genetic explanation

• What is the XYY Genotype?

  A genetic condition characterised by the presence of two male Y chromosomes
• How is the XYY gene associated with aggression?

  Associated with an increased tendency towards aggression
• What are XYY men referred to as?

  'super males
• What is the prevalence of XYY in the general population?

  1 per 1,000
• What is the prevalence of XYY in the prison population?

  15 per 1,000
• What does MAOA gene affect the production of?

  The enzyme monoamine oxidase
• What does monoamine oxidase do?

  Allows the metabolising of noradrenaline, serotonin and dopamine
• Which variant of MAOA has been linked to aggression?

  Low activity
• What has the low activity variant of MAOA gene been called?

  The 'warrior gene
• What does the low activity variant of MAOA gene result in?

  Noradrenaline, serotonin and dopamine not being broken down in the body
• What happens if adrenaline isn't metabloised?

  Hypersensitivity in the fight or flight response
• What does hypersensitivity in the fight or flight response lead to?


  May overreact to an external stimulus and perceive a threat where one does not exist
• What happens if dopamine isn't metabolised?

  Increased levels of dopamine are linked to aggression
• What happens if serotonin isn't metabolised?

  Reduces its inhibitory effect on other neurotransmitters
• Low activity of serotonin has been linked to what?

  A reduction of control over impulsive behaviour
• Who conducted opposing evidence into the XYY gene?

  Theilgaard (1984)
• What did Theilgaard (1984) do?

  Studied XY men and XYY men
• What did Theilgaard (1984) find?

  found that XYY can cause increase in height but not aggression
• Who conducted supporting evidence into the MAOA gene?

  Brunner (1993)
• What did Brunner (1993) do?

  A study on the males in a large family from the Netherlands, whose members were displaying abnormal violent behaviour.
• What did Brunner (1993) find?

  Five of the males were found to have the dysfunctional version of the MAOA gene. The unaffected male members within the family did not carry this mutation.
• what did Brown-Court discover

  314 patients had the XXY chromosome and put forward the view that they should remain hospitalised given their increased likelihood of aggression
• who put forward opposing evidence for the Maoa gene

  boys with MAOA-L were significantly more likely to grow up to exhibit antisocial behaviour only if they had been maltreated -diathesis stress model? reductionist?
• what have twin studies found about aggression

  when studying concordance rates of aggression in twins they found that it indicates aggression has a genetic element
• who conducted experiment on genetic inheritance of of aggression in twins

  Coccaro
• what did coccaro do

  compared mono and di twins and were examined for the concordance rates of criminal behaviour
• what did coccaro find

  Aggression (operationalised as physical assault) had 50% concordance in MZ twins + 19% in DZ twins
• who conducted studies with adoption

  Hutchings and Mednick
• what did Hutchings and Mednick do

  studies over 14000 adoptions in denmark
• what did Hutchings and Mednick find

  many of the boys with criminal convictions also had biological parents with criminal conviction
• what is an evaluation point of adoption and twin studies

  a lot of studies use self assessment, social desirability bias? subjectivity? reduces validity