Attention toward emotions is modulated by familiarity with the expressor: A comparison between bonobos and humans

Why can humans be intolerant of, yet also be empathic toward strangers? This cardinal question can be tackled by studying emotions in our closest living relatives, bonobos. Their striking xenophilic tendencies make them an interesting model for reconstructing the socioemotional capacities of the last common ancestor of hominids. Within two dot-probe studies, we compared bonobos’ and humans’ attention toward scenes depicting familiar (kith and kin) or unfamiliar individuals with emotional or neutral expressions. Results show that the attention of bonobos is biased toward emotional scenes depicting unfamiliar bonobos, but not toward emotional groupmates (Study 1). In contrast, Study 2 shows that human attention is biased toward emotional rather than neutral expressions of family and friends, but not toward unfamiliar others. On the one hand, our results show that an attentional bias toward emotions is a shared phenomenon between humans and bonobos, but on the other, both species have their own unique evolutionarily informed biases. These findings support previously proposed adaptive explanations for xenophilia in bonobos that potentially biases them toward emotional expressions of unfamiliar conspecifics, and parochialism in humans, which makes them sensitive to the emotional expressions of close others.