Abstract # 2982 Event # 138:

Scheduled for Sunday, September 18, 2011 11:15 AM-11:30 AM: Session 18 (Meeting Room 410) Oral Presentation


CHIMPANZEE (PAN TROGLODYTES) SELF-CONTROL: CHOOSING SYMBOLIC TOKENS FOR TRADE LATER INSTEAD OF CHOOSING FOOD NOW

M. J. Beran, D. Hoyle, J. McIntyre and T. A. Evans
Georgia State University, Language Research Center, Decatur, GA 30034, USA
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Chimpanzees will wait for food to accumulate before eating any if that means they can get more food overall instead of less food. This experiment assessed whether they could learn to accumulate arbitrary tokens or symbols that were exchangeable for food reward at a later time. Four chimpanzees were presented with trials in which either food accumulated or tokens exchangeable for food accumulated until the chimpanzees took the accumulated items. Three performed well in both conditions, demonstrating that they would wait for delayed rewards represented by tokens just as they would for actual food items. Next, the chimpanzees were given repeated choices of either 3 tokens or a single candy, and this continued until they chose the single candy. At that point, they could trade any accumulated tokens for candies. Only one chimpanzee consistently chose the three tokens. Then, chimpanzees made repeated choices between foods and lexigram tokens exchangeable later for foods, and after each block of trials they could exchange any collected tokens. When the available food was more preferred than the food represented by the token, the chimpanzees selected the food item. But, when the token represented a better food than the one immediately available, the chimpanzees often chose the token. Thus, chimpanzees delayed gratification by choosing tokens representing more preferred but delayed foods over less preferred but immediately available food items.