This is Hidden Brain and I'm Shankar Vedantam reporting

from your school cafeteria.

Okay, not really.

But play along with me for a second and picture a typical scene

at an elementary school lunchroom.

There are kids holding trays with tata tots and turkey sandwiches,

the milk is in those little cardboard cartons.

There are long tables that serve not just as a place to sit,

but as a kind of marketplace.

Hey, I'll trade you two cookies for a bag of potato chips.

One young businessman tries to score a deal while trying not to get ripped off.

No, that's a bad trade.

Of course, if you want to eat on one of these deals,

you have to trade stuff that others want.

I would so bum that I can have anything to trade.

Because no one wants, you know, like a Clementine.

This is Esther.

Hi, I'm Esther Bly.

Esther's long since graduated from her elementary school cafeteria days.

Growing up, her mom kept the kitchen free from food coloring and high fructose corn syrup.

Esther's lunch box was subject to the same rules about healthy food.

So I would have snap peas, I would have an orange.

...