Psychopathy is a mental disorder characterized primarily by a lack of empathy and remorse, shallow emotions, egocentricity, and deceptiveness. Psychopaths are highly prone to antisocial behavior and abusive treatment of others, and are very disproportionately responsible for violent crime. Though lacking empathy and emotional depth, they often manage to pass themselves off as average individuals by feigning emotions and lying about their past.

Until the 1980s, the term formally referred to a personality disorder

Personality disorder

Personality disorders, formerly referred to as character disorders, are a class of personality types and behaviors. Personality disorders are noted on Axis II of the Diagnostic and Statistical Manual of Mental Disorders or DSM-IV-TR of the American Psychiatric Association.Personality disorders are...

 characterized by the inability to form human attachment and an abnormal lack of empathy

Empathy

Empathy is the capacity to recognize and, to some extent, share feelings that are being experienced by another sapient or semi-sapient being. Someone may need to have a certain amount of empathy before they are able to feel compassion. The English word was coined in 1909 by E.B...

, masked by an ability to appear outwardly normal.