Monkey See, Monkey Yawn: Bonobos and humans 'catch' contagious yawns from friends more than strangers

Have you ever found yourself taking on the tones, gestures, or turns of phrase of people you admire? Has watching someone yawn forced your jaw into an involuntary mirror-yawn? Well you’re not alone, neither in your species nor in the animal kingdom.

It was already known that our closest cousins, the chimpanzees, yawn in response to viewing another individual’s yawn, but in a recent study, Italy-based primate researchers have compared the empathetic yawning rates of two simian species: bonobos and humans.

Regardless of its purpose, yawning is a useful tool for scientists to measure empathy — where empathy is the capacity to feel another’s emotional state and place yourself in their shoes (even if they’re not wearing shoes). And ‘contagious yawning’ is just what it sounds like: a yawn being passed from a yawner to an observer.

The phenomenon of contagious yawning is thought to be associated with a system in our brains appropriately known as the ‘mirror neuron system’.

Imagine you’re watching someone cooking and they accidentally rest their hand on a red-hot stove element. For the person watching, this visual information is sent to the brain, interpreted, and often ‘imitated’ or re-enacted by the brain's mirror neuron system. You might wince or gasp in pain. And this is real pain, too, processed by the same regions as physical pain perception.

In the case of watching someone yawn with gaping jaws and flexing cheek muscles, our mirror neurons set off the brain regions responsible for controlling our own jaw and cheek movements, thus eliciting a yawn.

The mirror neuron system may have evolved for learning through observation, imitating actions such as throwing or foraging. It likely also evolved to strengthen relationships; by acting out the emotional state of others by physical imitation, it’s much easier to empathise — “you’re sad? Now I’m sad,” or “you’re laughing? I don’t know what’s funny, but now I’m laughing maniacally too and I can’t stop…how embarrassing.”

Intriguingly, children are not influenced by contagious yawning until they are four, the age when they begin to develop sophisticated empathy and social skills. Contagious yawning is also less likely in individuals with an autism spectrum disorder.

The current study, headed up by Elisabetta Palagi et al. at The University of Pisa, has added yet more nuance to the exciting story of empathy and contagious yawning.

The researchers observed people in their natural habitat (cafés and the like) and bonobos (pygmy chimpanzees) in a primate park and zoo. The researchers observed social interactions and took data on each yawn, how soon sympathetic yawns took place, and the relationship between the yawners.

The study found that humans were more likely to copy a yawn if the initial yawner was a friend, family member or close colleague, as opposed to a stranger. Bonobos, too, were more likely to catch a yawn if the yawner was a feeding or grooming partner.

Further, when a stranger or mere acquaintance yawned, humans and bonobos were equally likely to copy them. That is, bonobos are as empathetic to strangers as we are.

 Here’s where the difference occurred though, humans were more likely to copy a friend yawning, than bonobos were to copy their friends' yawns.

The researchers suggest that humans catch friendly contagious yawns quicker than bonobos because we humans have more sophisticated relationships and are more highly attuned to our friends than are bonobos with their friends (or grooming pals). Though I’m sure they still have some cracker conversations whilst nitpicking.

So, what have we learnt? We’ve learnt that imitating others was likely a key stone in our primate evolution, both for learning and social bonding. We’ve learnt that other species can catch emotional contagions such as yawning (dogs do it too).

And finally, we’ve learnt that individuals — be they human apes or bonobo apes — are discerning in whom they copy. We are more likely to catch an emotional contagion from a friend than a stranger. By catching contagions from friends, we imitate them, they imitate us, and we grow closer and more alike.

So next time you’re at the chimp enclosure at the zoo, cast out a yawn, and if you’re imitated by your furry cousin, feel flattered because indeed: ‘imitation is the sincerest form of flattery’.

Header image: Jeroen Kransen/Flickr/CC BY-SA 2.0

Embedded Image: A 17 year old male bonobo yawning. Photograph by Fiona Rogers, Getty

Original paper: Palagi, E., Norscia, I., and Demuru, E. (2014) Yawn contagion in humans and bonobos: emotional affinity matters more than species.PeerJ 2:e519