Why Do We Yawn?

You are now part of an experiment.How many times will you yawn before the end of this sentence?

People, on average, yawn eight times a day. And for about 70% of people, yawning is contagious. So we know a picture or a video might get one out of you. But researchers say that just talking about yawning is enough to make you do it.
So let’s test that theory, and find out why we yawn.

We associate yawning with sleepiness and boredom, but do you think it’s possible to be bored with life before you’re even born? A human fetus starts to yawn during its first trimester. And the fact that it’s involuntary must mean that this biological reflex has a purpose. But that purpose has been widely debated since 400 BCE.

Hippocrates believed yawning was a sign of fever. That the body had to expel bad air that had accumulated inside it. Today’s theories are a little more sophisticated, but none have been confirmed.

You may have heard that yawning gives us a big gulp of oxygen-rich air, which enters our bloodstream, and perks us up when we need it most. That’s a myth. Yawning might be something we do when we’re bored, but definitely not always. Olympic athletes have been caught yawning before big events, famous musicians before concerts, and Green Berets before their first jump out of a plane.

Neuroscientist Robert Provine believes yawning could signal a physiological transition. A transition from sleep to wakefulness, anxiety to calm, boredom to alertness, and vice versa. Another leading theory comes from psychology professor, Andrew Gallup, who proposed that yawning cools the brain. As our most complex system, the brain uses up 40% of the body’s metabolic energy. And like with any technological device you may be familiar with, the more energy something takes, the hotter it gets over time.

Inside your nose and mouth are tons of blood vessels that lead right up to the brain. Opening wide increases blood flow to the brain, and taking in a big gulp of air when you yawn, cools the blood on its way up and therefore, cools the brain as well.
This might explain why you yawn closer to bedtime and shortly after waking up. At the end of a long day, your brain temperature and body temperature are at their highest point in the sleep/wake cycle. But those temperatures fall when you sleep, and rise when you wake up. So you yawn to normalize your internal temperature to keep it in sync with other bodily processes.

This theory may be supported by the fact that we tend to yawn more when it’s cooler outside than when it’s hot. Another thing about yawning is that it relieves pressure that builds up behind the eardrum when you change altitudes. So really, the reason why we yawn might not have much consensus, but we do know that it’s contagious.

You yawn when people around you yawn. You yawn when you see pictures or videos of people yawning. You yawn when you talk about yawning, you yawn when you hear people talk about yawning!

But do you know why?

Behaviouralists believe it’s a primal sign of human empathy. Others suggest it might have something to do with room temperature or climate.

For now, the exact reason is yet to be determined.