Search Here

Chimpanzees make friends with those who are similar to them, according to a new study.

Researchers Jorg Massen of the University of Vienna and Sonja Koski of the University of Zurich measured chimpanzee personality in two zoos with behavioral experiments and observations of chimp behavior.

Massen and Koski focused on which chimpanzee sat in body contact with whom most.

"This is a clear sign of friendship among chimpanzees," Massen said in a news release.

Afterwards, researchers examined whether chimpanzees who like to sit together have similar or different personality types.

"We found that, especially among unrelated friends, the most sociable and bold individuals preferred the company of other highly sociable and bold individuals, whereas shy and less sociable ones spent time with other similarly aloof and shy chimpanzees," researchers wrote in the study.

Researchers said that chimpanzees' tendencies to friend those with similar personalities are most likely adaptive. Partners with similar behavioral tendencies and emotion states are more likely to cooperate with each other, researchers explained.

Researchers said that the latest finding strongly resembles the "similarity effect" in humans. The "similarity effect" states that people tend to make friends with people who share similar personality traits.

"It appears that what draws and keeps both chimpanzee and human friends together is similarity in gregariousness and boldness, suggesting that preference for self-like friends dates back to our last common ancestor," Massen concluded.

The findings are published in the journal Evolution and Human Behavior.