genetic explanations of aggression

• genetic explanation?

  • aggression can be inherited though our genes
• research from twin studies?

  1. coccaro 1997
• coccaro 1997?

  • studied adult male mz & dz twins for aggressive behaviour - defined as direct physical assault
  • concordance rates for mz - 50% compared to 19% for dz twins
  • shows genetics do play role in aggression
  • those more genetically similar more likely to both be aggressive compared to those who are less genetically similar
• importance of twin studies?

  • looking at mz & dz twins allows us to see whether genetics does play role in aggression as mz twins share 100% genes & dz share 50%
  • so should be a higher concordance rates for aggression with mz twins
• research from adoption studies?

  1. mednick, gabrielli & hutchings 1987
• mednick, gabrielli & hutchings 1987?

  • carried out adoption study over 14000 participants
  • studied criminal records of all danish children adopted outside of biological family between 1924 & 1947
  • found having criminal biological father increaased childs risk of criminality & aggression more than having adoptive criminal father
  • shows genetics are factor influencing aggression
  • even when children not raised around aggressive dad they were still aggressive
  • suggests its innate & passed through genetic code
  • aggression roots lie within nature opposed to nurture
• importance of adoption studies?

  • looking at adoption studies allows us to look at children who have been adopted to see whether theyre more similar in terms of aggression to biological/adoptive parent
  • allows us to see whether genetics/environment plays more of a role in aggression
• what is MAOA gene?

  monoamine oxidase A - enzyme
• role of MAOA?

  • everyone has this gene & it codes for enzyme
  • found that mice who had this gene - extremely aggressive
  • enzyme breaks down serotonin in brain
  • high levels of serotonin causes aggression
• MAOA - L?

  faulty gene where less of the enzyme is made
• MAOA - H?

  faulty gene where more of the enzyme is made
• defective MAOA-L?

  • does not break down serotonin
  • higher amounts of serotonin in brain
  • increases aggression
• 2 * of genetic explanation?

  1. evidence from cases et al
  2. evidence from brunner
• 2 X of genetic explanation?

  1. contradictory social psychological cause
  2. biologically determinstic
• * evidence from cases et al 1995?

  • genetically engineered mice with MAOA-L
  • found that these had atypical aggression levels & behaviour
  • as adult mice showed increased levels of aggression
  • shows genetic influence
  • having faulty MAOA-L found to increase aggression due to failure of breaking down serotonin
  • so increased levels of serotonin so higher levels of aggression
  • further adds validity to explanation of role of genetics in aggressive behaviour
• contradictory evidence from cases et al?

  • more ethical to research on animals
  • too unethical to genetically modify humans to see effects of aggression
  • HOWEVER difficult to generalise findings to humans as our biology is much more complex
  • we have different intellectual/social/emotional experiences that affect behaviour
  • so cannot say that having faulty MAOA gene in humans will cause aggression same as mice
• * evidence form brunner 1993?

  • studied 28 male members of large dutch family who were repeatedly involved in aggressive/violen crime - rape/attempted murder/assault
  • found that all these men had MAOA-L gene
  • men with defective MAOA-L gene had increased levels of aggression meaning less of enzyme so increased levels of aggression
  • suggests genetics must play role in aggression
  • those who were most aggressive possessed faulty gene
• X contradictory social psychological cause?

  • slt would suggest that instead of being down to innate biological factors (nature) aggression can be explained in terms of environmental exposure (nurture)
  • believes its a learnt behaviour developed through observation & imitation of role models - providing theyre vicariously reinforced
  • ignores role of environment
  • would be best to look at aggression from more holistic pov & take into account more environmental factors - learning
• X biologically determinstic?

  • pro: cause & effect so empirical & used to develop practical applications to treat agg
  • allows us predict & prevent future behaviour eg identify whos at risk look at genetic code & give coping mechanisms to handle anger
  • con: implies that aggression caused by peoples genetics - out of our control/not in free will
  • potential socially sensitive - criminals being absolved - less responsible for crimes due to inherited characteristics
  • may upset/offend victims/families
  • feel removal of blame minimises significance of trauma & excuse/normalise aggression in others