Genetic Factors in Aggression

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Is Aggression Inherited?

  • nature and nurture
  • twin and adoption studies
  • Twin Studies
  • monozygotic and dizygotic twins help to determine whether the cause is down to genes.
  • Most twin studies have focused on criminal behaviour but one has studid aggressive behaviour using adult twin pairs to find that nearly 50% of variance in direct aggressive behaviour could be down to genetic factors.
  • Adoption Studies
  • If a positive correlation is found between aggressive behaviour in adopted children and their biological parents, genetic effect is implied.
  • 14,000 adoptions were studied in Denmark to find a signifcant number of adopted boys with criminal convictions had biological parents with criminal convictions which provided evidence for a genetic affect.
  • A Gene for Aggression?
  • The Role of MAOA
  • gene responsible for producing a protein called MAOA has been associated with aggressive behaviour.
  • MAOA regulates the metabolism of seretonin in the brain and low levels are connected with impulsive and aggressive behaviour. 
  • Gene-Environmental Interaction
  • A study linking MAOA to aggressive behaviour involved 500 male children.
  • A variant of the gene associated with high levels of MAOA was discovered.
  • Those with low levels were more likely to group up to exhibit antisocial behaviour but only if they were maltreated as children. 
  • Interaction between genes and environment determines behaviours.
  • Genetics and Violent Crime
  • Researchers do not say there is a gene for violent crime but it is claimed that an inherited temperamental or personality characteristic places some individuals more at risk


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