Genetic explanations

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    Created by
    Solly Bussell

    Cards (10)

    • Twin study by Lange (1930)
      -        Lange (1930) investigate 13 identical twins and 17 non-identical twins, where one of each of the twins in each pair had served time in prison. Lange found that 10 of the identical twins but only 2 of the non-identical twins had a co-twin in prison.
      -        This suggests that identical twins (who share more genes than DZ twins) are more likely to both go to prison, showing that there could be a genetic component similar in criminals.
    • Twin study by Rain (1993)
      -        Additionally, Raine (1993) reviewed research on delinquent behaviour of twins and found a 52% concordance for MZ twins and 21% for DZ twins.
      -        However, the issue here is that if criminality was purely genetic then the concordance rate would be 100% for MZ twins, suggesting that there is an environmental component as well.
    • Kray twins
      -        Notorious London gangsters, boxers when young and violence runs in the family (grandad and older brother boxers).
    • Candidate genes
      One gene seems to be associated with violent crime:
      -        Low levels of the MAOA gene – MAOA gene is responsible for production of monoamine oxidase A.
      -        This breaks down neurotransmitters in the brain (e.g. serotonin, dopamine and noradrenaline). Low levels of MAOA have been linked to aggression and impulsive behaviour.
    • Mobley case and the MAOA gene
      -        Mobley’s statement that he should not be held responsible due to having a criminal gene was based on the research of Brunner (1978).
      -        Brunner studied 28 male members of a Dutch family (family study) who had histories of impulsive & violent criminal behaviour such as rape and attempted murder.
      -        They all shared a gene that led to low MAOA levels.
    • Moffit et al (1992)
      -        Conducted a longitudinal study on 442 New Zealander males recording which ps had been abused as children and what level of MAOA gene they had.
      -        Abuse + low activity MAOA = 9x more likely to be aggressive.
      -        Suggests there is an environmental and genetic component to aggression – interactionist approach.
    • Diathesis stress model – a better explanation?
      -        Diathesis – a predisposition or vulnerability
      o   Inherited predisposition to develop the disorder.
      -        +
      -        Stress – environmental stressors
      o   Prenatal trauma, childhood sexual or physical abuse, family conflict, significant life changes.
      -        Development of the disorder
      o   The stronger the diathesis, the less stress is necessary to produce the disorder.
    • -        One limitation is the methodological problems with twin studies of criminality.
      o   Lange’s research was poorly controlled (e.g. judgements of whether twin pairs were MZ or DZ based on appearance not DNA testing.)
      o   Also, most twins are reared in the same environment – so concordance rates may be due to shared learning experiences rather than genetics.
      o   Methodological issues such as confounding variables mean twin studies of criminality may lack internal validity.
    • -        One strength is the support for a diathesis-stress model of crime.
      o   Mednick et al. (1984) studied 13,000 Danish adoptees and criminality (operationalised as having at least one court conviction which was checked against police records).
      o   When neither biological nor adoptive parents had convictions, the percentage of adoptees that had a conviction was 13.5%. This rose to 20% when either of the biological parents did, and 24.5% when both adoptive parents and biological parents did.
    • -        A final limitation is that these explanations are also biologically determinist.
      o   The notion of a ‘criminal gene’ presents a dilemma. The legal system is based on the premise that criminals have personal and moral responsibility for their crimes.
      o   Only in extreme cases (e.g. diagnosis of mental illness) can someone claim that they were not acting entirely of their own free will.
      o   This raises ethical questions about what society does with people who are suspected of carrying criminal genes and who therefore have limited choice.
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