Those Empathic Rats: Motivation and a Missing Measure

N.B.-- 12/14: I may have been wrong in my remarks here. Read the comments that follow, too.

On NPR, in blogs, in Science, in the New York Times' Science Times, everybody’s talking about a study reported by Peggy Mason of the University of Chicago and her co-authors. To people’s surprise, these researchers reported that rats would make a lot of effort to open a door that would release a confined fellow-rat, and they would do this even if the other rat was beyond a barrier and they could not play together. The free rats opened the door to release the confined one as much as they opened it to get chocolate chips.

Quite a few people have interpreted the free rat’s “jailbreak” behavior as due to empathy with the confined one-- that the free rat feels unhappy when he or she perceives the displeasure of the rat in the container, and feels better when the other rat is happier, just as many human beings feel relieved when they can help a suffering human. Others have asked whether there might be an alternative explanation. Could it be that the confined rat squeals in distress, at frequencies higher than humans can hear, and that the free rat works to get rid of that awful squeaking? No, it seems that most of the confined rats did not squeal, so that explanation cannot replace empathy as a reason for the behavior.

Several bloggers have been extremely interested in the implications of the idea that rats, like humans, might be motivated by empathy. Some have argued that this is a blow for human exceptionalism and suggests that humans are not qualitatively different from other species.

Before we go to town on the implications of the study, though, it might be a good idea to consider whether avoidance of painful squeals is the only explanatory alternative to rat empathy. (I have no objection to the idea that rats could have empathic responses, but I don’t like conclusion-jumping.) As far as I can see, the study did not include an important comparison measure that might offer a better explanation for the behavior: it did not test what the rats did if given the chance to open a container with nothing in it. As a result, it confounded opening containers in and of itself, with opening containers and getting an outcome that might be gratifying.

Why would a rat open a container “for nothing”? Why, for that matter, do toddlers carry large objects from place to place? Why does my cat meow outside every closed door until it is opened, then walk away without going in? Why do I shut a drawer left open by a 16th of an inch? All of these actions can be considered in terms of mastery motivation, a tendency found across species and across ages to behave in ways that control the environment, even when there is no evident advantage to exerting that kind of control.

Jerome Kagan, in his book Three seductive ideas, criticized what he called the “pleasure principle”, the idea that all behavior comes down to a search for gratification of needs. Of course much of what any organism does is associated with needs and satisfactions, but this does not mean that everything is motivated in exactly the same way. Like humans, rats may do things simply in order to do them, and this is probably especially true of lab rats in cages. They ordinarily exist in a boring environment that offers them none of the usual activities of their species’ normal habitats. They don’t get to tunnel, gnaw different kinds of things (they do gnaw at the cage’s wire mesh), catch and eat bugs or other small animals, court, or mate. Occasionally some clumsy student reaches in to pick them up the wrong way and they get to bite that person, but that’s about the sum of the drama in their lives. Now, in the study we’re discussing, they get an opportunity to deal with exciting new technology. It’s time to be motivated by the need for mastery of the environment... maybe. I’m not saying that mastery motivation explains it all-- just that there is at least one alternative to interpreting the free rat’s behavior as empathic in nature.

The NPR “Science Friday” discussion of the study alluded to maternal care as the foundation of empathy, and so it may be, but anyone who has observed a breeding colony of lab rats is not likely to think of these animals as displaying much empathy. When babies get out of the nest, get cold, and squeal, the mother retrieves them and brings them back in, but that’s about it. They can find nipples and latch on by themselves (and they are so tiny, pink and hairless that you can actually see the bubble of milk in each stomach). The mother doesn’t do much more except lick them clean. And let one be sick, or injured, or die-- well, Mom tidies up the nest by eating the pup. If a male rat gets into the area, he’ll often tidy up further by eating the live pups too.

Could be that assisting in the jailbreak has some cause other than empathy.