Trading up: chimpanzees (Pan troglodytes) show self-control through their exchange behavior
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Self-control is defined as the ability or capacity to obtain an objectively more valuable outcome rather than an objectively less valuable outcome though tolerating a longer delay or a greater effort requirement (or both) in obtaining that more valuable outcome. A number of tests have been devised to assess self-control in non-human animals, including exchange tasks. In this study, three chimpanzees (Pan troglodytes) participated in a delay of gratification task that required food exchange as the behavioral response that reflected self-control. The chimpanzees were offered opportunities to inhibit eating and instead exchange a currently possessed food item for a different (and sometimes better) item, often needing to exchange several food items before obtaining the highest valued reward. We manipulated reward type, reward size, reward visibility, delay to exchange, and location of the highest valued reward in the sequence of exchange events to compare performance within the same individuals. The chimpanzees successfully traded until obtaining the best item in most cases, although there were individual differences among participants in some variations of the test. These results support the idea that self-control is robust in chimpanzees even in contexts in which they perhaps anticipate future rewards and sustain delay of gratification until they can obtain the ultimately most valuable item.
KeywordsSelf-control Delay of gratification Chimpanzees Exchange
This research was supported by National Institutes of Health Grant HD060563, a 2CI Primate Social Cognition, Evolution & Behavior Fellowship and the Rumbaugh Fellowship from Georgia State University.
Compliance with ethical standards
All aspects of this research conformed to APA standards for the ethical treatment of animals and followed the Institute of Science guidelines for ethical research with chimpanzees.
Conflict of interest
The authors declare that they have no conflicts of interest.
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