Genes + Behaviour

• what am i using for genes, genetic similarities and evolutionary explanations

  genes - brunner 1993

  
  

  genetic similarities - Brunner 1993/Coccaro 1997

  
  

  evolutionary explanations - Wedekind 1997
• what is a gene? What is the MAOA gene

  gene - made of DNA, contain proteins and are shape behaviour. Are hereditary.

  
  

  MAOA gene - makes an enzyme (MAOA) which breaks down neurotransmitters (e.g., sweeps up serotonin in the synaptic gap). SSRIs prevent the MAOA gene (reuptake of serotonin) which makes serotonin more available.

  
  

  - Link between MAOA and aggression, mutations found on X chromosome produce aggression in males. Females aren't affected as they have 2 X chromosomes and a male only has 1.

  
  

  MAOA-L - low variant, meaning less MAOA is produced, affecting neurotransmitters. MAOA-L causing serotonin to be the opposite.
• Brunner 1993


  Background - Dutch family with violence behaviour in the family. Found when females in the family got genetic counselling due to wanting to have children.

  
  

  Males - prone to aggression, outburst, fights, raping's of siblings, arson and hit and runs.

  - Disorder in the X chromosomes.

  
  

  Aim - investigate behaviour of 5 members in the Dutch family where males are affected by abnormal violent behaviour.

  
  

  Procedure - Genetic material from urine collected and tested.

  
  

  Findings - Found a defect where the X chromosome produced MAOA.

  
  

  - Creates loads of serotonin making the men resistant to its affects, therefore no working serotonin available.

  
  

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  case study.

  
  

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  reductionist, deterministic.

  small sample.
• critical thinking for MAOA?

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  Brunners research; mutation in MAOA causing violent behaviours.

  
  

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  Deterministic, is difficult to separate bio and environmental factors. Also other genes which lead to aggression.
• Coccaro 1997


  Aim - investigate MZ (100%) versus DZ (50%) twins.

  
  

  Procedure - Male US veterans, 182 MZ and 118 DZ. Examined for concordance of criminal behaviour.

  
  

  Aggression measured on a 75 questionnaire for hostile behaviour (Verbal, direct, indirect and irritability behaviour).

  
  

  Findings - physical assault, MZ had 50% and DZ had 19%. Verbal aggression, MZ 28% and DZ 7%

  
  

  Conc - supports genetic explanations of aggression, as identical twins were both more likely to have criminal behaviour than non-identical.

  
  

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  Large sample size.

  
  

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  Only males

  Does the questionnaire really measure aggression.
• critical thinking for twins/kinship studies

  Twins r a great way of researching genetic inheritance - MZ 100%.

  
  

  Environmental differences for twins as twins may not have the same environment (live with different parents, teachers, friends).

  
  

  Twins r not highly representative of general population - hard to generalise findings.
• What is an evolutionary explanation?

  Biological approach to study behaviour.

  
  

  Sexual selection - natural selection, mates chose partners.

  
  

  Intersexual - Competition between same sex by intimidation and defeating rivals (e.g., lions).

  
  

  Intrasexual - Competition to attract a mate by making themselves attractive (e.g., birds).
• Wedekind 1995


  Background - MHC gene enables immune system to recognise pathogens. The more diver MHC the better immune system. Smell MHC.

  
  

  Aim - Investigate if MHC would affect mate choices. Sample - 49 females + 44 males from Uni. All types for MHC.

  
  

  Procedure - men asked to wear t-shirt for 2 nights and left in an open bag in the day. Perfume-free detergent and soap. No deodorant/perfume, no smoking/drinking, eating spicy food and no sex.

  - Women ranked 7 t-shirts for smell. Happened 2 weeks after menstruation and used a nose spray.

  - 3 similar MHC, 3 different and 1 control (unworn). Scored for intensity and pleasantness.

  
  

  Results - scored more pleasant for dissimilar MHC genes = MHC influences mate choice.

  
  

  Conc - Prefer men with different immune system due to better health of potential babies. Evo explanation of mate selection.

  
  

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  Double-blind experiment. High controls.

  -Unrepresentative - same age. Small sample size. Cannot explain same-sex relationships, can't procreate naturally.
• Critical thinking for evolutionary explanations

  Darwins theory of natural selection - supporting evidence, survival of the fittest.

  
  

  Ignores social and cultural differences.

  
  

  Ignores mate preferences for same-sex.

  
  

  Deterministic.