Dr. Matt Walker

That's well done.

Congratulations.

Wait a second.

I didn't get the choice.

It's genetics.

Well, it's the same with your chronotype.

But coming back to why for me, I included it in this sort of algorithm of what is good sleep.

If I were to take an extreme morning type and force them to stay awake until midnight, they're going to be incredibly tired.

They're going to be so tired and they're going to be grumpy and miserable and they will have no problem falling asleep.

The problem, however, is that they're still going to, because of their natural chronotype, which determines your circadian rhythm.

So everyone has this 24-hour circadian rhythm, as you've been a wonderful proponent of that and done incredible work in this area.

We all have this 24-hour rhythm and it looks like a sinusoidal wave.

It sort of goes up and we, as a diurnal species, were active and awake during the day.

And then you get this awesome downswing at night and we're inactive at night.

And it steps and repeats.

It's just a 24-hour cycle.

Everyone has that.

So why doesn't everyone fit the same chronotype timing model of sleep if we all have a 24-hour clock?

Well...

What's different is that where that peak and that trough sit on the 24-hour clock face varies from one individual to the next, and that is what we call chronotype.