Genetic theories of criminality

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  • Genetic theories of criminality
    • Assumes criminality is inherited and/or a result of genetic abnormalities
    • Twin studies
      • Twin studies are conducted to allow us to examine the extent a specific trait such as criminality, is a result of genes or the environment
        • Monozygotic twins are identical, and come from the same egg. Dizygotic twins are non identical and come from two separate eggs
        • Concordance rates are the probability that a pair of individuals will both have a certain characteristic.
      • CHRISTIANSEN (1977)
        • He examined over 3,500 twin pairs from Denmark. Studied both monozygotic and dizygotic
          • Found that concordance rates in MZ twins was 35%. For DZ twins it was 15%
            • The more genetically similar, the more similar they were in criminal behaviour
    • Family studies
      • Family studies are conducted to see if behaviour is inherited. The findings could be used to help predict behaviour and see the degree of risk a child may turn criminal
      • Brunner (1993)
        • Investigated a family in the Netherlands who had a high number of males involved in crime
          • Found that they had a genetic mutation of the X chromosome
            • This resulted in a deficiency in the MAOA enzyme which helps regulate neurotransmitters like seratonin
              • This became known as the warrior gene as it has been linked to aggression
      • Jacobs XYY (1965)
        • XYY syndrome is when a male has an extra Y chromosome
          • Jacobs studied inmates of a Scottish maximum security hospital.
            • 1 in 28 of the men had the extra Y chromosome. They were described as "dangerous, violent criminals"
    • Adoption Studies
      • Adoption studies are conducted to help with our understanding of whether behaviour is due to nature or nurture
        • Crowe (1972)
          • Crowe compared adopted children who's biological mother had a criminal record with adopted children who's biological mother did not.
            • 50% of children who's biological mother had a criminal record also had one by the age of 18
              • Only 5% of the adopted children who's biological mother did not have a criminal record had one by the time there were 18


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