Interspecies object exchange: Bartering in apes?

Of 114 chimpanzees, 55 exchanged non-edible items for food items, indicating a proportion significantly greater than chance. In addition, those animals which did exchange were more likely to when encouraged by human solicitation. These behaviors suggest a social significance beyond simple behavioral economics in processing information about giving and getting. Further, these and several observed manipulations of reward-getting suggest that chimpanzees may also have a limited understanding of the expression and manipulation of the relative values of certain items. The behavioral foundations of and theoretical implications for primate social cognition and economic psychology are discussed. (C) 1998 Elsevier Science B.V.