Great apes like teasing each other – which may be the origin of humour

Bonobos, orangutans, gorillas and chimpanzees all poke, tickle and even steal from their peers as a form of playful teasing. Understanding these apes’ mischievous behaviour could help biologists work out the origins of humans’ sense of humour.

Previous studies have found that chimpanzees may engage in agonistic teasing, or harassment, to reinforce their hierarchical positions. But when the right balance of enjoyment and aggression is struck, teasing can also be a form of play and amusement, says Isabelle Laumer at the Max Planck Institute of Animal Behavior in Germany.

“So far, the playful side of teasing has not yet been systematically studied,” she says. “So our goal was to identify and create a criteria for playful teasing in apes.”

To do that, Laumer and her colleagues collected videos of five species of great ape: bonobos (Pan paniscus), Sumatran orangutans (Pongo abelii), western and eastern gorillas (Gorilla gorilla and Gorilla beringei) and chimpanzees (Pan troglodytes). There were a total of 34 apes, all housed in zoos.

From 75 hours of video footage, the team documented 504 social interactions between individuals. Of those, 142 were classified as playful teasing events, consisting of 18 behaviours such as poking, hitting, pulling on hair, hindering movement and stealing.

“Teasing is characterised by a provocative element,” says Laumer. “It’s usually coming from the teaser and often one-sided, with lots of repetition.”

The researchers found that the teaser tended to look at their target’s face straight after an action, which suggests that the teaser anticipated a response. When there was no response from the target, the teaser would usually escalate the teasing, for example by poking them even more.

One of the most important signs that the teasing was playful, instead of antagonistic, was that it typically happened in a calm, comfortable setting. “The individuals tended to be relaxed during the interaction,” says Laumer.

Cases of stealing were considered playful when the object presented no obvious benefit to the teaser or if they lost interest in the object soon after pinching it.

“We find that playful teasing is present in all four great apes,” says Laumer. Much like play in general, this behaviour could be useful in building relationships between groupmates and even testing out social boundaries, she says.

The last common ancestor between humans and the other great apes may well have engaged in playful teasing too, which could have been the forerunner of our fondness for jokes, adds Laumer.

“Studying great apes is critical to understanding which features of human cognition and behaviour are shared and likely evolved millions of years ago in a common ancestor,” says Christopher Krupenye at Johns Hopkins University in Maryland. “This study provides exciting evidence that all apes seem to engage in playful teasing behaviour and also charts a path for future research in other species.”