Biological explanation

• Genetic influences

  Christiansen’s twin study into aggression, analysis of 3586 pairs of twins

  Twins of criminals more likely to become criminals as they share same genes however genes cannot be the only factor as the concordance rates are never 100%
• MAOA gene

  Enzyme involved in processing neurotransmitters including serotonin in the Brian

  Involved in aggression

  MAOA controls production of MAOA enzyme
• Strengths genetic:

  Twin studies

  Adoption studies

  Knockout studies suggest there is genetic element in aggression
• Limbic system

  Different areas of the brain including temporal lobe and the limbic system

  Amygdala has been found to have strong connection to aggression

  Animal studies- different parts of the amygdala either cause or reduce aggression

  Lesions in the amygdala found to cause cats to attack
• Amygdalotomy

  Procedure to discontet the amygdala from the rest of the brain studies shown patients experience loss of emotion and become less aggressive
• Serotonin

  Involved in aggression inhibit aggressive behaviour

  Low serotonin in the Brian linked to aggression

  Level of serotonin activity in the brain is measured by turnover
• Testosterone

  Androgen responsible for development of male behaviours also effect brain

  Statistically more in males therefore more violent behaviours

  Supported by Dabbs et al- criminals high testosterone however gender bias

  No cause and effect
• strengths of MAOA gene

  Brunner et al extended family in Netherlands, several male members showcased aggressive characteristics e.g violent crime

  identified fault in MAOA gene (deficient)