A2 Psychology AQA Unit 3 Aggression

A2 Psychology AQA Unit 3 Aggression

1. GENETICS

   • Aggressive people have a faulty gene responsible for producing MAOA
     • MAOA regulates the metabolism of serotonin in the brain
       • Low levels of serotonin lead to impulsive and aggressive behavior
         • However, research using 500 male children has found that children with the low producing MAOA gene were only more likely to exhibit antisocial behavior if they had been maltreated (Caspi et al. (2002)
           • This shows a gene-environment interaction is very important (diathesis-stress model)
   • COCARRO ET AL. (1997)
     • 182 MZ and 118 DZ adults
       • Genes responsible for 50% of individual differences in direct aggression - towards others (50% concordance rate)
         • Also found, environment responsible for 70% of individual differences in verbal aggression
   • HUTCHINGS AND MEDNICK (1973) Danish study
     • Study of 14,000 adoptees
       • Correlation between biological fathers and son of convictions for criminal violence
         • Where biological father had a criminal record for violence, their child ran 50% risk of acquiring one by 18, compared with only 5% risk where biological father had no criminal conviction
   • MILES AND CAREY (1997) Meta-analysis
     • 24 twin and adoption studies
       • Genetic are responsible for 50% of the variance in aggression
   • YOUNG ET AL. (2002)
     • Mice were selectively bred to 'knock out' the gene responsible for MAOA production for
       • Extremely aggressive towards other mice and displayed a dramatic sexual persistence towards females
   • CASPI et al. (2002)
     • Studies 500 male students
       • Discovered variant of the gene associated with high levels of the gene responsible for producing MAOA
         • Those with low levels of MAOA were significantly more likely to grow up to exhibit antisocial behaviour but only if they had been maltreated

2. NEURAL AND HORMONAL

   • Neurotransmitters
     • Low levels of serotonin mean aggressive people tend to respond more rashly and harshly to emotional stimuli
     • Individuals may actively seek out aggressive encounters because of the rewarding sensation of high dopamine levels
     • SCERBO & RAINE (1993)
       • Meta-analysis of studies concluded antisocial children and adults had higher levels of serotonin
         • However, found no significant correlation in changes in dopamine level
           • Only partially explains the explanation
     • MANN ET AL. (1990)
       • Administered dexfenfluramine to 35 healthy adults (depletes serotonin)
         • Participants filled in questionnaires which assessed hostility and aggression. Levels found to increase in males, bot not females
           • Low sample size - lacks population validity
           • Possibility to lie on questionnaires
   • Hormones
     • High levels of testosterone have been found to correlate with aggression
     • Likely linked to low levels of cortisol, as this hormone inhibits the production of testesterone
     • DABBS ET AL. (1995)
       • Measured testosterone in saliva of 692 adult male prisoners
         • Found higher levels in rapists and violent offenders than in burglars and thieves (less aggressive convictions)
           • Large sample size, high validity, can be generalised
             • Howvevr, only on male prisoners
     • POPE ET AL. (2000)
       • Groups of men given testosterone or placebo over 6 week period
         • Then paired with a fictitious participant and told they could reduce the amount of cash received by the participant by pushing a button
           • Testosterone group pushed the button significantly more
             • High level of control - laboratory study
               • Ethicsl issues - deception
     • MCBURNETT ET AL. (2000)
       • 4 year study of boys with behavioral problems
         • Those with low cortisol: Anti social behavior began earlier and 3 times as many aggressive symptoms
           • Difficult to keep contact with particionats for the length of time
             • Only conducted on boys, difficult to generalize to girls
   • There is contradictory research evidence on neurotransmitter role in aggression
     • Both increases and decreases in serotonin activity have been linked to increased aggression
   • The majority of studies into the link between testosterone and aggression have been conducted on men. There is a significant gender bias n the research, and it is therefore difficult to generalise the conclusions from the studies done on males to the female population. This is because, potentially, women have slightly different underlying genetics and socialistion
     • This issue can be demonstrated by one of the few studies that has looked into women, conducted by Eisenegger et al. (2001) that found high testosterone levels in women actually correlated with low aggression