I do all kinds of roles - nerd, psycho, nerd, psycho, nerd, psycho - and occasionally someone kind of normal. It's weird, when I lived in Austin I was always cast as pretty normal people. But when I moved to Los Angeles I was immediately branded a psycho.
Education can counteract the natural tendency to do the wrong thing, but the inexorable succession of generations requires that the basis for this knowledge be constantly refreshed.