The research team led by Tania Singer, at UCL, asked volunteers to play a game with employees of the lab, secretly instructing the employees to play either fairly or unfairly. Afterward, the scientists measured brain activity in the same volunteers under quite different circumstances: looking on as their former game opponents were subjected to various degrees of pain. In both male and female volunteers, the brain areas that signal pain became active, giving neural evidence of their empathy with the others’ pain. Strikingly, however, that empathy did not appear to extend to all the players who were hurting. When unfair-playing employees were seen experiencing pain, the male volunteers – but not the females – showed significantly less empathetic brain activity than when they saw fair-players perceiving pain. Thus, females showed the brain responses of empathy regardless of their moral judgment of the employees’ social behavior, whereas the men’s brain responses were conditional upon how fairly the employee had played.
That’s from The Neuroscience of Fair Play, by Donald Pfaff. The book should really be called “The Molecules of Morality,” since much of the discussion revolves around the role of various brain hormones (like oxytocin and vasopressin) in regulating human behavior. It’s a clear and lucid introduction to the field, even if I worry that the “oxytocin = love/trust/attachment” story is bound to get a lot more complicated.