Chimpanzees trade gestures at a rapid pace when socialising, similar to the rate at which humans engage in a back-and-forth conversation.
Researchers made the discovery by analysing five wild chimpanzee (Pan troglodytes) communities across East Africa, examining 8559 gestures made by 252 chimps 鈥� one of the largest studies of its kind. They recorded face-to-face interactions between the apes, noting the timing between one鈥檚 gesture and another鈥檚 response.
Their analysis of the ape 鈥渃onversations鈥� revealed that the time between chimp signals was remarkably similar to human exchanges 鈥� even a bit faster. 鈥淥n average, there are 120 milliseconds between the end of one gesture and the start of the next one,鈥� says at the University of St Andrews in the UK. 鈥淚n humans, the average is around 200 milliseconds, so it鈥檚 really close timing.鈥�
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Although all the chimp communities used quick responses, the exact timing varied from group to group. For instance, the Sonso community of chimps in Uganda took a few milliseconds longer to return a gesture than the other chimpanzee communities in the study.
Timing differences like these also exist in human languages. People who speak Japanese, for example, generally have a conversation style than those who speak Danish. 鈥淲e don鈥檛 know exactly why,鈥� says Badihi. 鈥淎s with humans, we don鈥檛 know if it鈥檚 a cultural difference, something we learn over time or a response to the environment.鈥�
Only 14 per cent of the interactions the team observed between chimps included some exchange. Instead, most interactions included a single gesture, such as 鈥済et away鈥� or 鈥渃ome with me鈥�, to which the other participant would respond by fleeing or following. But when the chimps were negotiating for food or grooming, back-and-forth exchanges were more common.
鈥淲hat is really exciting about this, is that it shows us that communication is a cooperative and socially engaging process in animals outside of humans,鈥� says Badihi. 鈥淚t could be that the processes involved in human language actually evolved much earlier than we thought.鈥�
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