Abstract: Evolutionary theory postulates that altruistic behavior evolved for the return-benefits it bears the performer. For return-benefits to play a motivational role, however, they need to be experienced by the organism. Motivational analyses should restrict themselves, therefore, to the altruistic impulse and its knowable consequences. Empathy is an ideal candidate mechanism to underlie so-called directed altruism, i.e., altruism in response to anothers's pain, need, or distress. Evidence is accumulating that this mechanism is phylogenetically ancient, probably as old as mammals and birds. Perception of the emotional state of another automatically activates shared representations causing a matching emotional state in the observer. With increasing cognition, state-matching evolved into more complex forms, including concern for the other and perspective-taking. Empathy-induced altruism derives its strength from the emotional stake it offers the self in the other's welfare. The dynamics of the empathy mechanism agree with predictions from kin selection and reciprocal altruism theory.

Abstract: This study focused on two aspects of the dynamics of reconciliation in stumptailed macaques, Macaca arctoides. First, we investigated the combined effects of multiple variables (i.e. sex, age, rank, conflict intensity, outcome, or number of participants, interopponent distance, kinship and friendship) on the occurrence of reconciliation. Second, we investigated whether opponents used different behaviour patterns in their postconflict reunions depending on the characteristics of their conflicts or their relationship with their opponents. We studied a multimale, multifemale group of 38 stumptailed macaques housed in a large outdoor compound. Three types of data were collected: (1) instantaneous scan sampling of contact sitting to infer 'friendship'; (2) ad libitum data on bared-teeth and teeth-chattering displays to infer dominance rank; (3) 10-min focal observations during postconflict (PC) and matched control (MC) periods in which we recorded interopponent distance at the beginning of the observation and all aggressive and affiliative behaviours between former opponents. Our study confirmed the high conciliatory tendency of stumptailed macaques previously reported for other groups. A stepwise logistic regression revealed that initial interopponent distance in PC, friendship and kinship were the only factors that independently contributed to explain the occurrence of reconciliation. Two main clusters of postconflict behavioural patterns emerged: allogrooming+contact sitting and sociosexual behaviours (e.g. hold-bottom). It is hypothesized that postconflict allogrooming and contact sitting may be used for the maintenance of valuable relationships, whereas sociosexual behaviours may be used more indiscriminately by any pair of opponents as a buffering mechanism to prevent immediate recurrence of aggression. Copyright 1999 The Association for the Study of Animal Behaviour.

Abstract: Chimpanzees (Pan troglodytes) frequently participate in social exchange involving multiple goods and services of variable value, yet they have not been tested in a formalized situation to see whether they can barter using multiple tokens and rewards. We set up a simple barter economy with two tokens and two associated rewards and tested chimpanzees on their ability to obtain rewards by returning the matching token in situations in which their access to tokens was unlimited or limited. Chimpanzees easily learned to associate value with the tokens, as expected, and did barter, but followed a simple strategy of favoring the higher-value token, regardless of the reward proffered, instead of a more complex but more effective strategy of returning the token that matched the reward. This response is similar to that shown by capuchin monkeys in our previous study. We speculate that this response, while not ideal, may be sufficient to allow for stability of the social exchange system in these primates, and that the importance of social barter to both species may have led to this convergence of strategies.

Abstract: Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus “mark test” for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation.

Abstract: Conflict management is one of the primary requirements for social complexity. Of the many forms of conflict management, one of the rarest and most interesting is third-party policing, or intervening impartially to control conflict. Third-party policing should be hard to evolve because policers personally pay a cost for intervening, while the benefits are diffused over the whole group. In this study we investigate the incidence and costs of policing in a primate society. We report quantitative evidence of non-kin policing in the nonhuman primate, the pigtailed macaque. We find that policing is effective at reducing the intensity of or terminating conflict when performed by the most powerful individuals. We define a measure, social power consensus, that predicts effective low-cost interventions by powerful individuals and ineffective, relatively costly interventions by low-power individuals. Finally, we develop a simple probabilistic model to explore whether the degree to which policing can effectively reduce the societal cost of conflict is dependent on variance in the distribution of power. Our data and simple model suggest that third-party policing effectiveness and cost are dependent on power structure and might emerge only in societies with high variance in power.