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Saturday, October 11, 2003

Monkey Business

I don't know how I missed this one when it first came out. The discovery is a lovely one, and serves to undeline how much of our core behaviour we share with some other animals. It is also very pleasant to blog this, since Frans de Waals was one of the first people to study Bonobos. A quick Google will soon take you to his other work if you are interested. Remember, Darwin had some very dangerous ideas, and we are only now coming to terms with their implications.

Cheated Monkeys Help Explain Economic Puzzle

In an experimental first, researchers have demonstrated that just like humans, nonhuman primates have a sense of fairness. Coupled with previous scientific data demonstrating strong similarities between human and nonhuman primate behavior, the findings suggest that economic decision-making is based as much on a universal sense of fairness as on rational considerations. "People often forgo an available reward because it is not what they expect or think is fair," says researcher Sarah Brosnan. "Such irrational behavior has baffled scientists and economists, who traditionally have argued all economic decisions are rational," she says. "Our findings in nonhuman primates indicate the emotional sense of fairness plays a key role in such decision-making."

Led by Brosnan and Frans de Waal at the Living Links Center and the Yerkes National Primate Research Center of Atlanta's Emory University, researchers conducted four tests, each including sessions of 25 trials on pairs of female capuchin monkeys. First, they gave capuchins cucumber in exchange for a token. Then they gave one capuchin cucumber and one a higher-value grape in exchange for various behaviors. "We showed the subjects compared their rewards with those of their partners and refused to accept a lower-value reward if their partners received a higher-value reward," says Brosnan, "This effect is amplified when the partner does not have to work for the reward."

The capuchins display similar reactions to humans when they feel they are being cheated. The researchers recorded a 95% exchange rate with subjects when both subjects received cucumber as payment for the same work. This fell to 60% during an inequity test, in which subjects observed their partners receiving a higher reward for doing the same work. In an effort-control test, in which partners received a higher reward for less work, the rate fell to 20%.

The results indicate that nonhuman primates respond the same emotionally as humans do to perceived inequity. This provides economists with food for thought as to why humans make decisions they do regarding efforts, gains and losses of others.Brosnan and de Waal will now conduct related studies with capuchins and chimpanzees. The findings from their latest study can be found in the journal Nature.
Source: Better Humans

Here's the abstract of the Nature article, and a link:

During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model, and may in fact be more inclusive than previous explanations. Although there exists substantial cultural variation in its particulars, this ‘sense of fairness’ is probably a human universal that has been shown to prevail in a wide variety of circumstances. However, we are not the only cooperative animals, hence inequity aversion may not be uniquely human.

Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources. Here we demonstrate that a nonhuman primate, the brown capuchin monkey (Cebus apella), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion.
Source: Nature

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