MASON LAB
Peggy Mason

Department of Neurobiology

University of Chicago
At the Mason Lab we are currently interested in the presence of empathy and helping behavior in rats. Recently we showed that rats help a cagemate who is trapped in a Plexiglass tube by deliberately, intentionally, and rapidly opening the door to the tube and liberating the cagemate. Rats do not open the door of either an empty restrainer or one containing a toy rat. This tells us that rats are not opening the door just because it is there (the "Mt. Everest" explanation), or because opening the door per se is rewarding (the motor mastery explanation). Furthermore, rats open the door to liberate a cagemate even when the setup is modified to prevent the two rats from playing together afterwards. This tells us that playing together (aka social reward) is not required to motivate helping. In conclusion, in the same vein as the duck test (if it looks like a duck, swims like a duck, and quacks like a duck, then it is probably a duck), the rats appear to motivated to help from an experience of empathy for the distress of the trapped rat. That being said, just as we can never know another's feelings (and are hard-pressed to accurately assess our own sometimes), we do not know how a rat experiences empathy, probably in some way that is unimaginable to humans.
In an effort to assess the value of empathic behavior, we tested rats who were devoted chocolate chip-eaters: when given a bowl of 20 chips, they ate more than 7 chocolate chips on average. These rats were placed in an arena with two restrainers, one containing 5 chocolate chips (less than a complete meal for these rats) and the other containing their trapped cagemate. We did not know what would happen. As it turned out, they opened both restrainers. And in no particular order! This finding told us that releasing a cagemate has a value on par with chocolate. Amazing! Finally, we noticed that the free rat did not eat all of the chocolate chips. So we went back and looked at videos to determine how many chocolate chips each rat ate. It turned out that the free rat ate only 3.5 chips on average, leaving 1.5 chips for his cagemate. This remarkable result told me that these rats are far more generous with their chocolate than my sister-in-law.