Here at Planet Money, we bring complex economic ideas down to Earth.

We find weird, fun, interesting stories that explain the way money shapes our lives.

Inflation, recessions, the price of gas we've got you.

Listen now to the Planet Money Podcast from NPR.

One of the cooler things that's happened in the last few decades

is that scientists have decided that emotions are worth studying.

And they found new ways to study them, not just in people, also in animals.

The guy who's taken the lead with the animals is a Dutch primatologist named Franz DeWall.

You know, emotions are sort of taboo topic. They used to be at least.

And so most of the time we don't explicitly discuss them.

We discuss the behavior that they produce, but not the emotions themselves.

That's DeWall himself. He's Dutch, but works in Atlanta at Emory University.

When he started out, no one thought you could study the emotions of animals.

A lot of people just assume that animals didn't have emotions, and scientists shouldn't care if they did.

But not supposed to talk about mental states or feelings or planning or thoughts or whatever.

And so there was a taboo for 100 years on talking about that.

And it's only in the last 20 years or so that taboo is being lifted and that the more and more

scientists are open about internal states.

Meaning emotions. They so clearly drive behavior in both animals and people.

Which brings me to Professor DeWall's most famous experiment.

I worked with Capuchin monkeys for a long time. We noticed in our lab that the monkeys were always

very keenly watching what somebody else would get. Not just what they themselves get for a task,

...