Abstract
Monkeys form expectations for outcomes based on interactions with human experimenters. Capuchins, a cooperative New World monkey species, not only anticipate receiving rewards that the experimenter indicates, but also apparently anticipate rewards based on what the experimenter has given to their partners. However, this could be due to subjects responding to either outcomes or experimenters. Here we examine whether capuchins will continue to interact with human experimenters who are occasionally unreliable. We tested 10 monkeys with a series of familiar human experimenters using an exchange task. The experimenters had never before participated in exchange studies with these monkeys, hence the monkeys learned about their behavior during the course of testing. Occasionally experimenters were unreliable, failing to give a reward after the monkey returned the token. The monkeys did recognize these interactions as different, responding much more quickly in trials following those that were nonrewarded than in other situations with the same experimenter. However, subjects did not change their preference for experimenters when given the opportunity to choose between the unreliable exchanger and another exchanger, nor did subjects learn to prefer reliable experimenters from watching other monkeys’ interactions. Instead, subjects returned the tokens to the same location from which they received it. These results indicate that capuchins may not be sensitive to isolated instances in which experimenters are unreliable, possibly because of a strong bias to returning the token to the location from which it was donated.
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Acknowledgments
We thank Lisa Bradley, Jason Davis, Marietta Dindo, May Lee Gong, and Laura Mullen for assisting with data collection; 2 anonymous reviewers for comments on an earlier draft of the manuscript; and the animal care and veterinary staff of the Yerkes National Primate Research Center for care for our subjects. S. F. Brosnan was funded by a National Science Foundation Human and Social Dynamics Grant (SES 0729244) and the laboratory was funded by NSF grant (IOS-0718010) to the senior investigator. The YNPRC is fully accredited by the American Association for Accreditation for Laboratory Animal Care.
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Brosnan, S.F., de Waal, F.B.M. Cebus apella Tolerate Intermittent Unreliability in Human Experimenters. Int J Primatol 30, 663–674 (2009). https://doi.org/10.1007/s10764-009-9366-x
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DOI: https://doi.org/10.1007/s10764-009-9366-x