Influence Of Group Size Research Articles

The effect of social and ecological factors on the time budget of wild vervet monkeys

AbstractAnimals often have a limited time to perform different fitness‐enhancing activities, such as the trade‐off between socializing versus foraging in group‐living species. Many previous studies have focused on how ecological and social factors influence activity budget at the individual or group level in various species. However, few primate studies have focused on multiple study groups living within a similar habitat. Here, we analyse group, season and sex effects on the individual activity budget of wild vervet monkeys (Chlorocebus pygerythrus) living in four groups with overlapping home ranges. Generally, our findings support previous studies on primates. Our results indicate that intragroup competition may force larger groups to spend more time feeding and less time resting. We also found that seasonal variation, and therefore food availability, has a strong influence on the monkeys’ activity budget. Females, which are the philopatric sex in vervet monkeys, spent more time socializing while, in general, males spent more time resting. However, we did not find any difference on the time spent socializing between groups. Since there is evidence that not only time constraints and habitat quality but also group size influence individual behaviours and ultimately group living, we advise that future studies should focus on multiple groups of the same species living in the same habitat in order to better understand how all these variables are interlinked.

Variation in sex allocation plasticity in three closely related flatworm species.

Sex allocation (SA) theory for simultaneous hermaphrodites predicts an influence of group size on SA. Since group size can vary within an individual's lifetime, this can favor the evolution of phenotypically plastic SA. In an emerging comparative context, we here report on SA plasticity in three closely related Macrostomum flatworm species, namely Macrostomum janickei, Macrostomum cliftonensis, and Macrostomum mirumnovem. For each species, we experimentally raised worms in three group sizes (isolated, pairs, and octets) and two enclosure sizes (small and large) in all factorial combinations and studied the effects of these factors on different estimates of SA. In addition, we also evaluated whether isolated worms engage in self‐fertilization. We found that all species have plastic SA, with M. cliftonensis being more plastic than the other two species, as assessed by comparing standardized effect sizes of (a) the presence/absence of mating partners and (b) the strength of sexual competition. Moreover, we found that sperm production rate—but not sperm morphology—is plastic in M. cliftonensis, and that only M. mirumnovem self‐fertilized during our observation period. Our study suggests that both SA and SA plasticity can diverge even between closely related species.

Social relations and presence of others predict bystander intervention: Evidence from violent incidents captured on CCTV.

Are individuals willing to intervene in public violence? Half a century of research on the “bystander effect” suggests that the more bystanders present at an emergency, the less likely each of them is to provide help. However, recent meta‐analytical evidence questions whether this effect generalizes to violent emergencies. Besides the number of bystanders present, an alternative line of research suggests that pre‐existing social relations between bystanders and conflict participants are important for explaining whether bystanders provide help. The current paper offers a rare comparison of both factors—social relations and the number of bystanders present—as predictors of bystander intervention in real‐life violent emergencies. We systematically observed the behavior of 764 bystanders across 81 violent incidents recorded by surveillance cameras in Copenhagen, Denmark. Bystanders were sampled with a case–control design, their behavior was observed and coded, and the probability of intervention was estimated with multilevel regression analyses. The results confirm our predicted association between social relations and intervention. However, rather than the expected reversed bystander effect, we found a classical bystander effect, as bystanders were less likely to intervene with increasing bystander presence. The effect of social relations on intervention was larger in magnitude than the effect of the number of bystanders. We assess these findings in light of recent discussions about the influence of group size and social relations in human helping. Further, we discuss the utility of video data for the assessment of real‐life bystander behavior.

Dynamics of social groups’ decision-making in evacuations

The possible presence of social groups amongst occupants in indoor evacuation scenarios and the potential discrepancies between their behaviour and that of single individuals have been acknowledged in the evacuation dynamics literature. Yet, empirical studies on the behavioural characteristics of social-group evacuees, particularly those related to their decision-making mechanism, are relatively underrepresented. This study reports on a lab-in-the-field experiment of evacuations that investigates the effect of group size and stress level on multiple aspects of groups’ behaviour. These aspects include pre-movement time, decision time (i.e. time taken to reach a directional exit decision), exit-choice behaviour, exit-choice changing and intra-group decision dynamics. Our main findings showed that:(I)Group size had a significant effect on pre-movement times and decision times (and to lesser extent, on evacuation times). People took longer to initiate their movement or to make a directional exit decision when in groups compared to when acting alone. The influence of group size on pre-movement and decision times, however, was not monotonic. For smaller group sizes (sizes 2 and 3), pre-movement and decision times increased with the group size. But for the larger group size (size 4), the effect was reversed.(II)The exit-choice mechanism of groups, overall, showed a great degree of similarity to that of single individuals. This suggests that, from a modelling perspective, the directional exit choices of groups could be approximated with the models obtained from datasets of individually-made choices.(III)Groups were more likely to revisit and change their initial exit decisions under the higher level of stress. In addition, social influence was a major factor in triggering changes in the exit choices of groups. Nearly 50% of the changes in group decisions occurred shortly after another neighbour group changed its exit decision. In other words, instances of group decision-changing was often followed by another group taking a similar action.(IV)As to the within-group dynamics of decision-making, our analyses suggested that, regardless of the group size, leadership was the dominant group decision-making mechanism (compared to the consensus or the conform-to-majority mechanisms). In nearly 50% of the cases, group decisions were made by one individual taking the lead and hinting the direction of the movement to other members of the group.

Does peer group size influence social preferences and risk taking?

AbstractThis paper examines whether the ex post relative payoffs of peers as well as the size of the peer group impact an agent's willingness to take risks. For example, persons in a flood plain may be less likely to purchase flood insurance if their neighbors also refrain from purchasing. We generalize the Fehr‐Schmidt (1999) model to allow the intensity of the social preferences to vary with the size of the peer group. Our experiment tests whether subjects are more or less likely to choose a lottery over a fixed payment when others have been assigned either the same lottery or the fixed payment. Using both between and within subject designs, we find risk‐taking behaviour is not responsive to the risks faced by others regardless of the size of peer group.

The Influence of Group Size in the Asynchronous Online Discussions on the Development of Critical Thinking Skills, and on Improving Students’ Performance in Online Discussion Forum

Asynchronous Online Discussions (AOD) are considered as one of the most ma-jor tools in learning management systems which are used in universities. The ex-ploitation of AODs forums offer students the possibility to teach and learn any-time and anywhere. They also provide students with the time needed to process learning, share ideas and points of view on e-course topics. The group size in the AODs is a substantial variable that affects the interaction and the participation of students. The purpose of our research lays in understanding the influence of the group size participating in the AODs on the development of critical thinking skills in information technology for students of the Faculty of Education, and im-proving students’ performance in online discussion forums. In this research, 103 university students from the bachelor's degree have participated in the study. The participating students are studying the Computer Application in Education Course, and the Education Technology Course on the Blackboard e-learning Management System, during a 15-week semester. The findings of the research have revealed very significant conclusions; and the researcher has come up with various recommendations and suggestions for future studies and further research.

The Effects of Group Size and Time on the Formation of Online Communities: Evidence From Reddit

These studies examine the influence of group size and the passage of time on two characteristics of online communities: dispersion of participation in group discussions and active member turnover from month to month. We used multilevel analysis to examine the dynamics of user contributions to discussions on Reddit, a popular website that hosts large-group discussions, across 30 groups over 6 years. As groups grow in size, participation becomes more highly concentrated among fewer members while turnover decreases. As time passes, participation becomes more widely dispersed while group member turnover increases. An increase in group member turnover appears to be the result of both a maturation effect (as each group ages, turnover increases) as well as a cohort effect (groups formed at a later date have higher turnover than groups formed earlier). We can conclude from these results that as time progresses and groups become larger, they become less community-like, but in different ways.

The influence of group size on distributional fairness under voting by veto

Voting by Veto [VBV], developed by Dennis C. Mueller, is a two-stage voting mechanism for committee decision making. In the first stage, every member of the committee makes a proposal. The proposals are joined with the current status quo (or another fallback option). For the second stage, a random mechanism determines the order of voting and the committee members sequentially eliminate one alternative each. After every committee member has exercised her veto, a single winning alternative remains. Game theory predicts that the equality of the resulting distribution under VBV varies with group size. Hence, decisions in two-member groups should result in highly unequal distributions of benefits. With increasing group size, however, VBV should generate more equally distributed outcomes. We examine the effect of group size under VBV in a series of laboratory experiments where groups with a varying number of members play a ‘divide the dollar game’. Our results confirm that larger groups choose more equal distributions than smaller groups. However, we also find deviations from the model's predictions. Some committees in our experiment do not select Pareto-optimal alternatives. An exploratory analysis of possible explanations suggests that individual behavior is most likely motivated by a combination of material self-interest and social preferences such as reciprocity and fairness.

Integration of individual and social information for decision-making in groups of different sizes.

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.

Aggressiveness in group-housed rabbit does: Influence of group size and pen characteristics

The aim of this work was to study how the group size and the number of doorways in a pen may influence the aggressive interactions throughout the reproductive cycle among does kept in a part-time group housing system. Thirty-two crossbred multiparous pregnant rabbit does were housed in individual modules (0.5m2) that were connected to form collective pens with two (P2) or four (P4) does (8 and 4 replications, respectively) by using one (D1) or two (D2) doorways. The females were maintained in stable groups from the start of the trial, 8 d before kindling (−8 d), until 2 d before kindling and from 18 d after kindling (+18 d) until weaning (31 d). The aggressive interactions were video recorded through 24 consecutive hours at −8 d and +18 d and at 21 d and 30 d after kindling. Aggressive behaviour at 21 d and 30 d after kindling was not analysed due to its scarce (total interactions per doe in 24h: 0.02 events) and null occurrences, respectively. Then, data of the first hour after grouping at −8 d and +18 d were analysed by Bayesian inference, and the posterior distributions of the differences between group size, number of doorways and observation day were estimated. Does in P4 pens showed a higher frequency of boxing (1.63 vs. 0.50 events per doe) and chasing (1.00 vs. 0.28) than those in P2 pens (probability of relevance, ProbR=0.87). Does in D2 pens showed a higher frequency of attacking (2.00 vs. 0.46 events per doe), chasing (0.83 vs. 0.21), and mount attempts (0.38 vs. 0.08) than those in D1 pens (ProbR 0.80–0.83). Aggressive interactions were higher at the first group formation (−8 d) than at regrouping (at +18 d) (10.5 vs. 6.25 events per doe; ProbR=0.69). In conclusion, aggression among does was affected by group size and pen characteristics and decreased throughout the reproductive cycle. Nevertheless, studies of more reproductive cycles and collective pens will be necessary to confirm the present results.

Impact of group size and social composition on group vocal activity and acoustic network in a social songbird

In social species individuals living in the same group may synchronize activities such as movements, foraging or antipredator vigilance. Synchronization of activities can also be observed between partners especially during breeding and can be crucial for breeding success. Vocalizations are behaviours that can be coordinated between individuals, but simultaneous vocalizations in groups have mostly been considered as noise that does not bear any information. Indeed, little is known about the structure and function of vocal communications involving a network of individuals. How individual vocal activity forms part of the communal sound and how the group influences individual vocal activity are questions that remain to be studied. Zebra finches, Taeniopygia guttata, are social, monogamous songbirds that form lifelong pair bonds. In the wild, they are typically found in small groups, with the pair as the primary social unit, and they gather in ‘social’ trees where both females and males produce vocalizations. Here we investigated in the laboratory the influence of group size and composition on general vocal activity and synchrony, as well as the influence of pair bond and spatial location on the finer characteristics of dyads' vocal interactions. We used a set-up that locked the birds at fixed spatial positions of our choosing to control the proximity network and allowed us to match most of the vocalizations with specific in- dividuals. We used an in-house software suite that automatically detects vocalizations from hours of passive recording. We found that zebra finch groups synchronized their general vocal activity with waves of collective vocalizations, which depended on both the size and the composition of the group. The acoustic network was shaped by pair bonds at different timescales. Birds preferentially vocalized close in time to (synchrony) or directly after (turn taking) their partner when it was present and the nearest neighbour when the partner was not available.

Long-term analysis on the variance of extra-group paternities in rhesus macaques

Extra-group paternity (EGP) has been described in various mammalian species; however, little is known about which factors contribute to the variation in EGP, as the majority of studies were restricted in time and the number of groups considered. Using longitudinal demographic and genetic data, we aim to investigate which factors predict rates of EGP in the free-ranging rhesus macaque population of Cayo Santiago, Puerto Rico (USA). Of the 1649 infants considered which were born into six social groups over 9 years, we identified an average of 16% of infants resulting from EGPs. We tested the influence of group size, breeding group sex ratio, female reproductive synchrony, and group instability on the occurrence of EGPs. Our results suggest a tendency for EGPs to increase as the proportion of females increased in larger groups, but no such effect in smaller groups. Furthermore, as group instability and female reproductive synchrony decreased, the number of EGPs tended to increase. Our results support the hypothesis that group structure affects the occurrence of EGPs, which might be mediated by male mating opportunities, male monopolization potential, and/or female choice.Significance statementIn several species, both sexes seek alternative reproductive strategies to enhance their reproductive success. For instance, females may pursue EGPs to potentially increase genetic compatibility with males, or males may seek EGPs to improve their mating opportunities. Our longitudinal analysis, including demographic and genetic data over 9 years of six social groups of rhesus macaques, revealed high variation in the occurrence of EGPs across groups and years, and this variation tended to depend on group characteristics such as breeding group size, sex ratio, female synchrony, and group instability. The data suggest that group structure affects the number of EGPs in this group-living primate. Our results show that EGPs can affect the distribution of paternity within social groups and should be taken into account when assessing reproductive success.

Evolution of students’ friendship networks: Examining the influence of group size

The main aim of this study was to examine the effect of the network size on formation and evolution of students’ friendship relations. Data was collected from two groups of sociology freshmen: a group from the University of Belgrade, which represents a larger group, and a group from the University of Novi Sad, which represents a smaller group. The data was collected in three periods of one academic year. We analyzed the structural features of students’ networks and constructed a stochastic model of network evolution in order to explore how friendships form and change during one year. The results showed that structural features of the larger and the smaller group differ in each stage of friendship formation. At the beginning of group forming, small world structure was noticeable in the larger group, although full small world structure was not confirmed in both groups. Furthermore, transitivity of triads had effect on the evolution of the larger network, while balance or structural equivalence had effect on the evolution of the smaller network. Results of the structural analysis are in line with findings of the network evolution model and together they provide an insight into how friendship evolves in groups of different sizes.

Does Group Size Matter for Behavior in Online Trust Dilemmas?

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.

Seismic response of pile-raft-clay system subjected to a long-duration earthquake: centrifuge test and finite element analysis

A series of seismic centrifuge model tests were performed to study the behavior of pile groups in soft kaolin clay. Several small-scale pile-raft models were fabricated, ranging from a 2×1 to a 4×3 pile group. Pile and raft were made of aluminum, rigidly connected each other at the pile head via a through bolt system. The excited long-duration ground motion of about 200s strong motion was employed to represent a far-field earthquake arising from Sunda Subduction Trench. Experimental investigation into the influence of group size on both raft acceleration and pile bending moment response was conducted. It was found that both acceleration and pile bending moment response were influenced by stiffness-to-mass ratio of the pile-raft system; while pile spacing had no evident influence on acceleration response but significantly influenced the pile bending moment response. Besides, pile bending moment was also influenced by the row location of pile in the 4×3 pile group. Furthermore, by employing a hyperbolic-hysteretic soil constitutive model to model the kaolin clay, a series of three-dimensional finite element analyses were carried out to compare with the seismic centrifuge tests. Reasonably well comparisons between centrifuge test and numerical computed results were obtained, which suggest that the 3D finite element modelling procedure with a hyperbolic-hysteretic soil constitutive model can be extended to complement seismic centrifuge tests.

The Influences of Group Size and Tie Strength on Customer Satisfaction to the Service provide in case of Other Customer misbehavior.

The Influences of Group Size and Tie Strength on Customer Satisfaction to the Service provide in case of Other Customer misbehavior.

Beneficial effects of group size on oxidative balance in a wild cooperative breeder

Social factors have important effects on individuals’ fitness, yet the proximate mechanisms remain virtually unknown. Oxidative stress, which results from the imbalance between the systemic effect of reactive oxygen species on molecules and an organism’s capacity to restore oxidative balance, is one potential mechanism mediating such effects. Although individuals’ oxidative balance seems to be affected by their social status, the effects of social environment, and particularly group size and composition, on oxidative balance have seldom been determined in wild populations. Here, we investigated the influence of group size and composition on the oxida- tive balance of wild dominant Alpine marmots (Marmota marmota). We simultaneously measured an index of circulating oxidative damage to lipids (thiobarbituric acid reactive substances) and specific activity of the main enzymatic antioxidant defense (superoxide dismutase). Our results showed a marked decrease in both oxidative damage and antioxidant activity in individuals from larger groups, highlighting a beneficial effect of group size on individuals’ oxidative balance. We discussed the possibility that these physiological benefits originate from social thermoregulation alleviating the cost of hibernation. This study extends our understanding of the proxi- mate factors underpinning the evolution of sociality and opens up novel perspectives within the field of evolutionary ecology.

Vigilance behaviour of the year-round territorial vicuña (Vicugna vicugna) outside the breeding season: Influence of group size, social factors and distance to a water source

We conducted focal observations of vicuña, a year-around territorial mammal, to compare vigilance behaviour between territorial and bachelor males outside the reproductive season. We hypothesized that the time spent vigilant would depend on male social status, considering the potential effects of several variables: sampling year, group size, distances to the nearest neighbour and to a vega (mountain wetland). We fit GLM models to assess how these variables, and their interactions, affected time allocation of territorial and bachelor males. We found non significant differences between territorial and bachelor males in the time devoted to vigilance behaviour. Vigilance of territorial males was influenced by the sampling year and the distance to the vega. In turn, vigilance in bachelor males was influenced mainly by the sampling year, the group size and the distance to the vega. Our results suggest that sampling year and distance to the vega are more important than social factors in conditioning the behaviour of male vicuñas, during the non-reproductive season. Future studies of behaviour in water-dependant ungulates, should consider the influence of water and forage availabilities, and the interactions between group size and other variables.

Acute phase cytokines, TAC1, and toll-like receptor4 mRNA expression and health associated with group size in veal calves

Chronic stressors are a major health and well-being issue in animals. Immune status of animals under chronic stress is compromised, thus reducing disease resistance and compromising well-being of the animal. The objective of this study was to determine the influence of group size of veal calves on immune status and leukocyte mRNA expression of acute phase cytokines, toll-like receptor 4 (TLR4) and tachykinin 1 (TAC1) over a five-month finishing period. Holstein bull calves (n=168), 44±3 days of age were assigned to one of three treatments; 2, 4, or 8calves/pen (pen space allowance of 1.82m2/calf). Jugular blood samples were collected at the day of grouping and then monthly for 4 months. The differential leukocyte counts were determined and mRNA was extracted from the leukocytes. Reverse transcription-qPCR was used to measure the gene expression of interleukin-1 (IL-1β), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor (TNF-α), TLR4, and TAC1 in leukocytes. Health was evaluated before grouping and monthly for 4 months. On the 1st month after grouping, veal calves that were housed in groups of 8 have greater expression of IL-1β mRNA than calves housed in groups of 4 or 2 (treatment×month, P=0.04). Also at 1 month, groups of 8 had greater TAC1 expression (P<0.05) than calves housed in groups of 4 or 2. However, the expression of IL-1Ra, TNF-α, and TLR4 were not influenced by group size. In the first month of the trial, calves in groups of 8 coughed more (P<0.05) than calves in groups of 2 and coughed more than calves in groups of 4 and 2 during the 2nd month (treatment×month, P=0.03). Calves housed in groups of 8 tended to have greater neutrophil percentage (P=0.09), neutrophil to lymphocyte ratio (P=0.06), and had lower lymphocyte percentage (P=0.06) than those housed in groups of 4 or 2. In conclusion, the number of veal calves in a group, given the same space during the finishing period did not alter IL-1Ra, TNF-α, and TLR4 mRNA expression. However, housing of calves in groups of 8 was associated with greater expression of IL-1β and TAC1 mRNA in peripheral blood leukocytes, and coughing during the first 2 months after grouping. Therefore, housing of veal calves in larger groups may lead to greater susceptibility to respiratory disease and stress.

Social Cueing in Human Attention within the Context of Orientation Tasks

Social cues are of general importance in human attention. Even when presented with task-oriented stimuli, social cues are preferred. In orientation tasks, the degree of the impact of social cues on the perception of signal cues is of high relevance for the behavior, such as in evacuation tasks. Therefore, we investigated the degree of this impact, using free-viewing and orientation task driven stimuli. To investigate the shift of attention in further detail, single persons and groups of persons were set into conflict with signage cues. In the experimental eye tracking study, images of an evacuation guidance system were displayed with appearance of guidance-related signs as well as with appearances of persons. To test the influence of group size, the number of depicted persons was varied. The scenes were observed, alternatively, (i) under free-viewing conditions and (ii) in an orientation task. From the results of the study we conclude that in orientation tasks there is a shift of attention from social to signage cues, while larger group sizes support the attention shift towards social cues.