info from the web...

The prevalence of APD [antisocial personality disorder] is estimated at three percent in males and one percent in females (American Psychiatric Association, 1994, p. 648), but the rate of psychopathy according to the Cleckley/Hare criteria is probably about one percent (Hare, 1993, p. 74).
________________________________________________________________

"Psychopaths are social predators who charm, manipulate and ruthlessly plow their way through life, leaving a broad trail of broken hearts, shattered expectations without the slightest sense of guilt or regret. Their bewildered victims desperately ask, 'Who are these people?'"

We often think of psychopaths as the disturbed criminals who capture headlines and crowd the nation's prisons. But not all psychopaths are killers. They are more likely to be men and women you know who move through life with supreme self-confidence -- but without a conscience. - Robert D Hare, "Without Conscience"
_________________________________________________________________

..the modern concept of 'psychopathy' was put forward by Hervey Cleckley (1903-1984) in his classic work The Mask of Sanity (1941). According to Cleckley's criteria a psychopath is an intelligent person characterised by poverty of emotions, who has no sense of shame, is superficially charming, is manipulative, who shows irresponsible behaviour, and is inadequately motivated. Interspersed in Cleckley's vivid clinical descriptions are phrases such as 'shrewdness and agility of mind,' 'talks entertainingly,' and 'exceptional charm' (Hare, 1993, p. 27).
____________________________________________________________________

Robert Hare remarks 'I can find no convincing evidence that psychopathy is the direct result of early social or environmental factors' (Hare, 1993, p. 170).
____________________________________________________________________

Is Psychopathy an Adaptation?