Martha Stout is a clueless idiot who only has prison population as a control group. Rest of her "expertise" is nothing but assumptions and personal opinions.
To voice my opinion to the original question i would have to say that i *think* psychopathy is something that develops at some point. The human brain doesn't stop growing until your mid 20s, if i remember right, so wouldn't it be plausible to think that at some point in the brains development some anomaly appears? It's just something i've thought of. We know so little about our brains that i can safely say that no one knows the cause.
Hmm --- Good point, maybe people are born with the predispition to turn into a psychopath and environment tips them over the edge? Im guessing here as I know little of psychopathy.