Abstract # 119:

Scheduled for Friday, June 19, 2015 10:00 AM-10:15 AM: (Cascade F) Oral Presentation


CHIMPANZEES RESPOND DIFFERENTLY TO INEQUITY BASED ON RELATIVE FOOD VALUES

K. Hall1,2, S. P. Lambeth1, S. J. Schapiro1 and S. F. Brosnan1,2
1MD Anderson Cancer Center, 650 Cool Water Drive, Bastrop, TX 78602, USA, 2Department of Psychology, Georgia State University, Atlanta, GA, USA
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     Recent evidence shows that chimpanzees (Pan troglodytes), like humans, react negatively to inequity in some experimental situations. The social inequity hypothesis suggests that subjects respond to social inequity, predicting diminished participation upon receiving lower value food than others, and that food rejections increase. The food expectation hypothesis suggests that subjects expect to receive the same higher value food as others, predicting that participation would increase upon receiving lower value food. We tested 11 subjects in 4 social groups in an hour-long token exchange paradigm with low-, medium-, and high-value foods present. Subjects were tested twice each in three inequity conditions, and twice each in three control conditions. We analyzed subjects’ responses across conditions, and to receiving a medium-value food reward when it was of relatively higher or lower value than other foods. Subjects rejected more food in inequity conditions in which other participants received higher value food, compared to control conditions in which all participants received the same value food (Friedman ?2(1)=4.455, p=0.035), replicating results of prior studies. Critically, subjects exchanged more tokens for medium-value food when it was of relatively higher value than the food that others received during a session, as compared to when the medium-value food was of lower value than the others’ food (Friedman ?2(1)=4.545, p=0.033). These data support the social inequity hypothesis, rather than the food expectation hypothesis.