genetic explanations

• genetic factors - lagerspetz

  25 generations of mice. most aggressive to breed together, most docile to breed together. resulted in two different strains, one strain super aggressive, one super docile

  genetic and generational link in aggression

  • extrapolation, massive difference in generations for humans vs mice
• XYY genotype

  males may have an extra Y chromosome which is linked with stereotypical behaviours of dominance, competitiveness and aggression

  link between extra Y chromosome and aggression

  males - taller, lower IQ, behavioural problems
• XYY genotype research

  price et al

  males in hospitals for the criminally insane (temporal validity?). 28% of the patients had an extra Y chromosome compared to 0.1% of general population

  extra chromosome correlates with aggression

  therefore there may be a genetic origin, if there wasnt a link it would also be 0.1% in the hospital

  • not 100%, other factors
• MAOA gene definition

  gene

  monoamine oxidase A

  implicated in aggression, mice possessing gene extremely aggression

  affects NT
• MAOA and aggression

  MAOA metabolises neurotransmitters

  a dysfunction is the operation of this may lead to abnormal activity, impacting levels of NT in brain

  low activity (MAOA-L) produce less = aggression
• han brunner et al

  studied 28 males from dutch family repeatedly involved in impulsively aggressive violent criminal behaviour. men had abnormally low levels of MAOA in their brains

  • + family study with 28 different males, definitely different environments, large genetic sample
• MAOA gene and environment

  MAOA-L is only related to adult aggression in combination with early trauma - diathesis stress model!!

  interactionist approach/more holistic

  frazzetto et al - association between higher antisocial aggression and MAOA-L in males, only the case if significant trauma in the first 15y of life
• MAOA - evaluation. cases

  genetically engineered mice with low MAOA levels

  abnormal serotonin levels. adults demonstrated increased aggression and aggression in mating

  support for link between lower MAOA and aggression, as well as serotonin

  • animal study, ethics
• MAOA - evaluation. cannot account for all

  MAOA-L is only present in a third of men in the Western population

  rarely expressed in women

  cannot account for most cases of aggression, gender bias+androcentrism

  suggests another explanation