Genetic Factors in Aggression

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  • Created on: 13-06-22 12:20
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  • Genetic Factors in Aggression
    • specific genes have been identified which have been shown to carry the aggression trait down to individuals.
      • MAOA gene, and one variant has been named the ‘warrior gene’ (low-activity form of the MAOA gene)
        • responsible for the production of the protein monoamine oxidase
          • This protein allows the metabolising of noradrenaline, serotonin and dopamine.
        • A dysfunction in this gene can result in these neurotransmitters not being broken down in the body
    • Twin studies
      • researchers compare the degree of similarity for a particular trait (such as aggression) between sets of monozygotic (MZ – share 100% of genes) and dizygotic (DZ – share 50% of genes) twins.
      • If the MZ twins are more alike in terms of behaviour, this supports a genetic approach as both types of twins share the same environment but MZ twins are genetically identical.
      • McGuffin and Gottesmann (1985) found a concordance rate of 87% for aggressive and antisocial behaviour for MZ twins compared with 72% for DZ twins.
    • Adoption studies
      • If a positive correlation is found between aggressive behaviour in adopted children and their biological parents, a genetic effect is implied.
      • If however a positive correlation in aggression is found between an adoptive child and its adoptive parents, an environmental effect is implied.
      • Hutchings and Mednick’s (1975) study of over 14,000 adoptions in Denmark found a significant number of adopted boys with criminal convictions had biological parents with criminal convictions. This provides support for a genetic effect.
      • P - There is a lot of research evidence to support the role of genetics in aggressive behaviour.
        • E - E For example, in Brunner (1993) study of a Dutch family, it was found that many of the male members behaved in a  aggressive manner and a large proportion had been involved in serious crimes of violence including **** and arson.
          • E - These men were found to have abnormally low levels of MAOA in their bodies and the low-activity variant of the MAOA gene.
            • L - This adds to the validity of the role of the MAOA gene in aggression.
      • P - Twin studies are used to support the genetic basis for aggression.
        • E - It is assumed that all twins share a similar upbringing and so the only difference between MZ and DZ twins is that MZ share the same genetic inheritance
          • E - However, many psychologists suggest that this is not true, MZ twins share a more similar upbringing than DZ twins as they can often be treated as the same person.
            • L  - This suggests that the higher concordance rate for MZ twins is a result of both genetics and environmental factors.
      • P - The genetic explanation for aggression is on the nature side of the nature nurture debates.
        • E - There are problems for this type of approach to explaining aggression as it focuses on nature and ignores the influence of nurture.
          • E - However, few would accept either as the sole cause of aggression and instead would adopt the diathesis-stress model.
            • L - When applied to aggression this would suggest that individuals may inherit a predisposition towards behaving in a more aggressive way but that environmental stressors and other factors are responsible for triggering the aggression.


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