Individuals who suffer from psychopathy usually show impulsive and antisocial behavior without accompanying anxiety or guilt, and are unable to form lasting and genuine personal relationships. McCord (1964) considered that the distinguishing features of psychopaths were lack of guilt and the inability to love. Buss (1966) listed psychopathic symptoms as the inability to control impulses or delay gratification, the failure to alter punishable behavior, pathological lying, asocial and antisocial behavior, thrill-seeking behavior, poor judgement of behavior, and rejection of authority, discipline and conventions. However, the lack of anxiety does not occur in all psychopaths. Those who lack anxiety have been called, by Karpman in 1941, "primary psychopaths", as distinct from "secondary" psychopaths who show a mixture of symptoms, including neurotic anxiety.
Although psychopaths seem unable to learn to avoid punishment, they do not show learning defect as such, nor do they suffer from memory defect as such. Psychopathic imperviousness to punishment was investigated directly by Painting in 1961. Gough (1948) suggested that psychopaths lack role-playing ability, that is to say, they are unable to regard themselves as part of society or to identify themselves with the viewpoint of other people. This suggestion was supported in a study by Reed and Cuadra who found that student nurses who tended to psychopathy were less able to predict how others would describe them.
Bowlby stressed early maternal deprivation as a source of psychopathy, quoting as evidence the frequency with which psychopaths were found to have been separated from their mother for six months or more in the first five years of their lives. It has also been demonstrated that institutionalized children were retarded socially and intellectually in comparison with fostered children. A psychopath's lack of empathy, his lack of awareness of behavioral cause and effect, and shallow personal relationships, all derive from his early rearing experiences; in particular, from a frequent change of milieu, a loveless environment, or very inconsistent environmental influence.