You can tell a lot about someone from how they treat their friends. As the results of a study of captive chimpanzees seem to show, our ape cousins are only in it for themselves.
The study, led by Joan Silk of the University of California, Los Angeles, looked for evidence that chimpanzees (Pan troglodytes) will help other members of their group. But the apes seem to be indifferent at best to the welfare of their fellows.
Silk and her colleagues presented captive chimps with an apparatus that allowed them to get food by pulling on one of two ropes. Choosing one of the ropes meant that the chimp could haul in a tasty titbit. Selecting the other yielded exactly the same reward, but another chimp in an adjacent cage also received a morsel to eat.
Given that the chimp in charge got the same food reward regardless of which rope was selected, one might expect them to have shown some compassion and chosen the one that gave food to their companion too. "All they had to do was be nice," Silk says.
But the 29 chimps tested were no more likely to choose the generous option than the selfish one, Silk and her colleagues report in this week's Nature1. This shows that the apes are not motivated to help others as a matter of course, they conclude.