Inequity aversion in monkeys.

May 7, 2008 | By | 1 Reply More

Frans de Waal was recently interviewed by Stephen J. Dubner in the Freakonomics blog of the NYT. Dubner co-authored Freakonomics with Steven D. Levitt. De Waal and Dubner discussed the ramifications of an experiment where capuchin monkeys received either a grape or a piece of cucumber in return for a simple task.

If both monkeys got the same reward, there never was a problem. Grapes are by far preferred (as real primates, like us, they go for sugar content), but even if both received cucumber, they’d perform the task many times in a row.

However, if they received different rewards, the one who got the short end of the stick would begin to waver in its responses, and very soon start a rebellion by either refusing to perform the task or refusing to eat the cucumber.

This is an “irrational” response in the sense that if profit-maximizing is what life (and economics) is about, one should always take what one can get. Monkeys will always accept and eat a piece of cucumber whenever we give it to them, but apparently not when their partner is getting a better deal. In humans, this reaction is known as “inequity aversion.”

I actually don’t think the response is irrational at all, but related to the fact that in a cooperative system, one needs to watch what kind of investment one makes and what one gets in return. If your partners always ends up getting a greater share, this means that you’re being taken advantage of. So, the rational thing to do is withhold cooperation until the reward division improves.

This holds an important message for American society which is becoming less fair by the day. . . If monkeys already have trouble accepting income inequality, you can imagine what it does to us. It creates great tensions within a society.

The post indicates that the U.S. now ranks 42 in longevity rating, suggesting that the increasing inequity in the U.S. is a contributing factor. The WashPo article linked to the blog post indicates that “Forty countries, including Cuba, Taiwan and most of Europe had lower infant mortality rates than the U.S. in 2004.”

For more on this study, which was done with Sarah Brosnan, see the DI post: Is it really possible to be unselfish?

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Category: American Culture, Friendships/relationships, Psychology Cognition, Science

About the Author ()

Erich Vieth is an attorney focusing on consumer law litigation and appellate practice. He is also a working musician and a writer, having founded Dangerous Intersection in 2006. Erich lives in the Shaw Neighborhood of St. Louis, Missouri, where he lives half-time with his two extraordinary daughters.

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