Dr. Matt Walker

So next time you see someone yawn, don't think, oh, they're bored or they didn't get enough sleep.

Go over to them, hug them and say, I know your brain is getting warm.

It's okay.

And then at that point,

the friendship will be terminated because no one should be hugging each other and saying, your brain is warm.

I'm so sorry.

But anyway, that aside, I'm sorry I took us down that tribute tree of my polluted stream of consciousness, but that's yawning explained.

Those are the four theories.

And we don't have a definitive answer, but I think the best one right now that will continue is that it's about brain cooling.

So it turns out that for you to drop your core body temperature, the opposite has to happen, which is that you have to warm up

to cool down to fall asleep and i mean warm up in a very specific way you have to have the outer surface of your brain warm up you have to get blood to the surface of your skin

And that surface is almost acts like a snake charmer, that it draws the warm blood from the core and it pushes it to the surface and you radiate the heat out.

And as you radiate the heat out, your core body temperature plummets.

So why would people be falling asleep sort of, you know, in an afternoon meeting when it starts to get a little warm?

Well, in part it's because the warmth of the room is starting to make the sort of face a little bit more rosy.

It's drawing the blood out to the surface.

So what's happening, the core of your brain and your body temperature are starting to drop.

And at that point, that's why you're going to start to feel a little bit more sleepy.

That's reason one.

The second that you described is that afternoon, you know, you're in meetings around a table and you start to get, as you said, those wonderful head nods and people listening, you all know that where the head goes down, it snaps back up.