Eysenck’s theory is known as the Biosocial Theory of Crime because it combines biological factors (genes, nervous system) with social experiences (parenting, environment). His work helped bridge the gap between nature (biology) and nurture (environment) in explaining crime.

Why Genetics Still Matters: Eysenck’s View
Most modern forensic psychologists believe that genetics plays only a minor role in crime. However, Eysenck argued that genetics has a significant influence.

He supported his argument using twin studies, noting that:

  • Monozygotic (MZ) twins share 100% of their genes
  • Dizygotic (DZ) twins share 50% of their genes

Studies showed higher similarities in criminal behavior among MZ twins than DZ twins.

 

Eysenck’s Biosocial Theory of Crime

Eysenck believed that criminal behavior results from a combination of:

  • Biological personality traits, AND
  • Poor socialization or weak conditioning during upbringing

These two factors together can create a higher risk for criminal behavior.

 

1. Three Personality Dimensions Linked to Crime

Eysenck argued that personality is made up of three main traits:

a. Extraversion (E)

Extroverts are:

  • Sociable
  • Impulsive
  • Risk-taking
  • Excited by stimulation

People high in extraversion often seek new and thrilling experiences, which can include rule-breaking or risky behavior.

b. Neuroticism (N)

Neurotic individuals:

  • Experience high anxiety
  • Have unstable emotions
  • React strongly to stress
  • May struggle with self-control

High neuroticism can make someone more likely to react impulsively or emotionally in stressful situations, increasing the risk of crime.

c. Psychoticism (P)

Psychoticism includes:

  • Aggressiveness
  • Hostility
  • Lack of empathy
  • Cold or cruel behavior

High psychoticism is strongly linked to antisocial, violent, or aggressive behaviors. According to Eysenck, people who score high on all three traits (E + N + P) are most likely to engage in criminal behavior.


2. Biological Basis of Personality
Eysenck believed these traits are rooted in the body's biological systems, especially the nervous system.

  • Extraversion: Extroverts have low cortical arousal, meaning their brains are less easily stimulated. Because of this, they seek excitement—sometimes in antisocial or dangerous ways.
  • Neuroticism: Linked to a highly reactive autonomic nervous system (ANS). This makes individuals easily stressed or emotionally unstable.
  • Psychoticism: Connected to high dopamine levels and other neurological imbalances. This may reduce empathy and increase aggression.

Eysenck argued that these biological differences influence how easily a person can learn social rules.

 

3. Socialization and Conditioning

Personality traits alone do not cause crime. Social environment also matters. Eysenck used ideas from Pavlov and Skinner to explain that:

  • Children learn right and wrong through conditioning (reward and punishment).
  • Good parenting strengthens a child’s conscience.
  • Poor socialization leads to weak conscience and low self-control.

Children who do not learn to feel guilt or fear punishment are more likely to commit crimes later.

 

4. Conditioning Difficulty in Criminals

Eysenck believed:

  • Extroverts learn slowly because they need strong stimulation to form habits.
  • Neurotic individuals are emotionally unstable, which disrupts learning.
  • People high in psychoticism lack empathy, making guilt-based conditioning hard.
  • This makes them less responsive to punishment, increasing the chance of criminal behavior.

 

5. Role of the Environment

Even with biological predispositions, the environment is crucial.

High-risk personality traits become dangerous mainly when paired with:

  • Poor parenting
  • Neglect or abuse
  • Criminal peer groups
  • Lack of supervision
  • Exposure to violence
  • Low-quality education

Eysenck stressed that biology creates vulnerability, but environment turns it into criminal behavior.

 

Criticisms of Eysenck’s Theory

Despite its influence, Eysenck’s theory has been criticized:

  1. It may oversimplify crime by focusing too much on personality.
  2. Social factors like poverty, education, and culture are equally important.
  3. Not all criminals score high on E, N, and P.
  4. Some research shows mixed results regarding twin studies.
  5. Many modern psychologists prefer multifactor theories that combine biology, psychology, and social factors.


References

  1. Eysenck, H. J. (1964). Crime and Personality. Routledge & Kegan Paul.
  2. Eysenck, H. J., & Gudjonsson, G. H. (1989). The Causes and Cures of Criminality. Springer-Verlag.
  3. Farrington, D. P., & Jolliffe, D. (2004). Personality and crime. In M. Tonry (Ed.), Crime and Justice: A Review of Research (Vol. 32, pp. 1–64). University of Chicago Press.
  4. Rushton, J. P., & Ankney, C. D. (1996). Brain size and cognitive ability. Psychonomic Bulletin & Review, 3(1), 21–36.
  5. Twin studies reference:
  6. Rhee, S. H., & Waldman, I. D. (2002). Genetic and environmental influences on antisocial behavior: A meta-analysis of twin and adoption studies. Psychological Bulletin, 128(3), 490–529.