This isn't news to me, but I like having a handy little article that I can send to people to point to and say "See? It's not just me. Science."
Science! It's not a real explanation, so much as a curiosity-stopper. You don't actually know anything more than you knew before I said the magic word. But you turn away, satisfied that nothing unusual is going on.
Written by a neuroscientist, it gives a thorough, scientifically tested framework for classifying traits of personality and changing them.