Biological factors to Agression

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  • Biological Model to explain Aggression
    • Genetic influences
      • Brunner et al
        • Studied the defect of the MAOA gene
        • Supported by a Dutch family
          • they had a violent and aggressive manner
          • large proportion involved in serious crime eg rape and arson
          • found to have abnormally low levels of MAOA
          • case study cant be generalised
      • Sandberg 1961
        • Identified the 47XYY karyotype
        • Court-brown 1965-1967
          • found that in a sample of 314 patients those with XYY would have an increased likelihood of aggressive behaviour
          • longitudinal study
        • Deterministic
          • generalises inmates behaviour to the general public
          • people with a predisposition can seek treatment
        • Theilgaard concluded that xyy males may seen more aggressive but this doesn't mean that they're likely to perform more violent acts
      • Gene- environment interaction
        • Caspi et al
          • studied 500 children
          • those with low levels of MAOA were more likely to show aggressive behaviour if they had been mistreated as a child
            • ignores free will
          • If they'd had a nurturing childhood then they would channel their aggression into entrepreneurialism
          • by being deterministic we can predict the children's behaviour
      • Twin studies
        • Coccaro studied monozygotic twins
          • 50% concordance
            • strong but since they are genetically  identical if there isn't a 95% concordance they're must be more than biological factors
    • The idea that Aggression is simply the by-product of complex internal physiological processes
    • Biochemical Factors
      • Low levels of serotonin are associated with aggressive behaviour
      • Mann et al
        • Drugs that deplete serotonin have been shown to increase likelihood of aggression
        • gender bias, all male sample
      • Putman And Larson
        • violent criminals had remarkably lower levels of serotonin
        • deterministic, free will not taken into consideration
      • Vervet reduced serotonin levels in monkeys and found increase in aggression
        • difficult to generalise findings to a different species
    • Brain structure
      • variations in the brain structure can influence   aggression
        • in particular the hypothalamus and amygdala
      • Brad and Mountcastle
        • detached the higher and lower brain though lesioning in cats
          • due to the hypothalamus being affected aggression increased
        • difficult to generalise animal studies
      • Phineas Gage
        • Brain damage after a tamping iron went through his head
        • before he had a shroud quite, hard working personality
        • after he became a negative and aggression individual
        • detailed rich data that cant be generalised
        • reductionist
          • could be due to increase of headaches or decrease of memory frustrating him


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