Most articles on psychopaths hit the same points: psychopaths are not always killers or even hard-core criminals; they are charming and use their charm to fool people; they are master manipulators; they play on the sympathy of non-psychopaths; they are self-confident in the extreme; they lie with great ease and without shame; they feel no remorse for hurting anybody, ever, although they can fake remorse and most other emotions pretty well.
The article quotes from an early work on psychopathy, "The Mask of Sanity":
...Checkley told stories of men and women - successful businessmen and professionals as well as con men, bigamists, and petty thieves - who were friendly, charismatic, and often brilliant at manipulating other people. Yet alongside the glib charm of these psychopaths was a kind of moral blindness, an apparent incapacity to feel moral sentiments such as guilt and empathy. Cleckly marveled at the psychological ease with which psychopaths lied, cheated, and betrayed their friends and families.
While the charming, cunning psychopath has become a stock character in Hollywood films, Cleckley's psychopaths bear little resemblance to Hannibal Lecter. Often, they look more like the bunglers in "Fargo," whose elaborate criminal plans are derailed by spectacularly boneheaded decisions. Cleckley's psychopaths are not simply blind to the interests of others: in some ways, they are also blind to their own. They consistently underestimate the intelligence of other people, lying needlessly, even in circumstances where they are certain to be caught...
...Cleckley keeps returning to words like "mimicry" and "simulation" to emphasize how psychopaths can use moral and emotional language skillfully without really feeling its depth and resonance. And yet, like a pianist with a tin ear, the psychopath can perform for only so long before his deficiencies become apparent.
The music analogy comes up again, in another New Yorker article, this one from 2008 Suffering Souls (this article is available in its entirety for free) which looks at possible physical brain markers of psychopathy:
In another study, at the Bronx V.A. Medical Center, Hare, Joanne Intrator, and others found that psychopaths processed emotional words in a different part of the brain. Instead of showing activity in the limbic region, in the midbrain, which is the emotional-processing center, psychopaths showed activity only in the front of the brain, in the language center. Hare explained to me, “It was as if they could only understand emotions linguistically. They knew the words but not the music, as it were.The Mask of Sanity is available for free online.