Abstract # 4266 Event # 101:

Scheduled for Friday, June 22, 2012 12:30 PM-12:45 PM: Session 14 (Magnolia) Oral Presentation


THE ONTOGENY OF SOCIAL COMPARISONS BY RHESUS MACAQUES (MACACA MULATTA)

S. F. Brosnan1,2,3, L. M. Hopper1,2,3, S. P. Lambeth3, S. J. Schapiro3,4 and B. J. Bernacky4
1Georgia State University, Department of Psychology, Atlanta, GA 30303-5010, USA, 2Language Research Center, Georgia State University, 3Michale E. Keeling Center for Comparative Medicine and Research, UT MD Anderson Cancer Center, 4Department of Experimental Medicine, University of Copenhagen
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     This longitudinal study investigated the development of ‘inequity aversion’ in rhesus macaques (Macaca mulatta). In humans, there is a developmental trajectory such that recognition of unequal outcomes appears in the second year of life. In certain primates, inequity aversion has been seen in adults, but its development has never been investigated. To investigate this, we used an exchange paradigm, in which four pairs of monkeys had to exchange tokens with the experimenter to get food rewards that differed in quality depending on the condition. Subjects were tested first when they were 15 months old and again at 27 months. Only when the monkeys were aged 27 months did they respond negatively to contrast; they exchanged less when the rewards they received were less preferred than their partner’s, compared to when both monkeys received the same reward (p=0.048). To pinpoint when this change occurred, we tested a further 12 monkeys aged 18 months. Like the 15 month old monkeys, the 18 month olds also showed no sensitivity to inequity but did to contrast effects. They refused more when there was a disparity in expected rewards (p=0.046) suggesting that social comparisons emerge between 18 and 24 months of age. This provides the first evidence for the ontogeny of social comparison in a non-human species and this development mirrors that seen in humans.