Radovanović Kia, Lorskens Anoek, Schütte Sebastian, Bräuer Juliane, Call Josep, Haun Daniel B M, van Leeuwen Edwin J C
Department of Biology, Utrecht University, Utrecht, The Netherlands.
Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
Proc Biol Sci. 2025 Apr;292(2045):20242873. doi: 10.1098/rspb.2024.2873. Epub 2025 Apr 16.
Inequity aversion (IA) is the resistance to unequitable rewards given similar investments. It has been postulated as an important mechanism by which human cooperation thrives. To understand the evolutionary origin of human IA and its distribution across the animal kingdom, many species have been tested on IA, with mixed results. Whereas chimpanzees were originally found to show IA, more recent studies showed that their IA response could be explained by social disappointment. We conducted two studies on IA in bonobos using established paradigms: a token-exchange task and the social disappointment task. Bonobos could exchange tokens for equal or less-preferred food rewards than their partners (Study 1) and were tested with humans and machines to control for social disappointment effects (Study 2). We found that bonobos responded aversively to unequal food distributions in both studies, which was reflected by more refusals to participate when disadvantaged. Notably, and contrary to chimpanzees, this effect could not be explained by social disappointment, although Study 2 was only partially consistent with an IA explanation. Overall, our findings indicate that bonobos possess the sensitivity to recognize and respond to unfair treatment, which supports the notion that IA may have coevolved as a stabilizing mechanism for cooperation.
不平等厌恶（IA）是指在相似投入情况下对不公平奖励的抵制。它被假定为人类合作得以繁荣的一种重要机制。为了理解人类IA的进化起源及其在动物界的分布情况，人们对许多物种进行了IA测试，结果不一。虽然最初发现黑猩猩表现出IA，但最近的研究表明，它们的IA反应可以用社会失望来解释。我们使用既定范式对倭黑猩猩进行了两项关于IA的研究：一个代币交换任务和社会失望任务。在研究1中，倭黑猩猩可以用代币换取比同伴获得的同等或更不喜欢的食物奖励；在研究2中，倭黑猩猩与人类和机器进行测试，以控制社会失望效应。我们发现，在两项研究中，倭黑猩猩对不平等的食物分配都有厌恶反应，这表现为处于劣势时更多地拒绝参与。值得注意的是，与黑猩猩不同，这种效应不能用社会失望来解释，尽管研究2只是部分符合IA的解释。总体而言，我们的研究结果表明，倭黑猩猩具有识别和应对不公平待遇的敏感性，这支持了IA可能作为合作的一种稳定机制而共同进化的观点。
