August 26, 2008

Study Finds Generous Monkeys

Researchers found monkeys are more generous with friends compared to strangers, and demonstrated advanced prosocial tendencies, according to a new study.

Scientists gathered data on capuchin monkeys at the Yerkes National Primate Research Center at Emory University in Atlanta.

During the experiment, monkeys were given a choice of receiving a food reward, or receiving a food reward and also having another monkey receive food.

When the monkeys were paired with relative or "friend" they overwhelmingly chose the double reward, known as the "prosocial" choice.

Frans de Waal led report that is published in Tuesday's edition of Proceedings of the National Academy of Sciences.

"The fact the capuchins predominantly selected the prosocial option must mean seeing another monkey receive food is satisfying or rewarding for them," said de Waal.

Researchers found they were more selfish when it came to strangers, and went with the "selfish" choice.

"We believe prosocial behavior is empathy based. Empathy increases in both humans and animals with social closeness, and in our study, closer partners made more prosocial choices. They seem to care for the welfare of those they know," de Waal said in a statement.

Now scientists are trying to understand if giving is self-rewarding to capuchins because they can eat together, or if the monkeys simply like to see the other monkey enjoying the food.

Eight adult female capuchins were given tokens to exchange for food. One token meant they received a slice of apple. The other also got an apple slice, plus a similar slice was given to another monkey they could see.

When the "partner" monkey was a relative or a familiar female from the same social group, the one choosing the token moved closer to the partner and they primarily chose the prosocial token that got them both food.

However, during the tests if the second monkey was a stranger, the selfish token was more likely to be chosen, often with the lead monkey turning her back to the stranger.

No matter what token the monkey chose, the reward was the same. Therefore, de Waal suggested there must be some intangible benefit to the prosocial choice, perhaps a sign of empathy.


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