On an individual level terrorism has been explained in terms of psychopathology. Terrorists have demonstrated to show narcissistic personality traits (Lasch, 1979, Pearlstein, 1991). Jerrold Post (2004) argues that narcissistic and borderline personality disorders are found in terrorists and that mechanisms such as splitting and externalization are used by terrorists. Others such as Silke (2004) and Mastors and Deffenbaugh (2007) refute this view. Crenshaw (2004) showed that certain terrorist groups are actually careful in not enlisting those demonstrating pathology. The authoritarian personality theory has also been used as an explanation for terrorist behavior in individuals.