Attention to emotional faces and bodies: A comparison of humans and bonobos

Abstract

The adaptive function of attentional preferences for emotional stimuli has been widely demonstrated in humans and other social animals, including bonobos. However, systematic cross-species comparisons - particularly regarding the relative salience of positive versus negative emotions and the influence of expression channel (e.g., face versus body) - remain limited. Using eye-tracking, we investigated these questions in humans and bonobos (Pan paniscus), one of humans' two closest living relatives. In humans, we found a robust emotion bias, independent of valence, evident in both initial orienting and sustained attention. The findings further indicate that body cues alone can effectively convey emotional states that capture attention. Unexpectedly, bonobos showed the opposite pattern for facial stimuli, prioritizing neutral faces over emotional ones in both orienting and sustained attention. Moreover, emotional body expressions did not elicit greater attentional engagement than neutral stimuli. While these results reaffirm the predominant role of facial cues in bonobo communication, the observed neutral bias contrasts with previous findings of emotion-driven attention. Considering potential variability across paradigms, stimulus sets, and individuals, future research should aim to replicate these findings across multiple bonobo populations to better clarify the extent and nature of species-specific attentional patterns.