Engelmann Jan M, Clift Jeremy B, Herrmann Esther, Tomasello Michael
Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany
Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.
Proc Biol Sci. 2017 Aug 30;284(1861). doi: 10.1098/rspb.2017.1502.
Chimpanzees' refusal of less-preferred food when an experimenter has previously provided preferred food to a conspecific has been taken as evidence for a sense of fairness. Here, we present a novel hypothesis-the social disappointment hypothesis-according to which food refusals express chimpanzees' disappointment in the human experimenter for not rewarding them as well as they could have. We tested this hypothesis using a two-by-two design in which food was either distributed by an experimenter or a machine and with a partner present or absent. We found that chimpanzees were more likely to reject food when it was distributed by an experimenter rather than by a machine and that they were not more likely to do so when a partner was present. These results suggest that chimpanzees' refusal of less-preferred food stems from social disappointment in the experimenter and not from a sense of fairness.
当实验者先前向同种个体提供了更受青睐的食物时，黑猩猩会拒绝不太受青睐的食物，这一现象被视为公平感的证据。在此，我们提出了一个新的假设——社会失望假设，根据这一假设，食物拒绝行为表达了黑猩猩对人类实验者的失望，因为实验者没有给予它们本可以得到的优厚奖励。我们采用二乘二设计对这一假设进行了测试，在该设计中，食物要么由实验者分发，要么由机器分发，并且有同伴在场或不在场。我们发现，当食物由实验者分发而非机器分发时，黑猩猩更有可能拒绝食物，而当有同伴在场时，它们这样做的可能性并没有增加。这些结果表明，黑猩猩拒绝不太受青睐的食物源于对实验者的社会失望，而非公平感。
