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. 2006 Dec 22;273(1605):3123-8.
doi: 10.1098/rspb.2006.3693.

Are apes really inequity averse?

Juliane Bräuer  1 , Josep Call, Michael Tomasello
Affiliations

Are apes really inequity averse?

Juliane Bräuer et al. Proc Biol Sci. .

Abstract

Brosnan et al. (Brosnan, S. F. Schiff, H. C. & de Waal, F. B. M. 2005 Tolerance for inequity may increase with social closeness in chimpanzees. Proc. R. Soc. B272, 253-258) found that chimpanzees showed increased levels of rejection for less-preferred food when competitors received better food than themselves and postulated as an explanation inequity aversion. In the present study, we extended these findings by adding important control conditions, and we investigated whether inequity aversion could also be found in the other great ape species and whether it would be influenced by subjects' relationship with the competitor. In the present study, subjects showed a pattern of food rejection opposite to the subjects of the above study by Brosnan et al. (2005). Our apes ignored fewer food pieces and stayed longer in front of the experimenter when a conspecific received better food than themselves. Moreover, chimpanzees begged more vigorously when the conspecific got favoured food. The most plausible explanation for these results is the food expectation hypothesis - seeing another individual receive high-quality food creates the expectation of receiving the same food oneself - and not inequity aversion.

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Figures

Figure 1
Figure 1
Mean number (+s.e.) of ignored food pieces of all subjects in the four conditions.
Figure 2
Figure 2
Mean percentage (+s.e.) of trial duration for which subjects were absent in the four conditions.
Figure 3
Figure 3
Mean number (+s.e.) of trials when subjects engaged in begging behaviour in the four conditions.
See this image and copyright information in PMC

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