Frans de Waal, PhD, director of the Living Links Center at the Yerkes Research Center, and Kristi Leimgruber, research specialist, led a team of researchers who exchanged tokens for food with eight adult female capuchins. Each capuchin was paired with a relative, an unrelated familiar female from her own social group or a stranger (a female from a different group). The capuchins then were given the choice of two tokens: the selfish option, which rewarded that capuchin alone with an apple slice; or the prosocial option, which rewarded both capuchins with an apple slice. The monkeys predominantly selected the prosocial token when paired with a relative or familiar individual but not when paired with a stranger.

The researchers concluded that the monkeys must find sharing to be pleasurable.

"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. "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," continued de Waal.

A recent imaging study on humans showed that there is activity in the reward centres of the brain when giving charitable donations. Empathy in seeing the pleasure of another's fortune is thought to be the impetus for sharing, a trait this study shows transcends primate species.

The study is available online in the Early Edition of the Proceedings of the National Academy of Sciences.

de Waal and his research team next will attempt to determine whether giving is self-rewarding to capuchins because they can eat together or if the monkeys simply like to see the other monkey enjoying food.




Source: Adapted from materials provided by EurekAlert