This is hidden brain.
I'm Shankar Vedantam.
In the classic children's film Willy Wonka and the chocolate factory.
A group of children win a private tour of a whimsical candy making plant.
There are massive gummy bears hanging from the branches of trees and larger than life mushrooms stuffed with whipped cream.
The centerpiece is a decadent river of chocolate.
A chocolate river.
That's the most fantastic thing I've ever seen.
10,000 gallons an hour.
The children's eyes grow wide, but their appetites are even bigger.
So many temptations are within easy reach.
The kids become greedy and self indulgent.
Hey, she's got two.
I want another one.
Stop squawking, you twist.
Everybody has had one, and one is enough for anybody.
Now come along.
Yielding to temptation comes at a cost.
One of the children falls down a trash chute.
One turns into a blueberry.