The basis of the theory

1. Hans Eysenck set out his Criminal Personality Theories in 1964 and 1992, and explained the biology behind them in the Biological Basis of Personality (1967).
2. He argued that personality is largely inherited, so the nervous system you are born with sets how you behave.
3. Personality sits on three dimensions: extraversion, neuroticism and psychoticism.
4. Each dimension is a scale, so you sit somewhere along it.
5. Eysenck measured all three with the Eysenck Personality Questionnaire (EPQ), a self-report questionnaire made up of closed questions.
6. Score high on all three at once and you have what he called the criminal personality.

The three dimensions

1. Extraversion: how much company, excitement and risk you look for.
   1. A high scorer is sociable, impulsive and easily bored, and needs strong stimulation before anything feels interesting.
   2. A low scorer is an introvert: quiet, reserved and satisfied with far less going on.
2. Neuroticism: how strongly and how quickly your emotions react.
   1. A high scorer is anxious and moody, reacts hard to anything unpleasant, and takes a long time to settle again.
   2. A low scorer is emotionally stable, staying steady when a day goes badly.
3. Psychoticism: how cold, aggressive and unconcerned about other people you are.
   1. A high scorer is egocentric, hostile and short on empathy, so someone else's distress does not hold them back.
   2. A low scorer is warm and considerate, and is troubled by the thought of hurting anyone.

How each dimension links to crime

1. A high extraversion score means ordinary life feels flat, and crime is one of the few things that supplies enough excitement.
2. Extraverts are impulsive too, so you take the opportunity before you have weighed up what follows.
3. A high neuroticism score means a small setback produces a large reaction, so an argument turns into violence more readily.
4. The anger is also slow to fade, so it lasts long enough to be acted on.
5. A high psychoticism score takes away the brake that empathy usually provides, so the harm done to a victim is no deterrent.
6. Psychoticism also brings aggression and anti-social behaviour, which is why Eysenck tied it most closely to violent offending.

The criminal personality

1. The criminal personality is a combination of scores: high extraversion, high neuroticism and high psychoticism in the same person.
2. That combination makes a child difficult to condition, so the rules taught during childhood never fully stick.
3. Eysenck therefore predicted that prisoners would score higher on all three dimensions than the general population.
4. Heaven (1996) tested that prediction and found psychoticism the strongest predictor of self-reported delinquency.

Turning this into marks

1. When the criminal personality is asked for, name all three dimensions and say the scores are high at the same time, because naming one dimension is not the same point as naming the combination.
2. Name the dimension that fits the behaviour described, such as psychoticism for a cold act with no concern for the victim, because writing that the offender has a criminal personality does not secure the knowledge mark.
3. The mark most often lost is pairing a dimension with the wrong biology, such as putting the limbic system with extraversion rather than with neuroticism.