Have you ever tapped someone on the far shoulder just to watch them spin around in the wrong direction and then proceeded to do it again moments later? Why is this funny? You might think that finding something like this amusing is an innately human characteristic, with complex communication and context needed for a gag to land, but you’d be wrong.
Fresh research published today in the journal Proceedings of the Royal Society B has found evidence of monkey business (sorry) in four species of great apes, shedding light on the evolutionary origins of humour.
The findings suggest playful teasing, an interaction exhibited by human children as young as eight months old, may have deeper roots in our primate relatives than previously thought.
Such behaviours involve deliberately violating others’ expectations; for example, by repeatedly offering and withdrawing objects or intentionally, and with an element of surprise, disrupting others’ activities.
To uncover these behaviours, the team observed spontaneous social interactions among populations of orangutans, chimpanzees, bonobos and gorillas. They analysed everything from the body movements and facial expressions of the teaser to how the targets of the teasing (the teasee?) responded in turn.
As well as this, the researchers sought to examine the intention behind a teasing action by looking for whether it targeted a specific individual, whether it continued or escalated over time and whether the teaser awaited a reaction from the target.
“Our results support the idea that teasing in great apes is a provocative, intentional and often playful behaviour,” Isabelle Laumer, a postdoctoral researcher and lead author of the study, told BBC Science Focus. “It is typically asymmetric and can take different forms with varying proportions of playful and aggressive features.”
In all, the researchers identified 18 distinct teasing behaviours. These included repeatedly waving or swinging objects in the middle of the target’s field of vision, hitting or poking them, staring closely at their face and pulling their hair – how charming!
Unlike play, which is exhibited by animals across the animal kingdom, playful teasing has several unique characteristics. “Playful teasing in great apes is one-sided, very much coming from the teaser,” explained Erica Cartmill, senior author of the study.
“The animals also rarely use play signals like the primate ‘play face’, which is similar to what we would call a smile, or ‘hold’ gestures that signal their intent to play,” she continued.
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Cartmill recalled first seeing such behaviour in apes back in 2006 when she observed an infant orangutan pestering its mother by repeatedly waving a stick in front of her. “It didn’t look like a joke that would make it onto a Netflix standup special, but it looked like the sort of simple joking around a human toddler might do,” she said.
Nearly 20 years on from this interaction, this study has provided important insights into not only ape behaviour but also our own. “Depending on the species, great apes share 97–99 per cent of our DNA and we have many things in common,” Laumer noted.
“The presence of playful teasing in all four great apes and its similarities to playful teasing behaviour in human infants suggests that playful teasing and its cognitive prerequisites may have been present in our last common ancestor, at least 13 million years ago.”
Moving forward, Laumer and her team plan to investigate if other primate species and large-brained animals tease each other, hoping to better understand the evolution of this important (and highly entertaining) behaviour.
About our experts
Isabelle Laumer is a postdoctoral researcher at the Max Planck Institute of Animal Behavior, Radolfzell / Konstanz. She is a primatologist and cognitive biologist with ten years of experience studying great apes and Goffin cockatoos. Her primary research area falls within physical cognition, focusing on tool use and manufacture, tool innovation, template matching from memory and flexible multi-dimensional decision-making based on reward quality and tool functionality. Her work also delves into social cognition, exploring prosociality, inequity aversion, delay of gratification, theory of mind, and playful teasing in these animal subjects.
Erica Cartmill is a professor of anthropology, cognitive science and animal behaviour at Indiana University. Her research bridges the fields of biology and linguistics, utilising both comparative and developmental methods to examine communication. Both her great ape and human research involve observing spontaneous interactions between communicative partners as well as employing communication games that allow for more controlled experimentation. Her work is particularly focused on whether gestures played a role in the origins of human language.
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