Chimps respond to each other at a pace similar to human conversation

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 – one of the largest studies of its kind. They recorded face-to-face interactions between the apes, noting the timing between one’s gesture and another’s response.

Their analysis of the ape “conversations” revealed that the time between chimp signals was remarkably similar to human exchanges – even a bit faster. “On average, there are 120 milliseconds between the end of one gesture and the start of the next one,” says Gal Badihi at the University of St Andrews in the UK. “In humans, the average is around 200 milliseconds, so it’s really close timing.”

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 quicker turn-taking conversation style than those who speak Danish. “We don’t know exactly why,” says Badihi. “As with humans, we don’t know if it’s a cultural difference, something we learn over time or a response to the environment.”

Only 14 per cent of the interactions the team observed between chimps included some exchange. Instead, most interactions included a single gesture, such as “get away” or “come with me”, 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.

“What is really exciting about this, is that it shows us that communication is a cooperative and socially engaging process in animals outside of humans,” says Badihi. “It could be that the processes involved in human language actually evolved much earlier than we thought.”