Lisa Feldman Barrett

for what's coming because predicting and correcting is a much more efficient way to run a nervous system, really any system, than reacting to the world.

Here's another example.

Do you drink coffee?

Okay.

Do you drink coffee every day at the same time?

Okay.

And are you one of these people that if you miss having coffee at that time, you get a headache?

Well, I used to be a person who drank a lot of coffee.

And I love coffee, but I don't drink it anymore.

But I loved it, and I drank it always at the same time every day.

And if I didn't drink it, I would get, at that time of day, I would get a massive headache.

And the reason why, and this is true of every medicine you take, anything which affects your physiology, if you do it on a regular basis, your brain will come to expect it.

And what that means, come to expect it, is that coffee has chemicals in it that will constrict your blood vessels.

everywhere.

But in the brain, the brain is attempting to keep the blood flow pretty constant and even.

And so if every day at eight o'clock in the morning, you're drinking something that's going to constrict your blood vessels, then at 7.55 approximately, I don't know the exact timing, but a little bit before eight, your brain will dilate the blood vessels.

In preparation for that constriction so they remain constant.

And if you don't drink that substance, then you have this big dilation and you get a very, very bad headache.

Yeah, sure.

That's an example.