October 9, 2013
Chimpanzees Choose Friendships Based On Similar Personality
Lee Rannals for redOrbit.com – Your Universe Online
According to a new study published in the journal Evolution and Human Behavior, chimpanzees choose their friendships with others based on personality.
Cognitive Biologists of the University of Vienna, Austria, and the University of Zurich, Switzerland measured chimpanzee personality in two zoos with behavioral experiments and years of observations of the animals' behavior. The experiment included 38 captive chimpanzees. They also logged which chimpanzees sat in body contact with whom the most, which is a sign of friendship among the animals.
"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," Jorg Massen, from University of Vienna, said in a press release.
The scientists say that chimpanzees adapted to have a preference for self-like individuals because frequent cooperation becomes more reliable when both partners have similar behavioral tendencies and emotional states.
"We suggest that having friends similar to self in personality decreases uncertainty in interactions by promoting reliability especially in cooperative contexts, and is consequently adaptive," the researchers wrote in the journal.
Humans are known to have this "similarity effect" in that we tend to make friends with people who are equally extraverted, friendly and bold. However, this is the first time scientists have pinpointed this same behavior, called homophily in chimpanzees. The team said that their findings suggest that homophily in human friendships dates back at least to our last common ancestor with chimpanzees.
"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," said Massen.
A study published in September found that orphaned chimpanzees have less social success than chimps that were raised by their biological mother. A team studied eight orphaned and nine mother-reared juvenile chimpanzees at the Chimfunshi Wildlife Orphanage Trust in Zambia. They said that although the orphaned chimpanzees readily engaged in social play, it resulted more frequently in aggression than the social play of their peers that were raised by their mother.
“Mothers seem to prepare their offspring for challenges that are very important for successful group-living,” Edwin van Leeuwen, a cognitive anthropologist from the Max Planck Institute in Germany said. “For orphans, however, the presence of other adult role models may alternatively be beneficial for boosting social competence, which is an important consideration to entertain for sanctuaries dealing with integrations of chimpanzees.”