Roughly one in a hundred men (and many fewer women) are psychopaths. Most are not violent, but the ones who are commit nearly half of the most serious crimes, such as serial murder, serial rape, and the killing of police officers.28 Robert Hare, a leading researcher, defines psychopathy by two sets of features. There’s the unusual stuff that psychopaths do—impulsive antisocial behavior, beginning in childhood—and there are the moral emotions that psychopaths lack.
