—Robert Schreib, Jr., Toms River, N.J.
Daniel Lametti, a neuroscientist at McGill University, responds: The Montreal apartment where I live is rife with evildoers—well, to be precise, there is at least one. A couple of weeks ago my newspaper, routinely delivered at 5 a.m. to my building’s lobby, disappeared before I could scurry out of bed to collect it. To thwart the criminal, I asked my deliveryman to hurl the paper onto my third-floor balcony (thankfully, he has a good arm).
Admittedly, newspaper theft ranks low on the scale of evil acts. Still, I wouldn’t steal a newspaper. I would like to think that under most circumstances I wouldn’t steal at all. But many people do, and many also commit crimes that are much more sinister.
Scientists would like to know the root causes of evil behavior: Is it a product of our genes or environment? The answer appears to involve a combination of the two.
Since the 1960s psychologists have found that children who were abused and neglected are more likely to commit crimes later in life. Even so, researchers noted that most youngsters who are mistreated do not grow up to be criminals. Now our genes come into the picture.
A 2002 study found that a particular variation of a gene predicted antisocial behavior in men who were mistreated as children. The gene controls whether we produce an enzyme called monoamine oxidase A (MAOA), which at low levels has been linked to aggression in mice. The researchers found that boys who were neglected and who possessed a variation of the gene that produced low levels of MAOA were more likely to develop antisocial personality disorder, commit crimes and grow up to have a violent disposition. But those living in a similar environment who produced more of the enzyme rarely developed these problems.