American Scientist

To the Editors:

In the online video Q&A with biologist Lee Dugatkin, he discusses an intriguing study on empathy in rats. In it, one rat was trapped and could get out only if another rat on the outside unlocked the trap’s door, and the outside rat usually helped. Why couldn’t this behavior be attributed instead to something like an evolved stress response to another rat’s distress signal? For instance, if the rat distress signal causes an increase in cortisol levels in the rat who hears it, perhaps it is simply trying to reduce its own discomfort level by helping, rather than out of any empathy toward its cagemate?

Ram Ramabhadran
Cary, NC

Dr. Dugatkin responds:

Let me answer in two different ways: First, behavioral ecologists distinguish between proximate and ultimate causation. It may be that selection has favored empathy in the rats, and the proximate mechanism is that an increase in stress hormone in the helpful rat when it sees another in distress triggers the action we call empathy. Second, we could better understand what is happening with respect to stress and empathy if another treatment were run similar to the one I discussed in the interview, but also with a way for the free rat to leave the experimental area. If the behavior was really empathy, it would stay and free the trapped rat; if the free rat left, that would suggest something other than empathy.