Principes de coexistence pacifique chez les primates

Principes de coexistence pacifique chez les primatesDes études récentes sur les singes et les grands singes mettent en lumière le phénomène dit de réconciliation: à la suite d'épisodes agressifs ayant un effet initial de dispersion, les antagonistes ont tendance à rétablir la proximité et à communiquer au moyen de gestes apaisants. La forme que prend la réconciliation va du toilettage ou du claquement des lèvres chez les singes rhésus aux contacts sexuels intenses chez les chimpanzés nains. La réconciliation semble être une habileté sociale utilisée intelligemment dans le but de préserver des relations sociales importantes et de surmonter les conséquences négatives de l'agression. La généralité de ce phénomène chez les primates suggère que la coexistence pacifique chez l'homme est dérivée de racines phylogénétiques très anciennes.Principes of Paeceful Coexistence in PrimatesRecent studies of monkeys and apes demonstrate that following spontaneous aggressive incidents there is an increased probability of friendly body contact, specifically between the antagonists themselves. This implies individual recognition and memory, i.e. nunhuman primates remember with whom they have engaged in aggression, and seek comforting contact with this particular individual afterward. The form of the reconciliation varies per species, ranging from kissing and embracing in chimpanzees to grooming and lipsmacking in rhesus monkeys. Reconciliation is best regarded as a learned social skill, intelligently applied to preserve valuable relationships and to cope with the detrimental effects of aggressive behavior

Cebus Apella Tolerate Intermittent Unreliability in Human Experimenters

Monkeys form expectations for outcomes based on interactions with human experimenters. Not only do they anticipate receiving rewards which the experimenter indicates, but capuchin monkeys, a cooperative new world monkey species, apparently anticipate rewards based on what the experimenter has given to their partner. However, this could be due to subjects responding to either outcomes or experimenters. Here we examine whether capuchin monkeys will continue to interact with human experimenters who are occasionally unreliable. We tested ten monkeys with a series of familiar human experimenters using an exchange task. The experimenters had never before participated in exchange studies with these monkeys, hence the monkeys learned about their behavior during the course of testing. Occasionally experimenters were unreliable, failing to give a reward after the monkey returned the token. We found that monkeys did recognize these interactions as different, responding much more quickly in trials following those which were non-rewarded than in other situations with the same experimenter. However, subjects did not change their preference for experimenters when given the opportunity to choose between the unreliable exchanger and another exchanger, nor did subjects learn to prefer reliable experimenters from watching other monkeys’ interactions. Instead, subjects returned the tokens to the same location from which they received it. These results indicate that capuchin monkeys may not be sensitive to isolated instances in which experimenters are unreliable, possibly because of a strong bias to returning the token to the location from which it was donated

Fairness in Animals: Where to from Here?

In the last decade, there has been an explosion of work investigating non-human species’ behavior as it relates to the human sense of fairness and justice. This work has provided a much-needed evolutionary perspective on humans, and highlighted ways in which humans’ behavior is both similar to and different from that of other species. In this concluding paper, we outline the major threads of the work highlighted in this and the previous special issues of Social Justice Research and provide thoughts on future directions for the field. This is a very exciting time in our exploration of the evolution of human justice and fairness, and we eagerly await the developments of the next decade

How Fairly do Chimpanzees Play the Ultimatum Game?

Humans can behave fairly, but can other species? Recently we tested chimpanzees on a classic human test for fairness, the Ultimatum Game, and found that they behaved similarly to humans. In humans, Ultimatum Game behavior is cited as evidence for a human sense of fairness. By that same logic, we concluded that chimpanzees behaved fairly in our recent study. However, we make a distinction between behavior and motivation. Both humans and chimpanzees behaved fairly, but determining why they did so is more challenging

Ape duos and trios: spontaneous cooperation with free partner choice in chimpanzees

The purpose of the present study was to push the boundaries of cooperation among captive chimpanzees (Pan troglodytes). There has been doubt about the level of cooperation that chimpanzees are able to spontaneously achieve or understand. Would they, without any pre-training or restrictions in partner choice, be able to develop successful joint action? And would they be able to extend cooperation to more than two partners, as they do in nature? Chimpanzees were given a chance to cooperate with multiple partners of their own choosing. All members of the group (N = 11) had simultaneous access to an apparatus that required two (dyadic condition) or three (triadic condition) individuals to pull in a tray baited with food. Without any training, the chimpanzees spontaneously solved the task a total of 3,565 times in both dyadic and triadic combinations. Their success rate and efficiency increased over time, whereas the amount of pulling in the absence of a partner decreased, demonstrating that they had learned the task contingencies. They preferentially approached the apparatus when kin or nonkin of similar rank were present, showing a preference for socially tolerant partners. The forced partner combinations typical of cooperation experiments cannot reveal these abilities, which demonstrate that in the midst of a complex social environment, chimpanzees spontaneously initiate and maintain a high level of cooperative behavior

Chimpanzees Play the Ultimatum Game

Is the sense of fairness uniquely human? Human reactions to reward division are often studied by means of the Ultimatum Game (UG), in which both partners need to agree on a distribution for both to receive rewards. Humans typically offer generous portions of the reward to their partner, a tendency our close primate relatives have thus far failed to show in experiments. Here, we tested chimpanzees (Pan troglodytes) and human children on a modified UG. One individual chose between two tokens that, with their partner\u27s cooperation, could be exchanged for rewards. One token offered equal rewards to both players, whereas the other token favored the chooser. Both apes and children responded like humans typically do. If their partner\u27s cooperation was required, they split the rewards equally. However, with passive partners -- a situation akin to the so-called Dictator Game -- they preferred the selfish option. Thus, humans and chimpanzees show similar preferences regarding reward division, suggesting a long evolutionary history to the human sense of fairness

Competing Demands of Prosociality & Equity in Monkeys

Prosocial decisions may lead to unequal payoffs among group members. Although an aversion to inequity has been found in empirical studies of both human and nonhuman primates, the contexts previously studied typically do not involve a trade-off between pro-sociality and inequity. Here we investigate the apparent co-existence of these two factors, specifically the competing demands of prosociality and equity. We directly compare the responses of brown capuchin monkeys (Cebus apella) among situations where pro-social preferences conflict with equality, using a paradigm comparable to other studies of cooperation and inequity in this species. By choosing to pull a tray towards themselves, subjects rewarded themselves and/or another in conditions in which the partner either received the same or different rewards, or the subject received no reward. In unequal payoff conditions, subjects could obtain equality by choosing not to pull in the tray, so that neither individual was rewarded. The monkeys showed prosocial preferences even in situations of moderate disadvantageous inequity, preferring to pull in the tray more often when a partner was present than absent. However when the discrepancy between rewards increased, prosocial behavior ceased

Transmission of Multiple Traditions within and between Chimpanzee Groups

SummaryField reports provide increasing evidence for local behavioral traditions among fish, birds, and mammals [1–7]. These findings are significant for evolutionary biology because social learning affords faster adaptation than genetic change and has generated new (cultural) forms of evolution [8–10]. Orangutan and chimpanzee field studies [3, 4, 11–13] suggest that like humans [14, 15], these apes are distinctive among animals in each exhibiting over 30 local traditions. However, direct evidence is lacking in apes and, with the exception of vocal dialects [16, 17], in animals generally for the intergroup transmission that would allow innovations to spread widely and become evolutionarily significant phenomena. Here, we provide robust experimental evidence that alternative foraging techniques seeded in different groups of chimpanzees spread differentially not only within groups but serially across two further groups with substantial fidelity. Combining these results with those from recent social-diffusion studies in two larger groups [18–20] offers the first experimental evidence that a nonhuman species can sustain unique local cultures, each constituted by multiple traditions. The convergence of these results with those from the wild implies a richness in chimpanzees' capacity for culture, a richness that parsimony suggests was shared with our common ancestor

Coalitions in theory and reality: a review of pertinent variables and processes

Coalitions and alliances are ubiquitous in humans and many other mammals, being part of the fabric of complex social systems. Field biologists and ethologists have accumulated a vast amount of data on coalition and alliance formation, while theoretical biologists have developed modelling approaches. With the accumulation of empirical data and sophisticated theory, we are now potentially able to answer a host of questions about how coalitions emerge and are maintained in a population over time, and how the psychology of this type of cooperation evolved. Progress can only be achieved, however, by effectively bridging the communication gap that currently exists between empiricists and theoreticians. In this paper, we aim to do so by asking three questions: (1) What are the primary questions addressed by theoreticians interested in coalition formation, and what ar