genetic explanation

• MAOA gene (monamine oxidase A)

  nickname - Warrior gene

  produces enzyme MAOA which breaks down neurotransmitters in brain. eg. serotonin, dopamine and noradrenaline.

  2 variations

  1. MAOA-L
  2. MAOA-H
• MAOA-L

  low active form

  • less enzyme produced
  • less breakdown neurotransmitters eg. dopamine
  • higher levels of dopamine in PFC
• MAOA-H

  active form

  • sufficient enzyme MAOA produced
  • less aggressive behaviour
  • stable neurotransmitter levels
• impact of high dopamine on PFC


  increased impulsive aggression

  • excessive neural activity
  • disrupts control mechanisms
• statistical frequency MAOA-L gene

  1/3 western population

  2/3 when history of warfare
• MAOA-L gene frequency in men

  recessive

  • need two copies for expression
  • males have Y and X chromosomes
  • only one allele inherited
  • increased chance of inheritance of trait
  • females have 2 copies so may just be carriers - no expression of gene so MAOA enzyme levels stable
  • effect is mainly observed in males - make up majority of gene research
• AO3: Support McDerott et al (2009)


  78 male pts form university of California

  • vocal task + earned money
  • anonymous partner (fictitious) steal Money away
  • choose to punish individual that took money by forcing them to eat hot sauce - had to pay to do so
  • computer used to standardise
• AO3: weakness reductionist 


  Complex concept aggression genetic factors ignoring role of environment

  Phenotype both genes and environment

  Epistasis
• AO3: weakness (support for reductionist argument)

  Moffitt studied 1037 children (442 boys)

  Longitudinal study (26 years - from birth)

  By 11 36% maltreated (8% severely)

  • Defined by frequent changes in primary caregiver, rejection of mother, physical or sexual abuse
  • If abused had MAOA-L gene
  • Symptoms antisocial behaviour (fighting, bullying)
  • Adults subjects repeatedly violated law
  • Impulsive and aggressive
  • Environment does have an impact
• AO3: weakness deterministic 


  Large percentage (30% Europe) of males carry gene yet are not aggressive

  Ability to ignore and control this impulsive behaviour as belief wrong