A new study suggests that rodents are far more altruistic than previously thought. In the new study, Mason, Bartal and University of Chicago colleague Jean Decety placed pairs of rats in Plexiglass pens. One rat was trapped in a cage in the middle of the pen, whereas the other rat was free to run around. Most free rats circled their imprisoned peer, gnawing at the cage and sticking their paws, noses and whiskers through any openings.
In this first set of experiments, most rats seemed quite willing to help their peers, but Mason wanted to give them a tougher test. She placed rats in a Plexiglass pen with two cages: in one was another rat, in the other was a pile of five milk chocolate chips—a favorite snack of these particular rodents. The unrestricted rats could easily have eaten the chocolate themselves before freeing their peers or been so distracted by the sweets that they would neglect their imprisoned friends. Instead, most of the rats opened both cages and shared in the chocolate chip feast.