Social complexity from within: how individuals experience the structure and organization of their groups

We argue that the study of social complexity can follow two different approaches, based on how it is seen from the outside or on how it is experienced from within. Recent focus has been on the former with social complexity emerging from the interactions of group members. Here, we take the view from within and deal with the social complexity that individual group members may experience, exploring complexity arising from aspects of the social structure and social organization. We review a variety of sources of social complexity in terms of variation between and within social relationships, variation in opportunities to interact with different group members, and the role of third parties. We then examine how individuals can cope with the social complexity they face. We conclude that a refined view of social relationships at different levels is needed to study the social complexity faced by individual group members and emphasize the potential contribution of the view from within to the study of social complexity and cognition. Animals may experience different degrees of complexity in their social groups. Instead of viewing social complexity as an emergent property of the interactions exchanged by group members, we focus on the social complexity individual group members may experience. We examine how aspects of social structure and social organization, such as the variation between and within social relationships, the variation in opportunities to interact with different group members, and the role of third parties, could create challenges and sources of complexity for individual group members. We then evaluate how emotions and cognitive abilities could be used by animals of different species to navigate the social complexity they experience and make appropriate decisions. We show that there are neglected sources of social complexity related to social relationships that derive from them changing over time and consisting of different components. We conclude by emphasizing that a change in perspective is needed to study how cognition is linked to the social complexity individual group members may experience

Symmetry-based reciprocity: evolutionary constraints on a proximate mechanism

Background. While the evolution of reciprocal cooperation has attracted an enormous attention, the proximate mechanisms underlying the ability of animals to cooperate reciprocally are comparatively neglected. Symmetry-based reciprocity is a hypothetical proximate mechanism that has been suggested to be widespread among cognitively unsophisticated animals. Methods. We developed two agent-based models of symmetry-based reciprocity (one relying on an arbitrary tag and the other on interindividual proximity) and tested their ability both to reproduce significant emergent features of cooperation in group living animals and to promote the evolution of cooperation. Results. Populations formed by agents adopting symmetry-based reciprocity showed differentiated “social relationships” and a positive correlation between cooperation given and received: two common aspects of animal cooperation. However, when reproduction and selection across multiple generations were added to the models, agents adopting symmetry-based reciprocity were outcompeted by selfish agents that never cooperated. Discussion. In order to evolve, hypothetical proximate mechanisms must be able to stand competition from alternative strategies. While the results of our simulations require confirmation using analytical methods, we provisionally suggest symmetry-based reciprocity is to be abandoned as a possible proximate mechanism underlying the ability of animals to reciprocate cooperative interactions

Grooming Up the Hierarchy: The Exchange of Grooming and Rank-Related Benefits in a New World Primate

Seyfarth's model assumes that female primates derive rank-related benefits from higher-ranking females in exchange for grooming. As a consequence, the model predicts females prefer high-ranking females as grooming partners and compete for the opportunity to groom them. Therefore, allogrooming is expected to be directed up the dominance hierarchy and to occur more often between females with adjacent ranks. Although data from Old World primates generally support the model, studies on the relation between grooming and dominance rank in the New World genus Cebus have found conflicting results, showing considerable variability across groups and species. In this study, we investigated the pattern of grooming in wild tufted capuchin females (Cebus apella nigritus) in Iguazú National Park, Argentina by testing both the assumption (i.e., that females gain rank-related return benefits from grooming) and predictions (i.e., that females direct grooming up the dominance hierarchy and the majority of grooming occurs between females with adjacent ranks) of Seyfarth's model. Study subjects were 9 adult females belonging to a single group. Results showed that grooming was given in return for tolerance during naturally occurring feeding, a benefit that higher-ranking females can more easily grant. Female grooming was directed up the hierarchy and was given more often to partners with similar rank. These findings provide supporting evidence for both the assumption and predictions of Seyfarth's model and represent, more generally, the first evidence of reciprocal behavioural interchanges driven by rank-related benefits in New World female primates

Self-Protective Function of Post-Conflict Bystander Affiliation in Mandrills

Background: Affiliative interactions exchanged between victims of aggression and individuals not involved in the original aggression (bystanders) have been observed in various species. Three hypothetical functions have been proposed for these interactions: consolation, self-protection and substitute reconciliation, but data to test them are scanty. Methodology/Principal Findings: We conducted post-conflict and matched control observations on a captive group of mandrills (Mandrillus sphinx). We found that victims often redirected aggression to bystanders, that they received most affiliation from those bystanders that were frequently the target of redirection, and that bystander affiliation reduced the likelihood of redirection. Bystander affiliation did not reduce the victim\u27s distress (as measured by its scratching rates) and was not received primarily from kin/friends. Finally, bystander affiliation did not reduce the likelihood of renewed aggression from the original aggressor. Conclusions/Significance: These results provide support for the self-protection hypothesis but not for the consolation and substitute reconciliation hypotheses

Feeling anxious? The mechanisms of vocal deception in tufted capuchin monkeys

An ability to deceive conspecifics is thought to have favoured the evolution of large brains in social animals, but evidence that such behaviours require cognitive complexity is lacking. Tufted capuchin monkeys (Sapajus spp.) have been documented to use false alarm calls during feeding in a manner that functions to deceive competitors. However, comparative evidence suggests that the production of vocalizations by nonhuman primates is largely underpinned by emotional mechanisms, calling into question more cognitive interpretations of this behaviour. To determine whether emotional states are plausibly necessary and sufficient to proximately explain deceptive alarm call production, we examined the association between self-directed behaviours (SDBs), as a proxy for anxiety, and the production of spontaneous false alarm calls among tufted capuchins. Specifically, we predicted that if anxiety is necessary for the production of false alarms, then individuals that produce spontaneous false alarms should exhibit more SDBs in those contexts in which they call. If anxiety is also sufficient to explain the false alarm call production, then we predicted that individuals that call more in a given context would show higher rates of SDBs in that context, and that high rates of calling would be temporally associated with high rates of SDBs. Our results support the contention that states of anxiety are necessary for an individual to spontaneously produce false alarms, but that such states are not sufficient to explain patterns of calling. The link between anxiety and deceptive calling thus appears complex, and cognitively based decision-making processes may play some role in call production

Birth sex ratio and social rank: consistency and variability within and between primate groups

Variations in birth sex ratios in primates are notoriously inconsistent and have been repeatedly suggested to be mainly owing to stochastic processes. An examination of temporal consistency within primate populations revealed that the effect of dominance rank on birth sex ratio tends to remains stable over time. Furthermore, a meta-analysis of published data on sex ratio variations in primates shows that although no overall effect was detectable, the relation between birth sex ratio and dominance rank was affected by level of resource availability and degree of sexual dimorphism. These results suggest that purely stochastic processes are unlikely to explain observed variations in primate birth sex ratios, and may explain why adaptive sex ratio variations in primates have been so difficult to demonstrate. Copyright 2004.maternal investment; meta-analysis; population growth; sexual dimorphism

C (2012) Self-protective function of post-conflict bystander affiliation in mandrills

Background: Affiliative interactions exchanged between victims of aggression and individuals not involved in the original aggression (bystanders) have been observed in various species. Three hypothetical functions have been proposed for these interactions: consolation, self-protection and substitute reconciliation, but data to test them are scanty. Methodology/Principal Findings: We conducted post-conflict and matched control observations on a captive group of mandrills (Mandrillus sphinx). We found that victims often redirected aggression to bystanders, that they received most affiliation from those bystanders that were frequently the target of redirection, and that bystander affiliation reduced the likelihood of redirection. Bystander affiliation did not reduce the victim’s distress (as measured by its scratching rates) and was not received primarily from kin/friends. Finally, bystander affiliation did not reduce the likelihood of renewed aggression from the original aggressor. Conclusions/Significance: These results provide support for the self-protection hypothesis but not for the consolation and substitute reconciliation hypotheses

Grooming reciprocation among female primates: a meta-analysis

The theory of reciprocal altruism offers an explanation for the evolution of altruistic behaviours among unrelated animals. Among primates, grooming is one of the most common altruistic behaviours. Primates have been suggested to exchange grooming both for itself and for rank-related benefits. While previous meta-analyses have shown that they direct their grooming up the hierarchy and exchange it for agonistic support, no comprehensive evaluation of grooming reciprocation has been made. Here we report on a meta-analysis of grooming reciprocation among female primates based on 48 social groups belonging to 22 different species and 12 genera. The results of this meta-analysis showed that female primates groom preferentially those group mates that groom them most. To the extent allowed by the availability of kinship data, this result holds true when controlling for maternal kinship. These results, together with previous findings, suggest that primates are indeed able to exchange grooming both for itself and for different rank-related benefits

Symmetry-based reciprocity: evolutionary constraints on a proximate mechanism

Background. While the evolution of reciprocal cooperation has attracted an enormous attention, the proximate mechanisms underlying the ability of animals to cooperate reciprocally are comparatively neglected. Symmetry-based reciprocity is a hypothetical proximate mechanism that has been suggested to be widespread among cognitively unsophisticated animals. Methods. We developed two agent-based models of symmetry-based reciprocity (one relying on an arbitrary tag and the other on interindividual proximity) and tested their ability both to reproduce significant emergent features of cooperation in group living animals and to promote the evolution of cooperation. Results. Populations formed by agents adopting symmetry-based reciprocity showed differentiated “social relationships” and a positive correlation between cooperation given and received: two common aspects of animal cooperation. However, when reproduction and selection across multiple generations were added to the models, agents adopting symmetry-based reciprocity were outcompeted by selfish agents that never cooperated. Discussion. In order to evolve, hypothetical proximate mechanisms must be able to stand competition from alternative strategies. While the results of our simulations require confirmation using analytical methods, we provisionally suggest symmetry-based reciprocity is to be abandoned as a possible proximate mechanism underlying the ability of animals to reciprocate cooperative interactions

Grooming for infant handling in tufted capuchin monkeys: a reappraisal of the primate infant market

Newborn infants can affect female social dynamics, and provide ideal conditions to test the biological market theory and its assumptions. In infant markets, infants are the desired commodity, mothers control access to them, and other females (potential handlers) trade grooming for infant handling. The supply/demand ratio corresponds to the number of available infants per potential handler. Variation in the number of infants causes changes in the supply/demand ratio that can alter the market equilibrium. We investigated whether grooming was interchanged for handling in wild tufted capuchin females, Cebus apella nigritus. Behavioural observations were conducted on 10 mothers in three groups. Potential handlers were strongly attracted to infants and grooming the mothers (specifically, its occurrence rather than its duration) increased their probability of handling infants. However, the number of infants in the group did not affect the amount of grooming needed for access to infants. At least three nonmutually exclusive hypotheses can explain differences from previous findings. First, grooming in capuchin monkeys may represent a signal of benign intent with no market value. Second, dominance relations among handlers may have prevented competition by outbidding among handlers and thus hindered free trade. Third, the increased grooming required by mothers when infants were scarcer may reflect the need to calm more stressed mothers that were the subject of more frequent harassment; since in our study mothers did not appear to be more stressed when fewer infants were available, no effect of the number of infants on grooming by handlers emerged