Sociopathy as spectrum disorder

I thought this was an interesting and straightforward explanation of what it means for something to be a spectrum disorder, particularly when we're talking about psychopathy, and the difficulties it introduces in terms of understanding and diagnosing individuals with that particular disorder. From a Wall Street Journal book review of the Wisdom of Psychopaths:

In one of her stand-up comedy routines, Ellen Degeneres riffs on those commercials for depression medications that begin: "Do you ever feel sad?" Ms. Degeneres's sardonic response: "Yes, I'm alive!" Everyone occasionally feels down, so mild depression might indeed be considered part and parcel of living. Recent research suggests that, like pain, it may be a way of coping with a bad situation by making a change. One problem with most psychological diagnostic tools, in fact, is that they attempt to squeeze into a well-defined box behaviors that are, on some level, not all that unusual. So the criteria lists grow and the diagnostic labels broaden into what psychologists call "spectrums."

"Psychopathy" is a spectrum personality disorder characterized by callousness, antisocial behavior, superficial charm, narcissism, grandiosity, a sense of entitlement, poor impulse control, and a lack of empathy or remorse. Popular culture invariably associates psychopathy with serial killers like Ted Bundy, who, after raping and murdering numerous women in the 1970s, boasted that "I'm the most cold-hearted son of a bitch you'll ever meet." Yet a slate of publications on psychopathy over the past two decades—from Robert Hare's path-breaking 1993 book "Without Conscience" to Simon Baron Cohen's 2011 "The Science of Evil"—reveals that about 1% to 3% of men in the general population could be classified as psychopaths. That is more than four million people in the United States alone, and they aren't all potential Ted Bundys.

The spectrum of psychopaths includes CEOs, surgeons, lawyers, salesmen, police officers and journalists. According to Kevin Dutton, the rest of us could learn a thing or two from many of them. In "The Wisdom of Psychopaths," the Cambridge University research psychologist notes that in many circumstances, such as in business, sports and other competitive enterprises, it is beneficial to be a little charming, tough-minded, impulsive, risk taking, courageous and even a bit socially manipulative. We have the makings of a dangerous psychopath only when that little bit of charm becomes devious manipulation; when self-confidence escalates to grandiosity; when occasional exaggeration morphs into pathological lying; when tough-mindedness devolves into cruelty; and when courageous risk taking slides into foolish impulsiveness. 

It's this sort of fuzziness that has led me to sometimes question whether I think that psychopathy is even a real thing. The difficulty is the heterogeneity in the psychopath population and fuzzy dividing lines between normal behavior (if perhaps a little extreme or rare), and disordered behavior. Of course there is evidence that psychopath brains look different, although the research is still very young. Still, I often have wondered what my brain would look like in one of these fMRI tests that some psychopath researchers perform, would it look normal or abnormal and in the same ways that psychopaths brains appear? I have often thought that my brain has to look abnormal, that there is no way I could have such a different way of thinking than everyone else without my brain reflecting that difference. But people say that is a common fallacy -- believing that you are different from everyone else. Then again, I probably prefer that error than to erroneously assume that everyone thinks exactly like me.