Tactical signalling by victims increases bystander consolation in bonobos

Abstract

Tactical emotion communication has long been considered uniquely-human. As a species, we readily exaggerate, inhibit and modify emotional expressions according to social context and audience. Notably, emitting emotional displays, such as those pertaining to distress states, can evoke empathic responses in others such as the offering of consolation to victims after a fight. Animal emotion expressions, by contrast, are traditionally viewed as uncontrollable arousal responses. Our study challenges this view by assessing the level of control in the emotional signalling of sanctuary-living bonobo victims following aggressive attacks (N = 27 victims, N = 144 attacks) and its and its corresponding effect on receivers. Results show that the production of paedomorphic signals by adult bonobo victims increased chances of receiving consolation from bystanders and reduced risk of future aggression from former opponents, highlighting a strategic function. Victim signalling also increased with audience size, yet strategies differed by age: immature bonobos were more likely to cease signalling in proximity of close-social partners, whereas adults were more likely to cease signalling after having been consoled. These data suggest that bonobo emotion communication has a developmental trajectory and that tactical emotion signalling is a Pan-human capacity, preceding the split of Homo.