Are apes inequity averse? New data on the token-exchange paradigm.
Recent studies have produced mixed evidence about inequity aversion in nonhuman primates. Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253-258, 2005] found inequity aversion in chimpanzees and argued that effort is crucial, if subjects are to evaluate how they are rewarded in comparison to a competitor for an identical performance. In this study we investigated inequity aversion with chimpanzees, bonobos and orangutans, using the method of Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253-258, 2005] after introducing some methodological improvements. Subjects always received a less-preferred food in exchange for a token, whereas the competitor received either the same type of food for their token (equity) or a more favored food for it (inequity). Apes did not refuse more of the less-preferred food when a competitor had received the more favored food. Thus, with an improved methodology we failed to reproduce the findings of Brosnan et al. [Proceedings of the Royal Society of London. Series B. Biological Sciences 272:253-258, 2005] that apes show inequity aversion.
Bräuer
Juliane
J
Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, Leipzig, Germany. jbraeuer@eva.mpg.de
Call
Josep
J
Tomasello
Michael
M
D000818:Animals; D003163:Competitive Behavior / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology; D015186:Hominidae / Q000502:physiology / Q000523:psychology*; D012919:Social Behavior; D013045:Species Specificity; D014741:Video Recording