Bartering of commodities between individuals is a hallmark of human behavior that is not commonly seen in other species. This is difficult to explain because barter is mutually beneficial, and appears to be within the cognitive capabilities of many species. It may be that other species do not recognize the gains of trade, or that they do not experience conditions (e.g., low risk) in which barter is most beneficial. To answer these questions, we instituted a systematic study of chimpanzees’ ability to barter with each other when doing so materially benefits them. Using tokens derived from symbols they have used since infancy, pairs of adult chimpanzees could trade between themselves to obtain tokens needed to get foods. Subjects flexibly used the tokens to obtain foods from an experimenter; however, they did not spontaneously trade with their partner. After extensive training, subjects engaged in accurate trade behavior as long as an experimenter enforced the structure of the interaction; however, trade between partners disappeared when this enforcement was removed. We discuss possible reasons for these findings as well as implications for the evolution of barter across the primate lineage.
Brosnan, S.F. & Beran, M.J. (2009). Trading behavior between conspecifics in chimpanzees, Pan troglodytes. Journal of Comparative Psychology, 123(2), 181-194. doi: 10.1037/a0015092