Sleep Science

Why Do We Yawn?

An image of Danielle Mowbray
20 Apr 20183 min read

When it’s edging close to bedtime and it’s been a long day, most of us will succumb to a yawn. If you’re stood waiting in a queue or in a meeting with your boss, yawning can seemingly creep in at any time. But what does it all mean?

Current theories suggest that we yawn in order to:

  • help the brain cool down
  • communicate
  • demonstrate empathy.

Can this mild inconvenience be part of a useful function that keeps us safe and well? Let’s look at the science behind those open mouths.

Theories of the past

Why we yawn is a question we humans have been attempting to answer since the time of Hippocrates. And in all truth, we’re not quite there when it comes to knowing all the ins and outs of yawning. One old thought believed that yawning helped to wake us up and make us feel more alert. This was because it provides a quick injection of oxygen into the bloodstream.

Several studies have since disproved this. Theories around yawning tend to focus on two separate aspects. Firstly, why we yawn and secondly, why yawning is contagious. At present, research around chasmology – the study of yawning - is still seeking to fully answer both of these questions.

Girl yawning.

Present thinking

Some of the most recent research suggests that yawning performs some kind of thermoregulatory function, helping to cool down the brain.

Scientist Andrew Gallup suggests that yawning stops the brain from overheating with the sharp movement. This encourages bloodflow around the skull and the inhalation of breath. This in turn likely brings cool air into the sinus cavities and also the carotid artery that goes back to the brain.

This theory makes sense when you consider that we typically yawn when we are tired or when we first wake up. Our body temperature tends to rise at both these times. It’s also backed up by research from Gallup and Princeton University.

Studies show there’s likely a thermal window for yawning, where factors like how much you’ve slept and ambient temperatures make an impact on frequency. This could also explain why humans become confused and disoriented when they overheat. Yawning as a mechanism to cool the brain may not be as effective in hot conditions.

Why yawning is contagious

Stifling a yawn is nigh on impossible. But it’s even harder to resist when someone near you is yawning. Yawning is indeed contagious but it’s not just geographical proximity of other yawners that factors in whether you’re likely to yawn or not. Science has shown that if your nearest and dearest yawn you’re more likely to join in than if a stranger yawns.

It’s thought that yawning is a subtle form of communication as well as an empathetic activity. Its contagious nature could help synchronize sleep. It could also mean that we’re more alert as a group to engage in an important task, or stay vigilant against a threat.

So, if you’re yawning in your morning meeting, it could actually just be your way of making sure the whole team is switched on and ready for action. Be sure to tell the boss that.

Which animals yawn?

Polar bear yawning.

A surprising number of animals yawn. Birds, fish, horses, in fact, all vertebrate animals yawn. However, it’s only dogs, humans and the chimpanzee families that yawn contagiously. What does this tell us?

Based on what we already know about contagious yawning, it strongly supports the idea that empathy is present among these species. In some form, yawning is perhaps a method of communication.

Yawning too much? Learn more about insomnia along with our other blog posts.