Yawning

See one person start yawning in a quiet library, and there’s a good chance you’ll yawn too.

That’s obviously because of the reduction in the total amount of oxygen in the room when the other person yawns. When you yawn, you’re basically doing a gasp-for-air on steroids.

Okay, okay—it’s really just social-neural mimicry, similar to the way you might want to smile when you see someone else smile. This is like how you might find yourself crossing your legs in a certain way, then notice someone else in the room has that exact same posture.

Yawning seems so casual, but it has more of a biological purpose than to amuse us by making everyone else yawn. In fact, there’s a lot going on under the hood.

It might be easiest to think of a yawn as a knob or dial. When you yawn, you’re turning your state of alertness up or down. Suddenly, your cardiovascular system and your neurochemical system align with your respiratory system, all rowing in the same direction.

There’s something really cool going on with temperature, too. Your brain performs differently depending on how hot or cold it is, and when you yawn, you’re actually cooling your brain. When you open your mouth wide, your jaw stretches that skin and muscle out and away from the center. Blood has to flow there, ultimately bringing heat away from your brain.

When your brain is cooler, everything runs a little bit more efficiently. That’s part of the reason why you can sometimes focus more after a yawn, although there are serious limitations to this.

Besides the face/blood mechanism, you’re also stretching your soft palate inside your sinus cavity out, so that it takes up a lot more surface area. This, too, contributes to cooling your brain, since cooler air gets into your nasal passage—very close to your brain.

You’re thinking: you mentioned a knob or dial, which implies that you can either turn your alertness up or down. Why have you only talked about turning alertness up so far, jerk? After all, doesn’t cooling the brain make everything more efficient?

Yes, but… there are other forces at play. There’s little controversy in saying that a cooler brain increases alertness. Being alert means your brain can now pay close attention to—well, to something.

In this case, that something is whether or not it’s safe to relax.

If your cool brain decides the coast is clear, the knob turns down. That rowing in the same direction thing happens again, but in reverse. Your breathing and heart rate begin to slow, and your neurochemical system becomes less vigilant.

I was going to say that I hope you’re not yawning as you read this, but since yawns are little inflection points, you might actually be paying more attention after yawning. Carry on.