There is increasing evidence that non-human great apes share our capacity for intentional goal-directed communication, allowing us to ask what great ape signals mean in the linguistic sense. But where to start? Can we ever ‘interview an animal in its own language'?
Given that intended meaning is an internal mental state, what are the external, measurable features of a communicative event that we can use to decode ape meaning? We have investigated the repertoire of gestural signals across four great ape species. Recently, in chimpanzees and bonobos, we have described the meanings for which these gestures are used across signallers and across species. However, the systems of gesture categorization have relied on human intuition. Now, after 10-years of data collection, we can use our understanding of behaviour to try to take the chimpanzee's perspective and re-ask the fundamental question: what is a gesture?