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Author  |
Brosnan, S.F.; de Waal, F.B.M. |
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Title |
Responses to a simple barter task in chimpanzees, Pan troglodytes |
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Journal Article |
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Year |
2005 |
Publication |
Primates |
Abbreviated Journal |
Primates |
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Volume |
46 |
Issue |
3 |
Pages |
173-182 |
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Keywords |
Analysis of Variance; Animals; Choice Behavior/*physiology; Conditioning (Psychology)/physiology; Learning/*physiology; Pan troglodytes/*physiology; Reward; Sex Factors; *Social Behavior; *Token Economy |
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Abstract |
Chimpanzees (Pan troglodytes) frequently participate in social exchange involving multiple goods and services of variable value, yet they have not been tested in a formalized situation to see whether they can barter using multiple tokens and rewards. We set up a simple barter economy with two tokens and two associated rewards and tested chimpanzees on their ability to obtain rewards by returning the matching token in situations in which their access to tokens was unlimited or limited. Chimpanzees easily learned to associate value with the tokens, as expected, and did barter, but followed a simple strategy of favoring the higher-value token, regardless of the reward proffered, instead of a more complex but more effective strategy of returning the token that matched the reward. This response is similar to that shown by capuchin monkeys in our previous study. We speculate that this response, while not ideal, may be sufficient to allow for stability of the social exchange system in these primates, and that the importance of social barter to both species may have led to this convergence of strategies. |
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Address |
Living Links, Yerkes National Primate Research Center, Atlanta, GA 30322, USA. sbrosna@emory.edu |
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0032-8332 |
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PMID:15824938 |
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no |
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Call Number |
refbase @ user @ |
Serial |
167 |
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Author |
Brosnan, S.F.; de Waal, F.B.M. |
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Title |
A concept of value during experimental exchange in brown capuchin monkeys, Cebus apella |
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Journal Article |
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Year |
2004 |
Publication |
Folia primatologica; international journal of primatology |
Abbreviated Journal |
Folia Primatol (Basel) |
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Volume |
75 |
Issue |
5 |
Pages |
317-330 |
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Keywords |
Animals; Cebus/*psychology; *Choice Behavior; Female; Food Preferences; *Learning; Male; Sex Factors; Statistics, Nonparametric; *Token Economy; Video Recording |
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Abstract |
We evaluated the response of brown capuchin monkeys to two differentially valued tokens in an experimental exchange situation akin to a simple barter. Monkeys were given a series of three tests to evaluate their ability to associate tokens with food, then their responses were examined in a barter situation in which tokens were either limited or unlimited. Capuchins did not perform barter in the typical sense, returning the tokens which were associated with the reward. However, females, but not males, showed a different response, preferring the higher-value token. This may indicate that they learned to prefer one token over the other rather than to associate the tokens with their specific rewards. This sex difference parallels previous findings of greater reciprocity in female brown capuchins than in males. |
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Address |
Living Links Center, Emory University, Yerkes National Primate Research Center, 954 N. Gatewood Drive, Atlanta, GA 30329, USA. sbrosna@emory.edu |
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0015-5713 |
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PMID:15486443 |
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refbase @ user @ |
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170 |
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Author |
Brosnan, S.F.; de Waal, F.B.M. |
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Title |
Socially learned preferences for differentially rewarded tokens in the brown capuchin monkey (Cebus apella) |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of comparative psychology (Washington, D.C. : 1983) |
Abbreviated Journal |
J Comp Psychol |
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Volume |
118 |
Issue |
2 |
Pages |
133-139 |
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Keywords |
Animals; Behavior, Animal; Cebus; *Choice Behavior; Female; *Learning; Male; *Reward; *Social Behavior |
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Abstract |
Social learning is assumed to underlie traditions, yet evidence indicating social learning in capuchin monkeys (Cebus apella), which exhibit traditions, is sparse. The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy. Capuchins change their preferences in favor of a token worth a high-value food reward after watching a conspecific model exchange 2 differentially rewarded tokens, yet they fail to develop a similar preference after watching tokens paired with foods in the absence of a conspecific model. They also fail to learn that the value of familiar tokens has changed. Information about token value is available in all situations, but capuchins seem to pay more attention in a social situation involving novel tokens. |
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Address |
Living Links Center, Yerkes National Primate Research Center, and Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30329, USA. sbrosna@emory.edu |
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ISSN |
0735-7036 |
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Notes |
PMID:15250800 |
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no |
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Call Number |
refbase @ user @ |
Serial |
173 |
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Author |
Brosnan, S.F.; De Waal, F.B.M. |
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Title |
Monkeys reject unequal pay |
Type |
Journal Article |
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Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
425 |
Issue |
6955 |
Pages |
297-299 |
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Keywords |
Aging; Animals; Cebus/*psychology; Choice Behavior; *Cooperative Behavior; Female; Male; *Reward; Social Justice |
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Abstract |
During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model, and may in fact be more inclusive than previous explanations. Although there exists substantial cultural variation in its particulars, this 'sense of fairness' is probably a human universal that has been shown to prevail in a wide variety of circumstances. However, we are not the only cooperative animals, hence inequity aversion may not be uniquely human. Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources. Here we demonstrate that a nonhuman primate, the brown capuchin monkey (Cebus apella), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion. |
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Living Links, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329, USA. sbrosna@emory.edu |
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English |
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ISSN |
1476-4687 |
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Notes |
PMID:13679918 |
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no |
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Call Number |
refbase @ user @ |
Serial |
179 |
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Author |
Brosnan, S.F.; Freeman, C.; De Waal, F.B.M. |
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Title |
Partner's behavior, not reward distribution, determines success in an unequal cooperative task in capuchin monkeys |
Type |
Journal Article |
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Year |
2006 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
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Volume |
68 |
Issue |
7 |
Pages |
713-724 |
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Keywords |
Animals; Behavior, Animal/*physiology; Cebus/*physiology; *Cooperative Behavior; Female; Food Preferences/physiology; Male; *Reward |
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Abstract |
It was recently demonstrated that capuchin monkeys notice and respond to distributional inequity, a trait that has been proposed to support the evolution of cooperation in the human species. However, it is unknown how capuchins react to inequitable rewards in an unrestricted cooperative paradigm in which they may freely choose both whether to participate and, within the bounds of their partner's behavior, which reward they will receive for their participation. We tested capuchin monkeys with such a design, using a cooperative barpull, which has been used with great success in the past. Contrary to our expectations, the equity of the reward distribution did not affect success or pulling behavior. However, the behavior of the partner in an unequal situation did affect overall success rates: pairs that had a tendency to alternate which individual received the higher-value food in unequal reward situations were more than twice as successful in obtaining rewards than pairs in which one individual dominated the higher-value food. This ability to equitably distribute rewards in inherently biased cooperative situations has profound implications for activities such as group hunts, in which multiple individuals work together for a single, monopolizable reward. |
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Address |
Living Links Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA. sbrosna@emory.edu |
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English |
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ISSN |
0275-2565 |
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Notes |
PMID:16786518 |
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no |
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Call Number |
refbase @ user @ |
Serial |
160 |
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Author |
Brosnan, S.F.; Schiff, H.C.; de Waal, F.B.M. |
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Title |
Tolerance for inequity may increase with social closeness in chimpanzees |
Type |
Journal Article |
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Year |
2005 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
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Volume |
272 |
Issue |
1560 |
Pages |
253-258 |
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Keywords |
Analysis of Variance; Animals; *Attitude; Group Processes; Pan troglodytes/*psychology; Reward; *Social Behavior; Socioeconomic Factors |
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Abstract |
Economic decision-making depends on our social environment. Humans tend to respond differently to inequity in close relationships, yet we know little about the potential for such variation in other species. We examine responses to inequity in several groups of chimpanzees (Pan troglodytes) in a paradigm similar to that used previously in capuchin monkeys (Cebus apella). We demonstrate that, like capuchin monkeys, chimpanzees show a response to inequity of rewards that is based upon the partner receiving the reward rather than the presence of the reward alone. However, we also found a great amount of variation between groups tested, indicating that chimpanzees, like people, respond to inequity in a variable manner, which we speculate could be caused by such variables as group size, the social closeness of the group (as reflected in length of time that the group has been together) and group-specific traditions. |
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Address |
Yerkes National Primate Research Center, Emory University, 954 North Gatewood Drive, Atlanta, GA 30329, USA. sbrosna@emory.edu |
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0962-8452 |
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Notes |
PMID:15705549 |
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no |
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Call Number |
refbase @ user @ |
Serial |
169 |
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