Abstract # 54:

Scheduled for Thursday, June 20, 2013 04:30 PM-04:45 PM: Session 8 (San Geronimo Ballroom C) Oral Presentation


CHIMPANZEES PLAY THE ULTIMATUM GAME

D. Proctor1,2, R. A. Williamson3, F. B. de Waal1,2 and S. F. Brosnan3
1Emory University, Yerkes National Primate Research Center, 2409 Taylor Lane, Lawrenceville, GA 30043, USA, 2Yerkes National Primate Research Center, 3Georgia State University
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     Is the sense of fairness uniquely human? Human reactions to reward division are often studied by means of the ultimatum game, 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; n=4 pairs; M=29.8 years old) and human children (Homo sapiens; n=20 pairs; M=3.8 years old) on a modified ultimatum game. One individual chose between two tokens that, with their partner’s cooperation, could be exchanged for rewards. One token offered equal rewards to both players, whereas the other token favored the chooser. With untrained partners who could not influence the reward distribution—a situation akin to the so-called dictator game—chimpanzees preferred the selfish option. But, significantly changed their behavior to be more equitable (McNemar, p<0.05) when their partner’s cooperation was required in the ultimatum game. Children showed a similar pattern of increasing equitable offers in the UG compared to the preference test (Mann–Whitney U, p=0.04). Thus, humans and chimpanzees show similar preferences regarding reward division, suggesting a long evolutionary history to the human sense of fairness.