Jan. 4 (UPI) -- Often described as the most laidback of the apes, new research shows bonobos prefer bad boys -- or girls.
Given a choice between two people, one mean and one nice, humans tend to prefer the nice one. Studies have shown infants as young as three months prefer a person they've witnessed doing a good deed over someone treating others badly.
"Humans might have this unique preference for helpers that is really at the heart of why we're so cooperative," Christopher Krupenye, a former Duke University doctoral student, said in a news release.
Researchers at Duke wanted to see if bonobos displayed similar tendencies.
To find out, Krupenye, now a postdoctoral fellow at the University of St. Andrews in Scotland, and Duke's Brian Hare, an associate professor of evolutionary anthropology, showed a series of cartoon videos to bonobos at a preserve in the Democratic Republic of Congo. The videos featured a Pac-Man-like figure trying to climb a hill. In some videos, a second character enters and pushes Pac-Man down the hill. In another, the second character assists Pac-Man with the climb.
After watching the videos, bonobos were given the choice to select one of two pieces of fruit, one placed beneath a cutout of the helpful character and one placed beneath a cutout of the mean character.
The apes preferred the mean character's fruit.
In a second, but similar, experiment, researchers used a skit featuring human actors instead of a cartoon. The skit features a person trying to return a lost stuffed animal to its rightful owner. Before the return hand-off can be made, a third actor snatches the animal and runs away.
Afterwards, apes were more willing to accept a piece of fruit from the thief than the good samaritan.
Scientists hypothesized bonobos behave this way not necessarily because they prize poor behavior, but because they perceive the mean characters as dominant. It's advantageous to maintain relations with those of higher social status, as such relations can lead to greater access to food, mates and reduce the chance of getting bullied.
In a final experiment, researchers showed the apes a cartoon video of one character giving up a seat to another. A second video featured a character unwilling to yield the seat. Once again, the bonobos preferred the less generous character.
Scientists suggest their findings -- published this week in the journal Current Biology -- show humans are truly unique in their preference for people who help others.