Chimpanzees and humans establish preferences over individuals they may benefit more from through scoring indirect reputation; however, humans prefer prosocial individuals even at their own cost

Effects of indirect reputation and type of rearing on food choices in chimpanzees (Pan troglodytes). Nereida Bueno-Guerra, Montserrat Colell & Josep Call. Behavioral Ecology and Sociobiology volume 74, Article number: 79 (2020). Jun 6 2020. https://doi.org/10.1007/s00265-020-02861-w

Abstract: Chimpanzees and humans establish preferences over individuals they may benefit more from through scoring indirect reputation. However, humans prefer prosocial individuals even at their own cost. Giving preference to prosocial reputation over material rewards might have permitted the establishment of cooperative human societies. We tested the evolutionary roots of this propensity: importantly, in our study, the reputation scored had no food involved. Eighteen chimpanzees watched a performance where an antisocial experimenter hit a human victim and a prosocial experimenter interrupted the fight and consoled the victim. Next, the chimpanzees begged food from one of them. In Phase 2, the experimenters offered different food amounts (antisocial + 4 vs. prosocial + 1). Chimpanzees significantly prioritized rewards over reputation (i.e., chose antisocial). In Phase 3, both experimenters offered two pieces of food. Most of the subjects showed indifference to reputation (i.e., chose randomly). Watching fights produced significantly more arousal than consolations. Emotional engagement could not account for chimpanzees’ choices since their choices varied between phases but their arousal did not. Ontogeny and rearing history might play a role in chimpanzees’ choices: the adolescent males (n = 3) consistently chose the antisocial individual whereas hand-reared subjects chose significantly different from mother-reared. We discuss whether the valence of the reputation is species-specific.

Significance statement: From an evolutionary perspective, being able to learn indirect reputation is relevant for the individual’s fitness. Both chimpanzees and humans have previously proved to choose those who will presumably behave in the future in a way they could benefit from, suggesting similar underlying cognitive processes that would have emerged at an earlier common ancestor. However, both species approach differently to prosocial individuals. Humans live in societies where there is common agreement about certain universal rights which should always prevail, and thus they are more willing to approach prosocial individuals, even at their own cost. By contrast, in our study, chimpanzees, whose societies are based on unequitable distribution of power and resources, were not that willing to consistently and costly approach prosocial individuals. Moreover, other interpersonal factors, such as the type of upbringing or age-related changes in behavior (aggressiveness during adolescence), might have accounted for these differences.