Of Mice and Men and Empathy and Schadenfreude

Scientific American: Mind has an article in their most recent issue about our increasing recognition of empathy in non-human animals. It summarizes the history of the attribution of moralistic emotions to non-humans, with the implication that now more than ever scientists are recognizing homologues of empathy in animals like mice and primates. Primatologist and psychologist Frans B.M. de Waal plays an important role in that history, as he has long argued other animals are capable of morally driven actions. He suggests the capacity for such actions played an important role in the evolution of humans, as they promote concern for the lives of others in one’s social group and also help resolve conflicts within that group.

The Scientific American article discusses several studies done within the last couple of years that seem to support the empathetic animal view. For example, a group of researchers at McGill University took pairs of mice separated by Plexiglas and injected either one or both of them with an acetic acid that causes a stomachache. The stomachache results in a restless discomfort, commonly referred to as “writhing”. They found that a mouse injected with the acid demonstrated more writhing when its partner was also showing discomfort. Even more importantly, this effect only occurred between mice who were cage mates before the experiment, suggesting an empathetic concern between mice who were closely connected. Interestingly, it also only happened with male and female or female and female mice. When a male mouse saw another male mouse in discomfort, the observing mouse’s pain tolerance actually rose and he exhibited less distress. Since male mice have a high level of competition with other males (for mates), it could be they were suppressing their pain in order to demonstrate strength. It also may indicate they felt less empathy for their rival.

A group of researchers at the University of Zurich studied this same empathetic effect in humans. They used neuroimaging to observe participants’ brain activity as they watched another person in pain. Prior to this the participants had played a game with the subject experiencing the pain. In some situations the person in pain had worked cooperatively with the participant, in others they had treated the participant unfairly in the game. The study found that viewing the subject in pain who had been cooperative activated areas in the brain related to pain (an empathetic reaction). In females this area was also activated even when viewing the subject who had treated them unfairly. When men watched the person who had treated them unfairly experience pain, however, the pleasure centers in their brain were activated.

The similarities between the human study and the mouse study could be interpreted to suggest rivalry and competition among males is a powerful, and possibly universal, emotion. Evolutionarily men have had to face much more vicious competition among themselves in order to attain a mate. This is one suggested reason why males of a species often grow to be larger than females, as the larger male has had an evolutionary advantage in being able to physically defeat competitors for available mates. Thus, it makes sense that males have less empathy for a known competitor. Evolutionarily those who were too trusting and friendly (less inclined to compete/fight) probably would have been the first to be pushed to the side when a contest for an available mate began.