Humans might be the masters of quick-fire banter, but it seems chimpanzees have their own rapid back-and-forths, albeit in the form of hand signals.
Researchers analysed thousands of gestures made by wild chimps in east Africa and found striking similarities with the turn-taking seen in human conversations, in particular how swiftly the apes responded to one another.
The work suggests that humans and apes share fundamental features of communication that either date back to their ancient ancestors or which developed in the species in parallel because of the benefits the behaviour brought.
“Human conversation follows very strict rules of turn-taking that are consistent across cultures and languages,” said Dr Gal Badihi, an animal behaviour expert at the University of St Andrews. “We started to wonder whether chimpanzee communication was governed by its own rules, or if the rules are similar to human conversation.”
Chimps have a rich repertoire of hand gestures, many of which amount to simple requests such as “stop it’, “follow me” or “groom me”. To learn more about the rules surrounding their use, the researchers studied more than 8,500 gestures recorded from 252 wild chimps in five wild communities in east Africa.
Most of the interactions were brief. In one, recorded at Budongo Conservation Field Station in Uganda, a chimp called Monica extended her hand towards another, called Ursus, after a physical altercation, prompting Ursus to respond with a reassuring tap.
But in other cases, chimps traded up to seven gestures in a row. In these exchanges, the apes typically took 120 milliseconds to respond to each other, similar to the average human conversational response time of 200 milliseconds.
“Chimpanzees use gestures in almost every aspect of their life,” said Badihi. Besides reconciling after a fight, she observed chimpanzees using gestures to avoid confrontation, to greet each other with a hug or kiss, to ask to share food and to indicate they wanted to travel together or go their separate ways. Grooming sessions were when most gestures took place.
“Some groups use a big, loud, scratch gesture and then start grooming together. In the middle of the grooming interactions they might gesture to each other to change position or to start grooming in a new place,” she said.
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Writing in Current Biology, the researchers describe how the timing between exchanges hardly varied between chimps of different ages, but there were some variations between different communities, akin to the subtle cultural differences seen in humans. For example, gestures were exchanged more slowly in the Sonso chimp community in Uganda. “In humans, it’s the Danish who are slower responders,” said Dr Catherine Hobaiter, a senior author on the study.
Since humans and chimps are both great apes, quick-fire communication may be a product of our shared evolutionary heritage. Alternatively, rapid turn-taking could be a broader feature of social communication, and exist in other species such as whales, dolphins, bats and hyenas, the researchers add.