September 19, 2003


Capuchins prove we are brothers under the skin (Roger Highfield, 18/09/2003, Daily Telegraph)

The idea of fair play and justice was probably invented by monkeys 40 million years ago, says a study today. [...]

The research is published in Nature by a team led by Ms Sarah Brosnan and Dr Frans de Waal at the Yerkes National Primate Research Centre of Emory University, and the Living Links Centre, Atlanta.

The team taught brown capuchin monkeys (Cebus apella) to swap tokens for food. Normally, capuchins were happy to exchange their tokens for cucumber. But if they saw their partner getting a grape - which is more coveted by capuchins - they took offence.

Some refused to pay, others took the cucumber but refused to eat it. The animal's umbrage was even greater if the other monkey was rewarded for doing nothing. They did more than sulk, sometimes throwing the food out of their cage.

These emotional reactions are akin to those which underpin economics. "The sense of fairness underpins co-operation and other economic decisions in humans," she said.

Previous experiments with humans have shown that they become less co-operative if treated unfairly, and punish the unco-operative - even if their own pay-off declines as a result. "People often forgo an available reward because it is not what they expect or think is fair," said Ms Brosnan.

This has baffled scientists and economists, who traditionally have argued all economic decisions are rational - in other words, it is better to eat cucumber than nothing at all.

However, the capuchin study reveals an emotional sense of fairness plays a key role in such decision-making, said Ms Brosnan. This sense of equality may be common among social primates.

The most interesting thing about the study is not how similar their reactions are to ours, but how different. Under the same circumstances Cain slew Abel.

Posted by Orrin Judd at September 19, 2003 12:35 PM

The problem with such economic thought is not that man is irrational, but that he values other principles than the mere economic - like honor and pride.

Posted by: Chris Durnell at September 19, 2003 1:27 PM

Dangit, he beat me to it. Economists of all people should know that utility is a broader concept than mere material gain.

Posted by: Chris at September 19, 2003 1:33 PM

The conclusion is clear: the UN General assembly should be replaced by capuchin monkeys.

Posted by: Mike Earl at September 19, 2003 2:43 PM

At the UN, bonobo's are more likely.

Posted by: oj at September 19, 2003 6:33 PM

Fairness has always been an overwhelming priority for me. Isn't that what conservative thought is really all about? Equal outcome is absolutely not fair. Equal opportunity is.

Posted by: genecis at September 19, 2003 8:39 PM

I always think of fairness as liberal, justice as conservative.

Posted by: David Cohen at September 19, 2003 9:36 PM


Equal outcome is fair if you believe that individual action is ineffectual.

Posted by: Mike Earl at September 19, 2003 11:57 PM

Anyone who has watched 2-yr olds play would know fairness--in the sense of self failing to obtain some--is innate.

Posted by: Jeff Guinn at September 20, 2003 5:55 AM

The original report in Nature ( ) contains this in the next-to-last paragraph: "Only female monkeys show this pique, the researchers found. Males were much less sensitive to inequality." This is kind of a major qualifier. Shouldn't the Telegraph article be titled "Capuchins prove we are *sisters* under the skin"?

Posted by: Bob Hawkins at September 20, 2003 5:15 PM


Alternatively, the Telegraph article could have been titled "Capuchin Males and Human Males Both Equally Socially Clueless"

Posted by: Jeff Guinn at September 20, 2003 6:38 PM

Mr. Hawkins:

That's extremely cool, because it jibes with men being politically conservative and women liberal.

Posted by: oj at September 21, 2003 2:57 PM