a group and the status of its members would reduce the permeability of a boundary around an interacting group. Two or 4 interacting people of high or low status interrupted the traffic flow in a university hallway. Results indicate…

  6. Dunbar's number: group size and brain physiology in humans reexamined.

    PubMed

    de Ruiter, Jan; Weston, Gavin; Lyon, Stephen M

    2011-01-01

    Popular academic ideas linking physiological adaptations to social behaviors are spreading disconcertingly into wider societal contexts. In this article, we note our skepticism with one particularly popular—in our view, problematic—supposed causal correlation between neocortex size and social group size. The resulting Dunbar's Number, as it has come to be called, has been statistically tested against observed group size in different primate species. Although there may be reason to doubt the Dunbar's Number hypothesis among nonhuman primate species, we restrict ourselves here to the application of such an explanatory hypothesis to human, culture-manipulating populations. Human information process management, we argue, cannot be understood as a simple product of brain physiology. Cross-cultural comparison of not only group size but also relationship-reckoning systems like kinship terminologies suggests that although neocortices are undoubtedly crucial to human behavior, they cannot be given such primacy in explaining complex group composition, formation, or management.

  7. Nonapeptides and the Evolution of Social Group Sizes in Birds

    PubMed Central

    Goodson, James L.; Kingsbury, Marcy A.

    2010-01-01

    Species-typical patterns of grouping have profound impacts on many aspects of physiology and behavior. However, prior to our recent studies in estrildid finches, neural mechanisms that titrate species-typical group-size preferences, independent of other aspects of social organization (e.g., mating system and parental care), have been wholly unexplored, likely because species-typical group size is typically confounded with other aspects of behavior and biology. An additional complication is that components of social organization are evolutionarily labile and prone to repeated divergence and convergence. Hence, we cannot assume that convergence in social structure has been produced by convergent modifications to the same neural characters, and thus any comparative approach to grouping must include not only species that differ in their species-typical group sizes, but also species that exhibit convergent evolution in this aspect of social organization. Using five estrildid finch species that differ selectively in grouping (all biparental and monogamous) we have demonstrated that neural motivational systems evolve in predictable ways in relation to species-typical group sizes, including convergence in two highly gregarious species and convergence in two relatively asocial, territorial species. These systems include nonapeptide (vasotocin and mesotocin) circuits that encode the valence of social stimuli (positive–negative), titrate group-size preferences, and modulate anxiety-like behaviors. Nonapeptide systems exhibit functional and anatomical properties that are biased toward gregarious species, and experimental reductions of nonapeptide signaling by receptor antagonism and antisense oligonucleotides significantly decrease preferred group sizes in the gregarious zebra finch. Combined, these findings suggest that selection on species-typical group size may reliably target the same neural motivation systems when a given social structure evolves independently. PMID

  8. Consequences of fluctuating group size for the evolution of cooperation.

    PubMed

    Brännström, Ake; Gross, Thilo; Blasius, Bernd; Dieckmann, Ulf

    2011-08-01

    Studies of cooperation have traditionally focused on discrete games such as the well-known prisoner's dilemma, in which players choose between two pure strategies: cooperation and defection. Increasingly, however, cooperation is being studied in continuous games that feature a continuum of strategies determining the level of cooperative investment. For the continuous snowdrift game, it has been shown that a gradually evolving monomorphic population may undergo evolutionary branching, resulting in the emergence of a defector strategy that coexists with a cooperator strategy. This phenomenon has been dubbed the 'tragedy of the commune'. Here we study the effects of fluctuating group size on the tragedy of the commune and derive analytical conditions for evolutionary branching. Our results show that the effects of fluctuating group size on evolutionary dynamics critically depend on the structure of payoff functions. For games with additively separable benefits and costs, fluctuations in group size make evolutionary branching less likely, and sufficiently large fluctuations in group size can always turn an evolutionary branching point into a locally evolutionarily stable strategy. For games with multiplicatively separable benefits and costs, fluctuations in group size can either prevent or induce the tragedy of the commune. For games with general interactions between benefits and costs, we derive a general classification scheme based on second derivatives of the payoff function, to elucidate when fluctuations in group size help or hinder cooperation.

  9. Differential associations between Social Anxiety Disorder, family cohesion, and suicidality across racial/ethnic groups: Findings from the National Comorbidity Survey-Adolescent (NCS-A).

    PubMed

    Rapp, Amy M; Lau, Anna; Chavira, Denise A

    2016-09-20

    The proposed research seeks to introduce a novel model relating Social Anxiety Disorder (SAD) and suicide outcomes (i.e., passive suicidal ideation, active suicidal ideation, and suicide attempts) in diverse adolescents. This model posits that family cohesion is one pathway by which suicide risk is increased for socially anxious youth, and predicts that the relationships between these variables may be of different strength in Latino and White subgroups and across gender. Data from a sample of Latino (n=1922) and non-Hispanic White (hereafter referred to as White throughout) (n=5648) male and female adolescents who participated in the National Comorbidity Survey-Adolescent were used for this study. Analyses were conducted using generalized structural equation modeling. Results showed that the mediation model held for White females. Further examination of direct pathways highlighted SAD as a risk factor unique to Latinos for active suicidal ideation and suicide attempt, over and above comorbid depression and other relevant contextual factors. Additionally, family cohesion showed a strong association with suicide outcomes across groups, with some inconsistent findings for White males. Overall, it appears that the mechanism by which SAD increases risk for suicidality is different across groups, indicating further need to identify relevant mediators, especially for racial/ethnic minority youth.

  10. A Systematic Review of Therapeutic Alliance, Group Cohesion, Empathy, and Goal Consensus/Collaboration in Psychotherapeutic Interventions in Cancer: Uncommon Factors?

    PubMed Central

    Schnur, Julie B.; Montgomery, Guy H.

    2010-01-01

    The effects of four empirically supported therapeutic relationship factors (therapeutic alliance, empathy, goal consensus/collaboration, and group cohesion) on the outcome of psychotherapeutic interventions conducted with individuals living with cancer were systematically reviewed. PubMed, PsycINFO, and CINAHL were searched from their inception through November 13, 2008. Studies of psychotherapeutic interventions targeted to individuals living with cancer, which also empirically assessed the association between any of these therapeutic relationship factors and psychotherapy outcome were included in the review (8 of 742 papers initially reviewed). Information on study methodology and results were abstracted independently by the authors using a standardized form. Results indicated that therapist-rated rapport and group cohesion were significantly related to positive psychotherapeutic outcomes. No studies examined empathy. The literature on collaboration was mixed, but showed some support for increased collaboration being related to positive therapeutic outcomes. Overall the current literature on the role of therapeutic relationship factors in the context of individuals living with cancer is scant, and much more research is needed to determine the overall contribution of these four relationship elements to the outcomes of psychotherapeutic interventions for individuals living with cancer. Results of such studies could have important clinical and research implications. PMID:20006414

  11. Maintaining social cohesion is a more important determinant of patch residence time than maximizing food intake rate in a group-living primate, Japanese macaque (Macaca fuscata).

    PubMed

    Kazahari, Nobuko

    2014-04-01

    Animals have been assumed to employ an optimal foraging strategy (e.g., rate-maximizing strategy). In patchy food environments, intake rate within patches is positively correlated with patch quality, and declines as patches are depleted through consumption. This causes patch-leaving and determines patch residence time. In group-foraging situations, patch residence times are also affected by patch sharing. Optimal patch models for groups predict that patch residence times decrease as the number of co-feeding animals increases because of accelerated patch depletion. However, group members often depart patches without patch depletion, and their patch residence time deviates from patch models. It has been pointed out that patch residence time is also influenced by maintaining social proximity with others among group-living animals. In this study, the effects of maintaining social cohesion and that of rate-maximizing strategy on patch residence time were examined in Japanese macaques (Macaca fuscata). I hypothesized that foragers give up patches to remain in the proximity of their troop members. On the other hand, foragers may stay for a relatively long period when they do not have to abandon patches to follow the troop. In this study, intake rate and foraging effort (i.e., movement) did not change during patch residency. Macaques maintained their intake rate with only a little foraging effort. Therefore, the patches were assumed to be undepleted during patch residency. Further, patch residence time was affected by patch-leaving to maintain social proximity, but not by the intake rate. Macaques tended to stay in patches for short periods when they needed to give up patches for social proximity, and remained for long periods when they did not need to leave to keep social proximity. Patch-leaving and patch residence time that prioritize the maintenance of social cohesion may be a behavioral pattern in group-living primates.

  12. Unit Cohesion and the Surface Navy: Does Cohesion Affect Performance

    DTIC Science & Technology

    1989-12-01

    Relationship of Group Cohe- sion to Group Performance: A Research Integration Attempt, by L. W. Oliver, A199069, July 1988. Cartwright , D., "The Nature of...Group Cohesiveness," in Darwin Cart- wright and Alvin Zander, eds., Group Dynamics: Research and Theory, New York: Harper and Row, 1968. Gujarati, D. N

  13. Infants use relative numerical group size to infer social dominance

    PubMed Central

    Pun, Anthea; Birch, Susan A. J.; Baron, Andrew Scott

    2016-01-01

    Detecting dominance relationships, within and across species, provides a clear fitness advantage because this ability helps individuals assess their potential risk of injury before engaging in a competition. Previous research has demonstrated that 10- to 13-mo-old infants can represent the dominance relationship between two agents in terms of their physical size (larger agent = more dominant), whereas younger infants fail to do so. It is unclear whether infants younger than 10 mo fail to represent dominance relationships in general, or whether they lack sensitivity to physical size as a cue to dominance. Two studies explored whether infants, like many species across the animal kingdom, use numerical group size to assess dominance relationships and whether this capacity emerges before their sensitivity to physical size. A third study ruled out an alternative explanation for our findings. Across these studies, we report that infants 6–12 mo of age use numerical group size to infer dominance relationships. Specifically, preverbal infants expect an agent from a numerically larger group to win in a right-of-way competition against an agent from a numerically smaller group. In addition, this is, to our knowledge, the first study to demonstrate that infants 6–9 mo of age are capable of understanding social dominance relations. These results demonstrate that infants’ understanding of social dominance relations may be based on evolutionarily relevant cues and reveal infants’ early sensitivity to an important adaptive function of social groups. PMID:26884199

  14. Group-size distribution of skeins of wild geese

    NASA Astrophysics Data System (ADS)

    Hayakawa, Yoshinori; Furuhashi, Sho

    2012-09-01

    In appropriate situations, large populations of geese exhibit dynamical rearrangements by repeated mergers and splits among the groups. We describe the grouping process in terms of a mean-field model based on the Smoluchowski equation of coagulation with fragmentation and observationally plausible kernels. To verify our model, we conducted field observations on skeins of airborne geese, noting both the group-size distribution and the group-forming processes. We found that the group-size distribution we obtained in our field measurements could be represented by a fractional power function with an exponential cutoff. This function matches the asymptotic form of the steady-state solution of our model. Furthermore, we estimated the effective number of individuals involved in interactions by comparison of the model to our field data.

  15. Effect of Work Group Size and Task Size on Observers' Job Characteristics Ratings.

    ERIC Educational Resources Information Center

    Greenberg, Carl I.; And Others

    The Job Characteristics Model proposed by Hackman and his associates postulates that positive personal and work outcomes are derived from five core job dimensions: skill variety, task identity, task significance, autonomy, and feedback from the job. The effects of the number of workers (work group size) and the number of tasks (task size) on…

  16. Effect of Work Group Size and Task Size on Observers' Job Characteristics Ratings.

    ERIC Educational Resources Information Center

    Greenberg, Carl I.; And Others

    The Job Characteristics Model proposed by Hackman and his associates postulates that positive personal and work outcomes are derived from five core job dimensions: skill variety, task identity, task significance, autonomy, and feedback from the job. The effects of the number of workers (work group size) and the number of tasks (task size) on…

  17. Cohesion Research: Conceptual and Methodological Issues

    DTIC Science & Technology

    1990-09-01

    project. 17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse If necessary Mnd Identify by block number) FIELD GROUP SUB.GROUP Group cohesion ... Social psychology Cohesion measurement Forecasting Database 19, ABSTRACT (Continue on reverse if necesiary and Identify by block number) S A quantitative

  18. The effects of group selection harvest size on logging productivity

    Treesearch

    Curt C. Hassler; Shawn T. Grushecky; Chris B. LeDoux

    2000-01-01

    Because increasing demands are being placed on industry to harvest timber by aesthetically, economically, and ecologically acceptable means, we investigated the effects of a ground-based group selection harvest on logging productivity. Results show that size of opening had little or no effect on skidding productivity. However, significant skidder operator differences...

  19. Learning Together while Designing: Does Group Size Make a Difference?

    ERIC Educational Resources Information Center

    Apedoe, Xornam S.; Ellefson, Michelle R.; Schunn, Christian D.

    2012-01-01

    As the use of project-based learning becomes more frequent in the K-12 science classroom, and in chemistry classrooms in particular, teachers have begun to identify practical questions about implementation that should be addressed empirically. One such question concerns whether there is an ideal group size that fosters individual student…

  20. Learning Together while Designing: Does Group Size Make a Difference?

    ERIC Educational Resources Information Center

    Apedoe, Xornam S.; Ellefson, Michelle R.; Schunn, Christian D.

    2012-01-01

    As the use of project-based learning becomes more frequent in the K-12 science classroom, and in chemistry classrooms in particular, teachers have begun to identify practical questions about implementation that should be addressed empirically. One such question concerns whether there is an ideal group size that fosters individual student…

  1. Specialization and group size: brain and behavioural correlates of colony size in ants lacking morphological castes

    PubMed Central

    Amador-Vargas, Sabrina; Gronenberg, Wulfila; Wcislo, William T.; Mueller, Ulrich

    2015-01-01

    Group size in both multicellular organisms and animal societies can correlate with the degree of division of labour. For ants, the task specialization hypothesis (TSH) proposes that increased behavioural specialization enabled by larger group size corresponds to anatomical specialization of worker brains. Alternatively, the social brain hypothesis proposes that increased levels of social stimuli in larger colonies lead to enlarged brain regions in all workers, regardless of their task specialization. We tested these hypotheses in acacia ants (Pseudomyrmex spinicola), which exhibit behavioural but not morphological task specialization. In wild colonies, we marked, followed and tested ant workers involved in foraging tasks on the leaves (leaf-ants) and in defensive tasks on the host tree trunk (trunk-ants). Task specialization increased with colony size, especially in defensive tasks. The relationship between colony size and brain region volume was task-dependent, supporting the TSH. Specifically, as colony size increased, the relative size of regions within the mushroom bodies of the brain decreased in trunk-ants but increased in leaf-ants; those regions play important roles in learning and memory. Our findings suggest that workers specialized in defence may have reduced learning abilities relative to leaf-ants; these inferences remain to be tested. In societies with monomorphic workers, brain polymorphism enhanced by group size could be a mechanism by which division of labour is achieved. PMID:25567649

  2. Specialization and group size: brain and behavioural correlates of colony size in ants lacking morphological castes.

    PubMed

    Amador-Vargas, Sabrina; Gronenberg, Wulfila; Wcislo, William T; Mueller, Ulrich

    2015-02-22

    Group size in both multicellular organisms and animal societies can correlate with the degree of division of labour. For ants, the task specialization hypothesis (TSH) proposes that increased behavioural specialization enabled by larger group size corresponds to anatomical specialization of worker brains. Alternatively, the social brain hypothesis proposes that increased levels of social stimuli in larger colonies lead to enlarged brain regions in all workers, regardless of their task specialization. We tested these hypotheses in acacia ants (Pseudomyrmex spinicola), which exhibit behavioural but not morphological task specialization. In wild colonies, we marked, followed and tested ant workers involved in foraging tasks on the leaves (leaf-ants) and in defensive tasks on the host tree trunk (trunk-ants). Task specialization increased with colony size, especially in defensive tasks. The relationship between colony size and brain region volume was task-dependent, supporting the TSH. Specifically, as colony size increased, the relative size of regions within the mushroom bodies of the brain decreased in trunk-ants but increased in leaf-ants; those regions play important roles in learning and memory. Our findings suggest that workers specialized in defence may have reduced learning abilities relative to leaf-ants; these inferences remain to be tested. In societies with monomorphic workers, brain polymorphism enhanced by group size could be a mechanism by which division of labour is achieved.

  3. Towards Understanding Terrorism: A Theoretical Examination of Internal Cohesion in Terrorist Groups and the Negative Dynamic of Violence.

    DTIC Science & Technology

    1995-03-01

    Terrorism, like other forms of political violence, has an organizational context. Few studies, however, have considered the influence of...organizational life upon the outward behavior of the terrorist group. This thesis explores the possibility that terrorism, in addition to its political context...oftentimes be dictated more by the need to satisfy the internal goal of group survival than to directly further the group’s external political agenda

  4. [Mechanisms in group formation and cohesion in Tupaia glis Diard, 1820. Results of long-term studies of a family group].

    PubMed

    Richarz, K

    1979-10-01

    aggressive gesture with their offspring of the same sex, is regarded as the time of reaching sexual maturity. A longer lasting integration of a female offspring (and a male) is described. The social organization of Tupaia glis is based on a permanent pair bonding. Through the addition of the young, a parental family with a maximum of two generations of brothers and sisters can arise. Limiting factors of the group size are incest barriers, a density stress, and the possibilities of communication of the species themselves.

  5. Prevalence of tooth-size discrepancy among different malocclusion groups.

    PubMed

    Laino, Alberto; Quaremba, Giuseppe; Paduano, Sergio; Stanzione, Simona

    2003-01-01

    This study was designed to estimate the prevalence of tooth-size discrepancy as a factor of skeletal malocclusion in the orthodontic patient population of the Campania region. The study employed the pretreatment models of 94 patients. The mesiodistal diameters of teeth were measured by digital electronic calipers (accurate to 0.01 mm) and Bolton's indices were calculated. The sample was grouped into three malocclusion groups based on the values of Steiner cephalometric analysis. Multiple regression analysis data indicated a significant linear relationship (r2 = 0.99, P = 0.0000) for Bolton's posterior, anterior and total indices. The discriminant multivariate analysis, based on stepwise Wilke's lambda, revealed five variables capable of classifying 88.6% of the sample in the four malocclusion groups. As no relationship between the four groups identified by the discriminant analysis and the types of skeletal malocclusions exists, it was unequivocally concluded that there is no evidence of any predisposition for a tooth-size discrepancy in any of the malocclusion groups.

  6. Parietal cortex mediates perceptual Gestalt grouping independent of stimulus size.

    PubMed

    Grassi, Pablo R; Zaretskaya, Natalia; Bartels, Andreas

    2016-06-01

    The integration of local moving elements into a unified gestalt percept has previously been linked to the posterior parietal cortex. There are two possible interpretations for the lack of involvement of other occipital regions. The first is that parietal cortex is indeed uniquely functionally specialized to perform grouping. Another possibility is that other visual regions can perform grouping as well, but that the large spatial separation of the local elements used previously exceeded their neurons' receptive field (RF) sizes, preventing their involvement. In this study we distinguished between these two alternatives. We measured whole-brain activity using fMRI in response to a bistable motion illusion that induced mutually exclusive percepts of either an illusory global Gestalt or of local elements. The stimulus was presented in two sizes, a large version known to activate IPS only, and a version sufficiently small to fit into the RFs of mid-level dorsal regions such as V5/MT. We found that none of the separately localized motion regions apart from parietal cortex showed a preference for global Gestalt perception, even for the smaller version of the stimulus. This outcome suggests that grouping-by-motion is mediated by a specialized size-invariant mechanism with parietal cortex as its anatomical substrate.

  7. The impact of cohesive groups in the trauma recovery context: police spouse survivors and duty-related death.

    PubMed

    Violanti, J M

    1996-04-01

    This paper examines the impact of surviving spouse social interactions on psychological distress following the death of a police officer. It was hypothesized that satisfactory interactions within the police work group would lower distress, and unsatisfactory interactions outside the police environment (justice system, media, community persons) would increase distress. Results indicated that increased quality of interaction with police groups lowered psychological distress scores. Despite increased satisfaction with groups outside of policing, spouse's distress still increased, suggesting that satisfaction with and support by police groups appears to ameliorate distress more effectively than others. These findings suggest that police agencies and personnel may be helpful to surviving spouses after the death of an officer and should formulate policy to provide long term contact and assistance.

  8. Mountain gorilla ranging patterns: influence of group size and group dynamics.

    PubMed

    Caillaud, Damien; Ndagijimana, Felix; Giarrusso, Anthony J; Vecellio, Veronica; Stoinski, Tara S

    2014-08-01

    Since the 1980s, the Virunga mountain gorilla population has almost doubled, now reaching 480 individuals living in a 430-km(2) protected area. Analysis of the gorillas' ranging patterns can provide critical information on the extent and possible effects of competition for food and space. We analyzed 12 years of daily ranging data and inter-group encounter data collected on 11 gorilla groups monitored by the Karisoke Research Center in Rwanda. During that period, the study population increased in size by almost 50% and the number of groups tripled. Groups had small yearly home ranges compared to other known gorilla populations, with an average 90% kernel density estimate of 8.07 km2 and large between-group variations (3.17-23.59 km2). Most groups had consistent home range location over the course of the study but for some, we observed gradual range shifts of up to 4 km. Neighboring groups displayed high home range overlap, which increased dramatically after the formation of new groups. On average, each group used only 28.6% of its 90% kernel home range exclusively, and in some areas up to six different groups had overlapping home ranges with little or no exclusive areas. We found a significant intra-group positive relationship between the number of weaned individuals in a group and the home range size, but the fitted models only explained 17.5% and 13.7% of the variance in 50% and 90% kernel home range size estimates, respectively. This suggests that despite the increase in size, the study population is not yet experiencing marked effects of feeding competition. However, the increase in home range overlap resulting from the formation of new groups led to a sixfold increase in the frequency of inter-group encounters, which exposes the population to elevated risks of fight-related injuries and infanticide.

  9. Metastable structures and size effects in small group dynamics.

    PubMed

    Lauro Grotto, Rosapia; Guazzini, Andrea; Bagnoli, Franco

    2014-01-01

    In his seminal works on group dynamics Bion defined a specific therapeutic setting allowing psychoanalytic observations on group phenomena. In describing the setting he proposed that the group was where his voice arrived. This physical limit was later made operative by assuming that the natural dimension of a therapeutic group is around 12 people. Bion introduced a theory of the group aspects of the mind in which proto-mental individual states spontaneously evolve into shared psychological states that are characterized by a series of features: (1) they emerge as a consequence of the natural tendency of (both conscious and unconscious) emotions to combine into structured group patterns; (2) they have a certain degree of stability in time; (3) they tend to alternate so that the dissolution of one is rapidly followed by the emergence of another; (4) they can be described in qualitative terms according to the nature of the emotional mix that dominates the state, in structural terms by a kind of typical "leadership" pattern, and in "cognitive" terms by a set of implicit expectations that are helpful in explaining the group behavior (i.e., the group behaves "as if" it was assuming that). Here we adopt a formal approach derived from Socio-physics in order to explore some of the structural and dynamic properties of this small group dynamics. We will described data from an analytic DS model simulating small group interactions of agents endowed with a very simplified emotional and cognitive dynamic in order to assess the following main points: (1) are metastable collective states allowed to emerge in the model and if so, under which conditions in the parameter space? (2) can these states be differentiated in structural terms? (3) to what extent are the emergent dynamic features of the systems dependent of the system size? We will finally discuss possible future applications of the quantitative descriptions of the interaction structure in the small group clinical setting.

  10. Metastable structures and size effects in small group dynamics

    PubMed Central

    Lauro Grotto, Rosapia; Guazzini, Andrea; Bagnoli, Franco

    2014-01-01

    In his seminal works on group dynamics Bion defined a specific therapeutic setting allowing psychoanalytic observations on group phenomena. In describing the setting he proposed that the group was where his voice arrived. This physical limit was later made operative by assuming that the natural dimension of a therapeutic group is around 12 people. Bion introduced a theory of the group aspects of the mind in which proto-mental individual states spontaneously evolve into shared psychological states that are characterized by a series of features: (1) they emerge as a consequence of the natural tendency of (both conscious and unconscious) emotions to combine into structured group patterns; (2) they have a certain degree of stability in time; (3) they tend to alternate so that the dissolution of one is rapidly followed by the emergence of another; (4) they can be described in qualitative terms according to the nature of the emotional mix that dominates the state, in structural terms by a kind of typical “leadership” pattern, and in “cognitive” terms by a set of implicit expectations that are helpful in explaining the group behavior (i.e., the group behaves “as if” it was assuming that). Here we adopt a formal approach derived from Socio-physics in order to explore some of the structural and dynamic properties of this small group dynamics. We will described data from an analytic DS model simulating small group interactions of agents endowed with a very simplified emotional and cognitive dynamic in order to assess the following main points: (1) are metastable collective states allowed to emerge in the model and if so, under which conditions in the parameter space? (2) can these states be differentiated in structural terms? (3) to what extent are the emergent dynamic features of the systems dependent of the system size? We will finally discuss possible future applications of the quantitative descriptions of the interaction structure in the small group clinical

  11. [Nutritional support groups at a hospital setting. Size, composition, relationships and actions].

    PubMed

    Santana Porbén, S; Barreto Penié, J

    2007-01-01

    The hospital Nutricional Support Group (NSG) represents the ultimate step in the evolution of the forms of provision of nutritional and feeding care to hospitalized patients. The NSG outdoes other preceeding forms for its harmony and cohesion among its members, the multi-, inter- and transdisciplinarity, the dedication to the activity on a full time basis, and the capability to self-finance by means of the savings derived from the implementation of a nutritional policy consistent with the Good Practices of Feeding and Nutrition. It is to be expected that the inception and operation of a NSG in a hospital environment allows the realization of the benefits embedded into the Metabolic, Nutritional and Feeding Intervention Programs. Guidelines and recommendations for the definition of the size and composition of an hospital NSG are presented in this article, along with the responsabilities, functions and tasks to be assumed by its members, and a timetable for its implementation, always from the experiencies of the authors after conducting a NSG in a tertiary-care hospital in Havana (Cuba).

  12. Group size adjustment to ecological demand in a cooperative breeder.

    PubMed

    Zöttl, Markus; Frommen, Joachim G; Taborsky, Michael

    2013-04-07

    Environmental factors can determine which group size will maximize the fitness of group members. This is particularly important in cooperative breeders, where group members often serve different purposes. Experimental studies are yet lacking to check whether ecologically mediated need for help will change the propensity of dominant group members to accept immigrants. Here, we manipulated the perceived risk of predation for dominant breeders of the cooperatively breeding cichlid fish Neolamprologus pulcher to test their response to unrelated and previously unknown immigrants. Potential immigrants were more readily accepted if groups were exposed to fish predators or egg predators than to herbivorous fish or control situations lacking predation risk. Our data are consistent with both risk dilution and helping effects. Egg predators were presented before spawning, which might suggest that the fish adjust acceptance rates also to a potential future threat. Dominant group members of N. pulcher apparently consider both present and future need of help based on ecological demand. This suggests that acceptance of immigrants and, more generally, tolerance of group members on demand could be a widespread response to ecological conditions in cooperatively breeding animals.

  13. Group size adjustment to ecological demand in a cooperative breeder

    PubMed Central

    Zöttl, Markus; Frommen, Joachim G.; Taborsky, Michael

    2013-01-01

    Environmental factors can determine which group size will maximize the fitness of group members. This is particularly important in cooperative breeders, where group members often serve different purposes. Experimental studies are yet lacking to check whether ecologically mediated need for help will change the propensity of dominant group members to accept immigrants. Here, we manipulated the perceived risk of predation for dominant breeders of the cooperatively breeding cichlid fish Neolamprologus pulcher to test their response to unrelated and previously unknown immigrants. Potential immigrants were more readily accepted if groups were exposed to fish predators or egg predators than to herbivorous fish or control situations lacking predation risk. Our data are consistent with both risk dilution and helping effects. Egg predators were presented before spawning, which might suggest that the fish adjust acceptance rates also to a potential future threat. Dominant group members of N. pulcher apparently consider both present and future need of help based on ecological demand. This suggests that acceptance of immigrants and, more generally, tolerance of group members on demand could be a widespread response to ecological conditions in cooperatively breeding animals. PMID:23390105

  14. Group demographics in the mental patient movement: group location, age, and size as structural factors.

    PubMed

    Emerick, R E

    1989-01-01

    This paper presents a descriptive overview of the mental patient selfhelp movement based on a sample of 104 groups. Groups are classified in terms of group structure, group affiliation, and evaluation of psychiatry and are then described in a demographic profile that includes the factors of location, age and size. After a review of the literature on functional models of selfhelp groups, the mental patient movement is shown to be composed of groups with widely varying political philosophies-from radical "separatist" groups promoting consciousness-raising, empowerment, and social reform to conservative "partnership" groups that emphasize individual reform through "alternative therapy". The movement is shown to be increasingly dominated by moderate "supportive" groups and, as such, is characterized as a true client-controlled social or "community" alternative to the professionally-controlled medical programs that dominate the mental health system today.

  15. The Impact of Synchronization on the Group Size

    NASA Astrophysics Data System (ADS)

    Dostálková, Iva; Dostálek, Libor

    2011-09-01

    For groups of animals to keep together, the group members have to perform switches between two types of behaviours (staying in one place or moving to another place) in synchrony ([1]). However, synchronization imposes a cost on individual animal, because animal is trying to keep its ideal switch time point that is generally not equal to common time of synchronization. We suppose that each animal is defined by this individual ideal switch time. The distribution of ideal time points is derived from normal distribution with zero mean. The density function is positive on finite interval (-1, 1). Maximization of individual benefit across the parameter space results in three types of optimal behaviours: 1) Non-synchronized switch - that defines individual switch independent on the group of animals. Switch points are ideal individual points. 2) Totally synchronized switch — all animals in the group are synchronized. 3) Partially synchronized switch — only the part of the group is synchronized ([2]). In the context of the degree of synchronization the splitting of the group is very important ([3], [4]). In the case of partially synchronized switch the non-synchronized rest of the group will stay in place. The first question is concerned in the comparison of the benefits for one and two partially synchronized switches. We analysed this problem for simplified symmetric case. Here the benefit for one switch is higher. After it we concentrated on the problem of the second departure of the rest of the group of animals and on possible stabilization of the group size.

  16. Cohesiveness and Performance on an Additive Task: Evidence for Multidimensionality.

    ERIC Educational Resources Information Center

    Zaccaro, Stephen J.; Lowe, Charles A.

    1988-01-01

    Presents a study designed to contrast the effects of task-based and interpersonal cohesiveness on group performance of students. Concludes that high task cohesion helped group performance, while interpersonal attraction had no apparent effect. Finding that increased interpersonal cohesion improved task commitment, the authors suggest that…

  17. Overestimation of the effect size in group sequential trials.

    PubMed

    Zhang, Jenny J; Blumenthal, Gideon M; He, Kun; Tang, Shenghui; Cortazar, Patricia; Sridhara, Rajeshwari

    2012-09-15

    Group sequential designs (GSD), which provide for interim monitoring of efficacy data and allow potential early trial termination while preserving the type I error rate, have become commonplace in oncology clinical trials. Although ethically appealing, GSDs tend to overestimate the true treatment effect size at early interim analyses. Overestimation of the treatment effect may exaggerate the benefit of a drug and provide imprecise information for physicians and their patients about a drug's true effect. The cause and effect of such a phenomenon are generally not well understood by many in clinical trial practice. In this article, we provide a graphical explanation for why the phenomenon of overestimation in GSDs occurs. The potential overestimation of the magnitude of the treatment effect is of particular concern in oncology, in which the more subjective endpoint of progression-free survival has increasingly been adopted as the primary endpoint in pivotal phase III trials. ©2012 AACR.

  18. The demographic benefits of belligerence and bravery: defeated group repopulation or victorious group size expansion?

    PubMed

    Lehmann, Laurent

    2011-01-01

    Intraspecific coalitional aggression between groups of individuals is a widespread trait in the animal world. It occurs in invertebrates and vertebrates, and is prevalent in humans. What are the conditions under which coalitional aggression evolves in natural populations? In this article, I develop a mathematical model delineating conditions where natural selection can favor the coevolution of belligerence and bravery between small-scale societies. Belligerence increases an actor's group probability of trying to conquer another group and bravery increase the actors's group probability of defeating an attacked group. The model takes into account two different types of demographic scenarios that may lead to the coevolution of belligerence and bravery. Under the first, the fitness benefits driving the coevolution of belligerence and bravery come through the repopulation of defeated groups by fission of victorious ones. Under the second demographic scenario, the fitness benefits come through a temporary increase in the local carrying capacity of victorious groups, after transfer of resources from defeated groups to victorious ones. The analysis of the model suggests that the selective pressures on belligerence and bravery are stronger when defeated groups can be repopulated by victorious ones. The analysis also suggests that, depending on the shape of the contest success function, costly bravery can evolve in groups of any size.

  19. Traversing the Lexical Cohesion Minefield

    ERIC Educational Resources Information Center

    McGee, Iain

    2009-01-01

    When teachers hear the word "cohesion", they usually think of grammatical cohesion--an aspect of cohesion reasonably well covered in student books and teacher materials. However, occupying an area that straddles both lexis "proper" and cohesion lies "lexical cohesion". In what follows, it is argued that the teaching and learning of certain aspects…

  20. Group size of a permanent large group of agile mangabeys (Cercocebus agilis) at Bai Hokou, Central African Republic.

    PubMed

    Devreese, Lieven; Huynen, Marie-Claude; Stevens, Jeroen M G; Todd, Angelique

    2013-01-01

    White-eyelid mangabeys (genus Cercocebus) live in groups of highly variable size. Because of their semi-terrestrial behaviour and preference for dense forest habitats, re-liable data on group size are scarce. During a 5-month study, we collected 17 group counts on a habituated group of agile mangabeys (C. agilis) at Bai Hokou in the Central African Republic. We found a stable group size of approximately 135 individuals. This permanent large grouping pattern is known to occur among several populations of white-eyelid mangabeys and is congruent with extreme group sizes reported in mandrills at Lopé in Gabon.

  1. Group size, individual role differentiation and effectiveness of cooperation in a homogeneous group of hunters

    PubMed Central

    Escobedo, R.; Muro, C.; Spector, L.; Coppinger, R. P.

    2014-01-01

    The emergence of cooperation in wolf-pack hunting is studied using a simple, homogeneous, particle-based computational model. Wolves and prey are modelled as particles that interact through attractive and repulsive forces. Realistic patterns of wolf aggregation readily emerge in numerical simulations, even though the model includes no explicit wolf–wolf attractive forces, showing that the form of cooperation needed for wolf-pack hunting can take place even among strangers. Simulations are used to obtain the stationary states and equilibria of the wolves and prey system and to characterize their stability. Different geometric configurations for different pack sizes arise. In small packs, the stable configuration is a regular polygon centred on the prey, while in large packs, individual behavioural differentiation occurs and induces the emergence of complex behavioural patterns between privileged positions. Stable configurations of large wolf-packs include travelling and rotating formations, periodic oscillatory behaviours and chaotic group behaviours. These findings suggest a possible mechanism by which larger pack sizes can trigger collective behaviours that lead to the reduction and loss of group hunting effectiveness, thus explaining the observed tendency of hunting success to peak at small pack sizes. They also explain how seemingly complex collective behaviours can emerge from simple rules, among agents that need not have significant cognitive skills or social organization. PMID:24694897

  2. Diversity and Social Cohesion

    ERIC Educational Resources Information Center

    Pagani, Camilla

    2014-01-01

    The issue of diversity, in its broadest sense, is discussed here in its relation to social cohesion, cross-cultural relations, ingroup-outgroup relations and educational interventions. The main thesis of the paper is that real social cohesion in an ingroup rests on the acknowledgment of and the dialog with the diversities of the members of the…

  3. Cohesion Is Not Coherence.

    ERIC Educational Resources Information Center

    Carrell, Patricia L.

    1982-01-01

    The concept of cohesion as a measure of a text's coherence is criticized in light of theoretical and empirical research on schema theory. Second-language teachers are cautioned not to expect cohesion theory to be the solution to ESL reading and writing coherence problems at the text level. (Author/MSE)

  4. Diversity and Social Cohesion

    ERIC Educational Resources Information Center

    Pagani, Camilla

    2014-01-01

    The issue of diversity, in its broadest sense, is discussed here in its relation to social cohesion, cross-cultural relations, ingroup-outgroup relations and educational interventions. The main thesis of the paper is that real social cohesion in an ingroup rests on the acknowledgment of and the dialog with the diversities of the members of the…

  5. Temperature Effect on Suspended Cohesive Sediment Concentration

    NASA Astrophysics Data System (ADS)

    Ramalingam, S.; Chandra, V.

    2016-12-01

    The deposition of suspended cohesive sediments takes place in the form of flocculation which is governed by flow and sediment characteristics. Suspended cohesive sediments adsorb contaminants from surrounding environment during their transport from river to the ocean. These sediments partially settle at low velocity regions along the river and huge amount of sediments settle at the estuaries. The settled sediments affect both biological and chemical dynamics of aquatic environment. Hence, it is important to understand the behaviour of suspended cohesive sediments under different flow and sediment conditions. Temperature is one such parameter which influences the flow behaviour. In literature, the effect of water temperature on the behaviour of suspended cohesive sediments has received very little attention. Research studies based on settling column experiments have stated that cohesive sediment settling velocity increases with an increase of water temperature. In contrary, annular flume based studies have reported that the settling velocity increases with decrease of water temperature. Hence, this research work is mainly focussed to find the effect of temperature on suspended cohesive sediment concentration. Experiments are conducted at high water temperatures (30°, 40° and 50°C) in an annular flume using Kaolin (d50=7.9μm) at different bed shear stresses (0.01, 0.05 and 0.1Pa) and concentrations (1, 2 and 4g/L). Ionized water is used for conducting the experiments. The temporal variation of suspended cohesive sediment concentration and corresponding mean floc size are reported.

  6. Rotation Induced Disruption of Cohesive Asteroids

    NASA Astrophysics Data System (ADS)

    Sanchez Lana, Diego; Scheeres, D. J.

    2013-10-01

    We use a Soft-Sphere Discrete Element Method (SSDEM) code to study the evolution of self-gravitating cohesive granular aggregates that are spun to disruption as a proxy to "rubble-pile" asteroids. Calculations have shown that the fine regolith in asteroids and molecular Van der Waals forces together may act as a cohesive matrix that provides enough structural strength to hold small NEAs together even at the observed high spin rates. With this in mind we have implemented cohesive forces between the large 10 m) particles that form our aggregates; its strength being controlled by the mean particle size of the matrix. The addition of rolling friction also has allowed us to obtain cohesionless aggregates with friction angles of at least 35° as measured by the Drucker-Prager yield criterion. A series of experiments were run with the code, keeping the size, density and number of grains constant while increasing the cohesive strength of the matrix holding the grains in place. It can be shown, through a scaling analysis, that when the cohesive strength between rubble pile components is increased by a factor of f, that the effective size of the asteroid being modeled will decrease by a factor of 1/√f. To evaluate this we ran a series of 12 cases with increasing cohesive strength, effectively modeling rubble piles of size from 0.1 km up to 100 km with a constant cohesive strength of 25 Pa. Some of our main results are as follows: 1. results from simulations are compatible with a simple model of asteroid strength that predicts, in the cohesion dominated case, that the spin rate for fission is inversely proportional to the size of the asteroid; 2. aggregates may disrupt by shedding or fission, depending on the cohesive strength and the size of the aggregate (shape and heterogeneity factors have not yet been considered); 3. disruption by fission is more likely for small aggregates than for larger aggregates with the same cohesive strength. Further results with spherical and a

  7. Fracture reveals clustering in cohesive granular matter

    NASA Astrophysics Data System (ADS)

    Tapia, Franco; Santucci, Stéphane; Géminard, Jean-Christophe

    2016-09-01

    We report an experimental study of the morphology of fractures in cohesive granular materials. Cohesion is introduced by equilibrating the grains with a humid atmosphere. The setup allows to produce a controlled crack in a thin layer of a glass beads assembly, and observe with an extremely high resolution the edge of the fracture at the free surface of the layer. The detailed multi-scale analysis of the fracture profile reveals the presence, in the bulk of the material, of clusters of grains whose size increases monotonically with the relative humidity. These results are important because the formation of clusters, resulting in a heterogeneity of the cohesion force, governs the mechanical properties of cohesive granular matter in contact with a humid atmosphere.

  8. Coagulation-Fragmentation Model for Animal Group-Size Statistics

    NASA Astrophysics Data System (ADS)

    Degond, Pierre; Liu, Jian-Guo; Pego, Robert L.

    2016-10-01

    We study coagulation-fragmentation equations inspired by a simple model proposed in fisheries science to explain data for the size distribution of schools of pelagic fish. Although the equations lack detailed balance and admit no H-theorem, we are able to develop a rather complete description of equilibrium profiles and large-time behavior, based on recent developments in complex function theory for Bernstein and Pick functions. In the large-population continuum limit, a scaling-invariant regime is reached in which all equilibria are determined by a single scaling profile. This universal profile exhibits power-law behavior crossing over from exponent -2/3 for small size to -3/2 for large size, with an exponential cutoff.

  9. Coagulation-Fragmentation Model for Animal Group-Size Statistics

    NASA Astrophysics Data System (ADS)

    Degond, Pierre; Liu, Jian-Guo; Pego, Robert L.

    2017-04-01

    We study coagulation-fragmentation equations inspired by a simple model proposed in fisheries science to explain data for the size distribution of schools of pelagic fish. Although the equations lack detailed balance and admit no H-theorem, we are able to develop a rather complete description of equilibrium profiles and large-time behavior, based on recent developments in complex function theory for Bernstein and Pick functions. In the large-population continuum limit, a scaling-invariant regime is reached in which all equilibria are determined by a single scaling profile. This universal profile exhibits power-law behavior crossing over from exponent -2/3 for small size to -3/2 for large size, with an exponential cutoff.

  10. Validation of French and German versions of a Perceived Neighborhood Social Cohesion Questionnaire among young Swiss males, and its relationship with substance use.

    PubMed

    Dupuis, Marc; Studer, Joseph; Henchoz, Yves; Deline, Stéphane; Baggio, Stéphanie; N'Goran, Alexandra; Mohler-Kuo, Meichun; Gmel, Gerhard

    2016-02-01

    This study main purpose was the validation of both French and German versions of a Perceived Neighborhood Social Cohesion Questionnaire. The sample group comprised 5065 Swiss men from the "Cohort Study on Substance Use Risk Factors." Multigroup Confirmatory factor analysis showed that a three-factor model fits the data well, which substantiates the generalizability of Perceived Neighborhood Social Cohesion Questionnaire factor structure, regardless of the language. The Perceived Neighborhood Social Cohesion Questionnaire demonstrated excellent homogeneity (α = 95) and split-half reliability (r = .96). The Perceived Neighborhood Social Cohesion Questionnaire was sensitive to community size and participants' financial situation, confirming that it also measures real social conditions. Finally, weak but frequent correlations between Perceived Neighborhood Social Cohesion Questionnaire and alcohol, cigarette, and cannabis dependence were measured.

  11. Grouping for reading instruction: does one size fit all?

    PubMed

    Schumm, J S; Moody, S W; Vaughn, S

    2000-01-01

    Twenty-nine third-grade teachers and selected students from their classes participated. Study 1 used teacher interviews and classroom observations to examine teachers' perceptions and practices for grouping for reading instruction; Study 2 examined the impact of these grouping practices on the academic progress, social progress, and attitudes about reading of students representing a range of achievement levels, including students with learning disabilities. Results indicated that, overall, teachers used whole class instruction for reading and the same materials for all students, including students with learning disabilities. Students with learning disabilities made little academic progress and their attitudes about reading did not improve over time.

  12. Perception of Groups, Size of Opposition, and Social Influence

    ERIC Educational Resources Information Center

    Wilder, David A.

    1977-01-01

    Two experiments investigated the relationship between social influence and the number of persons attempting influence. Findings suggest that the manner in which persons are initially organized into groups and aggregates of individuals affects their persuasive impact on observers. (Editor/RK)

  13. Intergroup Discrimination in Positive and Negative Outcome Allocations: Impact of Stimulus Valence, Relative Group Status, and Relative Group Size.

    ERIC Educational Resources Information Center

    Otten, Sabine; And Others

    1996-01-01

    Three studies investigated the determination of social discrimination by the valence of stimuli that are allocated between groups. The studies were based on either the minimal group paradigm or a more reality-based laboratory intergroup setting, with stimulus valence, group status, and group size as factors and with pull scores on Tajfel matrices…

  14. Size of the Group IVA Iron Meteorite Parent Body

    NASA Astrophysics Data System (ADS)

    Moskovitz, N.; Walker, R.

    2011-10-01

    The group IVA fractionally crystallized iron meteorites display a diverse range of metallographic cooling rates, ranging from 100 - 6600 K/Myr [1]. These have been attributed to their formation in a metallic core, ˜150 km in radius that cooled to crystallization without any appreciable insulating mantle. Such an exposed core may have resulted from a hit-and-run collision [2] between two large (˜ 103 km) protoplanetary bodies. Here we build upon this formation scenario by incorporating several new constraints. These include (i) a recent U-Pb radiometric closure age of 4565.3 Mya (<2.5 Myr after CAIs) for the group IVA iron Muonionalusta [3], (ii) new measurements and modeling of highly siderophile element compositions for a suite of IVAs, and (iii) consideration of the thermal effects of heating by the decay of the short-lived radionuclide 60Fe.

  15. Written cohesion in children with and without language learning disabilities.

    PubMed

    Koutsoftas, Anthony D; Petersen, Victoria

    2017-09-01

    Cohesion refers to the linguistic elements of discourse that contribute to its continuity and is an important element to consider as part of written language intervention, especially in children with language learning disabilities (LLD). There is substantial evidence that children with LLD perform more poorly than typically developing (TD) peers on measures of cohesion in spoken language and on written transcription measures; however, there is far less research comparing groups on cohesion as a measure of written language across genres. The current study addresses this gap through the following two aims. First, to describe and compare cohesion in narrative and expository writing samples of children with and without language learning disabilities. Second, to relate measures of cohesion to written transcription and translation measures, oral language, and writing quality. Fifty intermediate-grade children produced one narrative and one expository writing sample from which measures of written cohesion were obtained. These included the frequency, adequacy and complexity of referential and conjunctive ties. Expository samples resulted in more complex cohesive ties and children with TD used more complex ties than peers with LLD. Different relationships among cohesion measures and writing were observed for narrative verse expository samples. Findings from this study demonstrate cohesion as a discourse-level measure of written transcription and how the use of cohesion can vary by genre and group (LLD, TD). Clinical implications for assessment, intervention, and future research are provided. © 2016 Royal College of Speech and Language Therapists.

  16. Unit Cohesion and the Impact of DADT

    DTIC Science & Technology

    2010-01-01

    Construct Relations,” Journal of Applied Psychology 88, no. 6 (December 2003): 989. See also Dorwin Cartwright , “The Nature of Group Cohesiveness...in Dorwin Cartwright and Alvin Zander, eds., Group Dynamics: Research and Theory, 3d ed. (New York: Harper and Row, 1968); and James H. Davis, Group

  17. Density-Dependent Effects on Group Size Are Sex-Specific in a Gregarious Ungulate

    PubMed Central

    Vander Wal, Eric; van Beest, Floris M.; Brook, Ryan K.

    2013-01-01

    Density dependence can have marked effects on social behaviors such as group size. We tested whether changes in population density of a large herbivore (elk, Cervus canadensis) affected sex-specific group size and whether the response was density- or frequency-dependent. We quantified the probability and strength of changes in group sizes and dispersion as population density changed for each sex. We used group size data from a population of elk in Manitoba, Canada, that was experimentally reduced from 1.20 to 0.67 elk/km2 between 2002 and 2009. Our results indicated that functional responses of group size to population density are sex-specific. Females showed a positive density-dependent response in group size at population densities ≥0.70 elk/km2 and we found evidence for a minimum group size at population density ≤0.70 elk/km2. Changes in male group size were also density-dependent; however, the strength of the relationship was lower than for females. Density dependence in male group size was predominantly a result of fusion of solitary males into larger groups, rather than fusion among existing groups. Our study revealed that density affects group size of a large herbivore differently between males and females, which has important implications for the benefits e.g., alleviating predation risk, and costs of social behaviors e.g., competition for resources and mates, and intra-specific pathogen transmission. PMID:23326502

  18. Density-dependent effects on group size are sex-specific in a gregarious ungulate.

    PubMed

    Vander Wal, Eric; van Beest, Floris M; Brook, Ryan K

    2013-01-01

    Density dependence can have marked effects on social behaviors such as group size. We tested whether changes in population density of a large herbivore (elk, Cervus canadensis) affected sex-specific group size and whether the response was density- or frequency-dependent. We quantified the probability and strength of changes in group sizes and dispersion as population density changed for each sex. We used group size data from a population of elk in Manitoba, Canada, that was experimentally reduced from 1.20 to 0.67 elk/km(2) between 2002 and 2009. Our results indicated that functional responses of group size to population density are sex-specific. Females showed a positive density-dependent response in group size at population densities ≥0.70 elk/km(2) and we found evidence for a minimum group size at population density ≤0.70 elk/km(2). Changes in male group size were also density-dependent; however, the strength of the relationship was lower than for females. Density dependence in male group size was predominantly a result of fusion of solitary males into larger groups, rather than fusion among existing groups. Our study revealed that density affects group size of a large herbivore differently between males and females, which has important implications for the benefits e.g., alleviating predation risk, and costs of social behaviors e.g., competition for resources and mates, and intra-specific pathogen transmission.

  19. A community based intervention program to enhance neighborhood cohesion: The Learning Families Project in Hong Kong.

    PubMed

    Shen, Chen; Wan, Alice; Kwok, Lit Tung; Pang, Sally; Wang, Xin; Stewart, Sunita M; Lam, Tai Hing; Chan, Sophia S

    2017-01-01

    Neighborhood cohesion, which refers to the extent of the connectedness and solidarity among residents in a community or neighborhood, is an important determinant of human health. To enhance neighborhood cohesion, the "Learning Families Project" was developed with a series of intervention programs in Kwun Tong in Hong Kong, a district with low neighborhood cohesion. This project, based on the social ecological model, provided a platform for neighbors to learn, communicate and interact with each other. This quasi-experimental study included two nearby government subsidized low rent housing estates separated by busy main roads. One served as the intervention (Tsui Ping (South) Estate) and one as the control (Shun Tin Estate) estate. The intervention included promotion, resident training and learning programs, embodied by a series of community activities such as talks, day camp, thematic activities and horticulture class. Baseline (before the programs) and follow-up (one year after the programs) surveys were conducted both in the intervention and control estate to assess the impact of the programs on neighborhood cohesion. The number of residents who completed both the baseline and follow-up surveys was 502 in the intervention estate and 476 in the control estate. Neighborhood cohesion significantly improved in the intervention group after the programs (Cohen effect size d: 0.15). Compared with the control group, the improvements in closeness of the neighborhood and trust in neighbors were significantly greater in the intervention group (Cohen effect size d: 0.13 and 0.14, respectively). This brief intervention program using a quasi-experimental study design increased neighborhood cohesion in a low rent housing estate. ClinicalTrials.gov NCT02851667.

  20. The association between status and cohesion in sport teams.

    PubMed

    Jacob, C S; Carron, A V

    1998-02-01

    The main objective of this study was to establish the relationship between perceptions of status attributes and cohesion and status ranking and cohesion. A secondary aim was to determine whether age (operationalized by scholastic levels) or culture serves as a moderator in the relationship between either status attributes or status ranking and cohesion. Another secondary aim was to determine if differences are present in the importance attached by athletes to status attributes. Canadian and Indian athletes were tested. Although perceptions of the importance of status attributes and cohesiveness were related, the effect size was small (Green, 1991); perceptions of status ranking and cohesiveness were not related. Neither scholastic level nor culture served as a moderator in the association between either status attributes or status rank and cohesion. The importance that athletes attach to status attributes is similar between scholastic levels and across cultures. The results are discussed in terms of the role of status in sport teams.

  1. Group-size-mediated habitat selection and group fusion-fission dynamics of bison under predation risk.

    PubMed

    Fortin, Daniel; Fortin, Marie-Eve; Beyer, Hawthorne L; Duchesne, Thierry; Courant, Sabrina; Dancose, Karine

    2009-09-01

    For gregarious animals the cost-benefit trade-offs that drive habitat selection may vary dynamically with group size, which plays an important role in foraging and predator avoidance strategies. We examined how habitat selection by bison (Bison bison) varied as a function of group size and interpreted these patterns by testing whether habitat selection was more strongly driven by the competing demands of forage intake vs. predator avoidance behavior. We developed an analytical framework that integrated group size into resource selection functions (RSFs). These group-size-dependent RSFs were based on a matched case-control design and were estimated using conditional logistic regression (mixed and population-averaged models). Fitting RSF models to bison revealed that bison groups responded to multiple aspects of landscape heterogeneity and that selection varied seasonally and as a function of group size. For example, roads were selected in summer, but not in winter. Bison groups avoided areas of high snow water equivalent in winter. They selected areas composed of a large proportion of meadow area within a 700-m radius, and within those areas, bison selected meadows. Importantly, the strength of selection for meadows varied as a function of group size, with stronger selection being observed in larger groups. Hence the bison-habitat relationship depended in part on the dynamics of group formation and division. Group formation was most likely in meadows. In contrast, risk of group fission increased when bison moved into the forest and was higher during the time of day when movements are generally longer and more variable among individuals. We also found that stronger selection for meadows by large rather than small bison groups was caused by longer residence time in individual meadows by larger groups and that departure from meadows appears unlikely to result from a depression in food intake rate. These group-size-dependent patterns were consistent with the hypothesis

  2. The evolution of body size in extant groups of North American freshwater fishes: speciation, size distributions, and Cope's rule.

    PubMed

    Knouft, Jason H; Page, Lawrence M

    2003-03-01

    Change in body size within an evolutionary lineage over time has been under investigation since the synthesis of Cope's rule, which suggested that there is a tendency for mammals to evolve larger body size. Data from the fossil record have subsequently been examined for several other taxonomic groups to determine whether they also displayed an evolutionary increase in body size. However, we are not aware of any species-level study that has investigated the evolution of body size within an extant continental group. Data acquired from the fossil record and data derived from the evolutionary relationships of extant species are not similar, with each set exhibiting both strengths and weaknesses related to inferring evolutionary patterns. Consequently, expectation that general trends exhibited in the fossil record will correspond to patterns in extant groups is not necessarily warranted. Using phylogenetic relationships of extant species, we show that five of nine families of North American freshwater fishes exhibit an evolutionary trend of decreasing body size. These trends result from the basal position of large species and the more derived position of small species within families. Such trends may be caused by the invasion of small streams and subsequent isolation and speciation. This pattern, potentially influenced by size-biased dispersal rates and the high percentage of small streams in North America, suggests a scenario that could result in the generation of the size-frequency distribution of North American freshwater fishes.

  3. Predation, scramble competition, and the vigilance group size effect in dark-eyed juncos (Junco hyemalis)

    Treesearch

    Steven L. Lima; Patrick A. Zollner; Peter A. Bednekoff

    1999-01-01

    In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment and more time to feeding. This vigilance "group size effect" has long been attributed to the anti-predatory benefits of group living, but many investigators have suggested that this effect may be driven by scramble competition for limited...

  4. Parasite infection and host group size: a meta-analytical review.

    PubMed

    Patterson, Jesse E H; Ruckstuhl, Kathreen E

    2013-06-01

    Many studies have identified various host behavioural and ecological traits that are associated with parasite infection, including host gregariousness. By use of meta-analyses, we investigated to what degree parasite prevalence, intensity and species richness are correlated with group size in gregarious species. We predicted that larger groups would have more parasites and higher parasite species richness. We analysed a total of 70 correlations on parasite prevalence, intensity and species richness across different host group sizes. Parasite intensity and prevalence both increased positively with group size, as expected. No significant relationships were found between host group size and parasite species richness, suggesting that larger groups do not harbour more rare or novel parasite species than smaller groups. We further predicted that the mobility of the host (mobile, sedentary) and the mode of parasite transmission (direct, indirect, mobile) would be important predictors of the effects of group sizes on parasite infection. It was found that group size was positively correlated with the prevalence and intensity of directly and indirectly transmitted parasites. However, a negative relationship was observed between group size and mobile parasite intensity, with larger groups having lower parasite intensities. Further, intensities of parasites did not increase with group size of mobile hosts, suggesting that host mobility may negate parasite infection risk. The implications for the evolution and maintenance of sociality in host species are discussed, and future research directions are highlighted.

  5. Activity and social factors affect cohesion among individuals in female Japanese macaques: A simultaneous focal-follow study.

    PubMed

    Nishikawa, Mari; Suzuki, Mariko; Sprague, David S

    2014-07-01

    Understanding cohesion among individuals within a group is necessary to reveal the social system of group-living primates. Japanese macaques (Macaca fuscata) are female-philopatric primates that reside in social groups. We investigated whether individual activity and social factors can affect spatio-temporal cohesion in wild female Japanese macaques. We conducted behavioral observation on a group, which contained 38 individuals and ranged over ca. 60 ha during the study period. Two observers carried out simultaneous focal-animal sampling of adult female pairs during full-day follows using global positioning system which enabled us to quantify interindividual distances (IIDs), group members within visual range (i.e., visual unit), and separation duration beyond visual range as indicators of cohesion among individuals. We found considerable variation in spatio-temporal group cohesion. The overall mean IID was 99.9 m (range = 0-618.2 m). The percentage of IIDs within visual range was 23.1%, within auditory range was 59.8%, and beyond auditory range was 17.1%. IIDs varied with activity; they were shorter during grooming and resting, and longer during foraging and traveling. Low-ranking females showed less cohesion than high-ranking ones. Kin females stayed nearly always within audible range. The macaques were weakly cohesive with small mean visual unit size (3.15 counting only adults, 5.99 counting all individuals). Both-sex units were the most frequently observed visual unit type when they were grooming/resting. Conversely, female units were the most frequently observed visual unit type when they were foraging. The overall mean visual separation duration was 25.7 min (range = 3-513 min). Separation duration was associated with dominance rank. These results suggest that Japanese macaques regulate cohesion among individuals depending on their activity and on social relationships; they were separated to adapt food distribution and aggregated to maintain social

  6. Team Cohesion Effects on Business Game Performance.

    ERIC Educational Resources Information Center

    Wolfe, Joseph; Box, Thomas M.

    1988-01-01

    Discussion of teamwork and group decision making focuses on study of undergraduates conducted to identify the variables that affect team cohesion in a business game. A literature review on small groups and business games is presented, hypotheses tested are described, discriminant analyses are explained, and suggestions for further research are…

  7. Alterations in desmosome size and number coincide with the loss of keratinocyte cohesion in skin with homozygous and heterozygous defects in the desmosomal protein plakophilin 1.

    PubMed

    McMillan, James R; Haftek, Marek; Akiyama, Masashi; South, Andrew P; Perrot, Henri; McGrath, John A; Eady, Robin A J; Shimizu, Hiroshi

    2003-07-01

    Recessive mutations in the desmosomal plaque protein plakophilin 1 (PkP1) underlie ectodermal dysplasia/skin fragility syndrome (MIM 604536). We undertook an immunohistochemical and quantitative electron microscopic examination of suprabasal desmosomes from 4 skin samples from 3 PkP1 deficient patients, an unaffected carrier with a PKP1 heterozygous acceptor splice site mutation and 5 healthy control subjects. Desmosomal plaque size (>50 desmosomes per individual) and frequency (>20 high power fields, HPF) were assessed. Compared with controls, desmosomes were reduced dramatically both in size (49%) and frequency (61%) in the lower suprabasal layers (LSB) in PkP1 null patients (P<0.01). In the LSB compartment of the heterozygous carrier, corresponding reductions were 37% and 20%, respectively (P<0.01). Surprisingly, the PkP1 null patient's upper suprabasal layer, (USB), desmosome size was larger (59%, P<0.01) than the control value, and showed increased desmoglein 1 and PkP2 USB staining. The USB desmosome frequency in PKP1 null patients was similar to the LSB compartment (but reduced by 43% compared to USB controls). The carrier showed no difference in the USB desmosome size and frequency compared with the controls (P>0.05). The PKP1 null patients showed poorly developed inner and outer desmosomal plaques. Thus, both the patients and unaffected carrier showed reductions in the LSB desmosome size and number; despite only PkP1 null patients exhibiting any phenotype. These findings attest to the molecular recruiting and stabilizing roles of PkP1 in desmosome formation, particularly in the LSB compartment.

  8. Kinship-based politics and the optimal size of kin groups

    PubMed Central

    Hammel, E. A.

    2005-01-01

    Kin form important political groups, which change in size and relative inequality with demographic shifts. Increases in the rate of population growth increase the size of kin groups but decrease their inequality and vice versa. The optimal size of kin groups may be evaluated from the marginal political product (MPP) of their members. Culture and institutions affect levels and shapes of MPP. Different optimal group sizes, from different perspectives, can be suggested for any MPP schedule. The relative dominance of competing groups is determined by their MPP schedules. Groups driven to extremes of sustainability may react in Malthusian fashion, including fission and fusion, or in Boserupian fashion, altering social technology to accommodate changes in size. The spectrum of alternatives for actors and groups, shaped by existing institutions and natural and cultural selection, is very broad. Nevertheless, selection may result in survival of particular kinds of political structures. PMID:16091466

  9. Cohesive strength of iron ore granules

    NASA Astrophysics Data System (ADS)

    Contreras, Rafael Jaimes; Berger, Nicolas; Izard, Edouard; Douce, Jean-François; Koltsov, Alexey; Delenne, Jean-Yves; Azema, Emilien; Nezamabadi, Saeid; van Loo, Frédéric; Pellenq, Roland; Radjai, Farhang

    2017-06-01

    We present an experimental and numerical investigation of the mechanical strength of crude iron ore (Hematite) granules in which capillary bonds between primary particles are the source of internal cohesion. The strength is measured by subjecting the granules to vertical compression between two plates. We show that the behavior of the granules is ductile with a well-defined plastic threshold which increases with the amount of water. It is found that the compressive strength scales with capillary cohesion with a pre-factor that is nearly independent of size polydispersity for the investigated range of parameters but increases with friction coefficient between primary particles. This weak dependence may be attributed to the class of fine particles which, due to their large number, behaves as a cohesive matrix that controls the strength of the granule.

  10. A simple model for the size and shape dependent Curie temperature of freestanding Ni and Fe nanoparticles based on the average coordination number and atomic cohesive energy

    NASA Astrophysics Data System (ADS)

    Delavari, H.; Madaah Hosseini, H.; Simchi, A.

    2011-05-01

    To study the effect of size and shape of metallic nanoparticle on their Curie temperature, an analytical model is proposed. The core average coordination number (CAC) and surface average coordination number (SAC) of freestanding nanoparticles are considered in the model. Clusters of icosahedral (IC) and body centred cubic (BCC) structure without any vacancies and defects are modelled. A critical Curie temperature is introduced for metallic clusters with a diameter of 2-3 nm. This critical diameter is related to clusters which the ratio of surface atoms to total atoms is about 50%. The "shape effect" is shown to be important at sizes less than 20 nm. The obtained results are supported by available experimental results for nickel and iron nanoparticles.

  11. Cohesive Devices and Discourse Competence.

    ERIC Educational Resources Information Center

    Ehrlich, Susan

    1988-01-01

    Examines the development of cohesive discourse among second language learners in light of native speaker discourse norms. Previous studies of cohesion in second language acquisition have failed to consider restrictions on the distribution of cohesive devices in English. Two of these restrictions are discussed. (Author/DJD)

  12. Living in stable social groups is associated with reduced brain size in woodpeckers (Picidae).

    PubMed

    Fedorova, Natalia; Evans, Cara L; Byrne, Richard W

    2017-03-01

    Group size predicts brain size in primates and some other mammal groups, but no such relationship has been found in birds. Instead, stable pair-bonding and bi-parental care have been identified as correlates of larger brains in birds. We investigated the relationship between brain size and social system within the family Picidae, using phylogenetically controlled regression analysis. We found no specific effect of duration or strength of pair-bonds, but brain sizes were systematically smaller in species living in long-lasting social groups of larger sizes. Group-living may only present a cognitive challenge in groups in which members have individually competitive relationships; we therefore propose that groups functioning for cooperative benefit may allow disinvestment in expensive brain tissue.

  13. Interactions among social monitoring, anti-predator vigilance and group size in eastern grey kangaroos

    PubMed Central

    Favreau, François-René; Goldizen, Anne W.; Pays, Olivier

    2010-01-01

    Group size is known to affect both the amount of time that prey animals spend in vigilance and the degree to which the vigilance of group members is synchronized. However, the variation in group-size effects reported in the literature is not yet understood. Prey animals exhibit vigilance both to protect themselves against predators and to monitor other group members, and both forms of vigilance presumably influence group-size effects on vigilance. However, our understanding of the patterns of individual investment underlying the time sharing between anti-predator and social vigilance is still limited. We studied patterns of variation in individual vigilance and the synchronization of vigilance with group size in a wild population of eastern grey kangaroos (Macropus giganteus) subject to predation, in particular focusing on peripheral females because we expected that they would exhibit both social and anti-predator vigilance. There was no global effect of group size on individual vigilance. The lack of group-size effect was the result of two compensating effects. The proportion of time individuals spent looking at other group members increased, whereas the proportion of time they spent scanning the environment decreased with group size; as a result, overall vigilance levels did not change with group size. Moreover, a degree of synchrony of vigilance occurred within groups and that degree increased with the proportion of vigilance time peripheral females spent in anti-predator vigilance. Our results highlight the crucial roles of both social and anti-predator components of vigilance in the understanding of the relationship between group size and vigilance, as well as in the synchronization of vigilance among group members. PMID:20219737

  14. Developing Cohesive Leadership Means Addressing All Parts of the System

    ERIC Educational Resources Information Center

    Fisher, Troyce

    2010-01-01

    In her role with the School Administrators of Iowa leading Iowa's leadership grant from The Wallace Foundation, the author works with a coalition of individuals and groups striving to implement a cohesive leadership system for school leaders. Efforts to create a cohesive leadership system in Iowa for the past nine years have resulted in many…

  15. Community Cohesion: A Report of the Independent Review Team.

    ERIC Educational Resources Information Center

    Home Office, London (England).

    This study examined the views of English citizens and community leaders regarding problems related to disaffected, disadvantaged, culturally diverse groups. The Community Cohesion Review Team (CCRT) investigated issues needing to be addressed to bring about social cohesion. Communities were deeply polarized, with separate educational systems,…

  16. Cohesion in Online Student Teams versus Traditional Teams

    ERIC Educational Resources Information Center

    Hansen, David E.

    2016-01-01

    Researchers have found that the electronic methods in use for online team communication today increase communication quality in project-based work situations. Because communication quality is known to influence group cohesion, the present research examined whether online student project teams are more cohesive than traditional teams. We tested…

  17. Cohesion in Online Student Teams versus Traditional Teams

    ERIC Educational Resources Information Center

    Hansen, David E.

    2016-01-01

    Researchers have found that the electronic methods in use for online team communication today increase communication quality in project-based work situations. Because communication quality is known to influence group cohesion, the present research examined whether online student project teams are more cohesive than traditional teams. We tested…

  18. Effect of group size on behavior, health, production and welfare of veal calves

    USDA-ARS?s Scientific Manuscript database

    The objective of the present study was to determine the effect of group size on behavior, health, growth, and welfare of veal calves. Holstein-Friesian bull calves (n = 168), 44 ± 3 days of age, were used to investigate the effect of group size. Calves were randomly assigned into 1 of 3 treatments o...

  19. Adhesion and Cohesion

    PubMed Central

    von Fraunhofer, J. Anthony

    2012-01-01

    The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed. PMID:22505913

  20. Cohesive Elements for Shells

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.; Camanho, Pedro P.; Turon, Albert

    2007-01-01

    A cohesive element for shell analysis is presented. The element can be used to simulate the initiation and growth of delaminations between stacked, non-coincident layers of shell elements. The procedure to construct the element accounts for the thickness offset by applying the kinematic relations of shell deformation to transform the stiffness and internal force of a zero-thickness cohesive element such that interfacial continuity between the layers is enforced. The procedure is demonstrated by simulating the response and failure of the Mixed Mode Bending test and a skin-stiffener debond specimen. In addition, it is shown that stacks of shell elements can be used to create effective models to predict the inplane and delamination failure modes of thick components. The results indicate that simple shell models can retain many of the necessary predictive attributes of much more complex 3D models while providing the computational efficiency that is necessary for design.

  1. A framework for cohesive healthcare coalition formation.

    PubMed

    Cheah, Yu-N; Chong, Yong Han; Neoh, Siew Lan

    2006-01-01

    The mobilisation of cohesive and effective groups of healthcare human resource is important in ensuring the success of healthcare organisations. However, forming the right team or coalition in healthcare organisations is not always straightforward due to various human factors. Traditional coalition formation approaches have been perceived as 'materialistic' or focusing too much on competency or pay-off. Therefore, to put prominence on the human aspects of working together, we present a cohesiveness-focused healthcare coalition formation methodology and framework that explores the possibilities of social networks, i.e. the relationship between various healthcare human resources, and adaptive resonance theory.

  2. Validation of the Child Sport Cohesion Questionnaire

    ERIC Educational Resources Information Center

    Martin, Luc J.; Carron, Albert V.; Eys, Mark A.; Loughead, Todd

    2013-01-01

    The purpose of the present study was to test the validity evidence of the Child Sport Cohesion Questionnaire (CSCQ). To accomplish this task, convergent, discriminant, and known-group difference validity were examined, along with factorial validity via confirmatory factor analysis (CFA). Child athletes (N = 290, M[subscript age] = 10.73 plus or…

  3. Engineering molecular crystals with abnormally weak cohesion.

    PubMed

    Maly, Kenneth E; Gagnon, Eric; Wuest, James D

    2011-05-14

    Adding astutely placed methyl groups to hexaphenylbenzene increases molecular weight but simultaneously weakens key C-H···π interactions, thereby leading to decreased enthalpies of sublimation and showing that materials with abnormally weak cohesion can be made by identifying and then obstructing interactions that help control association.

  4. Validation of the Child Sport Cohesion Questionnaire

    ERIC Educational Resources Information Center

    Martin, Luc J.; Carron, Albert V.; Eys, Mark A.; Loughead, Todd

    2013-01-01

    The purpose of the present study was to test the validity evidence of the Child Sport Cohesion Questionnaire (CSCQ). To accomplish this task, convergent, discriminant, and known-group difference validity were examined, along with factorial validity via confirmatory factor analysis (CFA). Child athletes (N = 290, M[subscript age] = 10.73 plus or…

  5. Cohesion, Communication, Co-operation Program.

    ERIC Educational Resources Information Center

    Hoover, Betty-Bruce H.

    After an incident of student drinking, a committee was formed by parents, students, and school faculty to deal with the problem of alcohol abuse. Later a program was developed with the goals to inform parents, students, and faculty about the values of cohesive behavior and the means of working together as groups, about communicating clearly with…

  6. Left and right hemispheric contributions to discourse coherence and cohesion.

    PubMed

    Bloom, R L; Borod, J C; Santschi-Haywood, C; Pick, L H; Obler, L K

    1996-11-01

    Linguistic coherence and cohesion were examined in patients with unilateral left brain damage (LBD), unilateral right brain damage (RBD), and normal control (NC) right-handed adults. Groups were matched for age, gender, occupation, and education. Brain-damaged groups did not differ for months post onset or intrahemispheric lesion site. Contrary to previous literature, results indicated that LBDs, all of whom were aphasic, demonstrated impairments in coherence but not cohesion, relative to NCs and RBDs. Surprisingly, among RBDs, overall coherence and cohesion were spared. When the relationship between measures of coherence and cohesion was examined, there were few significant correlations and no systematic patterns. Results support the notion that coherence and cohesion represent coexisting and independent linguistic systems. Further, the findings suggest that descriptions of discourse integrity need to account for the perspective of both the speaker and listener.

  7. Effect of group size on parasitism in a natural population of the Baltimore checkerspot Euphydryas phaeton.

    PubMed

    Stamp, Nancy E

    1981-05-01

    The effect of group size of early instars on parasitism of Euphydryas phaeton (Nymphalidae) was examined. Different numbers of larvae were stocked per web to determine the effect of group size on parasitism. Larval aggregations of moderate size (the size occurring naturally) had the least parasitism. Larger larval groups had a disproportionately high rate of parasitism. The major larval parasitoids located vulnerable larvae within webs, instead of attacking larvae available on the outside of webs. Parasitism rates were similar for larvae of damaged and undamaged webs, a consequence of the behavior and location of larvae in the webs. Lower limit to group size was a function of facilitation of larval numbers in reaching the first feeding site, the top of the host plant. Feeding facilitation by larval aggregations was not a factor in larval survival or growth.

  8. Electronic paper display preferred viewing distance and character size for different age groups.

    PubMed

    Wu, Hsin-Chieh

    2011-09-01

    This study explores the preferred viewing distance and character size for an electronic paper display for three age groups. Proofreading speed and accuracy ratio were measured during Chinese proofreading tests using the preferred character size and minimum acceptable character size. Data analysis showed that the mean preferred viewing distance for young, middle-aged and older groups was 503, 455 and 444 mm, respectively. The mean preferred character size determined by young, middle-aged and older groups was 42.0, 50.0 and 55.2 min arc, respectively. The proofreading test results indicated that the older group proofread significantly more slowly (1.25 word/sec) than the young (1.76 word/sec) and middle-aged groups (1.74 word/sec). Further, the participants proofread more correctly with their preferred character size (73.3%) than with their minimum acceptable character size (65.4%). This study provides valuable information for the design of Chinese text presentations for various age groups. STATEMENT OF RELEVANCE: This study confirmed the preferred viewing distance and character size for E-paper display were influenced by age. The preferred Chinese character size for young, middle-aged and older people was 42, 50 and 55 min arc, respectively. Therefore, the age factor should be considered for E-paper displays design and video display terminal (VDT) guidelines.

  9. Nonlinear effects of group size on the success of wolves hunting elk

    USGS Publications Warehouse

    MacNulty, Daniel R.; Smith, Douglas W.; Mech, L. David; Vucetich, John A.; Packer, Craig

    2012-01-01

    Despite the popular view that social predators live in groups because group hunting facilitates prey capture, the apparent tendency for hunting success to peak at small group sizes suggests that the formation of large groups is unrelated to prey capture. Few empirical studies, however, have tested for nonlinear relationships between hunting success and group size, and none have demonstrated why success trails off after peaking. Here, we use a unique dataset of observations of individually known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to show that the relationship between success and group size is indeed nonlinear and that individuals withholding effort (free riding) is why success does not increase across large group sizes. Beyond 4 wolves, hunting success leveled off, and individual performance (a measure of effort) decreased for reasons unrelated to interference from inept hunters, individual age, or size. But performance did drop faster among wolves with an incentive to hold back, i.e., nonbreeders with no dependent offspring, those performing dangerous predatory tasks, i.e., grabbing and restraining prey, and those in groups of proficient hunters. These results suggest that decreasing performance was free riding and that was why success leveled off in groups with >4 wolves that had superficially appeared to be cooperating. This is the first direct evidence that nonlinear trends in group hunting success reflect a switch from cooperation to free riding. It also highlights how hunting success per se is unlikely to promote formation and maintenance of large groups.

  10. Nonlinear effects of group size on the success of wolves hunting elk

    USGS Publications Warehouse

    MacNulty, D.R.; Smith, D.W.; Mech, L.D.; Vucetich, J.A.; Packer, C.

    2012-01-01

    Despite the popular view that social predators live in groups because group hunting facilitates prey capture, the apparent tendency for hunting success to peak at small group sizes suggests that the formation of large groups is unrelated to prey capture. Few empirical studies, however, have tested for nonlinear relationships between hunting success and group size, and none have demonstrated why success trails off after peaking. Here, we use a unique dataset of observations of individually known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to show that the relationship between success and group size is indeed nonlinear and that individuals withholding effort (free riding) is why success does not increase across large group sizes. Beyond 4 wolves, hunting success leveled off, and individual performance (a measure of effort) decreased for reasons unrelated to interference from inept hunters, individual age, or size. But performance did drop faster among wolves with an incentive to hold back, i.e., nonbreeders with no dependent offspring, those performing dangerous predatory tasks, i.e., grabbing and restraining prey, and those in groups of proficient hunters. These results suggest that decreasing performance was free riding and that was why success leveled off in groups with >4 wolves that had superficially appeared to be cooperating. This is the first direct evidence that nonlinear trends in group hunting success reflect a switch from cooperation to free riding. It also highlights how hunting success per se is unlikely to promote formation and maintenance of large groups. ?? 2011 The Author.

  11. Domain-general mechanisms: what they are, how they evolved, and how they interact with modular, domain-specific mechanisms to enable cohesive human groups.

    PubMed

    MacDonald, Kevin

    2014-08-01

    Domain-general mechanisms are evolutionarily ancient, resulting from the evolution of affective cues signaling the attainment of evolutionary goals. Explicit processing is a particularly important set of domain-general mechanisms for constructing human groups - enabling ideologies specifying future goal states and rationalizing group aims, enabling knowledge of others' reputations essential to cooperation, understanding the rights and obligations of group membership, monitoring group members, and providing appropriate punishments to those who deviate from group aims.

  12. Group size alters postures, and maintenance, oral, locomotor and social behaviors of veal calves

    USDA-ARS?s Scientific Manuscript database

    The objective of this study was to evaluate the effect of group size on behavior of veal calves. Holstein-Friesian bull calves (n = 168; 44 ± 3 d of age), were randomly assigned to 1 of 3 treatments of group housing with 2, 4, or 8 calves per pen (1.82 m2 per calf for all groups). Behavior was obser...

  13. Cohesion in the Discourse of Normal and Head-Injured Adults.

    ERIC Educational Resources Information Center

    Mentis, Michelle; Prutting, Carol A.

    1987-01-01

    Cohesion strategies used by three normal and three head-injured adults were examined in both conversational and narrative conditions. Head-injured subjects used different cohesion patterns than normal adults in both conditions; and both groups used different cohesion patterns in the conversational and narrative conditions. (Author/DB)

  14. Prior Knowledge, Reading Skill, and Text Cohesion in the Comprehension of Science Texts

    ERIC Educational Resources Information Center

    Ozuru, Yasuhiro; Dempsey, Kyle; McNamara, Danielle S.

    2009-01-01

    This study examined how text features (i.e., cohesion) and individual differences (i.e., reading skill and prior knowledge) contribute to biology text comprehension. College students with low and high levels of biology knowledge read two biology texts, one of which was high in cohesion and the other low in cohesion. The two groups were similar in…

  15. Collaborative group work: effects of group size and assignment structure on learning gain, student satisfaction and perceived participation.

    PubMed

    Kooloos, Jan G M; Klaassen, Tim; Vereijken, Mayke; Van Kuppeveld, Sascha; Bolhuis, Sanneke; Vorstenbosch, Marc

    2011-01-01

    Collaborative group sessions in Nijmegen include 15 students who work all together on a group assignment. Sometimes, the group is split-up in three and every subgroup elaborates a part of the assignment. At the end, they peer-teach each other. It is believed that the split-up enhances participation and therefore learning gain. To establish the effect of group size and structure of the assignment on the perceived participation, the satisfaction and learning gain of collaborative group sessions. In this study, 27 groups of 15 students were equally divided into: A-group: all 15 students working on the complete assignment. B-group: subgroups of 5 students working on the complete assignment. C-group: subgroups of 5 students working on a smaller part, and peer-teaching each other at the end of the group session. All students took a pre-test, a post-test and a follow-up test and completed a questionnaire. Questionnaires were analyzed with a one-way analysis of variance (ANOVA) and post hoc by multiple comparisons. Learning gain was analyzed using a repeated measures ANOVA. A group size effect is observed in favor of working in subgroups. Perceived participation of the students differs between A and B (p ≤ 0.001) and between A and C (p ≤ 0.001), but not between B and C. Also, an assignment effect is found in favor of the smaller assignment combined with peer-teaching. The students' satisfaction differs between A and C (p ≤ 0.003) and between B and C (p ≤ 0.001), but not between A and B. The C-group also shows higher test results (p ≤ 0.043). The students prefer smaller groups as well as smaller assignments including peer-teaching. A possible larger learning gain of this format needs to be re-investigated.

  16. The Effects of Group Size, Memory Instruction, and Session Length on the Creative Performance in Electronic Brainstorming Groups

    ERIC Educational Resources Information Center

    Coskun, Hamit

    2011-01-01

    In the literature, there has been a focus on the effectiveness of larger sized electronic brainstorming groups; however, mechanisms for its effectiveness still remain open to question and some methodological concerns (e.g., the evaluation of ideas and the typing speed, and the use of different formats) continue to be important problems. To…

  17. Longitudinal analysis of virtual community perceptions of cohesion: The role of cooperation, communication, and competition.

    PubMed

    Lyles, Annmarie A; Loomis, Colleen; Mama, Scherezade K; Siddiqi, Sameer; Lee, Rebecca E

    2016-09-14

    Online, virtual group interactions may help adherence to health promotion programs. The purpose of this study was to explore longitudinal relationships among dimensions of group cohesion and group-interaction variables to inform and improve group-based strategies within programs aimed at promoting physical activity in virtual communities. In all, 56 online virtual users completed a group dynamics-based physical activity promotion intervention and assessments of group cohesion and group interaction at baseline and 4 weeks. Friendly competition and cooperation were consistently strong predictors of cohesion. Facilitating a sense of friendly competition and cooperation may increase engagement in physical activity programs by bolstering group cohesion.

  18. Social cohesion matters in health

    PubMed Central

    2013-01-01

    Introduction The concept of social cohesion has invoked debate due to the vagueness of its definition and the limitations of current measurements. This paper attempts to examine the concept of social cohesion, develop measurements, and investigate the relationship between social cohesion and individual health. Methods This study used a multilevel study design. The individual-level samples from 29 high-income countries were obtained from the 2000 World Value Survey (WVS) and the 2002 European Value Survey. National-level social cohesion statistics were obtained from Organization of Economic Cooperation and Development datasets, World Development Indicators, and Asian Development Bank key indicators for the year 2000, and from aggregating responses from the WVS. In total 47,923 individuals were included in this study. The factor analysis was applied to identify dimensions of social cohesion, which were used as entities in the cluster analysis to generate a regime typology of social cohesion. Then, multilevel regression models were applied to assess the influences of social cohesion on an individual’s self-rated health. Results and discussion Factor analysis identified five dimensions of social cohesion: social equality, social inclusion, social development, social capital, and social diversity. Then, the cluster analysis revealed five regimes of social cohesion. A multi-level analysis showed that respondents in countries with higher social inclusion, social capital, and social diversity were more likely to report good health above and beyond individual-level characteristics. Conclusions This study is an innovative effort to incorporate different aspects of social cohesion. This study suggests that social cohesion was associated with individual self-rated after controlling individual characteristics. To achieve further advancement in population health, developed countries should consider policies that would foster a society with a high level of social inclusion

  19. Social complexity can drive vocal complexity: group size influences vocal information in Carolina chickadees.

    PubMed

    Freeberg, Todd M

    2006-07-01

    One hypothesis to explain variation in vocal communication in animal species is that the complexity of the social group influences the group's vocal complexity. This social-complexity hypothesis for communication is also central to recent arguments regarding the origins of human language, but experimental tests of the hypothesis are lacking. This study investigated whether group size, a fundamental component of social complexity, influences the complexity of a call functioning in the social organization of Carolina chickadees, Poecile carolinensis. In unmanipulated field settings, calls of individuals in larger groups had greater complexity (more information) than calls of individuals in smaller groups. In aviary settings manipulating group size, individuals in larger groups used calls with greater complexity than individuals in smaller groups. These results indicate that social complexity can influence communicative complexity in this species.

  20. The effect of target group size on risk judgments and comparative optimism: the more, the riskier.

    PubMed

    Price, Paul C; Smith, Andrew R; Lench, Heather C

    2006-03-01

    In 5 experiments, college students exhibited a group size effect on risk judgments. As the number of individuals in a target group increased, so did participants' judgments of the risk of the average member of the group for a variety of negative life events. This happened regardless of whether the stimuli consisted of photographs of real peers or stick-figure representations of peers. As a result, the degree to which participants exhibited comparative optimism (i.e., judged themselves to be at lower risk than their peers) also increased as the size of the comparison group increased. These results suggest that the typical comparative optimism effect reported so often in the literature might be, at least in part, a group size effect. Additional results include a group size effect on judgments of the likelihood that the average group member will experience positive and neutral events and a group size effect on perceptual judgments of the heights of stick figures. These latter results, in particular, support the existence of a simple, general cognitive mechanism that integrates stimulus numerosity into quantitative judgments about that stimulus.

  1. The role of micro size computing clusters for small physics groups

    NASA Astrophysics Data System (ADS)

    Shevel, A. Y.

    2014-06-01

    A small physics group (3-15 persons) might use a number of computing facilities for the analysis/simulation, developing/testing, teaching. It is discussed different types of computing facilities: collaboration computing facilities, group local computing cluster (including colocation), cloud computing. The author discuss the growing variety of different computing options for small groups and does emphasize the role of the group owned computing cluster of micro size.

  2. Joint evolution of sex ratio and reproductive group size under local mate competition with inbreeding depression.

    PubMed

    Yamauchi, Atsushi; Kobayashi, Yutaka

    2011-02-07

    Local mate competition (LMC) may involve some amount of inbreeding between siblings. Because sib-mating is generally accompanied by inbreeding depression, natural selection may favor a reduced rate of sib-mating, possibly affecting the evolution of sex ratio and reproductive group size. The present study theoretically investigated the evolution of these traits under LMC in the presence of inbreeding depression. When the reproductive group size evolves, the determination mechanism of sex ratio is important because the timescale of the sex ratio response to reproductive group size can affect the evolutionary process. We consider a spectrum of sex ratio determination mechanisms from purely unconditional to purely conditional, including intermediate modes with various relative strengths of unconditional and conditional effects. This analysis revealed that both the evolutionarily stable reproductive group size and ratio of males increase with higher inbreeding depression and with a larger relative strength of an unconditional effect in sex ratio determination. Unexpectedly, when the sex ratio is controlled purely conditionally, the reproductive group size cannot exceed three even under the severest level of inbreeding depression (i.e., lethal effect). The present study reveals the conditions for LMC to evolve through the analysis of the joint evolution of reproductive group size and sex ratio.

  3. Rearing-group size determines social competence and brain structure in a cooperatively breeding cichlid.

    PubMed

    Fischer, Stefan; Bessert-Nettelbeck, Mathilde; Kotrschal, Alexander; Taborsky, Barbara

    2015-07-01

    Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups, the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny, depending on early social experience. Whether variation of social-group sizes affects development of social skills and related changes in brain structures remains unexplored. We investigated whether, in a cooperatively breeding cichlid, early group size (1) shapes social behavior and social skills and (2) induces lasting plastic changes in gross brain structures and (3) whether the development of social skills is confined to a sensitive ontogenetic period. Rearing-group size and the time juveniles spent in these groups interactively influenced the development of social skills and the relative sizes of four main brain regions. We did not detect a sensitive developmental period for the shaping of social behavior within the 2-month experience phase. Instead, our results suggest continuous plastic behavioral changes over time. We discuss how developmental effects on social behavior and brain architecture may adaptively tune phenotypes to their current or future environments.

  4. An examination of the relationship between athlete leadership and cohesion using social network analysis.

    PubMed

    Loughead, Todd M; Fransen, Katrien; Van Puyenbroeck, Stef; Hoffmann, Matt D; De Cuyper, Bert; Vanbeselaere, Norbert; Boen, Filip

    2016-11-01

    Two studies investigated the structure of different athlete leadership networks and its relationship to cohesion using social network analysis. In Study 1, we examined the relationship between a general leadership quality network and task and social cohesion as measured by the Group Environment Questionnaire (GEQ). In Study 2, we investigated the leadership networks for four different athlete leadership roles (task, motivational, social and external) and their association with task and social cohesion networks. In Study 1, the results demonstrated that the general leadership quality network was positively related to task and social cohesion. The results from Study 2 indicated positive correlations between the four leadership networks and task and social cohesion networks. Further, the motivational leadership network emerged as the strongest predictor of the task cohesion network, while the social leadership network was the strongest predictor of the social cohesion network. The results complement a growing body of research indicating that athlete leadership has a positive association with cohesion.

  5. Group Variables and Gaming Success.

    ERIC Educational Resources Information Center

    Norris, Dwight R.; Niebuhr, Robert E.

    1980-01-01

    Describes a study designed to determine the effects of group cohesiveness on group performance in a management game and, to examine the effects voluntary v assigned group membership has on the cohesiveness of the group. (Author/LLS)

  6. Group size and group composition of the mona monkey (Cercopithecus mona) on the Island of Grenada, West Indies.

    PubMed

    Glenn, M E

    1997-01-01

    Cercopithecus, the genus of guenons, is the largest of the African primate genera, and yet more than half of the species belonging to this group have never been the focus of a long-term field study. In this paper, I present data on group size and composition for a previously unstudied population of guenons on the Caribbean island of Grenada. The mona monkey, Cercopithecus mona, was introduced to Grenada from Africa approximately 200-300 years ago. Two types of social groups were found for Cercopithecus mona on Grenada: all-male groups consisting of two to four individuals and bisexual groups containing 5-32 individuals. All-male groups of Grenada mona monkeys contained any combination of juveniles, subadults, and/or adults. All-male groups were a common occurrence on Grenada but have never been reported for African C. mona and have been reported only in two other forest Cercopithecus species. Bisexual groups appeared to consist of one adult male, one to six adult females, subadult females, and juveniles and infants of both sexes. Even though no more than one adult male was ever seen in each bisexual group of monas on Grenada, other males were heard giving copulation calls simultaneously with resident adult male loud calls, suggesting that other males occasionally infiltrate bisexual groups.

  7. Optimal adaptive group sequential design with flexible timing of sample size determination.

    PubMed

    Cui, Lu; Zhang, Lanju; Yang, Bo

    2017-04-26

    Flexible sample size designs, including group sequential and sample size re-estimation designs, have been used as alternatives to fixed sample size designs to achieve more robust statistical power and better trial efficiency. In this work, a new representation of sample size re-estimation design suggested by Cui et al. [5,6] is introduced as an adaptive group sequential design with flexible timing of sample size determination. This generalized adaptive group sequential design allows one time sample size determination either before the start of or in the mid-course of a clinical study. The new approach leads to possible design optimization on an expanded space of design parameters. Its equivalence to sample size re-estimation design proposed by Cui et al. provides further insight on re-estimation design and helps to address common confusions and misunderstanding. Issues in designing flexible sample size trial, including design objective, performance evaluation and implementation are touched upon with an example to illustrate. Copyright © 2017. Published by Elsevier Inc.

  8. When is bigger better? The effects of group size on the evolution of helping behaviours.

    PubMed

    Powers, Simon T; Lehmann, Laurent

    2017-05-01

    Understanding the evolution of sociality in humans and other species requires understanding how selection on social behaviour varies with group size. However, the effects of group size are frequently obscured in the theoretical literature, which often makes assumptions that are at odds with empirical findings. In particular, mechanisms are suggested as supporting large-scale cooperation when they would in fact rapidly become ineffective with increasing group size. Here we review the literature on the evolution of helping behaviours (cooperation and altruism), and frame it using a simple synthetic model that allows us to delineate how the three main components of the selection pressure on helping must vary with increasing group size. The first component is the marginal benefit of helping to group members, which determines both direct fitness benefits to the actor and indirect fitness benefits to recipients. While this is often assumed to be independent of group size, marginal benefits are in practice likely to be maximal at intermediate group sizes for many types of collective action problems, and will eventually become very small in large groups due to the law of decreasing marginal returns. The second component is the response of social partners on the past play of an actor, which underlies conditional behaviour under repeated social interactions. We argue that under realistic conditions on the transmission of information in a population, this response on past play decreases rapidly with increasing group size so that reciprocity alone (whether direct, indirect, or generalised) cannot sustain cooperation in very large groups. The final component is the relatedness between actor and recipient, which, according to the rules of inheritance, again decreases rapidly with increasing group size. These results explain why helping behaviours in very large social groups are limited to cases where the number of reproducing individuals is small, as in social insects, or where

  9. Accounting for One-Group Clustering in Effect-Size Estimation

    ERIC Educational Resources Information Center

    Citkowicz, Martyna; Hedges, Larry V.

    2013-01-01

    In some instances, intentionally or not, study designs are such that there is clustering in one group but not in the other. This paper describes methods for computing effect size estimates and their variances when there is clustering in only one group and the analysis has not taken that clustering into account. The authors provide the effect size…

  10. An integrated approach for determining the size of hardwood group-selection openings

    Treesearch

    Chris B. LeDoux

    1999-01-01

    The use of group-selection methods is becoming more widespread as landowners and forest managers attempt to respond to public pressure to reduce the size of clearcut blocks. Several studies have shown that harvesting timber in smaller groups or clumps increases the cost of operations for both cable and ground-based logging systems. Recent regeneration studies have...

  11. A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size.

    PubMed

    Salali, Gul Deniz; Whitehouse, Harvey; Hochberg, Michael E

    2015-01-01

    One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics.

  12. A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size

    PubMed Central

    Salali, Gul Deniz; Whitehouse, Harvey; Hochberg, Michael E.

    2015-01-01

    One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics. PMID:26381745

  13. Does group size have an impact on welfare indicators in fattening pigs?

    PubMed

    Meyer-Hamme, S E K; Lambertz, C; Gauly, M

    2016-01-01

    Production systems for fattening pigs have been characterized over the last 2 decades by rising farm sizes coupled with increasing group sizes. These developments resulted in a serious public discussion regarding animal welfare and health in these intensive production systems. Even though large farm and group sizes came under severe criticism, it is still unknown whether these factors indeed negatively affect animal welfare. Therefore, the aim of this study was to assess the effect of group size (30 pigs/pen) on various animal-based measures of the Welfare Quality(®) protocol for growing pigs under conventional fattening conditions. A total of 60 conventional pig fattening farms with different group sizes in Germany were included. Moderate bursitis (35%) was found as the most prevalent indicator of welfare-related problems, while its prevalence increased with age during the fattening period. However, differences between group sizes were not detected (P>0.05). The prevalence of moderately soiled bodies increased from 9.7% at the start to 14.2% at the end of the fattening period, whereas large pens showed a higher prevalence (15.8%) than small pens (10.4%; P<0.05). With increasing group size, the incidence of moderate wounds with 8.5% and 11.3% in small- and medium-sized pens, respectively, was lower (P<0.05) than in large-sized ones (16.3%). Contrary to bursitis and dirtiness, its prevalence decreased during the fattening period. Moderate manure was less often found in pigs fed by a dry feeder than in those fed by a liquid feeding system (P<0.05). The human-animal relationship was improved in large in comparison to small groups. On the contrary, negative social behaviour was found more often in large groups. Exploration of enrichment material decreased with increasing live weight. Given that all animals were tail-docked, tail biting was observed at a very low rate of 1.9%. In conclusion, the results indicate that BW and feeding system are determining factors for

  14. Ecological Correlates of Group-Size Variation in a Resource-Defense Ungulate, the Sedentary Guanaco

    PubMed Central

    Marino, Andrea; Baldi, Ricardo

    2014-01-01

    For large herbivores, predation-risk, habitat structure and population density are often reported as major determinants of group size variation within and between species. However, whether the underlying causes of these relationships imply an ecological adaptation or are the result of a purely mechanistic process in which fusion and fragmentation events only depend on the rate of group meeting, is still under debate. The aim of this study was to model guanaco family and bachelor group sizes in contrasting ecological settings in order to test hypotheses regarding the adaptive significance of group-size variation. We surveyed guanaco group sizes within three wildlife reserves located in eastern Patagonia where guanacos occupy a mosaic of grasslands and shrublands. Two of these reserves have been free from predators for decades while in the third, pumas often prey on guanacos. All locations have experienced important changes in guanaco abundance throughout the study offering the opportunity to test for density effects. We found that bachelor group size increased with increasing density, as expected by the mechanistic approach, but was independent of habitat structure or predation risk. In contrast, the smaller and territorial family groups were larger in the predator-exposed than in the predator-free locations, and were larger in open grasslands than in shrublands. However, the influence of population density on these social units was very weak. Therefore, family group data supported the adaptive significance of group-size variation but did not support the mechanistic idea. Yet, the magnitude of the effects was small and between-population variation in family group size after controlling for habitat and predation was negligible, suggesting that plasticity of these social units is considerably low. Our results showed that different social units might respond differentially to local ecological conditions, supporting two contrasting hypotheses in a single species, and

  15. Horizontal transfer of fipronil is enhanced with increased group size in Coptotermes formosanus (Isoptera: Rhinotermitidae).

    PubMed

    Wang, Cai; Henderson, Gregg; Chen, Xuan; Gautam, Bal K

    2013-12-01

    Fipronil is a widely used insecticide for termite control. Although transfer of fipronil among termite cohorts has been investigated in previous studies, no study has yet focused on the influence of termite group size (density) on horizontal transfer. In this study, the mortality of donor and recipient Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) was compared among groups of 10, 25, and 50 workers. Most donor termites were dead within 20 h. There was a significantly higher mortality of recipient termites starting at 44 h when in bigger groups. LT50 and LT90 of recipient termites decreased with increase in group size, being significantly shorter in groups of 50 termites compared with groups of 10 termites. Moreover, the variance (within-group difference) of recipient mortality and lethal time estimations was lowest in the groups of 50 termites, indicating a more uniform horizontal transfer of fipronil by termites in bigger groups. Our findings suggest that group size has an influence on fipronil transfer among C. formosanus workers and should be considered as a variable of importance.

  16. Phylogeny of the Oenanthe lugens complex (Aves, Muscicapidae: Saxicolinae): paraphyly of a morphologically cohesive group within a recent radiation of open-habitat chats.

    PubMed

    Schweizer, Manuel; Shirihai, Hadoram

    2013-12-01

    The morphologically inferred Oenanthe lugens complex comprises nine taxa of open-habitat chats which occur in rocky and/or mountainous areas adjacent to the Saharo-Sindian desert belt. It has traditionally been divided into the lugubris group of north-east Africa, the lugentoides group of the southern part of the Arabian Peninsula and the lugens group of North Africa and the Middle East. Previous molecular phylogenetic studies have shown that the O. lugens complex might not be monophyletic. However, it remained unclear how this result might have been affected by incomplete taxon sampling, as the lugentoides group and two out of three taxa of the lugubris group have not been analyzed so far. In this study, we present a phylogenetic hypothesis of the O. lugens complex based on two mitochondrial genes and one nuclear intron using, for the first time, a complete taxon sampling. The application of a multispecies coalescent approach allowed us to simultaneously estimate the sequence and timing of speciation events. The O. lugens complex was consistently revealed as a polyphyletic assemblage and the traditionally recognized groups should be treated as at least three different species: O. lugens, Oenanthelugubris, and Oenanthelugentoides. While O. lugubris and O. lugentoides were revealed to be sister groups, O. lugens was found to be closely related to the species pair Oenanthechrysopygia/Oenanthexanthoprymna. The latter differ quite strongly in morphology and have traditionally not been associated with members of the lugens complex. We thus corroborate the results of previous studies, which demonstrated that morphology seems to be a poor predictor of phylogenetic relationships in Oenanthe. In contrast to the mtDNA markers analyzed, it was revealed that differences among taxa were not fixed in the nuclear intron. In the case of the taxa persica of the lugens group, an influence of introgression in autosomal markers cannot be excluded and deserves further study. The three

  17. Cohesion to the Group and Its Association with Attendance and Early Treatment Response in an Adult Day-Hospital Program for Eating Disorders: A Preliminary Clinical Investigation

    ERIC Educational Resources Information Center

    Crino, Natalie; Djokvucic, Ivana

    2010-01-01

    Treatment outcome studies demonstrate that day-hospital programs are effective in the treatment of eating disorders. Few descriptions are available on the specifics of treatment, particularly the process of therapy. The group therapy modality is thought to provide important therapeutic benefits. The present study aimed to examine the association…

  18. Cohesion to the Group and Its Association with Attendance and Early Treatment Response in an Adult Day-Hospital Program for Eating Disorders: A Preliminary Clinical Investigation

    ERIC Educational Resources Information Center

    Crino, Natalie; Djokvucic, Ivana

    2010-01-01

    Treatment outcome studies demonstrate that day-hospital programs are effective in the treatment of eating disorders. Few descriptions are available on the specifics of treatment, particularly the process of therapy. The group therapy modality is thought to provide important therapeutic benefits. The present study aimed to examine the association…

  19. Personality composition is more important than group size in determining collective foraging behaviour in the wild.

    PubMed

    Keiser, Carl N; Pruitt, Jonathan N

    2014-12-07

    Describing the factors that shape collective behaviour is central to our understanding of animal societies. Countless studies have demonstrated an effect of group size in the emergence of collective behaviours, but comparatively few have accounted for the composition/diversity of behavioural phenotypes, which is often conflated with group size. Here, we simultaneously examine the effect of personality composition and group size on nest architecture and collective foraging aggressiveness in the social spider Stegodyphus dumicola. We created colonies of two different sizes (10 or 30 individuals) and four compositions of boldness (all bold, all shy, mixed bold and shy, or average individuals) in the field and then measured their collective behaviour. Larger colonies produced bigger capture webs, while colonies containing a higher proportion of bold individuals responded to and attacked prey more rapidly. The number of attackers during collective foraging was determined jointly by composition and size, although composition had an effect size more than twice that of colony size: our results suggest that colonies of just 10 bold spiders would attack prey with as many attackers as colonies of 110 'average' spiders. Thus, personality composition is a more potent (albeit more cryptic) determinant of collective foraging in these societies. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  20. Personality composition is more important than group size in determining collective foraging behaviour in the wild

    PubMed Central

    Keiser, Carl N.; Pruitt, Jonathan N.

    2014-01-01

    Describing the factors that shape collective behaviour is central to our understanding of animal societies. Countless studies have demonstrated an effect of group size in the emergence of collective behaviours, but comparatively few have accounted for the composition/diversity of behavioural phenotypes, which is often conflated with group size. Here, we simultaneously examine the effect of personality composition and group size on nest architecture and collective foraging aggressiveness in the social spider Stegodyphus dumicola. We created colonies of two different sizes (10 or 30 individuals) and four compositions of boldness (all bold, all shy, mixed bold and shy, or average individuals) in the field and then measured their collective behaviour. Larger colonies produced bigger capture webs, while colonies containing a higher proportion of bold individuals responded to and attacked prey more rapidly. The number of attackers during collective foraging was determined jointly by composition and size, although composition had an effect size more than twice that of colony size: our results suggest that colonies of just 10 bold spiders would attack prey with as many attackers as colonies of 110 ‘average’ spiders. Thus, personality composition is a more potent (albeit more cryptic) determinant of collective foraging in these societies. PMID:25320170

  1. Social Cohesion and Voluntary Associations

    ERIC Educational Resources Information Center

    Heuser, Brian L.

    2005-01-01

    Voluntary organizations exert great influence over how social norms and ethical codes are guided into action. As such, they have a significant impact on societal levels of social cohesion. Although social capital involves generalized trust becoming manifest as spontaneous sociability, social cohesion is determined by how that sociability is…

  2. Coherence, Cohesion, and Writing Quality.

    ERIC Educational Resources Information Center

    Faigley, Lester; Witte, Stephen P.

    1981-01-01

    Differentiates the two concepts of cohesion and coherence. Points out the differences between highly-rated and lower-rated essays by the techniques the writers used to achieve cohesion. Offers references on text linguistics and on European writings about discourse. (RL)

  3. Group size and composition influence male and female reproductive success in black howler monkeys (Alouatta pigra).

    PubMed

    Van Belle, Sarie; Estrada, Alejandro

    2008-06-01

    It has been argued that grouping patterns might influence the reproductive performance of individuals. Increasing group size results in greater travel costs and competition over depletable food resources, which could lead to reduced individual reproductive success. However, in groups with an increasing number of males, female reproductive success is predicted to augment because larger male groups might better protect immatures from infanticidal attacks. In contrast, male reproductive success is predicted to decrease with number of males in a group because fertilization cannot be shared between males. In this paper, we test these predictions on the Mesoamerican black howler monkey (Alouatta pigra) with data on group size and composition for 120 groups from eight populations of black howler monkeys existing in eight protected forests in Mexico and Guatemala. Male and female reproductive success were calculated as a deviation of the observed number of infants (or immatures) from the expected number of infants (or immatures), relative to the number of males and females in a group. Results indicate that both male and female reproductive success decreased with group size. Male reproductive success decreased with an increasing number of males in a group and with increasing proportion of males relative to females in a group. Decreased female reproductive success was associated with increasing number of females in a group, and female reproductive success had a tendency to increase with increasing number of males in a group. These results suggest that in black howler monkeys, living in larger groups might negatively affect the reproductive success of each member. Our findings are similar to those reported for a population of a sister species, Alouatta palliata, living in larger groups.

  4. Rheotaxis performance increases with group size in a coupled phase model with sensory noise. The effects of noise and group size on rheotaxis

    NASA Astrophysics Data System (ADS)

    Chicoli, A.; Bak-Coleman, J.; Coombs, S.; Paley, D. A.

    2015-12-01

    Many fish exhibit rheotaxis, a behavior in which fish orient themselves relative to flow. Rheotaxis confers many benefits, including energetic cost savings and interception of drifting prey. Despite the fact that most species of fish school during at least some portion of their life, little is known about the importance of rheotactic behavior to schooling fish and, conversely, how the presence of nearby conspecifics affects rheotactic behavior. Understanding how rheotaxis is modified by social factors is thus of ecological importance. Here we present a mathematical model in the form of an all-to-all, coupled-oscillator framework over the non-Euclidean space of fish orientations to model group rheotactic behavior. Individuals in the model measure the orientation of their neighbors and the flow direction relative to their own orientation. These measures are corrupted by sensory noise. We study the effect of sensory noise and group size on internal (i.e., within the school) and external (i.e., with the flow) disagreement in orientation. We find that under noisy environmental conditions, increased group size improves rheotaxis. Results of this study have implications for understanding animal behavior, as well as for potential applications in bio-inspired engineering.

  5. Cohesion, Coherence, and the Comprehension of Text.

    ERIC Educational Resources Information Center

    Moe, Alden J.

    1979-01-01

    Describes the concept of cohesion in text, discusses the distinction between cohesion and coherence, and discusses the relationship of cohesion and coherence to the comprehension of written discourse. (DD)

  6. Mating group size and evolutionarily stable pattern of sexuality in barnacles.

    PubMed

    Yamaguchi, Sachi; Yusa, Yoichi; Yamato, Shigeyuki; Urano, Satoru; Takahashi, Satoshi

    2008-07-07

    Barnacles, marine crustaceans, have various patterns of sexuality depending on species including simultaneous hermaphroditism, androdioecy (hermaphrodites and dwarf males), and dioecy (females and dwarf males). We develop a model that predicts the pattern of sexuality in barnacles by two key environmental factors: (i) food availability and (ii) the fraction of larvae that settle on the sea floor. Populations in the model consist of small individuals and large ones. We calculate the optimal resource allocation toward male function, female function and growth for small and large barnacles that maximizes each barnacle's lifetime reproductive success using dynamic programming. The pattern of sexuality is defined by the combination of the optimal resource allocations. In our model, the mating group size is a dependent variable and we found that sexuality pattern changes with the food availability through the mating group size: simultaneous hermaphroditism appears in food-rich environments, where the mating group size is large, protandric simultaneous hermaphroditism appears in intermediate food environments, where the mating group size also takes intermediate value, the other sexuality patterns, androdioecy, dioecy, and sex change are observed in food-poor environments, where the mating group size is small. Our model is the first one where small males can control their growth to large individuals, and hence has ability to explain a rich spectrum of sexual patterns found in barnacles.

  7. Force Transmission Modes of Non-Cohesive and Cohesive Materials at the Critical State

    PubMed Central

    2017-01-01

    This paper investigates the force transmission modes, mainly described by probability density distributions, in non-cohesive dry and cohesive wet granular materials by discrete element modeling. The critical state force transmission patterns are focused on with the contact model effect being analyzed. By shearing relatively dense and loose dry specimens to the critical state in the conventional triaxial loading path, it is observed that there is a unique critical state force transmission mode. There is a universe critical state force distribution pattern for both the normal contact forces and tangential contact forces. Furthermore, it is found that using either the linear Hooke or the non-linear Hertz model does not affect the universe force transmission mode, and it is only related to the grain size distribution. Wet granular materials are also simulated by incorporating a water bridge model. Dense and loose wet granular materials are tested, and the critical state behavior for the wet material is also observed. The critical state strength and void ratio of wet granular materials are higher than those of a non-cohesive material. The critical state inter-particle distribution is altered from that of a non-cohesive material with higher probability in relatively weak forces. Grains in non-cohesive materials are under compressive stresses, and their principal directions are mainly in the axial loading direction. However, for cohesive wet granular materials, some particles are in tension, and the tensile stresses are in the horizontal direction on which the confinement is applied. The additional confinement by the tensile stress explains the macro strength and dilatancy increase in wet samples. PMID:28858238

  8. The Influence of Social Comparison and Peer Group Size on Risky Decision-Making.

    PubMed

    Wang, Dawei; Zhu, Liping; Maguire, Phil; Liu, Yixin; Pang, Kaiyuan; Li, Zhenying; Hu, Yixin

    2016-01-01

    This study explores the influence of different social reference points and different comparison group sizes on risky decision-making. Participants were presented with a scenario describing an exam, and presented with the opportunity of making a risky decision in the context of different information provided about the performance of their peers. We found that behavior was influenced, not only by comparison with peers, but also by the size of the comparison group. Specifically, the larger the reference group, the more polarized the behavior it prompted. In situations describing social loss, participants were led to make riskier decisions after comparing themselves against larger groups, while in situations describing social gain, they become more risk averse. These results indicate that decision making is influenced both by social comparison and the number of people making up the social reference group.

  9. The Influence of Social Comparison and Peer Group Size on Risky Decision-Making

    PubMed Central

    Wang, Dawei; Zhu, Liping; Maguire, Phil; Liu, Yixin; Pang, Kaiyuan; Li, Zhenying; Hu, Yixin

    2016-01-01

    This study explores the influence of different social reference points and different comparison group sizes on risky decision-making. Participants were presented with a scenario describing an exam, and presented with the opportunity of making a risky decision in the context of different information provided about the performance of their peers. We found that behavior was influenced, not only by comparison with peers, but also by the size of the comparison group. Specifically, the larger the reference group, the more polarized the behavior it prompted. In situations describing social loss, participants were led to make riskier decisions after comparing themselves against larger groups, while in situations describing social gain, they become more risk averse. These results indicate that decision making is influenced both by social comparison and the number of people making up the social reference group. PMID:27582723

  10. Cohesion, coherence, and declarative memory: Discourse patterns in individuals with hippocampal amnesia

    PubMed Central

    Kurczek, Jake; Duff, Melissa C.

    2012-01-01

    Background Discourse cohesion and coherence gives our communication continuity. Deficits in cohesion and coherence have been reported in patients with cognitive-communication disorders (e.g., TBI, dementia). However, the diffuse nature of pathology and widespread cognitive deficits of these disorders have made identification of specific neural substrates and cognitive systems critical for cohesion and coherence challenging. Aims Taking advantage of a rare patient group with selective and severe declarative memory impairments, the current study attempts to isolate the contribution of declarative memory to the successful use of cohesion and coherence in discourse. Methods & Procedures Cohesion and coherence were examined in the discourse of six participants with hippocampal amnesia and six demographically matched comparison participants. Specifically, this study (1) documents the frequency, type, and completeness of cohesive ties; (2) evaluates discourse for local and global coherence; and (3) compares use of cohesive ties and coherence ratings in amnesia and healthy participants. Outcomes & Results Overall, amnesia participants produced fewer cohesive ties per T-unit, the adequacy of their ties were more often judged to be incomplete, and the ratings of their local coherence were consistently lower than comparison participants. Conclusions These findings suggest that declarative memory may contribute to the discursive use of cohesion and coherence. Broader notions of cohesion, or interactional cohesion, i.e., cohesion across speakers (two or more people), time (days, weeks), and communicative resources (gesture), warrant further study as the experimental tasks used in the literature, and here, may actually underestimate or overestimate the extent of impairment. PMID:23136461

  11. Sample size determination in group-sequential clinical trials with two co-primary endpoints.

    PubMed

    Asakura, Koko; Hamasaki, Toshimitsu; Sugimoto, Tomoyuki; Hayashi, Kenichi; Evans, Scott R; Sozu, Takashi

    2014-07-30

    We discuss sample size determination in group-sequential designs with two endpoints as co-primary. We derive the power and sample size within two decision-making frameworks. One is to claim the test intervention's benefit relative to control when superiority is achieved for the two endpoints at the same interim timepoint of the trial. The other is when superiority is achieved for the two endpoints at any interim timepoint, not necessarily simultaneously. We evaluate the behaviors of sample size and power with varying design elements and provide a real example to illustrate the proposed sample size methods. In addition, we discuss sample size recalculation based on observed data and evaluate the impact on the power and Type I error rate.

  12. Resolving Microzooplankton Functional Groups In A Size-Structured Planktonic Model

    NASA Astrophysics Data System (ADS)

    Taniguchi, D.; Dutkiewicz, S.; Follows, M. J.; Jahn, O.; Menden-Deuer, S.

    2016-02-01

    Microzooplankton are important marine grazers, often consuming a large fraction of primary productivity. They consist of a great diversity of organisms with different behaviors, characteristics, and rates. This functional diversity, and its consequences, are not currently reflected in large-scale ocean ecological simulations. How should these organisms be represented, and what are the implications for their biogeography? We develop a size-structured, trait-based model to characterize a diversity of microzooplankton functional groups. We compile and examine size-based laboratory data on the traits, revealing some patterns with size and functional group that we interpret with mechanistic theory. Fitting the model to the data provides parameterizations of key rates and properties, which we employ in a numerical ocean model. The diversity of grazing preference, rates, and trophic strategies enables the coexistence of different functional groups of micro-grazers under various environmental conditions, and the model produces testable predictions of the biogeography.

  13. Nitrogen limitation as a driver of genome size evolution in a group of karst plants

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Wang, Jing; Huang, Hongwen

    2015-06-01

    Genome size is of fundamental biological importance with significance in predicting structural and functional attributes of organisms. Although abundant evidence has shown that the genome size can be largely explained by differential proliferation and removal of non-coding DNA of the genome, the evolutionary and ecological basis of genome size variation remains poorly understood. Nitrogen (N) and phosphorus (P) are essential elements of DNA and protein building blocks, yet often subject to environmental limitation in natural ecosystems. Using phylogenetic comparative methods, we test this hypothesis by determining whether leaf N and P availability affects genome sizes in 99 species of Primulina (Gesneriaceae), a group of soil specialists adapted to limestone karst environment in south China. We find that genome sizes in Primulina are strongly positively correlated with plant N content, but the correlation with plant P content is not significant when phylogeny history was taken into account. This study shows for the first time that N limitation might have been a plausible driver of genome size variation in a group of plants. We propose that competition for nitrogen nutrient between DNA synthesis and cellular functions is a possible mechanism for genome size evolution in Primulina under N-limitation.

  14. Nitrogen limitation as a driver of genome size evolution in a group of karst plants.

    PubMed

    Kang, Ming; Wang, Jing; Huang, Hongwen

    2015-06-25

    Genome size is of fundamental biological importance with significance in predicting structural and functional attributes of organisms. Although abundant evidence has shown that the genome size can be largely explained by differential proliferation and removal of non-coding DNA of the genome, the evolutionary and ecological basis of genome size variation remains poorly understood. Nitrogen (N) and phosphorus (P) are essential elements of DNA and protein building blocks, yet often subject to environmental limitation in natural ecosystems. Using phylogenetic comparative methods, we test this hypothesis by determining whether leaf N and P availability affects genome sizes in 99 species of Primulina (Gesneriaceae), a group of soil specialists adapted to limestone karst environment in south China. We find that genome sizes in Primulina are strongly positively correlated with plant N content, but the correlation with plant P content is not significant when phylogeny history was taken into account. This study shows for the first time that N limitation might have been a plausible driver of genome size variation in a group of plants. We propose that competition for nitrogen nutrient between DNA synthesis and cellular functions is a possible mechanism for genome size evolution in Primulina under N-limitation.

  15. Nitrogen limitation as a driver of genome size evolution in a group of karst plants

    PubMed Central

    Kang, Ming; Wang, Jing; Huang, Hongwen

    2015-01-01

    Genome size is of fundamental biological importance with significance in predicting structural and functional attributes of organisms. Although abundant evidence has shown that the genome size can be largely explained by differential proliferation and removal of non-coding DNA of the genome, the evolutionary and ecological basis of genome size variation remains poorly understood. Nitrogen (N) and phosphorus (P) are essential elements of DNA and protein building blocks, yet often subject to environmental limitation in natural ecosystems. Using phylogenetic comparative methods, we test this hypothesis by determining whether leaf N and P availability affects genome sizes in 99 species of Primulina (Gesneriaceae), a group of soil specialists adapted to limestone karst environment in south China. We find that genome sizes in Primulina are strongly positively correlated with plant N content, but the correlation with plant P content is not significant when phylogeny history was taken into account. This study shows for the first time that N limitation might have been a plausible driver of genome size variation in a group of plants. We propose that competition for nitrogen nutrient between DNA synthesis and cellular functions is a possible mechanism for genome size evolution in Primulina under N-limitation. PMID:26109237

  16. Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes.

    PubMed

    Vaughn-Hirshorn, Robin L; Muzi, Elisa; Richardson, Jessica L; Fox, Gabriella J; Hansen, Lauren N; Salley, Alyce M; Dudzinski, Kathleen M; Würsig, Bernd

    2013-09-01

    We characterized dusky dolphin (Lagenorhynchus obscurus) feeding behaviors recorded on underwater video, and related behaviors to variation in prey ball sizes, dolphin group sizes, and study site (Argentina versus New Zealand, NZ). Herding behaviors most often involved dolphins swimming around the side or under prey balls, but dolphins in Argentina more often swam under prey balls (48% of passes) than did dolphins in NZ (34% of passes). This result may have been due to differences in group sizes between sites, since groups are larger in Argentina. Additionally, in NZ, group size was positively correlated with proportion of passes that occurred under prey balls (p<0.001). Prey-capture attempts most often involved capturing fish from the side of prey balls, but dolphins in Argentina more often swam through prey balls (8% of attempts) than did dolphins in NZ (4% of attempts). This result may have been due to differences in prey ball sizes between sites, since dolphins fed on larger prey balls in Argentina (>74m(2)) than in NZ (maximum 33m(2)). Additionally, in NZ, dolphins were more likely to swim through prey balls to capture fish when they fed on larger prey balls (p=0.025). Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Experimental evidence for the influence of group size on cultural complexity.

    PubMed

    Derex, Maxime; Beugin, Marie-Pauline; Godelle, Bernard; Raymond, Michel

    2013-11-21

    The remarkable ecological and demographic success of humanity is largely attributed to our capacity for cumulative culture. The accumulation of beneficial cultural innovations across generations is puzzling because transmission events are generally imperfect, although there is large variance in fidelity. Events of perfect cultural transmission and innovations should be more frequent in a large population. As a consequence, a large population size may be a prerequisite for the evolution of cultural complexity, although anthropological studies have produced mixed results and empirical evidence is lacking. Here we use a dual-task computer game to show that cultural evolution strongly depends on population size, as players in larger groups maintained higher cultural complexity. We found that when group size increases, cultural knowledge is less deteriorated, improvements to existing cultural traits are more frequent, and cultural trait diversity is maintained more often. Our results demonstrate how changes in group size can generate both adaptive cultural evolution and maladaptive losses of culturally acquired skills. As humans live in habitats for which they are ill-suited without specific cultural adaptations, it suggests that, in our evolutionary past, group-size reduction may have exposed human societies to significant risks, including societal collapse.

  18. Predator biomass, prey density, and species composition effects on group size in recruit coral reef fishes

    USGS Publications Warehouse

    DeMartini, Edward E.; Anderson, Todd W.; Friedlander, Alan M.; Beets, James P.

    2011-01-01

    Group incidence and size are described for recruit parrotfishes, wrasses, and damselfishes on Hawaiian reefs over 3 years (2006–2008) at sites spanning the archipelago (20–28°N, 155–177°W). Coral-poor and coral-rich areas were surveyed at sites with both low (Hawaii Island) and high (Midway Atoll) predator densities, facilitating examination of relations among predator and recruit densities, habitat, and group metrics. Predator and recruit densities varied spatially and temporally, with a sixfold range in total recruit densities among years. Group (≥2 recruits) metrics varied with time and tracked predator and recruit densities and the proportion of schooling species. Groups often included heterospecifics whose proportion increased with group size. A non-saturating relationship between group size and recruit density suggests that the anti-predator benefits of aggregation exceeded competitive costs. Grouping behavior may have overarching importance for recruit survival—even at high recruit densities—and merits further study on Hawaiian reefs and elsewhere.

  19. Effect of Group-Selection Opening Size on Breeding Bird Habitat Use in a Bottomland Forest

    SciTech Connect

    Moorman, C.E.; D.C. Guynn, Jr.

    2001-12-01

    Research on the effects of creating group-selection openings of various sizes on breeding birds habitat use in a bottomland hardwood forest of the Upper Coastal Plain of South Carolina. Creation of 0.5-ha group selection openings in southern bottomland forests should provide breeding habitat for some field-edge species in gaps and habitat for forest-interior species and canopy-dwelling forest-edge species between gaps provided that enough mature forest is made available.

  20. Sample size planning with the cost constraint for testing superiority and equivalence of two independent groups.

    PubMed

    Guo, Jiin-Huarng; Chen, Hubert J; Luh, Wei-Ming

    2011-11-01

    The allocation of sufficient participants into different experimental groups for various research purposes under given constraints is an important practical problem faced by researchers. We address the problem of sample size determination between two independent groups for unequal and/or unknown variances when both the power and the differential cost are taken into consideration. We apply the well-known Welch approximate test to derive various sample size allocation ratios by minimizing the total cost or, equivalently, maximizing the statistical power. Two types of hypotheses including superiority/non-inferiority and equivalence of two means are each considered in the process of sample size planning. A simulation study is carried out and the proposed method is validated in terms of Type I error rate and statistical power. As a result, the simulation study reveals that the proposed sample size formulas are very satisfactory under various variances and sample size allocation ratios. Finally, a flowchart, tables, and figures of several sample size allocations are presented for practical reference.

  1. Tooth Size in Patients with Mild, Moderate and Severe Hypodontia and a Control Group

    PubMed Central

    Khalaf, Khaled

    2016-01-01

    Objectives: To compare tooth size between subjects with mild, moderate and severe hypodontia and a control group. Material and Methods: The study comprised 120 patients with hypodontia divided into three groups of 40 mild (≤2 teeth congenitally missing), 40 moderate (3-5 teeth congenitally missing) and 40 severe (≥6 teeth congenitally missing) hypodontia; and 40 age and sex matched controls. Tooth size was recorded by measuring the mesiodistal and buccolingual dimensions of all fully erupted teeth on study models using digital callipers and compared between all hypodontia and control groups using Two-way ANOVA and Post Hoc Tests of subgroup comparison. Results: Two-way ANOVA revealed patients with hypodontia had significantly smaller mesiodistal and buccolingual tooth dimensions compared with controls (p<0.05). Furthermore patients with more severe hypodontia demonstrated significantly smaller tooth dimensions than those in the mild and moderate hypodontia subgroups (p<0.05). The most affected tooth in terms of tooth size reduction was the maxillary lateral incisor and the least affected tooth was the mandibular first molar. Conclusion: Patients with hypodontia have smaller tooth dimensions than control. Tooth size appears to be affected by the degree of hypodontia, with severe hypodontia having a greater effect on tooth size reduction. The findings of this study may contribute to understanding the aetiology of hypodontia and aid the multidisciplinary management of this complex condition. PMID:27583048

  2. Effect of group size on behavior, health, production, and welfare of veal calves.

    PubMed

    Abdelfattah, E M; Schutz, M M; Lay, D C; Marchant-Forde, J N; Eicher, S D

    2013-11-01

    The objective of this study was to investigate the effect of group size on behavior, growth, health, and welfare of veal calves. Holstein-Friesian bull calves (n=168; 44±3 d of age) were assigned randomly to 1 of 3 treatments of group housing with 2, 4, or 8 calves per pen. The pens used for housing were 3 by 1.20 m (2 calves per pen), 3 by 2.40 m (4 calves per pen), and 3 by 4.80 m (8 calves per pen), supplying a total pen space allowance of 1.82 m2/calf, regardless of pen size. Behavior was recorded from video data throughout the day from 0700 to 1900 h during a single day each month for 5 mo using scan sampling every 5 min within 30-min observation sessions. On d 0, 1, 5, 14, 42, and 70 after grouping, continuous focal sampling around feeding time (30-min intervals before, during, and after feeding) focused on oral and aggressive behaviors. Calves housed in large groups (4 or 8 calves per pen) showed more (P≤0.001) conspecific contact, walking, and standing and less (P<0.001) manipulation of objects, self-licking, and lying when compared to calves housed in small groups (2 calves per pen). Group size had no effect on play behavior (P=0.11) throughout the experiment. During feeding times group size had no (P≥0.07) effect on any behavioral patterns except for duration of conspecific contact (P<0.01). Aggression at feeding time was not (P>0.23) affected by treatment. Group size treatments were similar for hip height change (P=0.41) and heart girth change (P=0.18) over the duration of the experiment; however, both hip height and heart girth increased (P=0.001) with calf age. During mo 1, calves in groups of 8 or 4 coughed more than calves in groups of 2 whereas calves in groups of 8 coughed more than calves in groups of 4 or 2 in mo 2 (treatment×month, P=0.03). Furthermore, during mo 4, calves in groups of 8 had less nasal discharge than calves in groups of 2 or 4 (treatment×month, P=0.02). Ocular discharge, ears, and fecal scores did not differ (P≥0

  3. Effect of Habitat Size, Quality, and Isolation on Functional Groups of Beetles in Hollow Oaks.

    PubMed

    Pilskog, Hanne Eik; Birkemoe, Tone; Framstad, Erik; Sverdrup-Thygeson, Anne

    2016-01-01

    One of the largest threats to biodiversity is land use change and habitat loss. Hollow oaks (Quercus spp. L.) are well-defined patches that are hotspots for biodiversity and red-listed species, but they are often rare and fragmented in the landscape. We investigated the effect of patch size, habitat quality, and isolation on functional groups and red-listed saproxylic beetles in hollow oaks (n = 40) in Norway. The groups were defined by host tree association, trophic grouping, and red-listed status. Habitat quality, represented by tree form was most important in explaining species richness for most groups. Patch size, represented by circumference and amount of dead branches, was most important in explaining abundance. Isolation, that is single oaks compared with oaks in groups, had a negative effect on the abundance of beetles feeding both on wood and fungi (xylomycethopagous), as well as on species associated with broadleaved trees (oak semi-specialists), but did not affect species richness. This indicates that at this scale and in this landscape, isolated oaks are as species rich and valuable for conservation as other oaks, although some functional groups may be more vulnerable to isolation than others. The red-listed species only responded to patch size, indicating that oaks with large circumference and many dead branches are especially important for red-listed species and for conservation.

  4. Effect of Habitat Size, Quality, and Isolation on Functional Groups of Beetles in Hollow Oaks

    PubMed Central

    Pilskog, Hanne Eik; Birkemoe, Tone; Framstad, Erik; Sverdrup-Thygeson, Anne

    2016-01-01

    One of the largest threats to biodiversity is land use change and habitat loss. Hollow oaks (Quercus spp. L.) are well-defined patches that are hotspots for biodiversity and red-listed species, but they are often rare and fragmented in the landscape. We investigated the effect of patch size, habitat quality, and isolation on functional groups and red-listed saproxylic beetles in hollow oaks (n = 40) in Norway. The groups were defined by host tree association, trophic grouping, and red-listed status. Habitat quality, represented by tree form was most important in explaining species richness for most groups. Patch size, represented by circumference and amount of dead branches, was most important in explaining abundance. Isolation, that is single oaks compared with oaks in groups, had a negative effect on the abundance of beetles feeding both on wood and fungi (xylomycethopagous), as well as on species associated with broadleaved trees (oak semi-specialists), but did not affect species richness. This indicates that at this scale and in this landscape, isolated oaks are as species rich and valuable for conservation as other oaks, although some functional groups may be more vulnerable to isolation than others. The red-listed species only responded to patch size, indicating that oaks with large circumference and many dead branches are especially important for red-listed species and for conservation. PMID:26945089

  5. Social structure mediates environmental effects on group size in an obligate cooperative breeder, Suricata suricatta.

    PubMed

    Bateman, A W; Ozgul, A; Nielsen, J F; Coulson, T; Clutton-Brock, T H

    2013-03-01

    Population dynamics in group-living species can be strongly affected both by features of sociality per se and by resultant population structure. To develop a mechanistic understanding of population dynamics in highly social species we need to investigate how processes within groups, processes linking groups, and external drivers act and interact to produce observed patterns. We model social group dynamics in cooperatively breeding meerkats, Suricata suricatta, paying attention to local demographic as well as dispersal processes. We use generalized additive models to describe the influence of group size, population density, and environmental conditions on demographic rates for each sex and stage, and we combine these models into predictive and individual-based simulation models of group dynamics. Short-term predictions of expected group size and simulated group trajectories over the longer term agree well with observations. Group dynamics are characterized by slow increases during the breeding season and relatively sharp declines during the pre-breeding season, particularly after dry years. We examine the demographic mechanisms responsible for environmental dependence. While individuals appear more prone to emigrate after dry years, seasons of low rainfall also cause reductions in reproductive output that produce adult-biased age distributions in the following dispersal season. Adult subordinates are much more likely to disperse or be evicted than immature individuals, and demographic structure thus contributes to crashes in group size. Our results demonstrate the role of social structure in characterizing a population's response to environmental variation. We discuss the implications of our findings for the population dynamics of cooperative breeders and population dynamics generally.

  6. Microsatellite DNA Suggests that Group Size Affects Sex-biased Dispersal Patterns in Red Colobus Monkeys

    PubMed Central

    Miyamoto, Michael M.; Allen, Julie M.; Gogarten, Jan F.; Chapman, Colin A.

    2013-01-01

    Dispersal is a major life history trait of social organisms influencing the behavioral and genetic structure of their groups. Unfortunately, primate dispersal is difficult to quantify, because of the rarity of these events and our inability to ascertain if individuals dispersed or died when they disappear. Socioecological models have been partially developed to understand the ecological causes of different dispersal systems and their social consequences. However, these models have yielded confusing results when applied to folivores. The folivorous red colobus monkey (Procolobus rufomitratus) in Kibale National Park, Uganda is thought to exhibit female-biased dispersal, although both sexes have been observed to disperse and there remains considerable debate over the selective pressures favoring the transfers of males and females and the causes of variation in the proportion of each sex to leave the natal group. We circumvent this problem by using microsatellite DNA data to investigate the prediction that female dispersal will be more frequent in larger groups as compared to smaller ones. The rationale for this prediction is that red colobus exhibit increased within-group competition in bigger groups, which should favor higher female dispersal rates and ultimately lower female relatedness. Genetic data from two unequally sized neighboring groups of red colobus demonstrate increased female relatedness within the smaller group, suggesting females are less likely to disperse when there is less within-group competition. We suggest that the dispersal system is mediated to some degree by scramble competition and group size. Since red colobus group sizes have increased throughout Kibale by over 50% in the last decade, these changes may have major implications for the genetic structure and ultimately the population viability of this endangered primate. PMID:23307485

  7. Microsatellite DNA suggests that group size affects sex-biased dispersal patterns in red colobus monkeys.

    PubMed

    Miyamoto, Michael M; Allen, Julie M; Gogarten, Jan F; Chapman, Colin A

    2013-05-01

    Dispersal is a major life history trait of social organisms influencing the behavioral and genetic structure of their groups. Unfortunately, primate dispersal is difficult to quantify, because of the rarity of these events and our inability to ascertain if individuals dispersed or died when they disappear. Socioecological models have been partially developed to understand the ecological causes of different dispersal systems and their social consequences. However, these models have yielded confusing results when applied to folivores. The folivorous red colobus monkey (Procolobus rufomitratus) in Kibale National Park, Uganda is thought to exhibit female-biased dispersal, although both sexes have been observed to disperse and there remains considerable debate over the selective pressures favoring the transfers of males and females and the causes of variation in the proportion of each sex to leave the natal group. We circumvent this problem by using microsatellite DNA data to investigate the prediction that female dispersal will be more frequent in larger groups as compared to smaller ones. The rationale for this prediction is that red colobus exhibit increased within-group competition in bigger groups, which should favor higher female dispersal rates and ultimately lower female relatedness. Genetic data from two unequally sized neighboring groups of red colobus demonstrate increased female relatedness within the smaller group, suggesting females are less likely to disperse when there is less within-group competition. We suggest that the dispersal system is mediated to some degree by scramble competition and group size. Since red colobus group sizes have increased throughout Kibale by over 50% in the last decade, these changes may have major implications for the genetic structure and ultimately the population viability of this endangered primate.

  8. Group sequential and discretized sample size re-estimation designs: a comparison of flexibility.

    PubMed

    Wu, Xiaoru; Cui, Lu

    2012-10-30

    In clinical trials, researchers usually determine a study sample size prior to the start of the study to provide a sufficient power at a targeted treatment difference. When the targeted treatment difference deviates from the true one, the study may either have insufficient power or use more subjects than necessary. To address the difficulty in sample size planning, researchers have developed various flexible sample size designs and compared their performances. Some previous work suggests that re-estimation designs are inefficient and that one can improve uniformly by using standard group sequential likelihood ratio tests, although more interim analyses are involved. However, researchers need to further study the statement and the minimal number of tests needed before a standard group sequential test might outperform a re-estimation design. In this paper, we conducted simulation studies to answer these questions using various optimality criteria.

  9. The Relationships among Group Size, Participation, and Performance of Programming Language Learning Supported with Online Forums

    ERIC Educational Resources Information Center

    Shaw, Ruey-Shiang

    2013-01-01

    This study examined the relationships among group size, participation, and learning performance factors when learning a programming language in a computer-supported collaborative learning (CSCL) context. An online forum was used as the CSCL environment for learning the Microsoft ASP.NET programming language. The collaborative-learning experiment…

  10. Within-Group Effect-Size Benchmarks for Problem-Solving Therapy for Depression in Adults

    ERIC Educational Resources Information Center

    Rubin, Allen; Yu, Miao

    2017-01-01

    This article provides benchmark data on within-group effect sizes from published randomized clinical trials that supported the efficacy of problem-solving therapy (PST) for depression among adults. Benchmarks are broken down by type of depression (major or minor), type of outcome measure (interview or self-report scale), whether PST was provided…

  11. Group Size and Organisational Conditions for Children's Learning in Preschool: A Teacher Perspective

    ERIC Educational Resources Information Center

    Sheridan, Sonja; Williams, Pia; Pramling Samuelsson, Ingrid

    2014-01-01

    Background: There is a limited amount of research about group size in preschool, and how it impacts on teachers' working conditions and their ability to support children's learning and knowledge development in line with curriculum intentions. Purpose: From a perspective on quality, this article examines the organisational conditions for children's…

  12. The Relationships among Group Size, Participation, and Performance of Programming Language Learning Supported with Online Forums

    ERIC Educational Resources Information Center

    Shaw, Ruey-Shiang

    2013-01-01

    This study examined the relationships among group size, participation, and learning performance factors when learning a programming language in a computer-supported collaborative learning (CSCL) context. An online forum was used as the CSCL environment for learning the Microsoft ASP.NET programming language. The collaborative-learning experiment…

  13. Interactions on an Elementary School Playground: Variations by Age, Gender, Race, Group Size, and Playground Area.

    ERIC Educational Resources Information Center

    Lewis, Tracey E.; Phillipsen, Leslie C.

    1998-01-01

    Observed 88 first and second graders and 76 fifth and sixth graders during playground interactions. A time-sampling procedure recorded gender, race, and group size of all interactive play in seven playground areas. Found that mixed-gender interactions were more likely than same-gender ones to include other races, and mixed-race interactions…

  14. INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS

    EPA Science Inventory

    Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB...

  15. Group Size and Organisational Conditions for Children's Learning in Preschool: A Teacher Perspective

    ERIC Educational Resources Information Center

    Sheridan, Sonja; Williams, Pia; Pramling Samuelsson, Ingrid

    2014-01-01

    Background: There is a limited amount of research about group size in preschool, and how it impacts on teachers' working conditions and their ability to support children's learning and knowledge development in line with curriculum intentions. Purpose: From a perspective on quality, this article examines the organisational conditions for children's…

  16. INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS

    EPA Science Inventory

    Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB...

  17. Group size and nest success in red-cockaded woodpeckers in the West Gulf Coastal Plain: helpers make a difference

    Treesearch

    Richard N. Conner; Daniel Saenz; Richard R. Schaefer; James R. McCormick; D. Craig Rudolph; D. Brent Burt

    2004-01-01

    We studied the relationships between Red-cockaded Woodpecker (Picoides borealis) group size and nest productivity. Red-cockaded Woodpecker group size was positively correlated with fledging success. Although the relationships between woodpecker group size and nest productivity measures were nor statistically significant, a pattern of...

  18. Spatial-size scaling of pedestrian groups under growing density conditions

    NASA Astrophysics Data System (ADS)

    Zanlungo, Francesco; Brščić, Dražen; Kanda, Takayuki

    2015-06-01

    We study the dependence on crowd density of the spatial size, configuration, and velocity of pedestrian social groups. We find that, in the investigated density range, the extension of pedestrian groups in the direction orthogonal to that of motion decreases linearly with the pedestrian density around them, both for two- and three-person groups. Furthermore, we observe that at all densities, three-person groups walk slower than two-person groups, and the latter are slower than individual pedestrians, the differences in velocities being weakly affected by density. Finally, we observe that three-person groups walk in a V-shaped formation regardless of density, with a distance between the pedestrians in the front and back again almost independent of density, although the configuration appears to be less stable at higher densities. These findings may facilitate the development of more realistic crowd dynamics models and simulators.

  19. An examination of the cohesion-performance relationship in university hockey teams.

    PubMed

    Slater, M R; Sewell, D F

    1994-10-01

    The objective of this study was to assess, using the Group Environment Questionnaire, whether team cohesion in university-level field hockey was a cause for, or an effect of, successful performance. A quasi-experimental longitudinal design with cross-lagged correlational analysis was adopted and measures of cohesion and performance were taken midway and later in the season. The results of the synchronous correlations showed a positive relationship (with good stationarity) between team cohesion and performance outcome. Although non-significant cross-lagged differentials indicated a circular relationship, the magnitudes of both the cross-lagged correlations and the partial correlations, together with multiple-regression analyses, revealed that the stronger flow was from cohesion to performance. The socially oriented aspects of cohesion, in particular, had significant associations with performance. The results imply that cohesion-performance relationships should be examined within a circular model, in which cohesion and performance are interdependent.

  20. Force transmission in cohesive granular media

    NASA Astrophysics Data System (ADS)

    Radjai, Farhang; Topin, Vincent; Richefeu, Vincent; Voivret, Charles; Delenne, Jean-Yves; Azéma, Emilien; El Youssoufi, Said

    2010-05-01

    We use numerical simulations to investigate force and stress transmission in cohesive granular media covering a wide class of materials encountered in nature and industrial processing. The cohesion results either from capillary bridges between particles or from the presence of a solid binding matrix filling fully or partially the interstitial space. The liquid bonding is treated by implementing a capillary force law within a debonding distance between particles and simulated by the discrete element method. The solid binding matrix is treated by means of the Lattice Element Method (LEM) based on a lattice-type discretization of the particles and matrix. Our data indicate that the exponential fall-off of strong compressive forces is a generic feature of both cohesive and noncohesive granular media both for liquid and solid bonding. The tensile forces exhibit a similar decreasing exponential distribution, suggesting that this form basically reflects granular disorder. This is consistent with the finding that not only the contact forces but also the stress components in the bulk of the particles and matrix, accessible from LEM simulations in the case of solid bonding, show an exponential fall-off. We also find that the distribution of weak compressive forces is sensitive to packing anisotropy, particle shape and particle size distribution. In the case of wet packings, we analyze the self-equilibrated forces induced by liquid bonds and show that the positive and negative particle pressures form a bi-percolating structure.

  1. Size Distribution of Star Clusters and Stellar Groups in IC2574

    NASA Astrophysics Data System (ADS)

    Pellerin, Anne; Meyer, Martin J.; Calzetti, Daniela

    2017-01-01

    We present an HST/ACS archival study of compact and dispersed star clusters and stellar groups found in the nearby galaxy IC 2574. In this work, we identified and characterized the properties of clusters with spatially unresolved stars. We combined these properties with those found in a companion work on the dispersed stellar groups in IC 2574 with spatially resolved stars. We find that the size distribution of all young stellar groups, sparse and compact together, is consistent with the hierarchical model of star formation.

  2. Group Size Effect on Cooperation in One-Shot Social Dilemmas II: Curvilinear Effect.

    PubMed

    Capraro, Valerio; Barcelo, Hélène

    2015-01-01

    In a world in which many pressing global issues require large scale cooperation, understanding the group size effect on cooperative behavior is a topic of central importance. Yet, the nature of this effect remains largely unknown, with lab experiments insisting that it is either positive or negative or null, and field experiments suggesting that it is instead curvilinear. Here we shed light on this apparent contradiction by considering a novel class of public goods games inspired to the realistic scenario in which the natural output limits of the public good imply that the benefit of cooperation increases fast for early contributions and then decelerates. We report on a large lab experiment providing evidence that, in this case, group size has a curvilinear effect on cooperation, according to which intermediate-size groups cooperate more than smaller groups and more than larger groups. In doing so, our findings help fill the gap between lab experiments and field experiments and suggest concrete ways to promote large scale cooperation among people.

  3. Habitat, density and group size of primates in a Brazilian tropical forest.

    PubMed

    Pinto, L P; Costa, C M; Strier, K B; da Fonseca, G A

    1993-01-01

    Habitats, population densities and group sizes of 5 primate species (Callithrix flaviceps, Callicebus personatus personatus, Cebus apella nigritus, Alouatta fusca clamitans, and Brachyteles arachnoides) were estimated, using the method of repeated transect sampling, in an area of montane pluvial forest in eastern Brazil (Atlantic forest). A. fusca and C. apella had the highest densities in terms of groups and individuals per square kilometer, respectively, while B. arachnoides was least abundant. The highest primate densities were observed in areas of secondary vegetation. Both group sizes and population densities for the 5 species were generally lower at the Reserva Biologica Augusto Ruschi than those reported in other areas of Atlantic forest. Hunting pressure and the different carrying capacity of the habitat are suggested as possible causes for the low number of sightings registered for these species.

  4. Social group size affects Mycobacterium bovis infection in European badgers (Meles meles).

    PubMed

    Woodroffe, Rosie; Donnelly, Christl A; Wei, Gao; Cox, D R; Bourne, F John; Burke, Terry; Butlin, Roger K; Cheeseman, C L; Gettinby, George; Gilks, Peter; Hedges, Simon; Jenkins, Helen E; Johnston, W Thomas; McInerney, John P; Morrison, W Ivan; Pope, Lisa C

    2009-07-01

    1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density.

  5. Effects of group size and floor space allowance on grouped sows: aggression, stress, skin injuries, and reproductive performance.

    PubMed

    Hemsworth, P H; Rice, M; Nash, J; Giri, K; Butler, K L; Tilbrook, A J; Morrison, R S

    2013-10-01

    A total of 3,120 sows, in 4 time replicates, were used to determine the effects of group size and floor space on sow welfare using behavioral, physiological, health, and fitness variables. Within 1 to 7 d postinsemination, sows were assigned randomly to treatments of a 3 by 6 factorial arrangement, with 3 group sizes (10, 30, or 80 sows/pen) and 6 floor space allowances (1.4, 1.8, 2.0, 2.2, 2.4, or 3.0 m(2)/sow). Sows were housed on partially slatted concrete floors, and overhead feeders delivered 4 times/day to provide a total of 2.5 kg of feed/sow. As pen space increased from 1.4 to 3.0 m(2)/sow, aggression at feeding decreased from about 9 to 7 bouts/sow (linear, P = 0.029) and plasma cortisol concentrations decreased from about 28 to 21 ng/mL (linear, P = 0.0089) at 2 d. Although the results are in accord with a linear decline from 1.4 to 3 m(2)/sow, the results are also in accord with a decline in these measurements from 1.4 to 1.8 m(2)/sow and no further decline greater than 1.8 m(2)/sow. Farrowing rate (percentage of inseminated sows that farrowed) also increased from about 60 to 75% as space increased from 1.4 to 3.0 m(2)/sow (linear, P = 0.012). Group size was related to skin injuries on d 9 (P = 0.0017), 23 (P = 0.0046), and 51 (P = 0.0006), with groups of 10 consistently having the lowest number of total injuries over this period. Based on the aggression and cortisol results, it is credible to judge that, within the range of floor space allowances studied, sow welfare improves with increased space. However, from a sow welfare perspective, the experiment had insufficient precision to determine what is an adequate space allowance for sows. Thus, although the results definitely support a space allowance of 1.4 m(2)/sow being too small, it is not possible to give guidance on an actual space allowance at mixing that is adequate.

  6. Incidence of Tooth Size Discrepancy in Different Groups of Malocclusion and its Relation to Extraction

    PubMed Central

    Gaddam, Rajkumar; Arya, Siddarth; Shetty, K Sadashiva

    2015-01-01

    Background: For proper intercuspation, the teeth must be proportional in size. If teeth are mismatched, with unusually large teeth in one arch compared to the other, then an ideal occlusion cannot be attained. This study has been done to determine the prevalence of tooth size discrepancies among orthodontic patients in general and also between different malocclusion groups, sex, and to analyze the change in the degree of severity in Bolton discrepancy before and after the hypothetical premolar extraction. Methods: The study was carried out on randomly collected 100 pre-treatment dental casts. Tooth size analyses were performed on these pre-treatment models and Mesio distal tooth size ratios were measured as described by Bolton before and after various patterns of hypothetical extraction. Result: The results were statistically evaluated using ANOVA and paired samples t-test. 5 out of 100 patients are seen with severe Bolton discrepancy with Bolton values (BV) ranging above and below 2 standard deviation. Statistically insignificant difference is seen between males and females and also between various groups of malocclusion. The difference between the pre-treatment and post extraction BV was found statistically significant for the first premolar extraction and insignificant for others. Conclusion: The results of this study indicate a new point of view to the question of which teeth to extract when evaluated for tooth size aspect only. PMID:26225105

  7. Cohesive Zone Model User Element

    SciTech Connect

    Tippetts, Trevor

    2007-04-17

    Cohesive Zone Model User Element (CZM UEL) is an implementation of a Cohesive Zone Model as an element for use in finite element simulations. CZM UEL computes a nodal force vector and stiffness matrix from a vector of nodal displacements. It is designed for structural analysts using finite element software to predict crack initiation, crack propagation, and the effect of a crack on the rest of a structure.

  8. What about N? A methodological study of sample-size reporting in focus group studies.

    PubMed

    Carlsen, Benedicte; Glenton, Claire

    2011-03-11

    Focus group studies are increasingly published in health related journals, but we know little about how researchers use this method, particularly how they determine the number of focus groups to conduct. The methodological literature commonly advises researchers to follow principles of data saturation, although practical advise on how to do this is lacking. Our objectives were firstly, to describe the current status of sample size in focus group studies reported in health journals. Secondly, to assess whether and how researchers explain the number of focus groups they carry out. We searched PubMed for studies that had used focus groups and that had been published in open access journals during 2008, and extracted data on the number of focus groups and on any explanation authors gave for this number. We also did a qualitative assessment of the papers with regard to how number of groups was explained and discussed. We identified 220 papers published in 117 journals. In these papers insufficient reporting of sample sizes was common. The number of focus groups conducted varied greatly (mean 8.4, median 5, range 1 to 96). Thirty seven (17%) studies attempted to explain the number of groups. Six studies referred to rules of thumb in the literature, three stated that they were unable to organize more groups for practical reasons, while 28 studies stated that they had reached a point of saturation. Among those stating that they had reached a point of saturation, several appeared not to have followed principles from grounded theory where data collection and analysis is an iterative process until saturation is reached. Studies with high numbers of focus groups did not offer explanations for number of groups. Too much data as a study weakness was not an issue discussed in any of the reviewed papers. Based on these findings we suggest that journals adopt more stringent requirements for focus group method reporting. The often poor and inconsistent reporting seen in these

  9. Separating the impact of group size, density, and enclosure size on broiler movement and space use at a decreasing perimeter to area ratio.

    PubMed

    Leone, Erin Hoerl; Christman, Mary C; Douglass, Larry; Estevez, Inma

    2010-01-01

    The goal of this study was to determine the impact of enclosure size on space use and movement patterns of domestic fowl (Gallus gallus domesticus), independent of group size and density. Research designed to estimate the effects of group size, density, or enclosure size involves inherent confounding between factors, clouding their individual effects. This experimental design enabled us to conduct multiple contrasts in order to tease apart the specific impacts. Treatments consisted of five combinations of three square enclosures: small (S; 1.5m(2)), medium (M; 3.0m(2)), and large (L; 4.5m(2)), and three group sizes of 10, 20, and 30 birds. We made comparisons while holding group size constant, holding density constant, and the third while maintaining a constant enclosure size. Nearest neighbor distances increased with enclosure size but appeared to be constrained by density. Net displacement and minimum convex polygons increased with enclosure size regardless of group size or density. We found no evidence of social restriction on space use. Results indicate that broilers adapted their use of space and movement patterns to the size of the enclosures, spreading out and utilizing a greater amount of space when it was available.

  10. Comparison of energy balance between two different-sized groups of Japanese macaques (Macaca fuscata yakui).

    PubMed

    Kurihara, Yosuke; Hanya, Goro

    2017-07-01

    Quantifying the energy balance is essential for testing socio-ecological models. To reveal costs and benefits of group living in Japanese macaques from the perspective of feeding competition, Kurihara and Hanya (Am J Primatol 77:986-1000, 2015) previously compared feeding behavior between two different-sized groups of macaques (larger group 30-35 individuals; smaller group 13-15 individuals) in the coastal forest of Yakushima, Japan. The results suggested that the larger group exhibited greater feeding effort because of intragroup scramble competition and that the smaller group suffered from higher travel costs, possibly owing to intergroup contest competition. However, it remained unclear whether the behavioral differences affected their energy budgets. The present study examined energetic consequences of the different feeding behaviors in the two groups. Using behavioral data from 10 to 13 adult females and nutritional composition of food items, we compared ingestion rates, energetic/nutritional content of diet, and energy budgets between the two groups. Ingestion rates and energetic/nutritional content of diet did not differ between the two groups. Despite the higher feeding effort of the larger group, energy intake did not differ between the two groups. Energy expenditure did not differ between the two groups because higher travel costs were negated by lower feeding effort in the smaller group. Consequently, the energy balance did not differ between the two groups. We demonstrated that the behavioral measures of feeding competition were not translated into their energetic condition; moreover, our findings re-emphasize the importance of quantifying behavioral and fitness measures for interpreting variation in feeding behavior properly.

  11. Object Discovery via Cohesion Measurement.

    PubMed

    Guo, Guanjun; Wang, Hanzi; Zhao, Wan-Lei; Yan, Yan; Li, Xuelong

    2017-02-16

    Color and intensity are two important components in an image. Usually, groups of image pixels, which are similar in color or intensity, are an informative representation for an object. They are therefore particularly suitable for computer vision tasks, such as saliency detection and object proposal generation. However, image pixels, which share a similar real-world color, may be quite different since colors are often distorted by intensity. In this paper, we reinvestigate the affinity matrices originally used in image segmentation methods based on spectral clustering. A new affinity matrix, which is robust to color distortions, is formulated for object discovery. Moreover, a cohesion measurement (CM) for object regions is also derived based on the formulated affinity matrix. Based on the new CM, a novel object discovery method is proposed to discover objects latent in an image by utilizing the eigenvectors of the affinity matrix. Then we apply the proposed method to both saliency detection and object proposal generation. Experimental results on several evaluation benchmarks demonstrate that the proposed CM-based method has achieved promising performance for these two tasks.

  12. Influence of Group Size on the Success of Wolves Hunting Bison

    PubMed Central

    MacNulty, Daniel R.; Tallian, Aimee; Stahler, Daniel R.; Smith, Douglas W.

    2014-01-01

    An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2–6 wolves, bison capture success levelled off at 9–13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey. PMID:25389760

  13. Influence of group size on the success of wolves hunting bison.

    PubMed

    MacNulty, Daniel R; Tallian, Aimee; Stahler, Daniel R; Smith, Douglas W

    2014-01-01

    An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2-6 wolves, bison capture success levelled off at 9-13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey.

  14. Barossa Night: cohesion in the British Army officer corps.

    PubMed

    Bury, Patrick

    2017-06-01

    Contrasting the classical explanation of military group cohesion as sustained by interpersonal bonds, recent scholars have highlighted the importance of ritualized communication, training and drills in explaining effective military performance in professional armies. While this has offered a welcome addition to the cohesion literature and a novel micro-sociological method of examining cohesion, its primary evidential base has been combat groups. Indeed, despite their prominent role in directing operations over the past decade, the British Army's officer corps has received relatively little attention from sociologists during this period. No attempt has been made to explain cohesion in the officer corps. Using a similar method to recent cohesion scholars, this paper seeks to address this imbalance by undertaking a micro-sociology of one ritual in particular: 'Barossa Night' in the Royal Irish Regiment. Firstly, it draws on the work of Durkheim to examine how cohesion amongst the officer corps is created and sustained through a dense array of practises during formal social rituals. It provides evidence that the use of rituals highlights that social solidarity is central to understanding officer cohesion. Secondly, following Hockey's work on how private soldiers negotiate order, the paper shows how this solidarity in the officer corps is based on a degree of negotiated order and the need to release organizational tensions inherent in a strictly hierarchical rank structure. It highlights how the awarding of gallantry medals can threaten this negotiated order and fuel deviancy. In examining this behaviour, the paper shows that even amongst an officer class traditionally viewed as the elite upholders of organizational discipline, the negotiation of rank and hierarchy can be fluid. How deviant behaviour is later accepted and normalized by senior officers indicates that negotiated order is as important to understanding cohesion in the British Army's officer corps as it is

  15. A Regression Framework for Effect Size Assessments in Longitudinal Modeling of Group Differences.

    PubMed

    Feingold, Alan

    2013-03-01

    The use of growth modeling analysis (GMA)--particularly multilevel analysis and latent growth modeling--to test the significance of intervention effects has increased exponentially in prevention science, clinical psychology, and psychiatry over the past 15 years. Model-based effect sizes for differences in means between two independent groups in GMA can be expressed in the same metric (Cohen's d) commonly used in classical analysis and meta-analysis. This article first reviews conceptual issues regarding calculation of d for findings from GMA and then introduces an integrative framework for effect size assessments that subsumes GMA. The new approach uses the structure of the linear regression model, from which effect sizes for findings from diverse cross-sectional and longitudinal analyses can be calculated with familiar statistics, such as the regression coefficient, the standard deviation of the dependent measure, and study duration.

  16. A Regression Framework for Effect Size Assessments in Longitudinal Modeling of Group Differences

    PubMed Central

    Feingold, Alan

    2013-01-01

    The use of growth modeling analysis (GMA)--particularly multilevel analysis and latent growth modeling--to test the significance of intervention effects has increased exponentially in prevention science, clinical psychology, and psychiatry over the past 15 years. Model-based effect sizes for differences in means between two independent groups in GMA can be expressed in the same metric (Cohen’s d) commonly used in classical analysis and meta-analysis. This article first reviews conceptual issues regarding calculation of d for findings from GMA and then introduces an integrative framework for effect size assessments that subsumes GMA. The new approach uses the structure of the linear regression model, from which effect sizes for findings from diverse cross-sectional and longitudinal analyses can be calculated with familiar statistics, such as the regression coefficient, the standard deviation of the dependent measure, and study duration. PMID:23956615

  17. Gender Similarities and Differences in Preadolescent Peer Groups

    ERIC Educational Resources Information Center

    Xie, Hongling; Shi, Bing

    2009-01-01

    The Social Cognitive Mapping procedure was used to identify peer social groups in 26 fifth-grade classrooms from six elementary schools in a northeastern urban school district. Four group structural features were examined: size, the number of subcliques, cohesion, and salience hierarchy. Ethnic diversity index was calculated for each group. An…

  18. Gender Similarities and Differences in Preadolescent Peer Groups

    ERIC Educational Resources Information Center

    Xie, Hongling; Shi, Bing

    2009-01-01

    The Social Cognitive Mapping procedure was used to identify peer social groups in 26 fifth-grade classrooms from six elementary schools in a northeastern urban school district. Four group structural features were examined: size, the number of subcliques, cohesion, and salience hierarchy. Ethnic diversity index was calculated for each group. An…

  19. Group size and visitor numbers predict faecal glucocorticoid concentrations in zoo meerkats.

    PubMed

    Scott, Katy; Heistermann, Michael; Cant, Michael A; Vitikainen, Emma I K

    2017-04-01

    Measures of physiological stress in zoo animals can give important insights into how they are affected by aspects of their captive environment. We analysed the factors influencing variation in glucocorticoid metabolites in faeces (fGCs) from zoo meerkats as a proxy for blood cortisol concentration, high levels of which are associated with a stress response. Levels of fGCs in captive meerkats declined with increasing group size. In the wild, very small groups of meerkats are at a higher risk of predation, while in larger groups, there is increased competition for resources. Indeed, group sizes in captivity resemble those seen in unstable coalitions in the wild, which may represent a stressful condition and predispose meerkats to chronic stress, even in the absence of natural predators. Individuals in large enclosures showed lower levels of stress, but meerkat density had no effect on the stress measures. In contrast with data from wild meerkats, neither sex, age nor dominance status predicted stress levels, which may reflect less food stress owing to more equal access to resources in captivity versus wild. The median number of visitors at the enclosure was positively correlated with fGC concentrations on the following day, with variation in the visitor numbers having the opposite effect. Our results are consistent with the hypothesis that there is an optimum group size which minimizes physiological stress in meerkats, and that zoo meerkats at most risk of physiological stress are those kept in small groups and small enclosures and are exposed to consistently high numbers of visitors.

  20. Group size and visitor numbers predict faecal glucocorticoid concentrations in zoo meerkats

    PubMed Central

    Scott, Katy; Heistermann, Michael

    2017-01-01

    Measures of physiological stress in zoo animals can give important insights into how they are affected by aspects of their captive environment. We analysed the factors influencing variation in glucocorticoid metabolites in faeces (fGCs) from zoo meerkats as a proxy for blood cortisol concentration, high levels of which are associated with a stress response. Levels of fGCs in captive meerkats declined with increasing group size. In the wild, very small groups of meerkats are at a higher risk of predation, while in larger groups, there is increased competition for resources. Indeed, group sizes in captivity resemble those seen in unstable coalitions in the wild, which may represent a stressful condition and predispose meerkats to chronic stress, even in the absence of natural predators. Individuals in large enclosures showed lower levels of stress, but meerkat density had no effect on the stress measures. In contrast with data from wild meerkats, neither sex, age nor dominance status predicted stress levels, which may reflect less food stress owing to more equal access to resources in captivity versus wild. The median number of visitors at the enclosure was positively correlated with fGC concentrations on the following day, with variation in the visitor numbers having the opposite effect. Our results are consistent with the hypothesis that there is an optimum group size which minimizes physiological stress in meerkats, and that zoo meerkats at most risk of physiological stress are those kept in small groups and small enclosures and are exposed to consistently high numbers of visitors. PMID:28484620

  1. Cohesion, Cracking, Dilation, and Flow -- Rheological Behavior of Cohesive Pharmaceutical Powders

    NASA Astrophysics Data System (ADS)

    Muzzio, Fernando

    2007-03-01

    Cohesive powders can be loosely defined as systems where the attractive forced between particles exceed the average particle weight. Cohesive powder flow is interesting from a wide range of reasons. Their main characteristic, intermittence, is evidenced both in the interruption of flow out of hoppers (a mundane issue causing great annoyance to industrial practitioners) and in the sudden avalanching of snow and dirt that has terrified and terrified mankind since the dawn of time. At the present time, our ability to predict either of these phenomena (and many more involving cohesive powders) is very limited, primarily due to an incomplete understanding of their constitutive behavior. To wit, consider just a simple fact: a flowing powder never has constant density. Equations describing the relationship between velocity, shear, stress, and density are rudimentary at best. Computational and experimental approaches for characterizing flow behavior are in their infancy. In this talk, I will describe some recent progress achieved at Rutgers by our group. New instruments have been developed to determine simultaneously powder density and cohesive flow effects. Extensive measurements have been carried out focusing on pharmaceutical blends. These results have been used to fine-tune computational models that accurately predict dilation, flow in drums, and flow in hoppers. Impact of these observations for pharmaceutical manufacturing applications will be discussed in some detail.

  2. Effects of Reproductive Status, Social Rank, Sex and Group Size on Vigilance Patterns in Przewalski's Gazelle

    PubMed Central

    Li, Chunlin; Jiang, Zhigang; Li, Linlin; Li, Zhongqiu; Fang, Hongxia; Li, Chunwang; Beauchamp, Guy

    2012-01-01

    Background Quantifying vigilance and exploring the underlying mechanisms has been the subject of numerous studies. Less attention has focused on the complex interplay between contributing factors such as reproductive status, social rank, sex and group size. Reproductive status and social rank are of particular interest due to their association with mating behavior. Mating activities in rutting season may interfere with typical patterns of vigilance and possibly interact with social rank. In addition, balancing the tradeoff between vigilance and life maintenance may represent a challenge for gregarious ungulate species rutting under harsh winter conditions. We studied vigilance patterns in the endangered Przewalski's gazelle (Procapra przewalskii) during both the rutting and non-rutting seasons to examine these issues. Methodology/Principal Findings Field observations were carried out with focal sampling during rutting and non-rutting season in 2008–2009. Results indicated a complex interplay between reproductive status, social rank, sex and group size in determining vigilance in this species. Vigilance decreased with group size in female but not in male gazelles. Males scanned more frequently and thus spent more time vigilant than females. Compared to non-rutting season, gazelles increased time spent scanning at the expense of bedding in rutting season. During the rutting season, territorial males spent a large proportion of time on rutting activities and were less vigilant than non-territorial males. Although territorial males may share collective risk detection with harem females, we suggest that they are probably more vulnerable to predation because they seemed reluctant to leave rut stands under threats. Conclusions/Significance Vigilance behavior in Przewalski's gazelle was significantly affected by reproductive status, social rank, sex, group size and their complex interactions. These findings shed light on the mechanisms underlying vigilance patterns and

  3. The effect of group size on the interplay between dominance and reproduction in Bombus terrestris.

    PubMed

    Amsalem, Etya; Hefetz, Abraham

    2011-03-28

    Social insects provide good model systems for testing trade-offs in decision-making because of their marked reproductive skew and the dilemma workers face when to reproduce. Attaining reproductive skew requires energy investment in aggression or fertility signaling, creating a trade-off between reproduction and dominance. This may be density-dependent because the cost of achieving dominance may be higher in larger groups. We investigated the effect of group-size in B. terrestris queenless workers on two major reproduction-dominance correlates: between-worker aggression, and pheromone production, aiming at mimicking decision-making during the transition of worker behavior from cooperation and sterility to aggressive reproductive competition in whole colonies. Despite the competition, reproductive division of labor in colonies can be maintained even during this phase through the production of a sterility signal by sterile workers that has an appeasement effect on dominant nestmates. Worker-worker aggression, ovary activation, and production of sterility-appeasement signals may therefore constitute components of a trade-off affecting worker reproduction decisions. By constructing queenless groups of different size and measuring how this affected the parameters above, we found that in all groups aggression was not evenly distributed with the α-worker performing most of the aggressive acts. Moreover, aggression by the α-worker increased proportionally with group-size. However, while in small groups the α-worker monopolized reproduction, in larger groups several workers shared reproduction, creating two worker groups: reproductives and helpers. It appears that despite the increase of aggression, this was evidently not sufficient for the α-worker to monopolize reproduction. If we compare the α-worker to the queen in full-sized colonies it can be hypothesized that worker reproduction in B. terrestris colonies starts due to a gradual increase in the worker population

  4. Integration of individual and social information for decision-making in groups of different sizes

    PubMed Central

    Goïame, Sidney; O'Connor, David A.; Dreher, Jean-Claude

    2017-01-01

    When making judgments in a group, individuals often revise their initial beliefs about the best judgment to make given what others believe. Despite the ubiquity of this phenomenon, we know little about how the brain updates beliefs when integrating personal judgments (individual information) with those of others (social information). Here, we investigated the neurocomputational mechanisms of how we adapt our judgments to those made by groups of different sizes, in the context of jury decisions for a criminal. By testing different theoretical models, we showed that a social Bayesian inference model captured changes in judgments better than 2 other models. Our results showed that participants updated their beliefs by appropriately weighting individual and social sources of information according to their respective credibility. When investigating 2 fundamental computations of Bayesian inference, belief updates and credibility estimates of social information, we found that the dorsal anterior cingulate cortex (dACC) computed the level of belief updates, while the bilateral frontopolar cortex (FPC) was more engaged in individuals who assigned a greater credibility to the judgments of a larger group. Moreover, increased functional connectivity between these 2 brain regions reflected a greater influence of group size on the relative credibility of social information. These results provide a mechanistic understanding of the computational roles of the FPC-dACC network in steering judgment adaptation to a group’s opinion. Taken together, these findings provide a computational account of how the human brain integrates individual and social information for decision-making in groups. PMID:28658252

  5. Fewer but better: Proportionate size of the group affects evaluation of transgressive leaders.

    PubMed

    Travaglino, Giovanni A; Abrams, Dominic; Randsley de Moura, Georgina; Yetkili, Orkun

    2016-06-01

    A group may be badly affected if its leader transgresses important rules. Nonetheless, an emerging body of evidence suggests that in intergroup contexts, group members apply a double standard when judging ingroup leaders - They respond less punitively to transgressions by their leader than by non-leaders. In this article, two experiments investigated how proportionate ingroup size affects reactions to transgressive ingroup leaders. We demonstrate that ingroup leaders from larger, but not smaller, groups benefit from the double standard. The experiments testing the effects of two different types of transgressions (nepotistic favouritism and corruption, respectively) show that transgressive leaders from larger groups are evaluated more positively than both comparable non-leaders and leaders from smaller groups. In contrast, transgressive leaders from smaller groups are evaluated similarly to comparable transgressive non-leaders. Experiment 2 investigated a potential explanation for this phenomenon. Faced with a transgressive leader, members of a smaller group report greater embarrassment than do members of larger groups in relation to the leaders' actions. Implications of these findings and directions for future research are discussed. © 2015 The British Psychological Society.

  6. The role of host traits, season and group size on parasite burdens in a cooperative mammal.

    PubMed

    Viljoen, Hermien; Bennett, Nigel C; Ueckermann, Edward A; Lutermann, Heike

    2011-01-01

    The distribution of parasites among hosts is often characterised by a high degree of heterogeneity with a small number of hosts harbouring the majority of parasites. Such patterns of aggregation have been linked to variation in host exposure and susceptibility as well as parasite traits and environmental factors. Host exposure and susceptibility may differ with sexes, reproductive effort and group size. Furthermore, environmental factors may affect both the host and parasite directly and contribute to temporal heterogeneities in parasite loads. We investigated the contributions of host and parasite traits as well as season on parasite loads in highveld mole-rats (Cryptomys hottentotus pretoriae). This cooperative breeder exhibits a reproductive division of labour and animals live in colonies of varying sizes that procreate seasonally. Mole-rats were parasitised by lice, mites, cestodes and nematodes with mites (Androlaelaps sp.) and cestodes (Mathevotaenia sp.) being the dominant ecto- and endoparasites, respectively. Sex and reproductive status contributed little to the observed parasite prevalence and abundances possibly as a result of the shared burrow system. Clear seasonal patterns of parasite prevalence and abundance emerged with peaks in summer for mites and in winter for cestodes. Group size correlated negatively with mite abundance while it had no effect on cestode burdens and group membership affected infestation with both parasites. We propose that the mode of transmission as well as social factors constrain parasite propagation generating parasite patterns deviating from those commonly predicted.

  7. A cohesive granular material with tunable elasticity

    NASA Astrophysics Data System (ADS)

    Hemmerle, Arnaud; Schröter, Matthias; Goehring, Lucas

    2016-10-01

    By mixing glass beads with a curable polymer we create a well-defined cohesive granular medium, held together by solidified, and hence elastic, capillary bridges. This material has a geometry similar to a wet packing of beads, but with an additional control over the elasticity of the bonds holding the particles together. We show that its mechanical response can be varied over several orders of magnitude by adjusting the size and stiffness of the bridges, and the size of the particles. We also investigate its mechanism of failure under unconfined uniaxial compression in combination with in situ x-ray microtomography. We show that a broad linear-elastic regime ends at a limiting strain of about 8%, whatever the stiffness of the agglomerate, which corresponds to the beginning of shear failure. The possibility to finely tune the stiffness, size and shape of this simple material makes it an ideal model system for investigations on, for example, fracturing of porous rocks, seismology, or root growth in cohesive porous media.

  8. A cohesive granular material with tunable elasticity

    PubMed Central

    Hemmerle, Arnaud; Schröter, Matthias; Goehring, Lucas

    2016-01-01

    By mixing glass beads with a curable polymer we create a well-defined cohesive granular medium, held together by solidified, and hence elastic, capillary bridges. This material has a geometry similar to a wet packing of beads, but with an additional control over the elasticity of the bonds holding the particles together. We show that its mechanical response can be varied over several orders of magnitude by adjusting the size and stiffness of the bridges, and the size of the particles. We also investigate its mechanism of failure under unconfined uniaxial compression in combination with in situ x-ray microtomography. We show that a broad linear-elastic regime ends at a limiting strain of about 8%, whatever the stiffness of the agglomerate, which corresponds to the beginning of shear failure. The possibility to finely tune the stiffness, size and shape of this simple material makes it an ideal model system for investigations on, for example, fracturing of porous rocks, seismology, or root growth in cohesive porous media. PMID:27774988

  9. Species differences in group size and electrosensory interference in weakly electric fishes: implications for electrosensory processing.

    PubMed

    Stamper, Sarah A; Carrera-G, Erika; Tan, Eric W; Fugère, Vincent; Krahe, Rüdiger; Fortune, Eric S

    2010-03-05

    In animals with active sensory systems, group size can have dramatic effects on the sensory information available to individuals. In "wave-type" weakly electric fishes there is a categorical difference in sensory processing between solitary fish and fish in groups: when conspecifics are within about 1m of each other, the electric fields mix and produce interference patterns that are detected by electroreceptors on each individual. Neural circuits in these animals must therefore process two streams of information-salient signals from prey items and predators and social signals from nearby conspecifics. We investigated the parameters of social signals in two genera of sympatric weakly electric fishes, Apteronotus and Sternopygus, in natural habitats of the Napo River valley in Ecuador and in laboratory settings. Apteronotus were most commonly found in pairs along the Napo River (47% of observations; maximum group size 4) and produced electrosensory interference at rates of 20-300 Hz. In contrast, Sternopygus were alone in 80% of observations (maximum group size 2) in the same region of Ecuador. Similar patterns were observed in laboratory experiments: Apteronotus were in groups and preferentially approached conspecific-like signals in an electrotaxis experiment whereas Sternopygus tended to be solitary and did not approach conspecific-like electrosensory signals. These results demonstrate categorical differences in social electrosensory-related activation of central nervous system circuits that may be related to the evolution of the jamming avoidance response that is used in Apteronotus but not Sternopygus to increase the frequency of electrosensory interference patterns. Copyright 2009 Elsevier B.V. All rights reserved.

  10. The Cohesive Metastasis Phenotype in Human Prostate Cancer.

    PubMed

    Harryman, William L; Hinton, James P; Rubenstein, Cynthia P; Singh, Parminder; Nagle, Raymond B; Parker, Sarah J; Knudsen, Beatrice S; Cress, Anne E

    2016-12-01

    A critical barrier for the successful prevention and treatment of recurrent prostate cancer is detection and eradication of metastatic and therapy-resistant disease. Despite the fall in diagnoses and mortality, the reported incidence of metastatic disease has increased 72% since 2004. Prostate cancer arises in cohesive groups as intraepithelial neoplasia, migrates through muscle and leaves the gland via perineural invasion for hematogenous dissemination. Current technological advances have shown cohesive-clusters of tumor (also known as microemboli) within the circulation. Circulating tumor cell (CTC) profiles are indicative of disseminated prostate cancer, and disseminated tumor cells (DTC) are found in cohesive-clusters, a phenotypic characteristic of both radiation- and drug-resistant tumors. Recent reports in cell biology and informatics, coupled with mass spectrometry, indicate that the integrin adhesome network provides an explanation for the biophysical ability of cohesive-clusters of tumor cells to invade thorough muscle and nerve microenvironments while maintaining adhesion-dependent therapeutic resistance. Targeting cohesive-clusters takes advantage of the known ability of extracellular matrix (ECM) adhesion to promote tumor cell survival and represents an approach that has the potential to avoid the progression to drug- and radiotherapy-resistance. In the following review we will examine the evidence for development and dissemination of cohesive-clusters in metastatic prostate cancer.

  11. Intraspecific variation in space use, group size, and mating systems of caviomorph rodents

    PubMed Central

    Maher, Christine R.; Burger, Joseph Robert

    2012-01-01

    Intraspecific variation in social systems is widely recognized across many taxa, and specific models, including polygamy potential, resource defense, and resource dispersion, have been developed to explain the relationship between ecological variation and social organization. Although mammals from temperate North America and Eurasia have provided many insights into this relationship, rodents from the Neotropics and temperate South America have largely been ignored. In this review we focus on reports documenting intraspecific variation in spacing systems, group size, and mating systems of caviomorphs. This large group of New World hystricognath rodents occupies a diverse array of habitats; thus, members of the same species potentially exhibit different social systems in response to different ecological conditions. Spatial patterns vary in response to a diverse array of factors, including predation, food availability, population density, and soil characteristics. Changes in group size typically correlate with changes in resource availability, particularly food. Mating systems generally reflect the ability of males to control access to females, which may depend on population density or food distribution. In general, social organization in caviomorphs fits predictions of resource-based models; however, most studies have been purely observational, involving small numbers of animals over short time periods and reporting qualitative rather than quantitative levels of ecological correlates. In future studies the use of molecular techniques and controlled, experimental manipulations can increase our understanding of intraspecific variation in caviomorph social systems. This understudied group of rodents offers excellent opportunities to provide insights into the influence of ecological conditions on behavior such as social systems. PMID:22328790

  12. The transitional behaviour of avalanches in cohesive granular materials

    NASA Astrophysics Data System (ADS)

    Quintanilla, M. A. S.; Valverde, J. M.; Castellanos, A.

    2006-07-01

    We present a statistical analysis of avalanches of granular materials that partially fill a slowly rotated horizontal drum. For large sized noncohesive grains the classical coherent oscillation is reproduced, consisting of a quasi-periodic succession of regularly sized avalanches. As the powder cohesiveness is increased by decreasing the particle size, we observe a gradual crossover to a complex dynamics that resembles the transitional behaviour observed in fusion plasmas. For particle size below ~50 µm, avalanches lose a characteristic size, retain a short term memory and turn gradually decorrelated in the long term as described by a Markov process. In contrast, large grains made cohesive by coating them with adhesive microparticles display a distinct phenomenology, characterized by a quasi-regular succession of well defined small precursors and large relaxation events. The transition from a one-peaked distribution (noncohesive large beads) to a flattened distribution (fine cohesive beads) passing through the two-peaked distribution of cohesive large beads had already been predicted using a coupled-map lattice model, as the relaxation mechanism of grain reorganization becomes dominant to the detriment of inertia.

  13. Universal size effects for populations in group-outcome decision-making problems

    NASA Astrophysics Data System (ADS)

    Borghesi, Christian; Hernández, Laura; Louf, Rémi; Caparros, Fabrice

    2013-12-01

    Elections constitute a paradigm of decision-making problems that have puzzled experts of different disciplines for decades. We study two decision-making problems, where groups make decisions that impact only themselves as a group. In both studied cases, participation in local elections and the number of democratic representatives at different scales (from local to national), we observe a universal scaling with the constituency size. These results may be interpreted as constituencies having a hierarchical structure, where each group of N agents, at each level of the hierarchy, is divided in about Nδ subgroups with δ≈1/3. Following this interpretation, we propose a phenomenological model of vote participation where abstention is related to the perceived link of an agent to the rest of the constituency and which reproduces quantitatively the observed data.

  14. The effects of familiarity and group size on mating preferences in the guppy, Poecilia reticulata.

    PubMed

    Mariette, M M; Zajitschek, S R K; Garcia, C M; Brooks, R C

    2010-08-01

    In recent years, it has become evident that frequency dependence in the attractiveness of a particular phenotype to mates can contribute to the maintenance of polymorphism. However, these preferences for rare and unfamiliar male phenotypes have only been demonstrated in small, controlled experiments. Here, we tested the preference for unfamiliar mates in groups of six to 96 individuals over 13 days, in the guppy (Poecilia reticulata). We observed individual behaviour in situ to test whether fish discriminate two unfamiliar individuals among many familiar ones. We found that unfamiliar males and females were preferred over the familiar fishes in all groups and that this effect decayed over time. Increasing group sizes and levels of sexual activity did not hamper the preference for unfamiliar mates, providing further support for the role of frequency dependent mate choice in the maintenance of trait polymorphism in natural populations.

  15. Sex difference in strength and size ratios between reciprocal muscle groups in the lower leg.

    PubMed

    Akagi, R; Tohdoh, Y; Takahashi, H

    2013-05-01

    This study compared strength and size of reciprocal muscle groups in the lower leg between sexes. 20 young men and 14 young women volunteered as subjects. Joint torques developed during isometric maximal voluntary plantar flexion (TQPF) and dorsiflexion (TQDF) were measured using a dynamometer. Muscle volumes of plantar flexors (MVPF) and dorsiflexors (MVDF) were determined by magnetic resonance imaging. In each of the muscle groups, joint torque was significantly correlated with muscle volume in young men and women (r=0.610-0.848) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength ratio on muscle size ratio between the plantar flexors and dorsiflexors were investigated using joint torque and muscle volume. The correlations between the MVPF per MVDF and the TQPF per TQDF were significant both in young men (r=0.608) and women (r=0.773), suggesting that strength ratio is strongly affected by size ratio between the plantar flexors and dorsiflexors in young men and women.

  16. Size variation of 0-group plaice: Are earlier influences on growth potential a contributing factor?

    NASA Astrophysics Data System (ADS)

    Fox, Clive J.; Targett, Timothy E.; Ciotti, Benjamin J.; de Kroon, Kasper; Hortsmeyer, Lena; Burrows, Michael T.

    2014-04-01

    Over a decade of sampling has shown that there are consistent differences in the sizes of 0-group plaice by late summer comparing 21 nursery sites on the Scottish west coast. However, when young fish were collected from two sites which produce particularly small and large fish and reared using a common garden design, growth rates between fish from the two sites were indistinguishable. Either there is little selection for fast or slow growth up to a few weeks post-settlement, or such effects do not persist sufficiently strongly to influence later growth. There were also no significant correlations between the time-series of fish size comparing sites, although within some sites there was evidence of inter-annual density-dependent effects. Any influences of offshore regional-scale factors, such as sea temperature or pelagic primary productivity on growth thus appear to be heavily modified by local conditions on the nursery grounds. The field observations combined with the experimental results lead us to conclude that the size 0-group plaice attain in late summer is mainly controlled by post-settlement habitat quality.

  17. Random walk designs for selecting pool sizes in group testing estimation with small samples.

    PubMed

    Haber, Gregory; Malinovsky, Yaakov

    2017-08-09

    Group testing estimation, which utilizes pooled rather than individual units for testing, has been an ongoing area of research for over six decades. While it is often argued that such methods can yield large savings in terms of resources and/or time, these benefits depend very much on the initial choice of pool sizes. In fact, when poor group sizes are used, the results can be much worse than those obtained using standard techniques. Tools for addressing this problem in the literature have been based on either large sample results or prior knowledge of the parameter being estimated, with little guidance when these assumptions are not met. In this paper, we introduce and study random walk designs for choosing pool sizes when only a small number of tests can be run and prior knowledge is vague. To illustrate these methods, application is made to the estimation of prevalence for two diseases among Australian chrysanthemum crops. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Cross (Unit)-Level Effects of Cohesion on Relationships of Suicide Thoughts to Combat Exposure, Postdeployment Stressors, and Postdeployment Social Support.

    PubMed

    Griffith, James

    2015-01-01

    A behavioral health concern for the US military has been suicide, largely due to its increased prevalence in the last several years during US involvement in the Iraq and Afghanistan wars. Using hierarchical linear modeling (HLM), the present study examined relationships among combat exposure, postdeployment stressors, social support, and unit cohesion. Survey data were obtained from 4,567 soldiers who were members of 50 company-sized units. At the individual level, combat exposure and postdeployment stressors were associated with suicidal thoughts. Postdeployment social support was associated with fewer suicidal thoughts. There was no evidence of the stress-buffering effect of social support. At the group level, reduced risk for suicidal thoughts was associated with units having higher than average cohesion. Reduced risk for suicidal thoughts in conjunction with combat experiences was observed in units having higher than average cohesion, though not reaching a traditional level of statistical significance.

  19. Unravelling the size distribution of social groups with information theory in complex networks

    NASA Astrophysics Data System (ADS)

    Hernando, A.; Villuendas, D.; Vesperinas, C.; Abad, M.; Plastino, A.

    2010-07-01

    The minimization of Fisher’s information (MFI) approach of Frieden et al. [Phys. Rev. E 60, 48 (1999)] is applied to the study of size distributions in social groups on the basis of a recently established analogy between scale invariant systems and classical gases [Phys. A 389, 490 (2010)]. Going beyond the ideal gas scenario is seen to be tantamount to simulating the interactions taking place, for a competitive cluster growth process, in a scale-free ideal network - a non-correlated network with a connection-degree’s distribution that mimics the scale-free ideal gas density distribution. We use a scaling rule that allows one to classify the final cluster-size distributions using only one parameter that we call the competitiveness, which can be seen as a measure of the strength of the interactions. We find that both empirical city-size distributions and electoral results can be thus reproduced and classified according to this competitiveness-parameter, that also allow us to infer the maximum number of stable social relationships that one person can maintain, known as the Dunbar number, together with its standard deviation. We discuss the importance of this number in connection with the empirical phenomenon known as “six-degrees of separation”. Finally, we show that scaled city-size distributions of large countries follow, in general, the same universal distribution.

  20. Referential Cohesion and Logical Coherence of Narration after Closed Head Injury

    ERIC Educational Resources Information Center

    Davis, G. Albyn; Coelho, Carl A.

    2004-01-01

    A group with closed head injury was compared to neurologically intact controls regarding the referential cohesion and logical coherence of narrative production. A sample of six stories was obtained with tasks of cartoon-elicited story-telling and auditory-oral retelling. We found deficits in the clinical group with respect to referential cohesion,…

  1. Referential Cohesion and Logical Coherence of Narration after Closed Head Injury

    ERIC Educational Resources Information Center

    Davis, G. Albyn; Coelho, Carl A.

    2004-01-01

    A group with closed head injury was compared to neurologically intact controls regarding the referential cohesion and logical coherence of narrative production. A sample of six stories was obtained with tasks of cartoon-elicited story-telling and auditory-oral retelling. We found deficits in the clinical group with respect to referential cohesion,…

  2. Group size effect on cooperation in one-shot social dilemmas

    PubMed Central

    Barcelo, Hélène; Capraro, Valerio

    2015-01-01

    Social dilemmas are central to human society. Depletion of natural resources, climate protection, security of energy supply, and workplace collaborations are all examples of social dilemmas. Since cooperative behaviour in a social dilemma is individually costly, Nash equilibrium predicts that humans should not cooperate. Yet experimental studies show that people do cooperate even in anonymous one-shot interactions. In spite of the large number of participants in many modern social dilemmas, little is known about the effect of group size on cooperation. Does larger group size favour or prevent cooperation? We address this problem both experimentally and theoretically. Experimentally, we find that there is no general answer: it depends on the strategic situation. Specifically, we find that larger groups are more cooperative in the Public Goods game, but less cooperative in the N-person Prisoner's dilemma. Theoretically, we show that this behaviour is not consistent with either the Fehr & Schmidt model or (a one-parameter version of) the Charness & Rabin model, but it is consistent with the cooperative equilibrium model introduced by the second author. PMID:25605124

  3. Sample size for a two-group comparison of repeated binary measurements using GEE.

    PubMed

    Jung, Sin-Ho; Ahn, Chul W

    2005-09-15

    Controlled clinical trials often randomize subjects to two treatment groups and repeatedly evaluate them at baseline and intervals across a treatment period of fixed duration. A popular primary objective in these trials is to compare the change rates in the repeated measurements between treatment groups. Repeated measurements usually involve missing data and a serial correlation within each subject. The generalized estimating equation (GEE) method has been widely used to fit the time trend in repeated measurements because of its robustness to random missing and mispecification of the true correlation structure. In this paper, we propose a closed form sample size formula for comparing the change rates of binary repeated measurements using GEE for a two-group comparison. The sample size formula is derived incorporating missing patterns, such as independent missing and monotone missing, and correlation structures, such as AR(1) model. We also propose an algorithm to generate correlated binary data with arbitrary marginal means and a Markov dependency and use it in simulation studies. Copyright (c) 2005 John Wiley & Sons, Ltd.

  4. Group size effect on cooperation in one-shot social dilemmas.

    PubMed

    Barcelo, Hélène; Capraro, Valerio

    2015-01-21

    Social dilemmas are central to human society. Depletion of natural resources, climate protection, security of energy supply, and workplace collaborations are all examples of social dilemmas. Since cooperative behaviour in a social dilemma is individually costly, Nash equilibrium predicts that humans should not cooperate. Yet experimental studies show that people do cooperate even in anonymous one-shot interactions. In spite of the large number of participants in many modern social dilemmas, little is known about the effect of group size on cooperation. Does larger group size favour or prevent cooperation? We address this problem both experimentally and theoretically. Experimentally, we find that there is no general answer: it depends on the strategic situation. Specifically, we find that larger groups are more cooperative in the Public Goods game, but less cooperative in the N-person Prisoner's dilemma. Theoretically, we show that this behaviour is not consistent with either the Fehr &Schmidt model or (a one-parameter version of) the Charness &Rabin model, but it is consistent with the cooperative equilibrium model introduced by the second author.

  5. Modeling Asteroid Spin-up with Cohesion

    NASA Astrophysics Data System (ADS)

    Walsh, Kevin J.; Richardson, D. C.; Michel, P.

    2008-09-01

    Recent work has shown that the gradual spin-up of cohesionless gravitational aggregates produces a wide range of outcomes depending on the specific configuration of the body, such as particle size distribution. One important outcome is the creation of binary asteroids, which requires bodies that can maintain spherical/oblate shapes as the body is spun to rapid rotation (Walsh et al., 2008, Nature, 454, 188-191). Our recent work includes a similar model which also models cohesion within the gravitational aggregate by way of a spring-like restoring force between neighboring particles that vanishes under high strain. We will present early results of gradual spin-up tests on gravitational aggregates covering a large range of starting conditions including the initial body shape and size, as well as varying configurations for the cohesion properties. These results will be compared to previous spin-up work as well as analytical theory. KJW and PM had the support of the French Programme National de Planétologie and the ACT Team of ESA and Ariadna Study 07/4111"Asteroid Rotational Fragmentation". KJW is also supported by the Henri Poincaré fellowship at the Observatoire de la Côte d'Azur, Nice, France, and Rotary International -- District 1730. DCR acknowledges support from the National Science Foundation under grant AST0708110 and the National Aeronautics and Space Administration under Grant No. NNX08AM39G.

  6. CF45-1, a Secreted Protein Which Participates in Dictyostelium Group Size Regulation

    PubMed Central

    Brock, Debra A.; Hatton, R. Diane; Giurgiutiu, Dan-Victor; Scott, Brenton; Jang, Wonhee; Ammann, Robin; Gomer, Richard H.

    2003-01-01

    Developing Dictyostelium cells aggregate to form fruiting bodies containing typically 2 × 104 cells. To prevent the formation of an excessively large fruiting body, streams of aggregating cells break up into groups if there are too many cells. The breakup is regulated by a secreted complex of polypeptides called counting factor (CF). Countin and CF50 are two of the components of CF. Disrupting the expression of either of these proteins results in cells secreting very little detectable CF activity, and as a result, aggregation streams remain intact and form large fruiting bodies, which invariably collapse. We find that disrupting the gene encoding a third protein present in crude CF, CF45-1, also results in the formation of large groups when cells are grown with bacteria on agar plates and then starve. However, unlike countin− and cf50− cells, cf45-1− cells sometimes form smaller groups than wild-type cells when the cells are starved on filter pads. The predicted amino acid sequence of CF45-1 has some similarity to that of lysozyme, but recombinant CF45-1 has no detectable lysozyme activity. In the exudates from starved cells, CF45-1 is present in a ∼450-kDa fraction that also contains countin and CF50, suggesting that it is part of a complex. Recombinant CF45-1 decreases group size in colonies of cf45-1− cells with a 50% effective concentration (EC50) of ∼8 ng/ml and in colonies of wild-type and cf50− cells with an EC50 of ∼40 ng/ml. Like countin− and cf50− cells, cf45-1− cells have high levels of cytosolic glucose, high cell-cell adhesion, and low cell motility. Together, the data suggest that CF45-1 participates in group size regulation in Dictyostelium. PMID:12912898

  7. Impact of group size on female reproductive success of free-ranging Rhinopithecus roxellana in the Qinling Mountains, China.

    PubMed

    Zhao, Dapeng; Li, Baoguo; Watanabe, Kunio

    2011-01-01

    Group size influences female reproductive success through scramble/contest feeding competition, predation pressures and infanticide risks in primates. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is an endangered folivorous colobine species living in a multilevel society. From 2002 to 2008, we studied a free-ranging band of R. roxellana in the Qinling Mountains of China to examine the effect of group size on female reproductive success. During our observation period, the number of monkeys in the study band fluctuated from 61 to 108, and the number of one-male/multi-female groups within it varied from 7 to 10. A significant negative linear relationship was found between group size and birth rate, but group size was not significantly correlated with infant survival rate or interbirth interval. These results suggest that group size influences female reproductive success via within-group scramble competition in this folivorous species.

  8. Side-group size effects on interfaces and glass formation in supported polymer thin films

    NASA Astrophysics Data System (ADS)

    Xia, Wenjie; Song, Jake; Hsu, David D.; Keten, Sinan

    2017-05-01

    Recent studies on glass-forming polymers near interfaces have emphasized the importance of molecular features such as chain stiffness, side-groups, molecular packing, and associated changes in fragility as key factors that govern the magnitude of Tg changes with respect to the bulk in polymer thin films. However, how such molecular features are coupled with substrate and free surface effects on Tg in thin films remains to be fully understood. Here, we employ a chemically specific coarse-grained polymer model for methacrylates to investigate the role of side-group volume on glass formation in bulk polymers and supported thin films. Our results show that bulkier side-groups lead to higher bulk Tg and fragility and are associated with a pronounced free surface effect on overall Tg depression. By probing local Tg within the films, however, we find that the polymers with bulkier side-groups experience a reduced confinement-induced increase in local Tg near a strongly interacting substrate. Further analyses indicate that this is due to the packing frustration of chains near the substrate interface, which lowers the attractive interactions with the substrate and thus lessens the surface-induced reduction in segmental mobility. Our results reveal that the size of the polymer side-group may be a design element that controls the confinement effects induced by the free surface and substrates in supported polymer thin films. Our analyses provide new insights into the factors governing polymer dynamics in bulk and confined environments.

  9. The kinetics of mechanically coupled myosins exhibit group size-dependent regimes.

    PubMed

    Hilbert, Lennart; Cumarasamy, Shivaram; Zitouni, Nedjma B; Mackey, Michael C; Lauzon, Anne-Marie

    2013-09-17

    Naturally occurring groups of muscle myosin behave differently from individual myosins or small groups commonly assayed in vitro. Here, we investigate the emergence of myosin group behavior with increasing myosin group size. Assuming the number of myosin binding sites (N) is proportional to actin length (L) (N = L/35.5 nm), we resolve in vitro motility of actin propelled by skeletal muscle myosin for L = 0.2-3 μm. Three distinct regimes were found: L < 0.3 μm, sliding arrest; 0.3 μm ≤ L ≤ 1 μm, alternation between arrest and continuous sliding; L > 1 μm, continuous sliding. We theoretically investigated the myosin group kinetics with mechanical coupling via actin. We find rapid actin sliding steps driven by power-stroke cascades supported by postpower-stroke myosins, and phases without actin sliding caused by prepower-stroke myosin buildup. The three regimes are explained: N = 8, rare cascades; N = 15, cascade bursts; N = 35, continuous cascading. Two saddle-node bifurcations occur for increasing N (mono → bi → mono-stability), with steady states corresponding to arrest and continuous cascading. The experimentally measured dependence of actin sliding statistics on L and myosin concentration is correctly predicted.

  10. The Kinetics of Mechanically Coupled Myosins Exhibit Group Size-Dependent Regimes

    PubMed Central

    Hilbert, Lennart; Cumarasamy, Shivaram; Zitouni, Nedjma B.; Mackey, Michael C.; Lauzon, Anne-Marie

    2013-01-01

    Naturally occurring groups of muscle myosin behave differently from individual myosins or small groups commonly assayed in vitro. Here, we investigate the emergence of myosin group behavior with increasing myosin group size. Assuming the number of myosin binding sites (N) is proportional to actin length (L) (N = L/35.5 nm), we resolve in vitro motility of actin propelled by skeletal muscle myosin for L = 0.2–3 μm. Three distinct regimes were found: L < 0.3 μm, sliding arrest; 0.3 μm ≤ L ≤ 1 μm, alternation between arrest and continuous sliding; L > 1 μm, continuous sliding. We theoretically investigated the myosin group kinetics with mechanical coupling via actin. We find rapid actin sliding steps driven by power-stroke cascades supported by postpower-stroke myosins, and phases without actin sliding caused by prepower-stroke myosin buildup. The three regimes are explained: N = 8, rare cascades; N = 15, cascade bursts; N = 35, continuous cascading. Two saddle-node bifurcations occur for increasing N (mono → bi → mono-stability), with steady states corresponding to arrest and continuous cascading. The experimentally measured dependence of actin sliding statistics on L and myosin concentration is correctly predicted. PMID:24047998

  11. Effect size indices for analyses of measurement equivalence: understanding the practical importance of differences between groups.

    PubMed

    Nye, Christopher D; Drasgow, Fritz

    2011-09-01

    Because of the practical, theoretical, and legal implications of differential item functioning (DIF) for organizational assessments, studies of measurement equivalence are a necessary first step before scores can be compared across individuals from different groups. However, commonly recommended criteria for evaluating results from these analyses have several important limitations. The present study proposes an effect size index for confirmatory factor analytic (CFA) studies of measurement equivalence to address 1 of these limitations. The application of this index is illustrated with personality data from American English, Greek, and Chinese samples. Results showed a range of nonequivalence across these samples, and these differences were linked to the observed effects of DIF on the outcomes of the assessment (i.e., group-level mean differences and adverse impact).

  12. Radiative Capture Processes in Multi-Size-Scale Algebraic Version of Resonating Group Model

    NASA Astrophysics Data System (ADS)

    Solovyev, A. S.; Igashov, S. Yu; Tchuvil'sky, Yu M.

    2017-06-01

    Novel microscopic approach based on so-called multi-size-scale algebraic version of the resonating group model to describing radiative capture reactions is developed. The main idea of the approach is to expand nuclear system wave functions of discrete spectrum and continuum over basis wave functions of the algebraic version of the resonating group model with different values of oscillator radius. It allows to calculate astrophysical S-factor or cross section for radiative capture reaction and at the same time to reproduce exactly the experimental values for breakup thresholds of the final nucleus states into two fragments -colliding nuclei, as well as to obtain corresponding scattering phase shifts fitting existing experimental data. The approach is applied to description of the important mirror3H(α, γ)7Li and3He(α, γ)7Be reactions to demonstrate its possibilities. Calculated results are in good agreement with experimental data.

  13. Q -voter model with nonconformity in freely forming groups: Does the size distribution matter?

    NASA Astrophysics Data System (ADS)

    Radosz, Wojciech; Mielnik-Pyszczorski, Adam; Brzezińska, Marta; Sznajd-Weron, Katarzyna

    2017-06-01

    We study a q -voter model with stochastic driving on a complete graph with q being a random variable described by probability density function P (q ) , instead of a constant value. We investigate two types of P (q ) : (1) artificial with the fixed expected value , but a changing variance and (2) empirical of freely forming groups in informal places. We investigate also two types of stochasticity that can be interpreted as different kinds of nonconformity (anticonformity or independence) to answer the question about differences observed at the macroscopic level between these two types of nonconformity in real social systems. Moreover, we ask the question if the behavior of a system depends on the average value of the group size q or rather on probability distribution function P (q ) .

  14. The effect of group size on vigilance in a semi-solitary, fossorial marsupial (Lasiorhinus latifrons).

    PubMed

    Descovich, Kristin A; Lisle, Allan T; Johnston, Stephen; Phillips, Clive J C

    2013-11-01

    Prey species that congregate gain protection against predatory attacks and this advantage is often reflected by a reduction in vigilance behaviour by individuals in larger groups. Comparatively few studies have investigated vigilance in solitary animals, but those that have, found that vigilance increases as group size increases because of the threat posed by conspecifics and/or competition for resources. The southern hairy-nosed wombat (Lasiorhinus latifrons) is a large fossorial, nocturnal marsupial that is neither strictly solitary nor gregarious, sharing warren systems with multiple conspecifics. We investigated the effects of conspecific presence on vigilance behaviour in this semi-solitary species. We observed wild-born, adult L. latifrons wombats in three group sizes (Large (1♂, 3♀), Medium (1♂, 2♀) and Small (1♂, 1♀)) in a captive, naturalistic environment that allowed above-ground and den behaviour monitoring. Vigilance behaviours were performed less frequently by wombats in large groups (e.g. scanning, counts/day, Large: 55, Medium: 69, Small: 115, P=0.002) and more frequently as the distance from their nearest conspecific increased (r64=0.30, P= 0.016). Vigilance within burrows was also affected by social influences, with solitary wombats significantly more vigilant than those denning with a conspecific (e.g. scanning: conspecific absent: 0.13/5min, present: 0.03/5min, P<0.0001). It is concluded that the presence of conspecifics reduces vigilance in L. latifrons wombats, even within burrows, and this may partially explain the occurrence of warren sharing in the wild.

  15. Oscillations in shoal cohesion in zebrafish (Danio rerio).

    PubMed

    Miller, Noam Y; Gerlai, Robert

    2008-11-03

    In many species, group cohesion may be the result of a compromise between opposing forces (e.g. predator avoidance and competition for food). However, little empirical data exists on the dynamics of group cohesion. We present moment-to-moment positional data on zebrafish shoals and analyze temporal changes in inter-individual distances. We demonstrate that the distance between shoal members does not settle at any given value, as has previously been assumed, but oscillates with a period between 5 and 15s.

  16. Wormlike micelles in poly(oxyethylene) surfactant solution: Growth control through hydrophilic-group size variation.

    PubMed

    Ahmed, Toufiq; Aramaki, Kenji

    2008-11-01

    Viscoelastic micellar solutions are formed in poly(oxyethylene) cholesteryl ether (ChEO(m), m=15, 30) aqueous solutions on addition of tri(ethyleneglycol) mono n-dodecyl ether (C(12)EO(3)). The steady-shear and dynamic rheological behavior of the systems is characteristic of wormlike micellar solution. In either system, the plateau modulus (G(0)) and relaxation time (tau) are found to increase with increasing cosurfactant mixing fractions. The plateau modulus of the ChEO(30)-C(12)EO(3) system at the maximum viscosity region is found to be higher than that in the ChEO(15)-C(12)EO(3) system at the maximum viscosity region, whereas for the relaxation time the opposite relation is found. The maximum viscosities obtained in the two systems are of the same order of magnitude. In the ChEO(30)-C(12)EO(3) system, the maximum viscosity is obtained at a higher cosurfactant mixing fraction than that in the ChEO(15)-C(12)EO(3) system. It is concluded that decreasing the head-group size of the hydrophilic surfactant favors micellar growth. Monolaurin, another hydrophobic surfactant known to induce growth in some systems, is found to cause phase separation before significant micellar growth occurs in ChEO(m) solutions, although the effect of head-group size of ChEO(m) is found to be similar to the ChEO(m)-C(12)EO(3) systems.

  17. One is not enough: Group size modulates social gaze-induced object desirability effects.

    PubMed

    Capozzi, Francesca; Bayliss, Andrew P; Elena, Marco R; Becchio, Cristina

    2015-06-01

    Affective evaluations of objects are influenced by the preferences expressed by other people via their gaze direction, so that objects looked at are liked more than objects looked away from. But when can others' preferences be trusted? Here, we show that group size influences the extent to which individuals tend to conform to others' gaze preferences. We adopted the conventional gaze-cuing paradigm and modified the design in such a way that some objects were consistently cued by only one face (single-face condition), whereas other objects were consistently cued by several different faces (multiple-faces condition). While response time measures revealed equal gaze-cuing effects for both conditions, a boost in affective evaluation was observed only for objects looked at by several different faces. Objects looked at by a single face were not rated differently than objects looked away from. These findings suggest that observers make use of group size to evaluate the generalizability of the epistemic information conveyed by others' gaze: Objects looked at are liked more than objects looked away from, but only when they are looked at by multiple faces.

  18. Redundancy and the Cohesion Cloze.

    ERIC Educational Resources Information Center

    Bensoussan, Marsha

    1990-01-01

    Investigates the usefulness of using grammatical cohesion to evaluate the macro- or discourse-level, and the micro-level reading comprehension of English-as-a-Foreign-Language (EFL) students. Finds a relationship between anaphora and coherence that contributes to reading difficulty. (MG)

  19. Promoting Community Cohesion in England

    ERIC Educational Resources Information Center

    Morris, Andrew B.; McDaid, Maggie; Potter, Hugh

    2011-01-01

    Following serious disturbances in some northern cities in England in 2001, concerns about possible rising inter-communal tension have led to a statutory duty to promote community cohesion being placed on schools. Inspectors from the Office for Standards in Education (Ofsted) are required to make judgements in the leadership and management section…

  20. Writing Quality, Coherence, and Cohesion.

    ERIC Educational Resources Information Center

    McCulley, George A.

    1985-01-01

    Using a random sample of 493 persuasive papers written by 17-year-olds during the 1978-79 National Assessment of Educational Progress writing evaluation, a study investigated the relationships among features of textual cohesion and primary trait assessments of writing quality and coherence, with manuscript length held statistically constant. (HOD)

  1. The Ethics of Social Cohesion

    ERIC Educational Resources Information Center

    Heuser, Brian L.

    2005-01-01

    With trust as its antecedent, social capital comprises the potential capacities of a people to prosper. Building on the presence of social capital, social cohesion involves the internalization of social ethics and constitutes the level of realized propensity among citizens to engage in virtuous behavior for the common good. This theory elaboration…

  2. Fish otoliths: do sizes correlate with taxonomic group, habitat and/or luminescence?

    PubMed

    Paxton, J R

    2000-09-29

    Otoliths are dense structures in the ears of fishes that function in hearing and gravity perception. Otolith (sagitta) diameters, as percentages of standard length (% SL), are calculated for 247 marine fish species in 147 families and compared by taxonomic group (usually order), habitat and presence or absence of luminescence. Otolith sizes range from 0.4-31.4 mm and 0.08-11.2% SL. The eel and spiny eel orders Anguilliformes and Notacanthiformes have small to very small otoliths, as do the triggerfish order Tetraodontiformes, pipefish order Gasterosteiformes, billfish suborder Scombroidei and many of the dragonfish order Stomiiformes. The soldierfish order Beryciformes has moderate to very large otoliths. The perch order Perciformes has a wide range of otolith sizes but most have small to moderate otoliths 2-5% SL. Only 16 out of the 247 species have the relatively largest otoliths, over 7% SL. Seven out of these 16 species are also luminous from a variety of habitats. Luminous species have slightly to much larger otoliths than non-luminous species in the same family Both beryciforms and luminous fishes live in low-light environments, where acute colour vision is probably impossible. Most fishes of the epipelagic surface waters have very small otoliths, perhaps due to background noise and/or excessive movement of heavy otoliths in rough seas. Bathypelagic species usually have small otoliths and regressed or absent swimbladders. Other habitats have species with a range of otolith sizes. While the relationship between hearing ability and otolith length is unknown, at least some groups with modified swim-bladders have larger otoliths, which may be associated with more acute hearing.

  3. Development of an online database of typical food portion sizes in Irish population groups.

    PubMed

    Lyons, Jacqueline; Walton, Janette; Flynn, Albert

    2013-01-01

    The Irish Food Portion Sizes Database (available at www.iuna.net) describes typical portion weights for an extensive range of foods and beverages for Irish children, adolescents and adults. The present paper describes the methodologies used to develop the database and some key characteristics of the portion weight data contained therein. The data are derived from three large, cross-sectional food consumption surveys carried out in Ireland over the last decade: the National Children's Food Survey (2003-2004), National Teens' Food Survey (2005-2006) and National Adult Nutrition Survey (2008-2010). Median, 25th and 75th percentile portion weights are described for a total of 545 items across the three survey groups, split by age group or sex as appropriate. The typical (median) portion weights reported for adolescents and adults are similar for many foods, while those reported for children are notably smaller. Adolescent and adult males generally consume larger portions than their female counterparts, though similar portion weights may be consumed where foods are packaged in unit amounts (for example, pots of yoghurt). The inclusion of energy under-reporters makes little difference to the estimation of typical portion weights in adults. The data have wide-ranging applications in dietary assessment and food labelling, and will serve as a useful reference against which to compare future portion size data from the Irish population. The present paper provides a useful context for researchers and others wishing to use the Irish Food Portion Sizes Database, and may guide researchers in other countries in establishing similar databases of their own.

  4. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder

    PubMed Central

    Cram, Dominic L.; Blount, Jonathan D.; Young, Andrew J.

    2015-01-01

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies. PMID:26582023

  5. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder.

    PubMed

    Cram, Dominic L; Blount, Jonathan D; Young, Andrew J

    2015-11-22

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies.

  6. Transport and deposition of cohesive pharmaceutical powders in human airway

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Chu, Kaiwei; Yu, Aibing

    2017-06-01

    Pharmaceutical powders used in inhalation therapy are in the size range of 1-5 microns and are usually cohesive. Understanding the cohesive behaviour of pharmaceutical powders during their transportation in human airway is significant in optimising aerosol drug delivery and targeting. In this study, the transport and deposition of cohesive pharmaceutical powders in a human airway model is simulated by a well-established numerical model which combines computational fluid dynamics (CFD) and discrete element method (DEM). The van der Waals force, as the dominant cohesive force, is simulated and its influence on particle transport and deposition behaviour is discussed. It is observed that even for dilute particle flow, the local particle concentration in the oral to trachea region can be high and particle aggregation happens due to the van der Waals force of attraction. It is concluded that the deposition mechanism for cohesive pharmaceutical powders, on one hand, is dominated by particle inertial impaction, as proven by previous studies; on the other hand, is significantly affected by particle aggregation induced by van der Waals force. To maximum respiratory drug delivery efficiency, efforts should be made to avoid pharmaceutical powder aggregation in human oral-to-trachea airway.

  7. Social Cohesion as the Goal: Can Social Cohesion Be Directly Pursued?

    ERIC Educational Resources Information Center

    Koonce, Kelly A.

    2011-01-01

    This article establishes an understanding of social cohesion in general and discusses organizations and activities that are known to promote social cohesion before introducing organizations that claim to work toward social cohesion as one of their main priorities. The Council of Europe's Directorate General of Social Cohesion represents a…

  8. The Effect of Grouping by Formal Reasoning Ability, Formal Reasoning Ability Levels, Group Size, and Gender on Achievement in Laboratory Chemistry.

    ERIC Educational Resources Information Center

    Moody, Judith D.; Gifford, Vernon D.

    This study investigated the grouping effect on student achievement in a chemistry laboratory when homogeneous and heterogeneous formal reasoning ability, high and low levels of formal reasoning ability, group sizes of two and four, and homogeneous and heterogeneous gender were used for grouping factors. The sample consisted of all eight intact…

  9. The Effect of Grouping by Formal Reasoning Ability, Formal Reasoning Ability Levels, Group Size, and Gender on Achievement in Laboratory Chemistry.

    ERIC Educational Resources Information Center

    Moody, Judith D.; Gifford, Vernon D.

    This study investigated the grouping effect on student achievement in a chemistry laboratory when homogeneous and heterogeneous formal reasoning ability, high and low levels of formal reasoning ability, group sizes of two and four, and homogeneous and heterogeneous gender were used for grouping factors. The sample consisted of all eight intact…

  10. Social Cohesion, Social Capital and the Neighbourhood.

    ERIC Educational Resources Information Center

    Forrest, Ray; Kearns, Ade

    2001-01-01

    Outlines key dimensions of social cohesion, exploring whether societies are facing a new crisis in this area. Examines where contemporary residential neighborhoods fit into social cohesion debates, particularly regarding the interaction between social cohesion and social capital. Outlines key debates over social capital, showing how it can be…

  11. Cohesion in Written Business Discourse: Some Contrasts.

    ERIC Educational Resources Information Center

    Johns, Ann M.

    1980-01-01

    Describes study to determine whether "constellations" of cohesive items occur in letters, reports, and textbooks. Concludes cohesive elements can be identified in each type of discourse but generalizations cannot be made about cohesive features in broad classes of applied and academic English for Business and Economics (EBE) discourse.…

  12. The Influence of Physical & Biological Cohesion on Dune Development

    NASA Astrophysics Data System (ADS)

    Schindler, Robert; Parsons, Daniel; Ye, Leiping; Baas, Jaco; Hope, Julie; Manning, Andy; Malarkey, Jonathan; Aspden, Rebecca; Lichtman, Dougal; Thorne, Peter; Peakall, Jeff; Patterson, David; Davies, Alan; Bass, Sarah; O'Boyle, Louise

    2014-05-01

    Existing predictions for dune bedforms are based on simplified physical parameters, with assumptions that sediment consists only of cohesionless sand. They do not include the complexities of mud: physical cohesion is imparted by cohesive clays and biological cohesion is created by the presence of organisms which, among other things, generate extra-cellular polymers (EPS). Using controlled experiments we show the profound influence on the size, development and equilibrium morphology of dune bedforms of both physical and biological cohesion. Experiments were completed at the Total Environment Simulator facility at Hull University, UK in a 10 x 2 m channel. A flat sediment bed was laid to 0.15 m depth. A unidirectional flow of 0.25 m depth was passed over the sediment for 10 h. In Phase 1 eight different sand:clay mixes were examined, where clay content was 18.0 - 2.1%. In Phase 2, the same mixtures were used with additions of EPS. A velocity of 0.8 m s-1 was used throughout, corresponding to the dune regime for the selected sand. Bedform development was monitored via ultrasonic ranging transducers, sediment cores and water samples. Phase 1 showed substantial differences in bedform type with clay content, with size inversely related to clay content, e.g. Run 1 (18.0% clay) generated 2D ripples; Run 7 (2.1% clay) generated 3D dunes. Transitional forms, included dunes with superimposed ripples, were present between these extremes. In Phase 2, EPS contents equivalent to only 1/30th of 1% by mass prevented the development of bedforms. Bedforms were generated in sediments with 1/20th and 1/10th of 1%, with an inverse relationship between bedform size and EPS content. Comparison of Phase 1 and Phase 2 runs with equal sand:mud ratios reveals that EPS acts to severely inhibit bedform development compared with the mud-only case. We can conclude that (1) the ripple-dune transition can occur under constant flow conditions, i.e. clay content may dictate bedform type, that (2) EPS

  13. Cohesive and coherent connected speech deficits in mild stroke.

    PubMed

    Barker, Megan S; Young, Breanne; Robinson, Gail A

    2017-05-01

    Spoken language production theories and lesion studies highlight several important prelinguistic conceptual preparation processes involved in the production of cohesive and coherent connected speech. Cohesion and coherence broadly connect sentences with preceding ideas and the overall topic. Broader cognitive mechanisms may mediate these processes. This study aims to investigate (1) whether stroke patients without aphasia exhibit impairments in cohesion and coherence in connected speech, and (2) the role of attention and executive functions in the production of connected speech. Eighteen stroke patients (8 right hemisphere stroke [RHS]; 6 left [LHS]) and 21 healthy controls completed two self-generated narrative tasks to elicit connected speech. A multi-level analysis of within and between-sentence processing ability was conducted. Cohesion and coherence impairments were found in the stroke group, particularly RHS patients, relative to controls. In the whole stroke group, better performance on the Hayling Test of executive function, which taps verbal initiation/suppression, was related to fewer propositional repetitions and global coherence errors. Better performance on attention tasks was related to fewer propositional repetitions, and decreased global coherence errors. In the RHS group, aspects of cohesive and coherent speech were associated with better performance on attention tasks. Better Hayling Test scores were related to more cohesive and coherent speech in RHS patients, and more coherent speech in LHS patients. Thus, we documented connected speech deficits in a heterogeneous stroke group without prominent aphasia. Our results suggest that broader cognitive processes may play a role in producing connected speech at the early conceptual preparation stage. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. The Impact of Group Size on Welfare Indicators of Ewes during Pregnancy.

    PubMed

    Averós, Xavier; Beltrán de Heredia, Ignacia; Ruiz, Roberto; Estevez, Inma

    2016-01-01

    Group size (GS) and space allowance have major implications for the welfare of production species, however their effects are often confounded. In a previous study we investigated the impact of varying space allowance at constant GS. In the present work we report the consequences of varying GS on pregnant ewes while controlling space allowance. We housed ewes at 6 (GS6) or 12 ewes/enclosure (GS12), while controlling space allowance to 1.5 m2/ewe (3 enclosures/treatment), and necessarily varying enclosure size. Therefore, when indicating GS effects we implicitly reflect a confounding effect with that of enclosure size. Movement, use of space, behaviour, serum cortisol concentration and body condition score (BCS) were collected during the last 12 gestation weeks. Movement, use of space, and behaviour were collected every other week, during 2 days/week, using 10 minute continuous scan samplings. Blood was collected during weeks 10, 13, 17, and 21 of gestation, and BCS during weeks 15 and 21. Data were analysed using repeated measures, generalized linear mixed models, with GS, week, and their interaction as fixed effects, and enclosure as random effect. GS mainly affected movement and use of space. GS12 ewes walked longer distances using longer steps (P<0.001). An interaction GS by week was observed for angular dispersion (P<0.0001), which was smaller for GS12 from week 10 onwards. Initial restlessness levels were lower for GS12, as shown by the reduced frequency of location changes (P<0.0001). Furthest and mean neighbour distances increased with GS (P<0.0001). The effect of GS on behaviour was only evident for eating behaviour as an interaction with gestation week (P<0.05). Changes in behaviour, movement and use of space along the study indicated an activity peak during weeks 3 to 5. Cortisol changes during gestation (P<0.01) also reflected this activity peak, while BCS (P<0.001) reflected normal physical condition changes during pregnancy. Although the separate

  15. The Impact of Group Size on Welfare Indicators of Ewes during Pregnancy

    PubMed Central

    Averós, Xavier; Beltrán de Heredia, Ignacia; Ruiz, Roberto; Estevez, Inma

    2016-01-01

    Group size (GS) and space allowance have major implications for the welfare of production species, however their effects are often confounded. In a previous study we investigated the impact of varying space allowance at constant GS. In the present work we report the consequences of varying GS on pregnant ewes while controlling space allowance. We housed ewes at 6 (GS6) or 12 ewes/enclosure (GS12), while controlling space allowance to 1.5 m2/ewe (3 enclosures/treatment), and necessarily varying enclosure size. Therefore, when indicating GS effects we implicitly reflect a confounding effect with that of enclosure size. Movement, use of space, behaviour, serum cortisol concentration and body condition score (BCS) were collected during the last 12 gestation weeks. Movement, use of space, and behaviour were collected every other week, during 2 days/week, using 10 minute continuous scan samplings. Blood was collected during weeks 10, 13, 17, and 21 of gestation, and BCS during weeks 15 and 21. Data were analysed using repeated measures, generalized linear mixed models, with GS, week, and their interaction as fixed effects, and enclosure as random effect. GS mainly affected movement and use of space. GS12 ewes walked longer distances using longer steps (P<0.001). An interaction GS by week was observed for angular dispersion (P<0.0001), which was smaller for GS12 from week 10 onwards. Initial restlessness levels were lower for GS12, as shown by the reduced frequency of location changes (P<0.0001). Furthest and mean neighbour distances increased with GS (P<0.0001). The effect of GS on behaviour was only evident for eating behaviour as an interaction with gestation week (P<0.05). Changes in behaviour, movement and use of space along the study indicated an activity peak during weeks 3 to 5. Cortisol changes during gestation (P<0.01) also reflected this activity peak, while BCS (P<0.001) reflected normal physical condition changes during pregnancy. Although the separate

  16. Discourse Cohesion in the Verbal Interactions of Individuals Diagnosed with Autistic Disorder or Schizotypal Personality Disorder.

    ERIC Educational Resources Information Center

    Baltaxe, Christiane A. M.; And Others

    1995-01-01

    This study compared high functioning adolescents and young adults with autism (n=8) or schizotypal personality disorder (n=9) in use of social language referencing. Both groups had similar rates, types, and patterns of cohesive reference errors, though subjects with schizotypal disorder used cohesive ties of reference more often and more correctly…

  17. The Cohesion Concept's Relationship to the Coherence of Text. Technical Report No. 221.

    ERIC Educational Resources Information Center

    Tierney, Robert J.; Mosenthal, James H.

    Using M. A. K. Halliday's and R. Hasan's concept of cohesion, a study examined statistical accounting of cohesive ties as a means of measuring and evaluating text coherence. Twelve grade twelve students were provided outlines on two topics and asked to write essays for each topic. One group of six students was familiar with the topics, the other…

  18. Cohesion, coherence, and declarative memory: Discourse patterns in individuals with hippocampal amnesia.

    PubMed

    Kurczek, Jake; Duff, Melissa C

    2011-01-01

    BACKGROUND: Discourse cohesion and coherence gives our communication continuity. Deficits in cohesion and coherence have been reported in patients with cognitive-communication disorders (e.g., TBI, dementia). However, the diffuse nature of pathology and widespread cognitive deficits of these disorders have made identification of specific neural substrates and cognitive systems critical for cohesion and coherence challenging. AIMS: Taking advantage of a rare patient group with selective and severe declarative memory impairments, the current study attempts to isolate the contribution of declarative memory to the successful use of cohesion and coherence in discourse. METHODS #ENTITYSTARTX00026; PROCEDURES: Cohesion and coherence were examined in the discourse of six participants with hippocampal amnesia and six demographically matched comparison participants. Specifically, this study (1) documents the frequency, type, and completeness of cohesive ties; (2) evaluates discourse for local and global coherence; and (3) compares use of cohesive ties and coherence ratings in amnesia and healthy participants. OUTCOMES #ENTITYSTARTX00026; RESULTS: Overall, amnesia participants produced fewer cohesive ties per T-unit, the adequacy of their ties were more often judged to be incomplete, and the ratings of their local coherence were consistently lower than comparison participants. CONCLUSIONS: These findings suggest that declarative memory may contribute to the discursive use of cohesion and coherence. Broader notions of cohesion, or interactional cohesion, i.e., cohesion across speakers (two or more people), time (days, weeks), and communicative resources (gesture), warrant further study as the experimental tasks used in the literature, and here, may actually underestimate or overestimate the extent of impairment.

  19. Exchange and cohesion in dyads and triads: A test of Simmel's hypothesis.

    PubMed

    Yoon, Jeongkoo; Thye, Shane R; Lawler, Edward J

    2013-11-01

    This paper uses social exchange theory to address a classic question posed by Simmel (1964) regarding dyads and triads. The question is whether exchanges in a triad will generate more cohesion at the group level than exchanges in an isolated dyad. The main hypotheses, integrating several ideas from Simmel and social exchange theories, are as follows. First, triads generate less variability of behavior than dyads; that is, there is more uniformity or convergence in triads. Second, in the context of repeated exchange, we predict higher levels of cohesion in triads than in dyads. Third, positive emotion or affect has a stronger impact on cohesion in dyads than in triads, whereas uncertainty reduction has a stronger impact on cohesion in triads. To test these hypotheses, an experiment compared isolated dyads to dyads nested in a triadic exchange network. Subjects engaged in exchanges across a series of distinct episodes, using standard experimental procedures from research on relational cohesion (Lawler and Yoon, 1996) and exchange networks (Molm and Cook, 1995; Willer, 1999). Consistent with the hypotheses, the results reveal more convergence of behavior and higher cohesion in triads than in dyads; moreover, uncertainty reduction is the primary basis for cohesion in the triad, whereas positive affect was the primary basis for cohesion in the dyad. These results are discussed in relation to Simmelian dyad-triad dynamics and the theory of relational cohesion.

  20. Dependence of ripple dimensions on cohesive and non-cohesive bed properties in the intertidal Dee Estuary

    NASA Astrophysics Data System (ADS)

    Lichtman, Ian; Thorne, Peter; Baas, Jacobus; O'Boyle, Louise; Cooke, Richard; Amoudry, Laurent; Bell, Paul; Aspden, Rebecca; Bass, Sarah; Davies, Alan; Hope, Julie; Malarkey, Jonathan; Manning, Andrew; Parsons, Daniel; Paterson, David; Peakall, Jeffrey; Schindler, Robert; Ye, Leiping

    2014-05-01

    There is a need to better understand the effects of cohesive and mixed sediments on coastal processes, to improve sediment transport models for the management of coastal erosion, siltation of navigation channels and habitat change. Although reasonable sediment transport predictors are available for pure sands, it still is not the case for mixed cohesive and non-cohesive sediments. Existing predictors mostly relate ripple dimensions to hydrodynamic conditions and median sediment grain diameter, assuming a narrow unimodal particle size distribution. Properties typical of mixed conditions, such as composition and cohesion for example, are not usually taken into account. This presents severe shortcomings to predictors' abilities. Indeed, laboratory experiments using mixed cohesive sediments have shown that bedform dimensions decrease with increasing bed mud content. In the field, one may expect current predictors to match data for well-sorted sands closely, but poorly for mixed sediments. Our work is part of the COHBED project and aims to: (1) examine, in field conditions, if ripple dimensions are significantly different for mixed cohesive sediment beds compared to beds with pure sand; (2) compare the field data with laboratory results that showed reduced ripple length due to cohesive mud content; and (3) assess the performance of a selection of ripple predictors for mixed sediment data. The COHBED project was set up to undertake laboratory experiments and fieldwork to study how physical and biological processes influence bedform development in a mixed cohesive-cohesionless sediment environment. As part of COHBED, a suite of instruments was deployed on tidal flats in the Dee Estuary (on the NW coast of England), collecting co-located measurements of the hydrodynamics, suspended sediment properties and bed morphology. The instruments occupied three sites collecting data over different bed compositions during a two week period (21 May to 4 June 2013). One site was

  1. Persistent telomere cohesion triggers a prolonged anaphase.

    PubMed

    Kim, Mi Kyung; Smith, Susan

    2014-01-01

    Telomeres use distinct mechanisms (not used by arms or centromeres) to mediate cohesion between sister chromatids. However, the motivation for a specialized mechanism at telomeres is not well understood. Here we show, using fluorescence in situ hybridization and live-cell imaging, that persistent sister chromatid cohesion at telomeres triggers a prolonged anaphase in normal human cells and cancer cells. Excess cohesion at telomeres can be induced by inhibition of tankyrase 1, a poly(ADP-ribose) polymerase that is required for resolution of telomere cohesion, or by overexpression of proteins required to establish telomere cohesion, the shelterin subunit TIN2 and the cohesin subunit SA1. Regardless of the method of induction, excess cohesion at telomeres in mitosis prevents a robust and efficient anaphase. SA1- or TIN2-induced excess cohesion and anaphase delay can be rescued by overexpression of tankyrase 1. Moreover, we show that primary fibroblasts, which accumulate excess telomere cohesion at mitosis naturally during replicative aging, undergo a similar delay in anaphase progression that can also be rescued by overexpression of tankyrase 1. Our study demonstrates that there are opposing forces that regulate telomere cohesion. The observation that cells respond to unresolved telomere cohesion by delaying (but not completely disrupting) anaphase progression suggests a mechanism for tolerating excess cohesion and maintaining telomere integrity. This attempt to deal with telomere damage may be ultimately futile for aging fibroblasts but useful for cancer cells.

  2. Correlation effects in metallic cohesion

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    2014-03-01

    The electronic contribution to the cohesive energy of a correlated metal is the sum of the transition energies for adding successive electrons at successive Fermi levels until the system reaches its final electron density. This can be computed as the integral of energy over the projected density of transitions for adding single electrons to localized orbitals. In the case of independent electrons, this reduces to the usual integral over the projected density of states. As an example, cohesive energies for some simple transition metal structures are calculated using the recursion method* with a Hubbard repulsion between electrons. * Phys. Rev. B 61, 7953-64 Work supported by the Richmond F. Snyder gift to the University of Oregon.

  3. Solubilization of lipid bilayers by myristyl sucrose ester: effect of cholesterol and phospholipid head group size.

    PubMed

    Toro, C; Sanchez, S A; Zanocco, A; Lemp, E; Gratton, E; Gunther, G

    2009-02-01

    The solubilization of biological membranes by detergents has been used as a major method for the isolation and purification of membrane proteins and other constituents. Considerable interest in this field has resulted from the finding that different components can be solubilized selectively. Certain membrane constituents are incorporated into small micelles, whereas others remain in the so-called detergent-resistant membrane domains that are large enough to be separated by centrifugation. The detergent-resistant fractions contain an elevated percentage of cholesterol, and thus its interaction with specific lipids and proteins may be key for membrane organization and regulation of cellular signaling events. This report focuses on the solubilization process induced by the sucrose monoester of myristic acid, beta-D-fructofuranosyl-6-O-myristyl-alpha-D-glucopyranoside (MMS), a nonionic detergent. We studied the effect of the head group and the cholesterol content on the process. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and dioctadecyl-dimethyl-ammonium chloride (DODAC) vesicles were used, and the solubilization process was followed using Laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) generalized polarization (GP) measurements, carried out in the cuvette and in the 2-photon microscope. Our results indicate that: (i) localization of the MMS moieties in the lipid bilayer depends on the characteristics of the lipid polar head group and influences the solubilization process. (ii) Insertion of cholesterol molecules into the lipid bilayer protects it from solubilizaton and (iii) the microscopic mechanism of solubilization by MMS implies the decrease in size of the individual liposomes.

  4. Solubilization of lipid bilayers by myristyl sucrose ester: effect of cholesterol and phospholipid head group size

    PubMed Central

    Toro, C.; Sanchez, S. A.; Zanocco, A.; Lemp, E.; Gratton, E.

    2010-01-01

    The solubilization of biological membranes by detergents has been used as a major method for the isolation and purification of membrane proteins and other constituents. Considerable interest in this field has resulted from the finding that different components can be solubilized selectively. Certain membrane constituents are incorporated into small micelles, whereas others remain in the so-called detergent-resistant membrane domains that are large enough to be separated by centrifugation. The detergent resistant fractions contain an elevated percentage of cholesterol, and thus its interaction with specific lipids and proteins may be key for membrane organization and regulation of cellular signaling events. This report focuses on the solubilization process induced by the sucrose monoester of myristic acid, β-D-Fructofuranosyl-6-O-myristyl-α-D-glucopyranoside (MMS), a nonionic detergent. We studied the effect of the head group and the cholesterol content on the process. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and Dioctadecyl dimethylammonium chloride (DODAC) vesicles were used, and the solubilization process was followed using Laurdan (6-Dodecanoyl-2-dimethylaminonaphthalene) Generalized Polarization (GP) measurements, carried out in the cuvette and in the 2-photon microscope. Our results indicate that: (i) Localization of the MMS moieties in the lipid bilayer depend on the characteristics of the lipid polar head group and influence the solubilization process. (ii) Insertion of cholesterol molecules into the lipid bilayer protects it from solubilizaton and (iii) the microscopic mechanism of solubilization by MMS implies the decrease in size of the individual liposomes. PMID:19071100

  5. Hyphal responses of Neurospora crassa to micron-sized beads with functional chemical surface groups

    NASA Astrophysics Data System (ADS)

    Held, Marie; Edwards, Clive; Nicolau, Dan V.

    2011-02-01

    Filamentous fungi include serious plant and animal pathogens that explore their environment efficiently in order to penetrate the host. This environment is physically and chemically heterogeneous and the fungi rely on specific physical and chemical signals to find the optimal point/s of attack. This study presents a methodology to introduce distinct structures with dimensions similar to the hyphal diameter and specific chemical surface groups into a controllable environment in order to study the fungal response. We introduced 3.3 μm polystyrene beads covered with Epoxy surface groups into microfluidic channels made from PDMS by rapid replica molding. The experimental setup resulted in different areas with low and high densities of beads as well as densely packed patches. The observations of the fungus exploring the areas long-term showed that the growth parameters were altered significantly, compared with the values measured on agar. The fungus responded to both, the physical and chemical parameters of the beads, including temporary directional changes, increased branching angles, decreased branching distances, decreased apical extension velocities and occasional cell wall lysis. The wealth and magnitude of the observed responses indicates that the microfluidic structures provide a powerful platform for the investigation of micron-sized features on filamentous fungi.

  6. Cohesive detachment of an elastic pillar from a dissimilar substrate

    NASA Astrophysics Data System (ADS)

    Fleck, N. A.; Khaderi, S. N.; McMeeking, R. M.; Arzt, E.

    The adhesion of micron-scale surfaces due to intermolecular interactions is a subject of intense interest spanning electronics, biomechanics and the application of soft materials to engineering devices. The degree of adhesion is sensitive to the diameter of micro-pillars in addition to the degree of elastic mismatch between pillar and substrate. Adhesion-strength-controlled detachment of an elastic circular cylinder from a dissimilar substrate is predicted using a Dugdale-type of analysis, with a cohesive zone of uniform tensile strength emanating from the interface corner. Detachment initiates when the opening of the cohesive zone attains a critical value, giving way to crack formation. When the cohesive zone size at crack initiation is small compared to the pillar diameter, the initiation of detachment can be expressed in terms of a critical value Hc of the corner stress intensity. The estimated pull-off force is somewhat sensitive to the choice of stick/slip boundary condition used on the cohesive zone, especially when the substrate material is much stiffer than the pillar material. The analysis can be used to predict the sensitivity of detachment force to the size of pillar and to the degree of elastic mismatch between pillar and substrate.

  7. A Formula for Building Cohesion

    DTIC Science & Technology

    2007-11-02

    in World.War II to feel the tremendous outpouring of warmth , friendebip, banding and esprit that exist among its members. They"had cohesion. "In the... interpersonal relationships. Furthermore, if the company comniader elects to provide compensatorzy time for the company but cannot allow the entire unit...that a unit commander can devise to provide settings for interpersonal relationships to flourish. Having provided for face-to-face relationships to

  8. Family cohesion and posttraumatic intrusion and avoidance among war veterans: a 20-year longitudinal study.

    PubMed

    Zerach, Gadi; Solomon, Zahava; Horesh, Danny; Ein-Dor, Tsachi

    2013-02-01

    The bi-directional relationships between combat-induced posttraumatic symptoms and family relations are yet to be understood. The present study assesses the longitudinal interrelationship of posttraumatic intrusion and avoidance and family cohesion among 208 Israeli combat veterans from the 1982 Lebanon War. Two groups of veterans were assessed with self-report questionnaires 1, 3 and 20 years after the war: a combat stress reaction (CSR) group and a matched non-CSR control group. Latent Trajectories Modeling showed that veterans of the CSR group reported higher intrusion and avoidance than non-CSR veterans at all three points of time. With time, there was a decline in these symptoms in both groups, but the decline was more salient among the CSR group. The latter also reported lower levels of family cohesion. Furthermore, an incline in family cohesion levels was found in both groups over the years. Most importantly, Autoregressive Cross-Lagged Modeling among CSR and non-CSR veterans revealed that CSR veterans' posttraumatic symptoms in 1983 predicted lower family cohesion in 1985, and lower family cohesion, in turn, predicted posttraumatic symptoms in 2002. The findings suggest that psychological breakdown on the battlefield is a marker for future family cohesion difficulties. Our results lend further support for the bi-directional mutual effects of posttraumatic symptoms and family cohesion over time.

  9. Mode I Cohesive Law Characterization of Through-Crack Propagation in a Multidirectional Laminate

    NASA Technical Reports Server (NTRS)

    Bergan, Andrew C.; Davila, Carlos G.; Leone, Frank A.; Awerbuch, Jonathan; Tan, Tein-Min

    2014-01-01

    A method is proposed and assessed for the experimental characterization of through-the-thickness crack propagation in multidirectional composite laminates with a cohesive law. The fracture toughness and crack opening displacement are measured and used to determine a cohesive law. Two methods of computing fracture toughness are assessed and compared. While previously proposed cohesive characterizations based on the R-curve exhibit size effects, the proposed approach results in a cohesive law that is a material property. The compact tension specimen configuration is used to propagate damage while load and full-field displacements are recorded. These measurements are used to compute the fracture toughness and crack opening displacement from which the cohesive law is characterized. The experimental results show that a steady-state fracture toughness is not reached. However, the proposed method extrapolates to steady-state and is demonstrated capable of predicting the structural behavior of geometrically-scaled specimens.

  10. Interaction Chain Patterns of Online Text Construction with Lexical Cohesion

    ERIC Educational Resources Information Center

    Yeh, Hui-Chin; Yang, Yu-Fen; Wong, Wing-Kwong

    2010-01-01

    This study aims at arousing college students' metacognition in detecting lexical cohesion during online text construction as WordNet served as a lexical resource. A total of 83 students were requested to construct texts through sequences of actions identified as interaction chains in this study. Interaction chains are grouped and categorized as a…

  11. The Politics of Britishness: Multiculturalism, Schooling and Social Cohesion

    ERIC Educational Resources Information Center

    Keddie, Amanda

    2014-01-01

    This paper is set against a backdrop of contemporary concerns about Britishness. It explores the dominant view that unprecedented levels of cultural diversity within western contexts such as the UK are undermining social cohesion and are attributable to minority groups' failure to connect or assimilate with mainstream "British" (read…

  12. A simple ratio-based approach for power and sample size determination for 2-group comparison using Rasch models

    PubMed Central

    2014-01-01

    Background Despite the widespread use of patient-reported Outcomes (PRO) in clinical studies, their design remains a challenge. Justification of study size is hardly provided, especially when a Rasch model is planned for analysing the data in a 2-group comparison study. The classical sample size formula (CLASSIC) for comparing normally distributed endpoints between two groups has shown to be inadequate in this setting (underestimated study sizes). A correction factor (RATIO) has been proposed to reach an adequate sample size from the CLASSIC when a Rasch model is intended to be used for analysis. The objective was to explore the impact of the parameters used for study design on the RATIO and to identify the most relevant to provide a simple method for sample size determination for Rasch modelling. Methods A large combination of parameters used for study design was simulated using a Monte Carlo method: variance of the latent trait, group effect, sample size per group, number of items and items difficulty parameters. A linear regression model explaining the RATIO and including all the former parameters as covariates was fitted. Results The most relevant parameters explaining the ratio’s variations were the number of items and the variance of the latent trait (R2 = 99.4%). Conclusions Using the classical sample size formula adjusted with the proposed RATIO can provide a straightforward and reliable formula for sample size computation for 2-group comparison of PRO data using Rasch models. PMID:24996957

  13. Dependence of micelle size and shape on detergent alkyl chain length and head group.

    PubMed

    Oliver, Ryan C; Lipfert, Jan; Fox, Daniel A; Lo, Ryan H; Doniach, Sebastian; Columbus, Linda

    2013-01-01

    Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.

  14. Dependence of Micelle Size and Shape on Detergent Alkyl Chain Length and Head Group

    PubMed Central

    Oliver, Ryan C.; Lipfert, Jan; Fox, Daniel A.; Lo, Ryan H.; Doniach, Sebastian; Columbus, Linda

    2013-01-01

    Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2–1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions. PMID:23667481

  15. Size distributions of shocks and static avalanches from the functional renormalization group.

    PubMed

    Le Doussal, Pierre; Wiese, Kay Jörg

    2009-05-01

    Interfaces pinned by quenched disorder are often used to model jerky self-organized critical motion. We study static avalanches, or shocks, defined here as jumps between distinct global minima upon changing an external field. We show how the full statistics of these jumps is encoded in the functional-renormalization-group fixed-point functions. This allows us to obtain the size distribution P(S) of static avalanches in an expansion in the internal dimension d of the interface. Near and above d=4 this yields the mean-field distribution P(S) approximately S;{-3/2}e;{-S4S_{m}} , where S_{m} is a large-scale cutoff, in some cases calculable. Resumming all one-loop contributions, we find P(S) approximately S;{-tau}exp(C(SS_{m});{1/2}-B/4(S/S_{m});{delta}) , where B , C , delta , and tau are obtained to first order in =4-d . Our result is consistent to O() with the relation tau=tau_{zeta}:=2-2/d+zeta , where zeta is the static roughness exponent, often conjectured to hold at depinning. Our calculation applies to all static universality classes, including random-bond, random-field, and random-periodic disorders. Extended to long-range elastic systems, it yields a different size distribution for the case of contact-line elasticity, with an exponent compatible with tau=2-1/d+zeta to O(=2-d) . We discuss consequences for avalanches at depinning and for sandpile models, relations to Burgers turbulence and the possibility that the relation tau=tau_{zeta} be violated to higher loop order. Finally, we show that the avalanche-size distribution on a hyperplane of codimension one is in mean field (valid close to and above d=4 ) given by P(S) approximately K_{13}(S)S , where K is the Bessel- K function, thus tau_{hyperplane}=4/3 .

  16. RELATION OF PARTICLE SIZE OF C POLYSACCHARIDE COMPLEXES OF GROUP A STREPTOCOCCI TO TOXIC EFFECTS ON CONNECTIVE TISSUE

    PubMed Central

    Roberson, Bob S.; Schwab, John H.; Cromartie, William J.

    1960-01-01

    The component of Group A streptococci which is responsible for the chronic, remittent, multinodular lesion of connective tissue is derived from the cell wall. Further evidence is given to support the essential role of the group-specific C polysaccharide in the production of this lesion. A series of particles containing the group-specific C polysaccharide was prepared, ranging in size from large cell wall fragments to the relatively small hapten. A comparison of the lesion producing capacity of the particles in this spectrum revealed that maximum toxic activity is associated with C polysaccharide complexes of intermediate size. The discussion considers colloidal properties associated with C polysaccharide complexes of a certain size, and the influence particle size has on persistence in tissue, as possible explanations of the relationship between the size of the C polysaccharide complex and its ability to produce the chronic lesion of connective tissue. PMID:13742081

  17. Brain Size, IQ, and Racial-Group Differences: Evidence from Musculoskeletal Traits.

    ERIC Educational Resources Information Center

    Rushton, J. Philippe; Rushton, Elizabeth W.

    2003-01-01

    Correlated brain size differences with 37 musculoskeletal variables shown in evolutionary textbooks to change with brain size. Findings from a sample of more than 6,000 U.S. military personnel indicate that racial differences in brain size are securely established and are the most likely biological mediators of race differences in intelligence.…

  18. Brain Size, IQ, and Racial-Group Differences: Evidence from Musculoskeletal Traits.

    ERIC Educational Resources Information Center

    Rushton, J. Philippe; Rushton, Elizabeth W.

    2003-01-01

    Correlated brain size differences with 37 musculoskeletal variables shown in evolutionary textbooks to change with brain size. Findings from a sample of more than 6,000 U.S. military personnel indicate that racial differences in brain size are securely established and are the most likely biological mediators of race differences in intelligence.…

  19. Developing the Noncentrality Parameter for Calculating Group Sample Sizes in Heterogeneous Analysis of Variance

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2011-01-01

    Sample size determination is an important issue in planning research. In the context of one-way fixed-effect analysis of variance, the conventional sample size formula cannot be applied for the heterogeneous variance cases. This study discusses the sample size requirement for the Welch test in the one-way fixed-effect analysis of variance with…

  20. Developing the Noncentrality Parameter for Calculating Group Sample Sizes in Heterogeneous Analysis of Variance

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2011-01-01

    Sample size determination is an important issue in planning research. In the context of one-way fixed-effect analysis of variance, the conventional sample size formula cannot be applied for the heterogeneous variance cases. This study discusses the sample size requirement for the Welch test in the one-way fixed-effect analysis of variance with…

  1. A sign of the times: To have or to be? Social capital or social cohesion?

    PubMed

    Carrasco, Maria A; Bilal, Usama

    2016-06-01

    Among various social factors associated with health behavior and disease, social cohesion has not captured the imagination of public health researchers as much as social capital as evidenced by the subsuming of social cohesion into social capital and the numerous studies analyzing social capital and the comparatively fewer articles analyzing social cohesion and health. In this paper we provide a brief overview of the evolution of the conceptualization of social capital and social cohesion and we use philosopher Erich Fromm's distinction between "having" and "being" to understand the current research focus on capital over cohesion. We argue that social capital is related to having while social cohesion is related to being and that an emphasis on social capital leads to individualizing tendencies that are antithetical to cohesion. We provide examples drawn from the literature where this conflation of social capital and cohesion results in non-concordant definitions and subsequent operationalization of these constructs. Beyond semantics, the practical implication of focusing on "having" vs. "being" include an emphasis on understanding how to normalize groups and populations rather than providing those groups space for empowerment and agency leading to health. Published by Elsevier Ltd.

  2. Elongational rheology and cohesive fracture of photo-oxidated LDPE

    SciTech Connect

    Rolón-Garrido, Víctor H. Wagner, Manfred H.

    2014-01-15

    It was found recently that low-density polyethylene (LDPE) samples with different degrees of photo-oxidation represent an interesting system to study the transition from ductile to cohesive fracture and the aspects of the cohesive rupture in elongational flow. Sheets of LDPE were subjected to photo-oxidation in the presence of air using a xenon lamp to irradiate the samples for times between 1 day and 6 weeks. Characterisation methods included Fourier transform infrared spectroscopy, solvent extraction method, and rheology in shear and uniaxial extensional flows. Linear viscoelasticity was increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by the carbonyl index, acid and aldehydes groups, and gel fraction. The molecular stress function model was used to quantify the experimental data, and the nonlinear model parameter β was found to be correlated with the gel content. The uniaxial data showed that the transition from ductile to cohesive fracture was shifted to lower elongational rates, the higher the gel content was. From 2 weeks photo-oxidation onwards, cohesive rupture occurred at every strain rate investigated. The true strain and true stress at cohesive fracture as well as the energy density applied to the sample up to fracture were analyzed. At low gel content, rupture was mainly determined by the melt fraction while at high gel content, rupture occurred predominantly in the gel structure. The strain at break was found to be independent of strain rate, contrary to the stress at break and the energy density. Thus, the true strain and not the stress at break or the energy density was found to be the relevant physical quantity to describe cohesive fracture behavior of photo-oxidated LDPE. The equilibrium modulus of the gel structures was correlated with the true strain at rupture. The stiffer the gel structure, the lower was the deformation tolerated before the sample breaks.

  3. 3D model of radionuclide dispersion in coastal areas with multifraction cohesive and non-cohesive sediments

    NASA Astrophysics Data System (ADS)

    Brovchenko, Igor; Maderich, Vladimir; Jung, Kyung Tae

    2015-04-01

    We developed new radionuclide dispersion model that may be used in coastal areas, rivers and estuaries with non-uniform distribution of suspended and bed sediments both cohesive and non-cohesive types. Model describes radionuclides concentration in dissolved phase in water column, particulated phase on suspended sediments on each sediment class types, bed sediments and pore water. The transfer of activity between the water column and the pore water in the upper layer of the bottom sediment is governed by diffusion processes. The phase exchange between dissolved and particulate radionuclides is written in terms of desorption rate a12 (s-1) and distribution coefficient Kd,iw and Kd,ib (m3/kg) for water column and for bottom deposit, respectively. Following (Periáñez et al., 1996) the dependence of distribution coefficients is inversely proportional to the sediment particle size. For simulation of 3D circulation, turbulent diffusion and wave fields a hydrostatic model SELFE (Roland et. al. 2010) that solves Reynolds-stress averaged Navier-Stokes (RANS) equations and Wave Action transport equation on the unstructured grids was used. Simulation of suspended sediment concentration and bed sediments composition is based on (L. Pinto et. al., 2012) approach that originally was developed for non-cohesive sediments. In present study we modified this approach to include possibility of simulating mixture of cohesive and non-cohesive sediments by implementing parameterizations for erosion and deposition fluxes for cohesive sediments and by implementing flocculation model for determining settling velocity of cohesive flocs. Model of sediment transport was calibrated on measurements in the Yellow Sea which is shallow tidal basin with strongly non-uniform distribution of suspended and bed sediments. Model of radionuclide dispersion was verified on measurements of 137Cs concentration in surface water and bed sediments after Fukushima Daiichi nuclear accident. References Peri

  4. Human Activity Dampens the Benefits of Group Size on Vigilance in Khulan (Equus hemionus) in Western China.

    PubMed

    Wang, Mu-Yang; Ruckstuhl, Kathreen E; Xu, Wen-Xuan; Blank, David; Yang, Wei-Kang

    2016-01-01

    Animals receive anti-predator benefits from social behavior. As part of a group, individuals spend less time being vigilant, and vigilance decreases with increasing group size. This phenomenon, called "the many-eyes effect", together with the "encounter dilution effect", is considered among the most important factors determining individual vigilance behavior. However, in addition to group size, other social and environmental factors also influence the degree of vigilance, including disturbance from human activities. In our study, we examined vigilance behavior of Khulans (Equus hemionus) in the Xinjiang Province in western China to test whether and how human disturbance and group size affect vigilance. According to our results, Khulan showed a negative correlation between group size and the percentage time spent vigilant, although this negative correlation depended on the groups' disturbance level. Khulan in the more disturbed area had a dampened benefit from increases in group size, compared to those in the undisturbed core areas. Provision of continuous areas of high-quality habitat for Khulans will allow them to form larger undisturbed aggregations and to gain foraging benefits through reduced individual vigilance, as well as anti-predator benefits through increased probability of predator detection.

  5. The effects of group size and group economic factors on collaboration: a study of the financial performance of rural hospitals in consortia.

    PubMed Central

    Chan, B; Feldman, R; Manning, W G

    1999-01-01

    STUDY QUESTIONS: To determine factors that distinguish effective rural hospital consortia from ineffective ones in terms of their ability to improve members' financial performance. Two questions in particular were addressed: (1) Do large consortia have a greater collective impact on their members? (2) Does a consortium's economic environment determine the degree of collective impact on members? DATA SOURCES AND STUDY SETTING: Based on the hospital survey conducted during February 1992 by the Robert Wood Johnson Hospital-Based Rural Health Care project of rural hospital consortia. The survey data were augmented with data from Medicare Cost Reports (1985-1991), AHA Annual Surveys (1985-1991), and other secondary data. STUDY DESIGN: Dependent variables were total operating profit, cost per adjusted admission, and revenue per adjusted admission. Control variables included degree of group formalization, degree of inequality of resources among members (group asymmetry), affiliation with other consortium group(s), individual economic environment, common hospital characteristics (bed size, ownership type, system affiliation, case mix, etc.), year (1985-1991), and census region dummies. PRINCIPAL FINDINGS: All dependent variables have a curvilinear association with group size. The optimum group size is somewhere in the neighborhood of 45. This reveals the benefits of collective action (i.e., scale economies and/or synergy effects) and the issue of complexity as group size increases. Across analyses, no strong evidence exists of group economic environment impacts, and the environmental influences come mainly from the local economy rather than from the group economy. CONCLUSION: There may be some success stories of collaboration among hospitals in consortia, and consortium effects vary across different collaborations. RELEVANCE/IMPACT: When studying consortia, it makes sense to develop a typology of groups based on some performance indicators. The results of this study imply

  6. Optimizing trial design in pharmacogenetics research: comparing a fixed parallel group, group sequential, and adaptive selection design on sample size requirements.

    PubMed

    Boessen, Ruud; van der Baan, Frederieke; Groenwold, Rolf; Egberts, Antoine; Klungel, Olaf; Grobbee, Diederick; Knol, Mirjam; Roes, Kit

    2013-01-01

    Two-stage clinical trial designs may be efficient in pharmacogenetics research when there is some but inconclusive evidence of effect modification by a genomic marker. Two-stage designs allow to stop early for efficacy or futility and can offer the additional opportunity to enrich the study population to a specific patient subgroup after an interim analysis. This study compared sample size requirements for fixed parallel group, group sequential, and adaptive selection designs with equal overall power and control of the family-wise type I error rate. The designs were evaluated across scenarios that defined the effect sizes in the marker positive and marker negative subgroups and the prevalence of marker positive patients in the overall study population. Effect sizes were chosen to reflect realistic planning scenarios, where at least some effect is present in the marker negative subgroup. In addition, scenarios were considered in which the assumed 'true' subgroup effects (i.e., the postulated effects) differed from those hypothesized at the planning stage. As expected, both two-stage designs generally required fewer patients than a fixed parallel group design, and the advantage increased as the difference between subgroups increased. The adaptive selection design added little further reduction in sample size, as compared with the group sequential design, when the postulated effect sizes were equal to those hypothesized at the planning stage. However, when the postulated effects deviated strongly in favor of enrichment, the comparative advantage of the adaptive selection design increased, which precisely reflects the adaptive nature of the design.

  7. Physical activity promotion among churchgoing Latinas in San Diego, California: does neighborhood cohesion matter?

    PubMed

    Martinez, Suzanna M; Arredondo, Elva M; Roesch, Scott

    2013-10-01

    This study examined the reciprocal relationship between Latinas' leisure-time physical activity and neighborhood cohesion following the implementation of a 6-month promotora-delivered pilot intervention. A one-group study design was used to promote leisure-time physical activity and build neighborhood cohesion among 143 churchgoing Latinas in San Diego, California. Using a three-wave autoregressive cross-lagged panel model, leisure-time physical activity and neighborhood cohesion (assessed at baseline, 3 and 6 months) were analyzed. Leisure-time physical activity and neighborhood cohesion increased across time. Neighborhood cohesion at 3 months predicted leisure-time physical activity at 6 months. A promotora model in the context of a faith-based setting may be appropriate to promote Latinas' leisure-time physical activity and make socioenvironmental improvements.

  8. Patterns of discourse cohesion and coherence in Alzheimer's disease.

    PubMed

    Ripich, D N; Terrell, B Y

    1988-02-01

    Patterns of discourse--as reflected in the use of propositions, cohesion devices, and in judgments of coherence--in the speech of 6 well elderly and 6 patients with senile dementia of the Alzheimer type (SDAT) during topic-centered interviews were compared. Compared to the well elderly, SDAT patients used significantly more words and conversational turns. The interviewer also used more words and turns when interviewing SDAT patients, making those interviews more lengthy and more interactive than those of the elderly comparison group. Although significant differences in propositional form and cohesion devices were not found, a pattern of cohesion disruptions in SDAT patients was identified that appears consistent with previously noted patterns of language dissolution. Coherence judgements by four listeners showed significant differences between the two groups. The breakdowns in coherence were related to one subtype of cohesion disruption, missing element. This suggests that incoherence may result in part from a loss of the ability to take the listener's perspective in developing thematic structure during conversation. It is argued that SDAT results not only in the impairment of linguistic abilities but also in the impairment of discourse abilities that contribute to Alzheimer patients' incoherent speech.

  9. Effect of group size and maize silage dietary levels on behaviour, health, carcass and meat quality of Mediterranean buffaloes.

    PubMed

    Masucci, F; De Rosa, G; Barone, C M A; Napolitano, F; Grasso, F; Uzun, P; Di Francia, A

    2016-03-01

    The effects of different dietary levels of maize silage (10% v. 36% DM) and group size (7 v. 14 animals) were assessed on growth performance and in vivo digestibility of 28 male fattening buffaloes. In addition, the effects of diet on meat quality and group size on behaviour and immune response were separately evaluated. Animals were weighed and assigned to three groups. The high silage - low size group (HL) was fed a total mixed ration (TMR) containing 36% DM of maize silage and consisted of seven animals (age 12.7±2.6 months; BW 382.2±67.7 kg at the start of the study). The low silage - low size group (LL) was fed a TMR containing 10% DM of maize silage and consisted of seven animals (age 13.0±2.7 months; BW 389.4±72.3 kg). The high silage - high size group (HH) was fed the 36% maize silage DM diet and consisted of 14 animals (age 13.9±3.25 months; BW 416.5±73.9 kg). Total space allowance (3.2 indoor+3.2 outdoor m2/animal) was kept constant in the three groups, as well as the ratio of animals to drinkers (seven animals per water bowl) and the manger space (70 cm per animal). Growth performance, carcass characteristics and digestibility were influenced neither by dietary treatment nor by group size, even if the group fed 36% maize silage diet showed a higher fibre digestibility. No effect of diet was found on meat quality. Group size did not affect the behavioural activities with the exception of drinking (1.04±0.35% v. 2.60±0.35%; P<0.01 for groups HL and HH, respectively) and vigilance (2.58±0.46% v. 1.20±0.46%; P<0.05 for groups HL and HH, respectively). Immune responses were not affected by group size.

  10. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    SciTech Connect

    Hatzes, A.P.; Bridges, F.; Lin, D.N.C.; Sachtjen, S. McDonald Observatory, Austin, TX )

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a Velcro model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process. 14 refs.

  11. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    NASA Technical Reports Server (NTRS)

    Hatzes, A. P.; Bridges, F.; Lin, D. N. C.; Sachtjen, S.

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a 'Velcro' model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process.

  12. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    NASA Technical Reports Server (NTRS)

    Hatzes, A. P.; Bridges, F.; Lin, D. N. C.; Sachtjen, S.

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a 'Velcro' model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process.

  13. Determination of flow-regime boundaries for cohesive particles. Final report, September 20, 1988--March 31, 1992

    SciTech Connect

    Knowlton, T.M.; Findlay, J.G.; Arastoopour, H.; Gidaspow, D.

    1992-10-01

    Cohesive particles (Geldart Group C powders) are fine particles generally less than 30 microns in size. Interparticle forces are large relative to inertial forces in these particles, and cause clumping, sticking, and channeling when attempts are made to fluidize them. These solids do not flow easily through pipes, and bridge extremely easily. The objectives of the work in this program were (1) to develop a hydrodynamic model which can be applied to cohesive solids, and (2) to obtain data in a large-scale (30-cm-diameter) riser to test the model. The work was divided into six tasks: Task 1. Preparation of a Project Work Plan; Task 2. Hydrodynamic Model Development; Task 3. Determination of Rheological Properties for Incorporation into the Model; Task 4. Small-Scale Flow Tests; Task 5. Large-Scale Flow Tests; and Task 6. Comparison of Model With Data. The work was conducted by the Institute of Gas Technology (IGT) in collaboration with the Illinois Institute of Technology (IIT). This work combined the expertise of IIT in model development, with the large-scale experimental capabilities of IGT. IIT researchers developed the hydrodynamic model in the program, while the large-scale data were generated by IGT. Following the preparation of the Project Work Plan in Task 1, work was started on the development of a two-dimensional hydrodynamic model to enable the behavior of cohesive solids in a dilute-phase riser to be simulated. In Task 2, two hydrodynamic models were developed based on the kinetic theory model of granular flow. The models were used to predict data presented in the literature, as well as data generated in Task 5 of this study. In Task 3, rheological data on cohesive oil shale with an average particle size of approximately 12 microns was obtained using a unique device called a cohetester.

  14. Happier together. Social cohesion and subjective well-being in Europe.

    PubMed

    Delhey, Jan; Dragolov, Georgi

    2016-06-01

    Despite mushrooming research on "social" determinants of subjective well-being (SWB), little is known as to whether social cohesion as a collective property is among the key societal conditions for human happiness. This article fills this gap in investigating the importance of living in a cohesive society for citizens' SWB. For 27 European Union countries, it combines the newly developed Bertelsmann Foundation's Cohesion Index with individual well-being data on life evaluation and psychological functioning as surveyed in the recent European Quality of Life Survey. The main results from multi-level analyses are as follows. First, Europeans are indeed happier and psychologically healthier in more cohesive societies. Second, all three core domains of cohesion increase individuals' SWB. Third, citizens in the more affluent part of Europe feel the positivity of social cohesion more consistently than those in the less affluent part. Finally, within countries, cohesion is good for the SWB of resource-rich and resource-poor groups alike. Our findings also shed new light on the ongoing debate on economic progress and quality of life: what makes citizenries of affluent societies happier is, in the first place, their capacity to create togetherness and solidarity among their members-in other words, cohesion.

  15. Relationship between the cohesion of guest particles on the flow behaviour of interactive mixtures.

    PubMed

    Mangal, Sharad; Gengenbach, Thomas; Millington-Smith, Doug; Armstrong, Brian; Morton, David A V; Larson, Ian

    2016-05-01

    In this study, we aimed to investigate the effects cohesion of small surface-engineered guest binder particles on the flow behaviour of interactive mixtures. Polyvinylpyrrolidone (PVP) - a model pharmaceutical binder - was spray-dried with varying l-leucine feed concentrations to create small surface-engineered binder particles with varying cohesion. These spray-dried formulations were characterised by their particle size distribution, morphology and cohesion. Interactive mixtures were produced by blending these spray-dried formulations with paracetamol. The resultant blends were visualised under scanning electron microscope to confirm formation of interactive mixtures. Surface coverage of paracetamol by guest particles as well as the flow behaviour of these mixtures were examined. The flow performance of interactive mixtures was evaluated using measurements of conditioned bulk density, basic flowability energy, aeration energy and compressibility. With higher feed l-leucine concentrations, the surface roughness of small binder particles increased, while their cohesion decreased. Visual inspection of the SEM images of the blends indicated that the guest particles adhered to the surface of paracetamol resulting in effective formation of interactive mixtures. These images also showed that the low-cohesion guest particles were better de-agglomerated that consequently formed a more homogeneous interactive mixture with paracetamol compared with high-cohesion formulations. The flow performance of interactive mixtures changed as a function of the cohesion of the guest particles. Interactive mixtures with low-cohesion guest binder particles showed notably improved bulk flow performance compared with those containing high-cohesion guest binder particles. Thus, our study suggests that the cohesion of guest particles dictates the flow performance of interactive mixtures.

  16. Human Activity Dampens the Benefits of Group Size on Vigilance in Khulan (Equus hemionus) in Western China

    PubMed Central

    Wang, Mu-Yang; Ruckstuhl, Kathreen E.; Xu, Wen-Xuan; Blank, David; Yang, Wei-Kang

    2016-01-01

    Animals receive anti-predator benefits from social behavior. As part of a group, individuals spend less time being vigilant, and vigilance decreases with increasing group size. This phenomenon, called “the many-eyes effect”, together with the “encounter dilution effect”, is considered among the most important factors determining individual vigilance behavior. However, in addition to group size, other social and environmental factors also influence the degree of vigilance, including disturbance from human activities. In our study, we examined vigilance behavior of Khulans (Equus hemionus) in the Xinjiang Province in western China to test whether and how human disturbance and group size affect vigilance. According to our results, Khulan showed a negative correlation between group size and the percentage time spent vigilant, although this negative correlation depended on the groups’ disturbance level. Khulan in the more disturbed area had a dampened benefit from increases in group size, compared to those in the undisturbed core areas. Provision of continuous areas of high-quality habitat for Khulans will allow them to form larger undisturbed aggregations and to gain foraging benefits through reduced individual vigilance, as well as anti-predator benefits through increased probability of predator detection. PMID:26756993

  17. [Food education: health and social cohesion].

    PubMed

    Aparici, Eva Zafra

    2017-01-01

    Using a theoretical-reflexive approach, this article connects the results of various qualitative studies in social conflict and medical anthropology, in order to investigate how food can be a tool for social transformation in terms of health but also in terms of the dialogue, respect and coexistence among people, groups and communities. In this sense the article presents a first approximation to a new theoretical and methodological approach to food education. In this approach, food adopts a political, sociocultural and participatory perspective that brings us closer to an innovative understanding of the phenomenon of food: not only as an analytic and diagnostic tool, but also as an instrument for health education interventions toward conflict resolution and the promotion of healthier societies overall - nutritionally, but also in terms of equality and social cohesion.

  18. [Experimental test of the ideal free distribution in humans: the effects of reinforcer magnitude and group size].

    PubMed

    Yamaguchi, Tetsuo; Ito, Masato

    2006-02-01

    The ideal free distribution (IFD) theory describes how animals living in the wild distribute themselves between two different resource sites. The IFD theory predicts that the ratio of animals in the two resource sites is equal to the ratio of resources available in those sites. The present study investigated the effects of absolute reinforcer magnitude and group size on the distribution of humans between two resource sites. Two groups of undergraduate students (N = 10 and N = 20) chose blue or red cards to earn points. The ratio of points assigned to each color varied from 1 : 1 to 4 : 1 across five conditions. In each condition, absolute reinforcer magnitude was varied. The generalized ideal free distribution equation was fit to the data obtained under the different magnitude and group size conditions. These results suggest that larger absolute reinforcer magnitude and smaller group size produce higher sensitivity to resource distribution.

  19. Increases in Network Ties Are Associated With Increased Cohesion Among Intervention Participants.

    PubMed

    Gesell, Sabina B; Barkin, Shari L; Sommer, Evan C; Thompson, Jessica R; Valente, Thomas W

    2016-04-01

    Many behavior change programs are delivered in group settings to manage implementation costs and to foster support and interactions among group members in order to facilitate behavior change. Understanding the group dynamics that evolve in group settings (e.g., weight management, Alcoholics Anonymous) is important, yet rarely measured. This article examined the relationship between social network ties and group cohesion in a group-based intervention to prevent obesity in children. The data reported are process measures from an ongoing community-based randomized controlled trial. A total of 305 parents with a child (3-6 years) at risk of developing obesity were assigned to an intervention that taught parents healthy lifestyles. Parents met weekly for 12 weeks in small consistent groups. Two measures were collected at Weeks 3 and 6: a social network survey (people in the group with whom one discusses healthy lifestyles) and the validated Perceived Cohesion Scale. We used lagged random and fixed effects regression models to analyze the data. Cohesion increased from 6.51 to 6.71 (t= 4.4,p< .01). Network nominations tended to increase over the 3-week period in each network. In the combined discussion and advice network, the number of nominations increased from 1.76 to 1.95 (z= 2.59,p< .01). Cohesion at Week 3 was the strongest predictor of cohesion at Week 6 (b= 0.55,p< .01). Number of new network nominations at Week 6 was positively related to cohesion at Week 6 (b= 0.06,p< .01). In sum, being able to name new network contacts was associated with feelings of cohesion. This is the first study to demonstrate how network changes affect perceived group cohesion within a behavioral intervention. Given that many behavioral interventions occur in group settings, intentionally building new social networks could be promising to augment desired outcomes. © 2015 Society for Public Health Education.

  20. Increases in New Social Network Ties are Associated with Increased Cohesion among Intervention Participants

    PubMed Central

    Gesell, Sabina B.; Barkin, Shari L.; Sommer, Evan C.; Thompson, Jessica R.; Valente, Thomas W.

    2016-01-01

    Objective Many behavior change programs are delivered in group settings to manage implementation costs and to foster support and interactions among group members to facilitate behavior change. Understanding the group dynamics that evolve in group settings (e.g., weight management, Alcoholics Anonymous) is important, yet rarely measured. This paper examined the relationship between social network ties and group cohesion in a group-based intervention to prevent obesity in children. Method The data reported are process measures from an ongoing community-based randomized controlled trial. 305 parents with a child (3-6 years) at risk of developing obesity were assigned to an intervention that taught parents healthy lifestyles. Parents met weekly for 12 weeks in small consistent groups. Two measures were collected at weeks 3 and 6: a social network survey (people in the group with whom one discusses healthy lifestyles); and the validated Perceived Cohesion Scale (Bollen & Hoyle, 1990). We used lagged random and fixed effects regression models to analyze the data. Results Cohesion increased from 6.51 to 6.71 (t=4.4, p<0.01). Network nominations tended to increase over the 3-week period in each network. In the combined discussion and advice network, the number of nominations increased from 1.76 to 1.95 (z=2.59, p<0.01). Cohesion at week 3 was the strongest predictor of cohesion at week 6 (b=0.55, p<0.01). Number of new network nominations at week 6 was positively related to cohesion at week 6 (b=0.06, p<.01). In sum, being able to name new network contacts was associated with feelings of cohesion. Conclusion This is the first study to demonstrate how network changes affect perceived group cohesion within a behavioral intervention. Given that many behavioral interventions occur in group settings, intentionally building new social networks could be promising to augment desired outcomes. PMID:26286298

  1. The Effects of Sexual Composition and Group Size on Individual Effort.

    ERIC Educational Resources Information Center

    Jackson, Jeffrey M.; And Others

    This experiment was designed to test the motivation to perform a task for males and females in mixed and same-sex groups. Individuals in homogeneous groups (four males or four females) or heterogeneous groups (two males and two females) clapped their hands alone, in pairs and in foursomes. People exerted more effort alone than in groups,…

  2. The modulating role of group stability on fitness effects of group size is different in females and males of a communally rearing rodent.

    PubMed

    Ebensperger, Luis A; Correa, Loreto A; León, Cecilia; Ramírez-Estrada, Juan; Abades, Sebastian; Villegas, Álvaro; Hayes, Loren D

    2016-11-01

    Group size may influence fitness benefits and costs that emerge from cooperative and competitive interactions in social species. However, evidence from plural breeding mammals indicates that group size is insufficient to explain variation in direct fitness, implying other attributes of social groups were overlooked. We studied the natural population of a social rodent during 5 years to test the hypothesis that social stability - in terms of group composition - modulates the effects of increasing number of breeding females (a proxy of communal rearing) and males on the number of offspring weaned (sired) and on the number of offspring weaned (sired) surviving to breeding age (two proxies of direct fitness). We quantified the effects of social stability (measured as changes in female or male group members between mating and the onset of lactation) on these fitness measures. We used live trapping, telemetry and DNA markers to determine social and fitness measures. Social stability in degus was variable in terms of the number of changes in group composition across groups. Low stability was mostly due to mortality and emigration of group members. Results supported a modulating role of social stability on the relationship between group size and the number of offspring weaned (sired). Stability in female and male group composition were both modulators of fitness to females and males. The modulatory role of stability was sex specific, where high social stability was often fitness beneficial to the females. Instead, low social stability was fitness enhancing to the males. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

  3. An experimental evaluation of a group- versus computer-based intervention to improve food portion size estimation skills.

    PubMed

    Ayala, Guadalupe Xochitl

    2006-02-01

    The ability to accurately estimate and measure food portion sizes is important for preventing and treating obesity. This study describes the development, implementation and evaluation of a group- versus computer-based intervention to improve food portion estimation abilities using real food and food models. A convenience sample of 76 women was randomly assigned to one of three conditions: computer training, group training or a waitlist control condition. Assessments at baseline and 2 weeks post-intervention included portion size testing using real foods and food models, self-efficacy for judging portion sizes and using measuring utensils, and knowledge of portion information. At baseline, greater estimation errors were observed for amorphous foods. No group by time interaction was observed on estimation of real foods; however, both the computer and group training resulted in significant improvements in estimating the size of food models, greater self-efficacy for judging portion sizes and more accurate knowledge of portion information compared with the control condition. Process measures indicated that the group training was deemed more helpful and more personally relevant to the participants.

  4. Strong adhesion and cohesion of chitosan in aqueous solutions

    PubMed Central

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N.; Hwang, Dong Soo

    2014-01-01

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0–8.5), achieving a maximum value at pH 3.0 after a contact time of 1 hr (Wad ~6.4 mJ/m2). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~8.5 mJ/m2) between the films was measured with increasing contact times up to 1 hr at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan based load-bearing materials. PMID:24138057

  5. Strong adhesion and cohesion of chitosan in aqueous solutions.

    PubMed

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N; Hwang, Dong Soo

    2013-11-19

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0-8.5), achieving a maximum value at pH 3.0 after a contact time of 1 h (Wad ~ 6.4 mJ/m(2)). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~ 8.5 mJ/m(2)) between the films was measured with increasing contact times up to 1 h at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan-based load-bearing materials.

  6. Evaluation of Kindergarten Group Rooms in the Context of Size: Children and Teacher's Perspective in Turkey

    ERIC Educational Resources Information Center

    Sahin, B. Ece; Dostoglu, Neslihan

    2014-01-01

    Physical qualifications of group rooms are highly important in terms of child development during preschool education. First of all, the required space should be provided in order to create ideal conditions in a group room. The standards of the required space for a child in group rooms vary among countries. It is stated that in Turkey minimum 1.5…

  7. Asteroid Regolith Mechanical Properties: Laboratory Experiments With Cohesive Powders

    NASA Astrophysics Data System (ADS)

    Durda, Daniel D.; Scheeres, D. J.; Roark, S. E.; Dissly, R.; Sanchez, P.

    2012-10-01

    Despite clear evidence that small asteroids undergo drastic physical evolution, the geophysics and mechanics of many of the processes governing that evolution remain a mystery due to a lack of scientific data, both on the sub-surface and global geophysics of these small bodies and on the mechanical properties of regoliths in the unique micro-gravity regime they inhabit. We are beginning a three-year effort to study regolith properties and processes on low-gravity, small asteroids by conducting analog experiments with cohesive powders in a 1-g laboratory environment. Based on a rigorous comparison of forces it can be shown that van der Waals cohesive forces between millimeter to centimeter-sized grains on asteroids ranging in size from Eros to Itokawa, respectively, may exceed their ambient weight several-fold. This observation implies that regoliths composed of impact debris of those sizes should behave on the microgravity surfaces of small asteroids like flour or other cohesive powders do in the 1-g environment here on Earth. Our goal is to develop an improved understanding of the role of cohesion in affecting regolith processes and surface morphology of small Solar System bodies, some the targets of ongoing and proposed NASA New Frontiers and Discovery missions, and to quantify the range of expected mechanical properties of such regoliths. Our experiments will be conducted in ambient and vacuum conditions within an environmental test chamber at Ball Aerospace & Technologies Corporation (BATC) in Boulder, CO. To aid in validating our experiment chamber and support equipment performance, and before proceeding with experiments on geologic regolith simulant materials, we will perform a series of comparative, ‘calibration’ experiments with micro glass spheres; all primary experiments will be performed with at least one non-idealized regolith simulant, like JSC-1, that more realistically simulates the angular particle shapes expected in actual geologic fragments

  8. Reptiles: a group of transition in the evolution of genome size and of the nucleotypic effect.

    PubMed

    Olmo, E

    2003-01-01

    A comparison between genome size and some phenotypic parameters, such as developmental length and metabolic rate, showed in reptiles a nucleotypic correlation similar to the one observed in birds and mammals. Indeed, like homeotherms, reptiles exhibit a highly significant, inverse correlation of genome size with metabolic rate but unlike amphibians, no relationship with developmental length. Several lines of evidence suggest that these nucleotypic correlations are influenced by body temperature, which also affects the guanine + cytosine nuclear percentage, and that they play an important role in the adaptation of these amniotes. However, the reptilian suborders exhibit differences in the quantitative and compositional characters of the genome that do not completely correspond to differences in the phenotypic parameters commonly involved in the nucleotypic effect. Thus, additional factors could have influenced genome size in this class. These data could be explained with the model of Hartl and Petrov, who observed an inverse correlation between genome size, non-coding portion of the genome and rate of DNA loss and hypothesized a strong role for different spectra of spontaneous insertions and deletions (indels) in the variations of genome size. It is thus reasonable to surmise that variations in the reptilian genome were initially influenced by different indels spectra typical of the diverse lineages, possibly related to different chromosome compartmentalizations. The consequent size increases or decreases would have influenced various morphological and functional cell parameters, and through these some phenotypic characteristics of the whole organism, especially the metabolic rate, very important for environmental adaptation and thus subject to natural selection. Through this "nucleotypic" bond, natural selection would also have controlled genome size variations.

  9. Some Aspects of Discourse and Cohesion.

    ERIC Educational Resources Information Center

    Korpimies, Liisa

    Analysis of two Harold Pinter plays, "The Birthday Party" and "The Dumb Waiter," illustrates the complementarity of cohesion and coherence in discourse analysis. Coherence is defined as the structure of verbal interaction on a higher level than grammar. Cohesion is defined as the resources of a language that generates…

  10. Some Aspects of Discourse and Cohesion.

    ERIC Educational Resources Information Center

    Korpimies, Liisa

    Analysis of two Harold Pinter plays, "The Birthday Party" and "The Dumb Waiter," illustrates the complementarity of cohesion and coherence in discourse analysis. Coherence is defined as the structure of verbal interaction on a higher level than grammar. Cohesion is defined as the resources of a language that generates…

  11. Academic Social Cohesion within Higher Education

    ERIC Educational Resources Information Center

    Heuser, Brian L.

    2007-01-01

    This article explores the theoretical foundations of "social cohesion" as it relates to higher education institutions. In so doing it seeks (a) to understand the core elements of social cohesion--social capital, human capital and ethical behavioral norms that serve a common good--and (b) to establish a flexible framework for understanding the…

  12. Textual Cohesion and Coherence in Children's Writing.

    ERIC Educational Resources Information Center

    Fitzgerald, Jill; Spiegel, Dixie Lee

    1986-01-01

    Examined the relationship between cohesion and coherence in children's writing and investigated the degree to which this relationship would vary with quality of writing and grade level. Concludes that the relationship between cohesion and coherence did not vary according to quality of writing or grade level. (SRT)

  13. Networks, space, and residents' perception of cohesion.

    PubMed

    Boessen, Adam; Hipp, John R; Smith, Emily J; Butts, Carter T; Nagle, Nicholas N; Almquist, Zack

    2014-06-01

    Community scholars increasingly focus on the linkage between residents' sense of cohesion with the neighborhood and their own social networks in the neighborhood. A challenge is that whereas some research only focuses on residents' social ties with fellow neighbors, such an approach misses out on the larger constellation of individuals' relationships and the spatial distribution of those relationships. Using data from the Twin Communities Network Study, the current project is one of the first studies to examine the actual spatial distribution of respondents' networks for a variety of relationships and the consequences of these for neighborhood and city cohesion. We also examine how a perceived structural measure of cohesion-triangle degree-impacts their perceptions of neighborhood and city cohesion. Our findings suggest that perceptions of cohesion within the neighborhood and the city depend on the number of neighborhood safety contacts as well as on the types of people with which they discuss important matters. On the other hand, kin and social friendship ties do not impact cohesion. A key finding is that residents who report more spatially dispersed networks for certain types of ties report lower levels of neighborhood and city cohesion. Residents with higher triangle degree within their neighborhood safety networks perceived more neighborhood cohesion.

  14. Towards power and sample size calculations for the comparison of two groups of patients with item response theory models.

    PubMed

    Hardouin, Jean-Benoit; Amri, Sarah; Feddag, Mohand-Larbi; Sébille, Véronique

    2012-05-20

    Evaluation of patient-reported outcomes (PRO) is increasingly performed in health sciences. PRO differs from other measurements because such patient characteristics cannot be directly observed. Item response theory (IRT) is an attractive way for PRO analysis. However, in the framework of IRT, sample size justification is rarely provided or ignores the fact that PRO measures are latent variables with the use of formulas developed for observed variables. It might therefore be inappropriate and might provide inadequately sized studies. The objective was to develop valid sample size methodology for the comparison of PRO in two groups of patients using IRT. The proposed approach takes into account questionnaire's items parameters, the difference of the latent variables means, and its variance whose derivation is approximated using Cramer-Rao bound (CRB). We also computed the associated power. We realized a simulation study taking into account sample size, number of items, and value of the group effect. We compared power obtained from CRB with the one obtained from simulations (SIM) and with the power based on observed variables (OBS). For a given sample size, powers using CRB and SIM were similar and always lower than OBS. We observed a strong impact of the number of items for CRB and SIM, the power increasing with the questionnaire's length but not for OBS. In the context of latent variables, it seems important to use an adapted sample size formula because the formula developed for observed variables seems to be inadequate and leads to an underestimated study size.

  15. Winnowing and Flocculation in Bio-physical Cohesive Substrate: A Flume Experimental and Estuarine Study

    NASA Astrophysics Data System (ADS)

    Ye, L.; Parsons, D. R.; Manning, A. J.

    2016-12-01

    Cohesive sediment, or mud, is ubiquitously found in most aqueous environments, such as coasts and estuaries. The study of cohesive sediment behaviors requires the synchronous description of mutual interactions of grains (e.g., winnowing and flocculation), their physical properties (e.g., grain size) and also the ambient water. Herein, a series of flume experiments (14 runs) with different substrate mixtures of sand-clay-EPS (Extracellular Polymeric Substrates: secreted by aquatic microorganisms) are combined with an estuarine field survey (Dee estuary, NW England) to investigate the behavior of suspensions over bio-physical cohesive substrates. The experimental results indicate that winnowing and flocculation occur pervasively in bio-physical cohesive flow systems. Importantly however, the evolution of the bed and bedform dynamics and hence turbulence production can be lower when cohesivity is high. The estuarine survey also revealed that the bio-physical cohesion provided by both the clay and microorganism fractions in the bed, that pervasively exists in many natural estuarine systems, plays a significant role in controlling the interactions between bed substrate and sediment suspension and deposition, including controlling processes such as sediment winnowing, flocculation and re-deposition. Full understanding of these processes are essential in advancing sediment transport modelling and prediction studies across natural estuarine systems and the work will report on an improved conceptual model for sediment sorting deposition in bio-physical cohesive substrates.

  16. Influence of prey dispersion on territory and group size of African lions: a test of the resource dispersion hypothesis.

    PubMed

    Valeix, Marion; Loveridge, Andrew J; MacDonald, David W

    2012-11-01

    Empirical tests of the resource dispersion hypothesis (RDH), a theory to explain group living based on resource heterogeneity, have been complicated by the fact that resource patch dispersion and richness have proved difficult to define and measure in natural systems. Here, we studied the ecology of African lions Panthera leo in Hwange National Park, Zimbabwe, where waterholes are prey hotspots, and where dispersion of water sources and abundance of prey at these water sources are quantifiable. We combined a 10-year data set from GPS-collared lions for which information of group composition was available concurrently with data for herbivore abundance at waterholes. The distance between two neighboring waterholes was a strong determinant of lion home range size, which provides strong support for the RDH prediction that territory size increases as resource patches are more dispersed in the landscape. The mean number of herbivore herds using a waterhole, a good proxy of patch richness, determined the maximum lion group biomass an area can support. This finding suggests that patch richness sets a maximum ceiling on lion group size. This study demonstrates that landscape ecology is a major driver of ranging behavior and suggests that aspects of resource dispersion limit group sizes.

  17. N-body Simulations with Cohesion in Dense Planetary Rings

    NASA Astrophysics Data System (ADS)

    Perrine, Randall Patrick

    This dissertation is primarily focused on exploring whether weak cohesion among icy particles in Saturn's dense rings is consistent with observations---and if so, what limits can be placed on the strength of such cohesive bonds, and what dynamical or observable consequences might arise out of cohesive bonding. Here I present my numerical method that allows for N-body particle sticking within a local rotating frame ("patch")---an approach capable of modeling hundreds of thousands or more colliding bodies. Impacting particles can stick to form non-deformable but breakable aggregates that obey equations of rigid body motion. I then apply the method to Saturn's icy rings, for which laboratory experiments suggest that interpenetration of thin, frost-coated surface layers may lead to weak bonding if the bodies impact at low speeds---speeds that happen to be characteristic of the rings. This investigation is further motivated by observations of structure in the rings that could be formed through bottom-up aggregations of particles (i.e., "propellers" in the A ring, and large-scale radial structure in the B ring). This work presents the implementation of the model, as well as results from a suite of 100 simulations that investigate the effects of five parameters on the equilibrium characteristics of the rings: speed-based merge and fragmentation limits, bond strength, ring surface density, and patch orbital distance (specifically the center of either the A or B ring), some with both monodisperse and polydisperse particle comparison cases. I conclude that the presence of weak cohesion is consistent with observations of the A and B rings, and present a range of parameters that reproduce the observed size distribution and maximum particle size. The parameters that match observations differ between the A and B rings, and I discuss the potential implications of this result. I also comment on other observable consequences of cohesion for the rings, such as optical depth and

  18. A Note on Confidence Intervals for Two-Group Latent Mean Effect Size Measures

    ERIC Educational Resources Information Center

    Choi, Jaehwa; Fan, Weihua; Hancock, Gregory R.

    2009-01-01

    This note suggests delta method implementations for deriving confidence intervals for a latent mean effect size measure for the case of 2 independent populations. A hypothetical kindergarten reading example using these implementations is provided, as is supporting LISREL syntax. (Contains 1 table.)

  19. Reciprocal Relations Between Student-Teacher Relationship and Children's Behavioral Problems: Moderation by Child-Care Group Size.

    PubMed

    Skalická, Věra; Belsky, Jay; Stenseng, Frode; Wichstrøm, Lars

    2015-01-01

    In this Norwegian study, bidirectional relations between children's behavior problems and child-teacher conflict and closeness were examined, and the possibility of moderation of these associations by child-care group size was tested. Eight hundred and nineteen 4-year-old children were followed up in first grade. Results revealed reciprocal effects linking child-teacher conflict and behavior problems. Effects of child-teacher closeness on later behavior problems were moderated by group size: For children in small groups only (i.e., ≤ 15 children), greater closeness predicted reduced behavior problems in first grade. In consequence, stability of behavior problems was greater in larger than in smaller groups. Results are discussed in light of regulatory mechanisms and social learning theory, with possible implications for organization of child care. © 2015 The Authors. Child Development © 2015 Society for Research in Child Development, Inc.

  20. The effects of group size on aggression when mixing unacquainted sows in outdoor paddocks

    USDA-ARS?s Scientific Manuscript database

    Aggression is a challenge when pigs are kept in groups. Sows fight at mixing when space is limited but this project sought to determine the amount and type of aggression observed when unacquainted Berkshire sows were mixed in pairs or in two established sub-groups of three in outdoor paddocks. Treat...

  1. How Many Focus Groups Are Enough? Building an Evidence Base for Nonprobability Sample Sizes

    ERIC Educational Resources Information Center

    Guest, Greg; Namey, Emily; McKenna, Kevin

    2017-01-01

    Few empirical studies exist to guide researchers in determining the number of focus groups necessary for a research study. The analyses described here provide foundational evidence to help researchers in this regard. We conducted a thematic analysis of 40 focus groups on health-seeking behaviors of African American men in Durham, North Carolina.…

  2. Children's enduring PTSD symptoms are related to their family's adaptability and cohesion.

    PubMed

    Birmes, Philippe; Raynaud, Jean-Philippe; Daubisse, Laetitia; Brunet, Alain; Arbus, Christophe; Klein, Rémy; Cailhol, Lionel; Allenou, Charlotte; Hazane, Franck; Grandjean, Hélène; Schmitt, Laurent

    2009-08-01

    This study compared, 18-24 months after an industrial disaster, in two groups of children (those with clinically relevant PTSD symptoms versus those with low PTSD symptoms), the child's perception of family cohesion and adaptability, the child's experience of the explosion, and parental characteristics. Enmeshed family cohesion or rigid family adaptability were more frequently found in children with low PTSD symptoms. PTSD symptoms in the mother, living in a family of 3 or more children, and being female were significantly associated with PTSD symptoms in the children. The assessment of traumatized children should include assessment of family's adaptability and cohesion.

  3. Cohesive subgroups and drug user networks in Dhaka City, Bangladesh.

    PubMed

    Gayen, Tarun Kanti; Gayen, Kaberi; Raeside, Robert; Elliott, Lawrie

    2012-01-01

    The purpose of this paper was to explore group drug taking behaviour in a slum area of Dhaka, Bangladesh. We set out to examine the relationships between those who met, at least weekly, to take illegal drugs together, and how these relationships might shape their drug behaviour. Sociometric and behavioural data were collected using questionnaires via semi-structured interviews. We found that the likelihood of injecting drugs and sharing needles increased with age, duration of group membership and length of drug use. Drug users were classified into two clusters: one was more cohesive and comprised longer-term users, who were more likely to inject drugs and had poorer physical and mental health. The other cluster comprised younger, better educated members who were more transient, less cohesive, less likely to inject drugs and had better health. Qualitative data suggested that members of the first cluster were less accepting of outsiders and confirmed more to group norms. We conclude that emotionally bonded cohesive subgroups acquire norms, which reinforce problematic drug-using behaviour. Thus, health initiatives need to consider group relationships and norms and those initiatives which work with networks may be more effective and more appropriate for low-income countries.

  4. Defensive responses by a social caterpillar are tailored to different predators and change with larval instar and group size.

    PubMed

    McClure, Melanie; Despland, Emma

    2011-05-01

    Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through

  5. Defensive responses by a social caterpillar are tailored to different predators and change with larval instar and group size

    NASA Astrophysics Data System (ADS)

    McClure, Melanie; Despland, Emma

    2011-05-01

    Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through

  6. Group size modifies the patterns and muscle carbohydrate effects of aggression in Betta splendens.

    PubMed

    Haller, J

    1992-08-01

    Aggressive encounters of previously isolated individuals were investigated in dyads and groups of five. Fights were longer and more intense when they were performed in dyads compared to fights involving five fishes. During aggressive encounters, an elevation in carbohydrate catabolism was noticed in both dyads and groups. Losing a fight resulted in a reduction in glycogen content and an increase in glycogen synthesis. Similar changes in winners did not appear; thus, the metabolic response in losers was different from that noticed in winners, both in dyads and groups. In dyadic contest winners, a marked increase in the free glucose content and glucose consumption was noticed (without changes in losers). In groups, free glucose content of the winners was not modified, while glucose consumption was enhanced both in winners and losers. Thus, the differences existing between winners and losers were greater in dyads compared to those noticed in groups. The energy cost of aggression seems to be different in dyads compared to groups of five. The rate of glucose oxidation was strongly reduced in dyads (there were no differences between winners and losers in this respect), while in groups, this parameter was not modified.

  7. Beyond one-size-fits-all: Tailoring diversity approaches to the representation of social groups.

    PubMed

    Apfelbaum, Evan P; Stephens, Nicole M; Reagans, Ray E

    2016-10-01

    When and why do organizational diversity approaches that highlight the importance of social group differences (vs. equality) help stigmatized groups succeed? We theorize that social group members' numerical representation in an organization, compared with the majority group, influences concerns about their distinctiveness, and consequently, whether diversity approaches are effective. We combine laboratory and field methods to evaluate this theory in a professional setting, in which White women are moderately represented and Black individuals are represented in very small numbers. We expect that focusing on differences (vs. equality) will lead to greater performance and persistence among White women, yet less among Black individuals. First, we demonstrate that Black individuals report greater representation-based concerns than White women (Study 1). Next, we observe that tailoring diversity approaches to these concerns yields greater performance and persistence (Studies 2 and 3). We then manipulate social groups' perceived representation and find that highlighting differences (vs. equality) is more effective when groups' representation is moderate, but less effective when groups' representation is very low (Study 4). Finally, we content-code the diversity statements of 151 major U.S. law firms and find that firms that emphasize differences have lower attrition rates among White women, whereas firms that emphasize equality have lower attrition rates among racial minorities (Study 5). (PsycINFO Database Record

  8. Is bigger always better? The optimal size of a group practice.

    PubMed

    Hough, Douglas E

    2002-01-01

    The past decade saw several attempts to consolidate physician practices, but this sector remains one of the last cottage industries in the United States. This article develops a framework for analyzing the optimal size of a physician practice. The framework addresses technological factors (e.g., economies of scale and scope), behavioral factors (e.g., changing physician goals, costs of organizing and operating a practice), and market-driven factors (e.g., managed care contracting). Existing empirical research suggests three "optimal" sizes of practices: 5-10 physicians, based on economies of scale and decision-making; 20-30 physicians, based on economies of scope and initial development of a corporate structure; and 80+ (multi-specialty) physicians, which can create an system of referrals and utilization. The article concludes with observations about the challenges to physician practices as they grow.

  9. The Effects of Size, Shape, and Surface Functional Group of Gold Nanostructures on Their Adsorption and Internalization by Cells

    PubMed Central

    Cho, Eun Chul; Au, Leslie; Zhang, Qiang; Xia, Younan

    2010-01-01

    In this study, we examined the effects of size, shape, and surface chemistry of gold nanostructures on their uptake (including both adsorption and internalization) by SK-BR-3 breast cancer cells. We used both spherical and cubic Au nanostructures (nanospheres and nanocages, respectively) of two different sizes, and their surface was modified with poly(ethylene glycol) (PEG), antibody anti-HER2, or poly(allyamine hydrochloride) (PAA). Our results showed that the size of the Au nanostructures influenced their uptake by the cells in a similar way regardless of the surface chemistry, while the shape dependency could vary depending on the surface functional group. In addition, the cells preferred to take up the Au nanostructures covered by different surface groups in the following order: PAA>> anti-HER2> PEG. The fraction of Au nanostructures attached to the cell surface was also dependent on the aforementioned parameters. PMID:20029850

  10. Sustainable Group Sizes for Multi-Agent Search-and-Patrol Teams

    DTIC Science & Technology

    2010-07-01

    unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 (a) JCT ISR EAD (b) Fig. 1. In (a), the pride structure is shown; males (triangles...application of our work is determining the sustainable sizes for the US Navy suppression of enemy Report Documentation Page Form ApprovedOMB No. 0704-0188...combat teams (labeled JCT ) provide security for surveillance teams (labeled ISR) that are searching for vehicles (labeled EAD). air defenses (SEAD

  11. The Effect of Computer-Assisted Cooperative Learning Methods and Group Size on the EFL Learners' Achievement in Communication Skills

    ERIC Educational Resources Information Center

    AbuSeileek, Ali Farhan

    2012-01-01

    This study explored the effect of cooperative learning small group size and two different instructional modes (positive interdependence vs. individual accountability) on English as a Foreign Language (EFL) undergraduate learners' communication skills (speaking and writing) achievement in computer-based environments. The study also examined the…

  12. A Distorted Nation: Perceptions of Racial/Ethnic Group Sizes and Attitudes toward Immigrants and Other Minorities

    ERIC Educational Resources Information Center

    Alba, Richard D.; Rumbaut, Ruben G.; Marotz, Karen

    2005-01-01

    Using a special module (MEUS) of the 2000 General Social Survey, we investigate Americans' perceptions of the racial and ethnic composition of the United States. We show that, because of innumeracy, it is critical to gauge perceptions through relative, rather than absolute, group sizes. Even so, it appears that, as of 2000, roughly half of…

  13. Reciprocal Relations between Student-Teacher Relationship and Children's Behavioral Problems: Moderation by Child-Care Group Size

    ERIC Educational Resources Information Center

    Skalická, Vera; Belsky, Jay; Stenseng, Frode; Wichstrøm, Lars

    2015-01-01

    In this Norwegian study, bidirectional relations between children's behavior problems and child-teacher conflict and closeness were examined, and the possibility of moderation of these associations by child-care group size was tested. Eight hundred and nineteen 4-year-old children were followed up in first grade. Results revealed reciprocal…

  14. Comparisons of Improvement-Over-Chance Effect Sizes for Two Groups under Variance Heterogeneity and Prior Probabilities

    ERIC Educational Resources Information Center

    Henson, Robin K.; Natesan, Prathiba; Axelson, Erika D.

    2014-01-01

    The authors examined the distributional properties of 3 improvement-over-chance, I, effect sizes each derived from linear and quadratic predictive discriminant analysis and from logistic regression analysis for the 2-group univariate classification. These 3 classification methods (3 levels) were studied under varying levels of data conditions,…

  15. Attitudes, Behaviors, and Effectiveness of Black and White Leaders of Simulated Problem Solving Groups of Varying Size and Racial Composition.

    ERIC Educational Resources Information Center

    Hill, Walter A.; Allen, William R.

    A field experiment was used to investigate the effects, if any, of changing group size and racial composition on the attitudes, behaviors, and effectiveness of black and white leaders. Subjects were 288 naval recruits, half black and half white, performing two tasks which were watched by a pair of racially mixed observers through a one-way mirror.…

  16. Group size effects on survivorship and adult development in the gregarious larvae of Euselasia chrysippe (Lepidoptera, Riodinidae)

    Treesearch

    P. E. Allen

    2010-01-01

    Caterpillars living in aggregations may derive several benefits that outweigh the costs, including better survivorship and improved growth rates. I tested whether larval group size had an effect on these two vital rates in Euselasia chrysippe. These caterpillars feed gregariously during all instars and move in processionary form over the host plant...

  17. Comparisons of Improvement-Over-Chance Effect Sizes for Two Groups under Variance Heterogeneity and Prior Probabilities

    ERIC Educational Resources Information Center

    Henson, Robin K.; Natesan, Prathiba; Axelson, Erika D.

    2014-01-01

    The authors examined the distributional properties of 3 improvement-over-chance, I, effect sizes each derived from linear and quadratic predictive discriminant analysis and from logistic regression analysis for the 2-group univariate classification. These 3 classification methods (3 levels) were studied under varying levels of data conditions,…

  18. The Effect of Computer-Assisted Cooperative Learning Methods and Group Size on the EFL Learners' Achievement in Communication Skills

    ERIC Educational Resources Information Center

    AbuSeileek, Ali Farhan

    2012-01-01

    This study explored the effect of cooperative learning small group size and two different instructional modes (positive interdependence vs. individual accountability) on English as a Foreign Language (EFL) undergraduate learners' communication skills (speaking and writing) achievement in computer-based environments. The study also examined the…

  19. Effects of Violations of Data Set Assumptions When Using the Analysis of Variance and Covariance with Unequal Group Sizes.

    ERIC Educational Resources Information Center

    Johnson, Colleen Cook; Rakow, Ernest A.

    This research explored the degree to which group sizes can differ before the robustness of analysis of variance (ANOVA) and analysis of covariance (ANCOVA) are jeopardized. Monte Carlo methodology was used, allowing for the experimental investigation of potential threats to robustness under conditions common to researchers in education. The…

  20. New Analysis Techniques for Avalanches in a Conical Bead Pile with Cohesion

    NASA Astrophysics Data System (ADS)

    Tieman, Catherine; Lehman, Susan

    2015-03-01

    Avalanche statistics and pile geometry for 3 mm steel spheres dropped on a conical bead pile were studied at different drop heights and different cohesion strengths. The pile is initially built on a circular base and is subsequently slowly driven by adding one bead at a time to the apex of the pile. We investigate the dynamic response of the pile by recording avalanches off the pile over the course of tens of thousands of bead drops. The level of cohesion is tuned through use of an applied uniform magnetic field. Changes in the pile mass and geometry were investigated to determine the effect of cohesion and drop height on the angle of repose. The angle of repose increased with cohesion strength, and decreased somewhat for higher drop heights. The packing density of beads is expected to decrease as magnetic cohesion increases, but for our 20 000-bead pile, this effect has not been observed. The proportion of beads removed from the pile by different avalanche sizes was also calculated. Although larger avalanches are much rarer occurrences, they carry away a larger fraction of the total avalanched mass than small avalanches. As the pile cohesion increases, the number of small and medium avalanches decreases so that this mass loss distribution shifts more strongly to large sizes.