Lemurs can be sneaky. They’ll wait until a human’s back is turned to take a treat. But a new study shows that in the same situation, they don’t seem to realize that making a racket will draw unwanted attention.
Joel Bray, Christopher Krupenye, and Brian Hare of Duke University wanted to see if ring-tailed lemurs could take the perspective of others. Previous research showed that both chimpanzees and rhesus macaques seem to have an understanding of what others can see and hear. Like those primates, ring-tailed lemurs also live in large social groups. According to the social intelligence hypothesis, this kind of group living drives the evolution of sophisticated cognitive skills. When living in a group, it might be helpful to understand the perceptual or psychological states of other individuals, such as what they can see and hear or even that others have different beliefs and intentions.
To test the lemurs’ understanding of what others can see and hear, Bray, Krupenye, and Hare gave them a task in which they had to sneak food from a human competitor. Lemurs were presented with two boxes, each one containing a treat. One box had noisy bells attached to its lid so that it jangled when the box was opened. The human sat behind the boxes, with either his back turned or facing forward. If he saw or heard the lemur attempting to retrieve any food, the human would take it away. Lemurs approached the boxes more often and more quickly when the human’s back was turned than when he was facing them. This suggests the lemurs are sensitive to what others can see. But when the human had his back turned, the lemurs didn’t show any preference for the silent box, even though attempting to open the noisy box resulted in the human turning around and taking the food away. In other words, lemurs were not sensitive to what others can hear.
So while lemurs are clever (and sneaky when someone’s back is turned), they don’t appear to be able to take the perspective of another individual.