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.