Simon Baron-Cohen, professor of psychology at Cambridge Univ and author of the extreme male theory of autism (described in chap. 3 of my book), has written a new book, “The Science of Evil”. He is interested in understanding human cruelty, and wishes to replace the term “evil” with “the absence of empathy”. This is useful as “evil” is most often used in a religious context while empathy can be measured and quantified, and brain circuits mediating empathy can even be examined with functional brain imaging (fMRI). “Empathy” also lacks a definitive link with cruelty. For instance, subjects with autism spectrum disorder can display a lack of empathy by failing to read the social signals that people emit. This relates to the “theory of mind”, which is defined as the ability to attribute a mental state to oneself or to others, and autistic subjects can have deficits in this area. But this would certainly not be portrayed as cruelty or evil.
There are a few fascinating studies indicating that mice and rats can also display empathy. This could be useful in further characterizing rodent models of autistic features (chap. 6). In one test, a mouse becomes more sensitive to heat if it is watching another mouse in pain (Langford et al., 2006). In different test, a mouse watches (behind a transparent barrier) another mouse being socially defeated (an aggressor bullied him into a corner). The witness mouse subsequently displays signs of stress and even depression: his corticosteroid levels go up dramatically, his social interactions with other mice decrease, and he is more anxious (see chap. 6 for these and other assays of depression). These data were presented by Carlos Bolamos-Guzman at a meeting last year, but I have not seen a publication on this yet. Another, rather mysterious example comes from a new study of “bystander stress” in pregnant rats (Mychasiuk et al., 2011). In this experiment, a pregnant rat is not stressed herself, but she is housed with another female who is exposed to daily stress (removed from the cage and placed on an elevated table under bright lights for 30 min). In a control experiment, a pregnant rat is housed with another female who is removed from their cage but not stressed. The interesting result is that the offspring of the pregnant rat whose cage mate was stressed display some subtle changes in neuron structure 3 weeks after birth. Note that the pregnant rat does not actually see her cage mate being put in a stressful situation. The mechanism of this effect is completely unknown, but it suggests a form of empathy that alters fetal brain development.