PI: Fran B.M. deWaal Proposal # 9603923 Reciprocal exchange of goods and services is a universal human economic activity. In animals, so called reciprocal altruism is a much-discussed yet much less investigated issue. Data accumulated over the past two decades are largely based on observational research; there is little agreement about the strength of the evidence. Food-sharing among capuchin monkeys (Cebus apella) - one of the few nonhuman primate species in which such behavior is well - developed - may yield a handle on exchange: this behavioral lends itself uniquely to experimentation. After first having studied sharing behavior itself, and the degree to which it occurs reciprocally, the purpose the present study is to investigate to what extent, if at all, it is used by capuchins as a payment for cooperation. For reciprocal exchange to occur it would seem necessary that individuals not only assist conspecifics, but also take notice of received assistance. The central question here is whether rewards obtained through cooperation are more readily shared than rewards obtained through individual effort. Trained for temporary separation from their group, our capuchin monkeys have shown high rates of food transfer to each other through a mesh partition. Pairs of monkeys will be presented with tasks in which one subject cannot obtain food unless assisted by the other. Food will be placed outside a test chamber on a tray too heavy for a signal monkey to pull close. If both monkeys pull together, however, one of them will obtain food subsequently can be shared with the other. Variation on this task, and control procedures will be performed as well. If cooperative efforts do indeed promote sharing, this would suggest that the principle of one good turn deserve another is not limited to our own species.
