Usage and comprehension of manual gestures in wild chimpanzees

Abstract

Flexibility is considered a defining feature of great ape gestural communication. Previous research has suggested that there is a 'means-ends' dissociation between gesture type and context, whereby one signal may be used across contexts and several signals used within the same context. Such flexibility in signal production demands contextual comprehension, whereby recipients may perceive the context-free message of a given manual gesture, but also decide how to respond by inferring the signaller's goals from the accompanying context. We conducted naturalistic observations of wild East African chimpanzee, Pan troglodytes schweinfurthii, manual gestures, focusing on recipient perspective- during communicative interactions. Our results indicate that chimpanzees recognize the context-free meanings of gestures and they are also able to respond flexibly by inferring the meaning from the combination of gesture and context, including relative rank. When analysed at the level of gesture type, some gestures were tightly associated with dominant responses and outcomes. Chimpanzee manual gestures are primarily used for directing a recipient's movement or attention but the motivation underlying these gestural requests is inferred by the recipient from the context.