You're listening to TED Talks Daily. I'm Elise Hu.

If you have kids who have ever fought over treats or toys or time with you, today's talk from

Sarah Brasman is going to help really shed some light on these battles.

The primatologist talk at TED Salon 2020 describes a simple study on the social dynamics among monkeys,

which points the way to better understanding our sometimes irrational human judgments when it comes to fairness.

My first year in graduate school, studying cooperation in monkeys, I spent a lot of time outside,

just watching our groups of capuchin monkeys interact. One afternoon, I was out back feeding peanuts to one of our groups,

which required distracting one of our males, Ozzy, enough so that the other monkeys could get some.

Ozzy loved peanuts, and he always tried to do

anything he could to grab some. On that day, however, he began trying to bring other things from his

enclosure to me and trade them with me in order to get a peanut. Now, Capuchins are smart,

so this wasn't necessarily a surprise, but what was a surprise was that

some of the things that he was bringing me, I was pretty sure he liked better than peanuts.

First, he brought me a piece of monkey chow, which is like dried dog food. It was even made by

Purina, and for a monkey is about as worthless as it gets. Of course I didn't give him a

peanut for that. But he kept trying, and eventually he brought me a quarter of an orange and

tried to trade it with me for a peanut. Now, oranges are a valuable monkey commodity, so this trade

seemed, shall I say, a little bit nuts.

Now you may be wondering how we know what monkeys prefer? Well, we ask them by giving them a choice

between two foods and seeing which one they pick. Generally speaking, their preferences are a lot like

ours. The sweeter it is, the more they like it. So, much like humans prefer cupcakes to kale,

monkeys prefer fruits, like oranges or grapes to vegetables like cucumbers, and all of this to

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