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 genetic² relatives found that stress was reduced in chimps³ that were victims of aggression⁴ if a third chimp¹ stepped in to offer consolation⁵.

"Consolation usually took the form of a kiss or embrace," said Dr. Orlaith N. Fraser of the Research Center in Evolutionary⁶ Anthropology⁷ and Paleoecology at Liverpool John Moores University in England.

"This is particularly interesting," she said, because this behavior is rarely seen other than after a conflict.

"If a kiss was used, the consoler would press his or her open mouth against the recipient⁸'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 behavior such as scratching or self-grooming by the victim of aggression, Fraser and colleagues report in Tuesday's edition of Proceedings⁹ of the National Academy of Sciences.

Consolation was most likely to occur between chimpanzees who already had valuable relationships, Fraser added.

Dr. Frans de Waal of the Yerkes Primate¹⁰ Center 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.

"This study removes doubt that consolation really does what the term suggests: provide relief to distressed¹¹ parties after conflict. The evidence is compelling and makes it likely that consolation behavior 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 behavior in children includes touching¹² 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.