Unpeeling the layers of language: Bonobos and chimpanzees engage in cooperative turn-taking sequences

TLDR

Human language is a cooperative enterprise that evolved as part of a broader adaptation, yet bonobos and chimpanzees, while cooperative, lack the cooperative nature of human conversation. We systematically compared mother‑infant communicative interactions across bonobo and chimpanzee communities in the wild, analyzing joint‑travel‑initiation gestures with conversation‑analysis parameters. We analyzed joint‑travel‑initiation gestures between mothers and infants using conversation‑analysis parameters. Both bonobos and chimpanzees exhibit cooperative turn‑taking sequences, with bonobos using gaze and overlapping responses and chimpanzees engaging in extended negotiations, supporting the idea that interactional intelligence underlies human language and that social context shapes communication styles.

Abstract

Human language is a fundamentally cooperative enterprise, embodying fast-paced and extended social interactions. It has been suggested that it evolved as part of a larger adaptation of humans' species-unique forms of cooperation. Although our closest living relatives, bonobos and chimpanzees, show general cooperative abilities, their communicative interactions seem to lack the cooperative nature of human conversation. Here, we revisited this claim by conducting the first systematic comparison of communicative interactions in mother-infant dyads living in two different communities of bonobos (LuiKotale, DRC; Wamba, DRC) and chimpanzees (Taï South, Côte d'Ivoire; Kanyawara, Uganda) in the wild. Focusing on the communicative function of joint-travel-initiation, we applied parameters of conversation analysis to gestural exchanges between mothers and infants. Results showed that communicative exchanges in both species resemble cooperative turn-taking sequences in human conversation. While bonobos consistently addressed the recipient via gaze before signal initiation and used so-called overlapping responses, chimpanzees engaged in more extended negotiations, involving frequent response waiting and gestural sequences. Our results thus strengthen the hypothesis that interactional intelligence paved the way to the cooperative endeavour of human language and suggest that social matrices highly impact upon communication styles.