Chimps calm each other with hugs

For most folks, a nice hug and some sympathy can help a bit after we get pushed around. Turns out, chimpanzees use hugs and kisses the same way. And it works. Researchers studying people’s closest genetic relatives found that stress was reduced in chimps that were victims of aggression if a third chimp stepped in to offer consolation.

"Consolation usually took the form of a kiss or embrace," said Orlaith Fraser of the Research Centre in Evolutionary Anthropology and Paleoecology at Liverpool John Moores University in England. "This is particularly interesting," she said, because this behaviour is rarely seen other than after a conflict.

"If a kiss was used, the consoler would press his or her open mouth against the recipient’s body, usually on the top of the head or their back. An embrace consisted of the consoler wrapping one or both arms around the recipient."

The result was a reduction of stress behaviour such as scratching or self-grooming by the victim of aggression, Fraser and colleagues report in Proceedings of the National Academy of Sciences.

Frans de Waal of the Yerkes Primate Centre at Emory University in Atlanta said the study is important because it shows the relationship between consolation and stress reduction. Previous researchers have claimed that consolation had no effect on stress, said de Waal, who was not part of Fraser’s research team.

"This study removes doubt that consolation really does what the term suggests: provide relief to distressed parties after conflict. The evidence is compelling and makes it likely that consolation behaviour is an expression of empathy," de Waal said. De Waal suggested that this evidence of empathy in apes is "perhaps equivalent to what in human children is called ’sympathetic concern’."

That behaviour in children includes touching and hugging of distressed family members and "is in fact identical to that of apes, and so the comparison is not far-fetched", he said. While chimps show this empathy, monkeys do not, he added.

There is also suggestive evidence of such behaviour in large-brained birds and dogs, said Fraser, but it has not yet been shown that it reduces stress levels in those animals.