Abstract: Stable cooperation requires that each party's pay-offs exceed those available through individual action. The present experimental study on brown capuchin monkeys (Cebus apella) investigated if decisions about cooperation are (a) guided by the amount of competition expected to follow the cooperation, and (b) made instantaneously or only after a period of familiarization. Pairs of adult monkeys were presented with a mutualistic cooperative task with variable opportunities for resource monopolization (clumped versus dispersed rewards), and partner relationships (kin versus nonkin). After pre-training, each pair of monkeys (N=11) was subjected to six tests, consisting of 15 2 min trials each, with rewards available to both parties. Clumped reward distribution had an immediate negative effect on cooperation: this effect was visible right from the start, and remained visible even if clumped trials alternated with dispersed trials. The drop in cooperation was far more dramatic for nonkin than kin, which was explained by the tendency of dominant nonkin to claim more than half of the rewards under the clumped condition. The immediacy of responses suggests a decision-making process based on predicted outcome of cooperation. Decisions about cooperation thus take into account both the opportunity for and the likelihood of subsequent competition over the spoils.

Abstract: Stumptailed macaques, Macaca arctoides, are characterized by high levels of postconflict affiliative contacts between opponents. We investigated the occurrence of postconflict affiliative contacts between opponents and third parties that were not involved in the original conflict. We collected 10-min focal observations during postconflict and control periods in which we recorded all aggressive and affiliative behaviours between opponents and third parties. We distinguished three types of third parties depending on the relationship with the focal animal: own kin, opponent's kin and individuals unrelated to both opponents. We analysed the interactions with third parties separately, while distinguishing two classes of affiliative behaviours: (1) allogrooming and contact sitting and (2) sociosexual behaviours (e.g. genital inspection). The macaques showed differences between postconflict and control periods in their affiliative contacts with third parties. Aggressors received more postconflict grooming and contact sitting from their opponents' kin, received more sociosexual behaviour from their own kin and unrelated individuals, and directed more sociosexual behaviour to unrelated individuals. Victims received and directed less postconflict grooming from and towards their own kin. They received more postconflict sociosexual behaviour from all partners except their own kin and directed more sociosexual behaviour to all partners except the opponent's kin. This study establishes the occurrence of multiple postconflict triadic affiliation in stumptailed macaques, and is the first to show that victims receive contacts from third parties in a cercopithecine species, a behaviour previously described only in chimpanzees. It also highlights the importance of analysing the different affiliative behaviours separately in postconflict situations. Otherwise, many of the patterns we report, especially those involving victims, would have been missed.

Abstract: Conflict management mechanisms have a direct, critical effect on system robustness because they mitigate conflict intensity and help repair damaged relationships. However, robustness mechanisms can also have indirect effects on system integrity by facilitating interactions among components. We explore the indirect role that conflict management mechanisms play in the maintenance of social system robustness, using a perturbation technique to 'knockout' components responsible for effective conflict management. We explore the effects of knockout on pigtailed macaque (Macaca nemestrina) social organization, using a captive group of 84 individuals. This system is ideal in addressing this question because there is heterogeneity in performance of conflict management. Consequently, conflict managers can be easily removed without disrupting other control structures. We find that powerful conflict managers are essential in maintaining social order for the benefit of all members of society. We show that knockout of components responsible for conflict management results in system destabilization by significantly increasing mean levels of conflict and aggression, decreasing socio-positive interaction and decreasing the operation of repair mechanisms.

Abstract: Handclasp grooming is a unique social custom, known to occur regularly among some, but not all populations of chimpanzees (Pan troglodytes). As with other cultural behaviors, it is assumed that this distinctive grooming posture is learned socially by one individual from another. However, statistical comparisons among factors thought to influence how a behavior spreads within a group have never, to our knowledge, been conducted. In the present study, the origination and spread of handclasp grooming in a group of captive chimpanzees was followed throughout more than 1,500 h of observation over a period of 12 years. We report on the frequency, bout duration, and number and demography of performers throughout the study period, and compare these findings to those reported for wild populations. We predicted that dyads with strong affiliative ties, measured by time spent in proximity to and grooming one another, were likely to develop a handclasp grooming partnership during the study period. A quadratic assignment procedure was used to compare correlations among observed frequencies of grooming and proximity with handclasp grooming in all possible dyads within the group. As predicted, the formation of new handclasp grooming dyads was positively correlated with the rate of overall grooming and proximity within a dyad. In addition, in nearly all dyads formed, at least one individual had been previously observed to handclasp groom. We concluded that affiliation and individual experience determines the transmission of handclasp grooming among captive chimpanzees.

Abstract: There is disagreement in the literature about the exact nature of the phenomenon of empathy. There are emotional, cognitive, and conditioning views, applying in varying degrees across species. An adequate description of the ultimate and proximate mechanism can integrate these views. Proximately, the perception of an object's state activates the subject's corresponding representations, which in turn activate somatic and autonomic responses. This mechanism supports basic behaviors (e.g., alarm, social facilitation, vicariousness of emotions, mother-infant responsiveness, and the modeling of competitors and predators) that are crucial for the reproductive success of animals living in groups. The Perception-Action Model (PAM), together with an understanding of how representations change with experience, can explain the major empirical effects in the literature (similarity, familiarity, past experience, explicit teaching, and salience). It can also predict a variety of empathy disorders. The interaction between the PAM and prefrontal functioning can also explain different levels of empathy across species and age groups. This view can advance our evolutionary understanding of empathy beyond inclusive fitness and reciprocal altruism and can explain different levels of empathy across individuals, species, stages of development, and situations.