Scientists just got closer to understanding why yawns are so contagious


All over the world, a whole bunch of animals are yawning right now. Maybe they are ready to sleep; maybe it’s because they’re hot and bored.

But if one thing is certain, the mere thought of yawning makes us want to open our mouths and take a deep breath for some reason. (I’ve stifled several yawns already, and I’m barely down to a paragraph.)

While scientists are reasonably confident that they understand the physiological purpose of yawning, why it’s so contagious in social animals is still unclear.

As is often the case in science, the answers could already be scattered in the literature we have collected on animal neurology, psychology, and social behavior.

To determine what the existing evidence says on the subject, evolutionary biologist Andrew Gallup of the Polytechnic Institute of the State University of New York in the United States researched past research and collated the results in a unique explanatory model.

According to Gallup, yawning could be a way for groups of animals to synchronize their behavior and promote collective alertness.

Along with that other weird gasping reflex, hiccups, yawning doesn’t seem to have an obvious purpose. In moments of serenity (usually when we’re tired), our jaw muscles contract, our diaphragm flexes sharply, and we take in a long breath of cool, clean air.

Once supposed to be a means of replenish oxygen or remove carbon dioxideit now appears to be more about moderating blood temperature in an effort to cool the brain.

This means of thermoregulation must be important – practically everything with a spine does. From mice to monkeys, fish to flamingos, yawning is a function that may have evolved some time ago among our common ancestors.

If so, why should one good yawn deserve another? The triggering of successive yawns between individuals – a behavior so contagious that it can cross species barriers – would insinuate a benefit for a group of brains cooling off together.

It may not be far off. According to Gallup, this benefit is a real wake-up call that helps offset people’s drowsiness.

Yawning usually occurs when we go from one state of activity to another, whether it’s lying down to rest or waking up after a long sleep. We yawn too when anticipating a changetrigger or maintain arousal when an environment is unlikely to be stimulating.

A quick “brain chill” of this influx of fresh air might be the perfect way to give it a brief shake in preparation for a possible task, without starting it up in fight-or-flight mode.

With that in mind, it might not hurt to have a few friends tending to your back while you wander off or drowsily sink into a potentially hairy situation. By sharing this yawn, a group of brains can take over, increasing alertness as one or more members of the group show signs of a change in state.

Interview with Tess Joosse at Scientific journalGallup remembers an experiment he conducted last year.

“We showed people image boards that included threatening stimuli – images of snakes – and non-threatening stimuli – images of frogs – and timed how quickly they could choose those images after viewing videos of people yawning or otherwise moving their mouth”, Gallup Explain.

“After seeing other people yawn, their ability to identify and detect snakes, threatening stimuli, improved rapidly. However, following observation of yawning, frog detection was not affected. .”

As far as explanatory models go, it’s a compelling idea that’s ripe for experimentation. Discovering the secrets of a good yawn could tell us a lot about the subtle forms of communication within and between social species, including our own.

This research was published in animal behavior.


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