Dr. Matt Walker

It's not that people are listening to good music and sort of doing this head bobbing.

It's that they're falling prey to what we know is a genetically hardwired pre-programmed drop in your afternoon alertness.

It's called the postprandial dip in alertness.

and that infers that it's after some kind of a meal it turns out it's not really related to a meal people say well i had a heavy lunch i had sort of pastor at lunch and i always feel sleepy afterwards maybe in part but

If I remove it, I prevent you from having lunch.

And we've done these studies too.

Your brain still shows this very reliable drop in alertness somewhere between, it's quite wide, but somewhere between about 1 to 4 p.m.

Get that rise back up, don't you?

And it sort of swings back up.

And so that's in part the reason, though, explaining the yawning and that warm feeling of I'm in the meeting room, the boardroom meeting, and the blinds are open, the sun is coming through, I've got the sun on my back, I'm starting to get very warm, but I'm starting to get really, really sleepy.

It's the...

It's the collusion of two things.

It's that you're going into this higher frequency sleep zone in the afternoon, this postprandial drop in your brain alertness, and we can measure it.

It's very reliable.

You can see this dip in your brain electrical activity, and you're getting warm at the surface, which brings blood to the surface, releases that heat from the core, it drops, and boy, do you want to fall asleep.

I'm always the bearer of doom and gloom.

And it really is quite a stunning state of idiocy when you consider it, because when you're asleep, you're not finding a mate, you're not reproducing, you're not foraging for food, you're not caring for your young, and worse still, you are vulnerable to predation.

On any one of those grounds, but especially all of them as a collective, sleep should have been strongly selected against in the course of evolution.

And in fact, one of the founding fathers of sleep research, Alan Rechaffen, once said that if sleep doesn't serve an absolutely vital function, it is the biggest mistake the evolutionary process has ever made.

And now what we've learned through, you know, almost 10,000 plus research studies over the past certainly 70, 80 years now is that nature did not make a spectacular blunder in creating this thing called sleep.