Genetic factors

• What have twin studies suggested?

  Heritability accounts for 50% of variance in aggression
• Who did research into twin studies?

  Coccaro
• What percentage of monozygotic twins were verbally aggressive according to Coccaro?

  28%
• What percentage of dizygotic twins were verbally aggressive according to Coccaro?

  7%
• What do similarities between adopted child and adoptive parents suggest?

  Environmental influences in operation
• Who completed a meta-analysis of adoption studies?

  Rhee and Waldman
• What did Rhee and Waldman's meta-analysis into adoption studies find?

  Genetic influences accounted for 41% of variance in aggression
• What enzyme does the MAOA gene control production of?

  MAO-A
• What does the enzyme MAO-A regulate?

  Serotonin
• What is MAOA-L?

  Low activity MAOA
• What does MAOA-L result in?

  Low activity of MAO-A enzyme
• What is the nickname for MAOA?

  'Warrior' gene
• Who found MAOA-L was possessed by 56% of New Zealand men?

  Lea and Chambers
• Who found MAOA-L was possessed by 34% of Caucasians?

  Lea and Chambers
• Who compared MAOA-L in New Zealand men and Caucasians?

  Lea and Chambers
• What percentage of New Zealand men possessed MAOA-L according to Lea and Chambers?

  56%
• What percentage of Caucasians possessed MAOA-L according to Lea and Chambers?

  34%
• Who found aggressive men had abnormally low MAO-A and MAOA?

  Brunner
• What did Brunner find?

  Aggressive men had abnormally low MAO-A and MAOA
• What is gene-environment syndrome?

  MAO-L only related to aggression combined with trauma
• Who found an association between high aggression, MAOA-L and trauma?

  Frazzeto
• What did Frazzeto find?

  Association between high aggression, MAOA-L and trauma
• What is gene-environment syndrome sometimes described as?

  Diathesis-stress