Abstract # 2156 Poster # 141:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Token Exchange and the Selective-Value Effect in Capuchin Monkeys (Cebus apella)

M. E. Huntsberry1,2, P. G. Roma2, C. J. Christensen2, A. M. Ruggiero1 and S. J. Suomi1
1National Institutes of Health Animal Center, NICHD, Poolesville, MD, USA, 2American University, Washington DC
     The use of currency (tokens) to barter with experimenters is believed to inhibit impulsive choice behavior among nonhuman primates. The present study tested whether token use allows capuchin monkeys to maximize income (food) by overcoming the "selective-value" effect (SV). SV has been demonstrated in several Old World species, and is defined by indifference in choice between a more-preferred food or combination of more-preferred and less-preferred. Experiment 1 tested whether token-exchange affects this response. Three token-trained male capuchins (Cebus apella) selected from an experimenter one of two options: a more-preferred item (Marshmallow=M) or the combination of M and a less-preferred item (Orange=O). Items were presented simultaneously with M+O randomly assigned to one hand. Selections were between M vs. M+O for 25 free-choice trials; testing the following day was identical but required token placement in the hand containing the chosen item(s) before retrieval. Regardless of token exchange, no monkey preferred M or M+O [Ns=75, binomial ps>0.10], thereby exhibiting SV. Experiment 2 was identical to Experiment 1, but selections were between O vs. M+O. Here, monkeys chose O+M significantly more than O in both conditions, maximizing income regardless of token exchange [ps(68 to 69:75, 0.50)<0.01]. These data extend SV to a New World species, and suggest that even though failure to maximize income is not due to indiscriminate choice behavior, currency use does not correct the selective-value effect.