The New Yorker | 

A pair of brown capuchin monkeys are sitting in a cage. From time to time, their caretakers give them tokens, which they can then exchange for food. It’s a truth universally acknowledged that capuchin monkeys prefer grapes to cucumbers. So what happens when unfairness strikes—when, in exchange for identical tokens, one monkey gets a cucumber and the other a grape?

When Sarah Brosnan and Frans de Waal carried out just this experiment, in 2003, focussing on female capuchin monkeys, they found that monkeys hate being disadvantaged. A monkey in isolation is happy to eat either a grape or a slice of cucumber. But a monkey who sees that she’s received a cucumber while her partner has gotten a grape reacts with anger: she might hurl her cucumber from her cage. Some primates, Brosnan and de Waal concluded, “dislike inequity.” They hate getting the short end of the stick. Psychologists have a technical term for this reaction: they call it “disadvantageous-inequity aversion.” This instinctual aversion to getting less than others has been found inchimpanzees and dogs, and it occurs, of course, in people, in whom it seems to develop from a young age. The psychologists Alessandra Geraci and Luca Surian have found, for example, that babies as young as twelve months prefer fair-minded cartoon animals to unfair ones.

And yet, for humans, an aversion to getting less is just one aspect of unfairness. Unlike other animals, we sometimes balk at receiving more than other people. Technically speaking, we experience “advantageous-inequity aversion.” In some situations, we’ll even give up something good because it’s more than someone else is getting. In those moments, we seek to insure that the distribution of goods remains fair. We don’t want the long end of the stick, either.

It seems likely that our aversion to being disadvantaged is innate, because we share it with other animals. The question for psychologists is whether our aversion to benefitting from inequality is innate, too—or, alternatively, if it’s learned through some form of socialization. In December, the psychologists Peter Blake, Katherine McAuliffe, Felix Warneken, and their colleaguespublished the results of experiments designed to answer this question. Their research spanned seven nations—India, Uganda, Peru, Senegal, Mexico, Canada, and the United States—and looked at close to nine hundred children, aged four to fifteen. They examined whether advantageous-inequity aversion—A.I., as they call it—emerges in all cultures, and, if it does, whether it emerges in the same way everywhere.

Their method was relatively simple. They sat two children down at a table, each in front of an empty bowl. Above each bowl was a tray, onto which the experimenter placed candy. Often, she distributed candy unfairly: she might place four candies on one tray and only one on the other. The child being tested then faced a choice. She could pull a green handle to accept the presented candies, causing them to fall into their respective bowls—or she could pull a red handle to reject them, causing all the candies to fall into a third, off-limits bowl, in the center.

The researchers found that, all over the world, children tended to reject the candies when the split favored the other child. (That is, they rejected disadvantageous inequity, or D.I.) They also found that some, older kids would reject advantageous offers. None of that is surprising. A.I. has been documented among adults many times in the past; in one early study, from behavioral economist George Loewenstein and his colleagues, as many as sixty-six per cent of participants disliked getting more than someone else. The surprising part is that the kids only displayed A.I. in three countries: Canada, the United States, and Uganda. In the other countries—Mexico, India, Senegal, and Peru—they enjoyed the sweet taste of inequality.

These results raise some fascinating questions. Why were kids from only certain countries bothered by having an unfair advantage? And were they rejecting those unfair offers because they cared about fairness—or for some other, less obvious reason?

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