Abstract # 44:

Scheduled for Thursday, June 20, 2013 03:45 PM-04:00 PM: Session 7 (Las Olas) Oral Presentation


CHIMPANZEES (PAN TROGLODYTES) ATTEMPT TO MAXIMIZE RETURNS, NOT “LEVEL THE PLAYING FIELD”

L. M. Hopper1,2, S. P. Lambeth3, S. J. Schapiro3,4 and S. F. Brosnan2,3,5
1Lincoln Park Zoo, Lester E. Fisher Center for the Study & Conservation of Apes, Chicago, IL 60614, USA, 2Language Research Center, Georgia State University, Atlanta, GA, 30302, USA, 3Michale E. Keeling Center for Comparative Medicine & Research, UT MD Anderson Cancer Center, Bastrop, TX, 78602, USA, 4Department of Experimental Medicine, University of Copenhagen, Copenhagen, Denmark, 5Department of Psychology & Neuroscience Institute, Georgia State University, Atlanta GA 30302, USA
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     We provided chimpanzees (Pan troglodytes) with control over rewards in a typical test of inequity to see if control over reward quality influenced behavior and if it was mediated by a social partner’s outcomes. We tested eight dyads using an exchange paradigm. We included four conditions: high-and low- value equity controls, an inequity condition (in which the subject received less-preferred rewards than their partner) and a “frustration” condition (in which higher-value rewards were shown, but never given, to both chimpanzees). We compared responses when the chimpanzees could not improve their rewards to those when they could. Refusals – to exchange or to eat rewards – increased in all conditions in which chimpanzees received low-value rewards, irrespective of what they were offered previously, or what their partner received. However, when the chimpanzees were given the opportunity to improve their reward outcomes, they chose to do so, and refusals decreased significantly (i.e. they participated more). The chimpanzees attempted to maximize their returns in all conditions, rather than just bring them in-line with their partner’s rewards. Importantly, the use of control was not an habituated response – it was not seen in the high-value equity condition – so the chimpanzees were selective about when they took advantage of the opportunity for control. We also found evidence that the chimpanzees’ responses were enhanced by social facilitation.