Attention towards emotions is modulated by familiarity with the expressor. A comparison between bonobos and humans.

Abstract

Why can humans be intolerant of, yet also be empathetic towards strangers? This cardinal question has rarely been studied in our closest living relatives, bonobos. Yet, their striking xenophilic tendencies make them an interesting model for reconstructing the socio-emotional capacities of the last common ancestor of hominids. Within a series of dot-probe experiments, we compared bonobos and humans attention towards scenes depicting familiar (kith and kin) or unfamiliar individuals with emotional or neutral expressions. Results show that attention of bonobos is immediately captured by emotional scenes depicting unfamiliar bonobos, but not by emotional groupmates (Experiment 1) or expressions of humans, irrespective of familiarity (Experiment 2). Using a large community sample, Experiment 3 shows that human attention is mostly captured by emotional rather than neutral expressions of family and friends. On the one hand, our results show that an attentional bias towards emotions is a shared phenomenon between humans and bonobos, but on the other, that both species have their own unique evolutionarily informed bias. These findings support previously proposed adaptive explanations for xenophilia in bonobos which potentially biases them towards emotional expressions of unfamiliar conspecifics, and parochialism in humans, which makes them sensitive to the emotional expressions of close others.