Eysenck (1947) proposed that personality could be represented along three dimensions:
Introversion-extraversion (E).
Neuroticism-stability (N).
Psychoticism-sociability (P).
The dimensions combine to form a variety of personality characteristics or types.
Eysenck suggested personality types are innate and based on the nervous system we inherit.
Extraverts have an underactive nervous system which means they seek excitement and engage in risk-taking.
Neurotic individuals have a high level of reactivity in the sympathetic nervous system - they respond quickly to situations of threat (fight or flight). This means they tend to be nervous, jumpy and overanxious so their behaviour is difficult to predict.
Psychotic individuals are suggested to have higher levels of testosterone - they are cold, unemotional and prone to aggression.
The criminal personality type is a combination:
Neurotics are unstable and therefore prone to overreact to situations of threat.
Extraverts seek more arousal and thus engage in dangerous activities.
Psychotics are aggressive and lacking empathy.
Eysenck saw offending behaviour as developmentally immature in that it is selfish and concerned with immediate gratification. Offenders are impatient and cannot wait for things.
During the process of socialisation children are taught to become more able to delay gratification and more socially orientated.
Eysenck believed that people with high E and N scores had nervous systems that made it difficult for them to learn (be conditioned).
As a result, they are less likely to learn anxiety responses to antisocial impulses and thus more likely to act antisocially.
The notion that personality can be measured is central to Eysenck's theory and useful in research. He developed the Eysenck Personality Questionnaire (EPQ), a psychological test that locates respondents along the E, N and P dimensions to determine their personality type.