Why Do We Yawn & Is It Really Contagious?

image of a woman yawning

Many people consider yawning a sign of boredom or tiredness.

And if someone yawns while you’re talking to them, it can feel a bit rude – even if they try their best to excuse themselves.

In this article, I’m going to challenge that negative view of yawning though.

Scientists have different ideas about why we yawn, but they all agree on one thing: yawning is a natural process that’s good for you.

Did you know?

  • The average length of a yawn is just 6 seconds.
  • Babies in the womb yawn.
  • We yawn more in the summer than the winter.
  • Many animals yawn too.

A rush of fresh air to the head

It’s a common misconception that you yawn simply because you haven’t had enough sleep. The relationship between yawning and tiredness isn’t so clear-cut.

Some scientists think that yawning is a way to get more oxygen into your bloodstream. It’s argued that the extra oxygen gained through yawning is used to support brain function.

For example, when you yawn after waking up, the fresh oxygen can jump start your cognitive processes and prepare you for the day ahead.

Yawning helps your tired brain function better

Sleep deprivation can have a profoundly negative impact on you (and your brain’s) ability to function the next day.

When you’re tired, your brain is less likely to be at its best. So a quick oxygen boost might temporarily increase your cognitive processes, and ability to function well.

So essentially, when you yawn, your tired brain is flooded with additional oxygen to help you concentrate.

By this theory, if someone yawns when you’re talking to them, they’re not being rude. Perhaps their yawn is a sign that they’re just tired, and are trying to concentrate on what you’re saying.

Cooling your brain

Not all scientists think that yawning is related to oxygen levels in your brain. And nowadays, a more widely supported theory is that it helps cool your brain.

The temperature in your brain isn’t constant – it increases and decreases in different circumstances.

So the idea is that yawning is an effective way for your body to ‘ventilate’ and reduce the temperature of your brain.

This is, in fact, one of the oldest theories about yawning. Over 2,400 years ago, Hippocrates described yawning as a way to cool down the yawner’s head; “like steam escaping from hot cauldrons.”

Evidence for the brain cooling theory

In 2014, a group of researchers explored this ‘thermoregulatory theory of yawning’.

In their study of 120 people, the researchers found that participants yawned twice as much in the summer than in the winter.

The chart below shows the percentage chance that people would yawn during the day at two different average temperatures:

yawning chart

Participants who were tested in summer (when the average temperature was around 19˚C, roughly 67 ˚F) had about a 40% chance of yawning during the day.

This compares to around an 18% chance of yawning amongst participants tested in winter (average temperature of just over 1˚C, or 35˚F).

The researchers took into account how much sleep the participants had. This means that differences in participants’ tiredness wouldn’t impact the results.

A tired brain is a hot brain

Like the ideas about yawning and oxygen, the thermoregulatory theory doesn’t mean that yawning and tiredness aren’t related.

When you’re tired, your body is worse at regulating its temperature. And your brain could therefore become hotter as your tiredness increases.

So if you’re tired, you’re more likely to need a good yawn to cool your head down.

Is yawning contagious?

You might have noticed that when you see someone yawning, you’re more likely to yawn yourself.

This phenomenon is sometimes called ‘catching a yawn.’ And scientists are actively studying how yawning spreads from one person to another.

Some researchers argue that there are 2 types of yawning:

  • Spontaneous yawning – a physiological action linked to either brain temperature or oxygen levels.
  • Contagious yawning – a social, psychological response. Seeing another person yawn can make you do it too. Reading or even just thinking about someone yawning can trigger it.

In fact, even reading an article about yawning might make you more likely to yawn (hopefully not from boredom!).

Animals yawn too

Interestingly, it isn’t just a human phenomenon. Our closest animal relatives, such as chimpanzees, are also prone to contagious yawning. It’s even been observed by researchers studying rats.

The image below is a photo of a wolf ‘catching’ a yawn from another member of the pack:

wolves yawning

Image Credit: Teresa Romero, PLOS One

Can everyone catch a yawn?

Not everyone is prone to contagious yawning. Only about half of adults are affected when those around them yawn.

Children don’t show signs of contagious yawning until around four years old, when their social skills become more advanced.

And children with autistic spectrum disorder are less likely to display contagious yawning.

People with autistic spectrum disorder often struggle with recognizing facial expressions and demonstrating empathy.

While contagious yawning isn’t an emotional response, scientists think that seeing someone else yawn activates the same parts of the brain responsible for empathy and social skills.

These social theories about contagious yawning call into question the link between yawning and sleep.

Was contagious yawning a form of communication?

Some researchers have proposed that contagious yawning has its origins as a form of communication.

Early humans needed to make each other aware of an approaching threat. So if one person spotted a threat and made a noise/movement which everyone copied (the yawn), the group as a whole was more vigilant and safe.

While this is an interesting idea, it’s difficult for researchers to prove. It also doesn’t account for all the evidence discussed for the links between yawning, oxygen levels and brain temperature.

Perhaps we used to yawn to boost our brain’s ability to perform under threat?

And of course, there’s the old argument that yawning is indeed a ‘subtle’ way to communicate to someone that their story is dragging on a bit.

Can you stop yourself yawning?

Even if it serves an important biological function, yawning can still be a social issue in the wrong time and place.

So what can you do to stop yourself when your boss or friend is rattling on? These simple tips might help next time:

  • Do some deep breathing through your nose.
  • Try to keep on top of your sleep, and don’t let yourself become sleep deprived.
  • Cool yourself down, especially in the summer months. If your office or social function is too warm, take a break in a cooler space, have a cold drink and get your body moving.


Which of the theories is correct? Perhaps more than one theory is needed to explain the different functions that yawning serves.

A tired brain is more prone to overheating. So perhaps we yawn as a form of mini biological air conditioning unit, with a little oxygen boost thrown in for good measure.

And the next time you see someone yawning, give them the benefit of the doubt. They might just be tired, feeling a bit too hot, or struggling with sleep deprivation.

Having said that, it can’t hurt to quietly assess whether your current story could be a little more concise!

cat yawning

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