Telling Right From Wrong

Are some people bad because of their genes? Or because of an unfavorable upbringing? In recent years, the highly charged nature-vs.-nurture debate has surged back and forth without resolution. Now neuroscientists at the University of Iowa report intriguing evidence that neither genes nor upbringing may be the full explanation.

In the latest Nature Neuroscience, Dr. Antonio Damasio and his colleagues describe two young adults--a woman, 20, and a man, 23--who suffered early injuries to the prefrontal cortex, an area of the brain thought to serve as a kind of moral and social compass. The woman was run over by a car at 15 months; the man had a brain tumor removed at three months. Both made remarkable recoveries until they began to display serious behavioral problems.

Though both came from "good" homes, the girl lied, shoplifted, ran away from home and had no friends. An indifferent student, the boy swung between anger and lethargy. He ate to the point of obesity, couldn't hold a job, engaged in petty thievery, lied and also had no friends.

Damasio knows that adults with injuries to the prefrontal cortex develop very similar problems, often quitting their jobs, gambling away their savings and alienating family and friends. But in those cases, the people still seem to know the difference between right and wrong. By contrast, the two young adults never seemed to have developed a moral compass in the first place.

Their cases could, of course, be just medical oddities, but Damasio thinks otherwise. In his view, more subtle malfunctions of the prefrontal cortex, including physical or psychological trauma caused by childhood abuse, could be at the root of many troubled lives. If so, his two cases may explain a much wider societal problem that cries out for medical and psychological intervention.