You know that guy on the freeway? The one who cut you off in traffic the other day, and flashed a vulgar salute as he zoomed by? We used to think of this as "road rage" - reckless rudeness, plain and simple. Silly us. Now, thanks to a new study, we understand that the poor man may simply be the victim of a medical condition: intermittent explosive disorder (IED). The study, paid for in part by the National Institute of Mental Health, gives us the lowdown on this "seldom-studied mental illness." IED, it informs us, is characterized by "recurrent episodes...