In a follow-up on the Virginia Tech massacre, Newsweek reports that scientists who study criminal violence now believe that its roots “are equally planted in the biology of an individual, the psychology that reflects the interaction of innate traits and experiences, and the larger culture.” No single cause is deterministic. “It’s like a kid piling up a tower of blocks,” says Loyola University (Chicago) psychologist James Garbarino. “Eventually, it falls over. You could point to the final block and say, that one’s the cause. But it’s an accumulation of risk factors.”
Adrian Raine of the University of Southern California classifies killers as either reactive, those who murder in response to an insult or slight (real or imagined), or proactive, who kill to achieve a thought-out goal such as robbery. Rather than being manipulative psychopaths, says Louis Schlesinger, professor of forensic psychology at the John Jay College of Criminal Justice in New York, mass killers tend to be aggrieved, hurt, clinically depressed, socially isolated and, above all, paranoid. Rates of criminal violence are higher in mobile, heterogeneous societies where it is hard to put down roots and establish the social glue that binds people into a community, Newsweek says. The U.S., as a highly mobile society, is a nation of strangers.