The term ‘personality’ is generally used to refer to relatively stable characteristics of a person that make their behaviour consistent across situations (but many other definitions are possible, depending on the approach being taken). Hans Eysenck (1964) put forward a theory of criminal behaviour based on a very influential theory of personality he had earlier devised. Although this theory is usually referred to as a personality theory of offending, it is important to appreciate that Eysenck’s theory conceives of criminal behaviour as the outcome of interactions between processes occurring at several different levels of explanation.

Eysenck’s theory suggests that crime arises from certain personality traits, which are biological in origin. Eysenck originally argued that the great variation between people’s personalities could be reduced to just two dimensions, which related to the underlying functioning of the individual’s nervous system. A person’s level of extraversion (E), neuroticism (N) can be measured using simple questionnaires such as the Eysenck Personality Questionnaire (EPQ). People with High E scores are sociable, active, lively and sensation seeking. Extraversion is determined by the overall level of arousal in the person’s Central Nervous System and Autonomic Nervous System. High E-scorers have a low level of arousal and therefore need more stimulation from their environment. People with high Neuroticism scores are anxious, depressed and react very strongly to aversive stimuli. The overall level of lability in the person’s CNS determines neuroticism. Where Neuroticism is low, the person has a stable, relatively unreactive nervous system whereas a high Neuroticism score results in a high degree of instability. Eysenck later added a third dimension of personality, psychoticism (P). People who score high on Psychoticism are aggressive, antisocial, cold