This behavior suggests that primates who live in larger social groups tend to have more "social intelligence," a new study shows. The results appear June 27 in PLOS ONE.

A Duke University experiment tested whether living in larger social networks directly relates to higher social abilities in animals. Working with six different species of lemurs living at the Duke Lemur Center, a team of undergraduate researchers tested 60 individuals to see if they would be more likely to steal a piece of food if a human wasn't watching them.

In one test, a pair of human testers sat with two plates of food. One person faced the plate and the lemur entering the room, the other had his or her back turned. In a second, testers sat in profile, facing toward or away from the plate. In a third, they wore a black band either over their eyes or over their mouths and both faced the plates and lemurs.