Emotional and intentional communication in bonobos (Pan paniscus)

Abstract

It has been hypothesized that egalitarian species living in complex social systems should show the highest communicative complexity. The bonobo (Pan paniscus) is an egalitarian species showing a very complex social structure and, therefore, it represents a good model to address the issue of communicative complexity. To reach this purpose, we firstly explored the issue of intentionality and emotionality by studying gestures and facial expressions performed during one of the most complex social activity, play. On the whole, our results confirmed the intentional nature of gestures, but also highlighted that facial expressions can be the outcome of both emotions and intentions. Then we investigated another phenomenon linked to the emotional and automatic communicative sphere, yawn contagion. We demonstrated, for the first time, that yawn contagion is present in bonobos and that it follows an empathic gradient, with “kin and friends” responding at higher frequencies. Our findings support the hypothesis that yawn contagion is a form of emotional contagion, the most basal layer of empathy. Afterwards, we examined the social dynamics around three birth events in bonobos. This is of particular interest given that only few anecdotic reports are available on this topic in the whole primate order. Our data showed that birth is a peculiar social event in bonobos, especially for females. We found that the frequency of affiliative interactions is higher within female-female dyads, whereas the frequency of agonistic interactions is higher within female-male dyads, mirroring the sociality that has been described when wild bonobos find a desirable resource. Interestingly, the more dominant and elderly females also provided a sort of ‘assistance’ to the parturient, by performing the same gesture performed by her to grab the infant during its birth, even though we found that only the mother actually grabbed the infant at the delivery. In conclusion, we can assert that bonobos show a highly complex communicative system and communicate their intentions and emotions by using a wide array of strategies, spanning from gestures to facial expressions, from playful interactions to emotional contagion, from spatial communication to emotional support.