Biological Explanations for Aggression

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  • Biological Explanations for Aggression
    • Limbic System
      • Hippocamus
        • Stores LTM, responsible for comparing the current stimuli to past experiences
          • Bacardi et al
            • Multiple violent offenders show abnormal hippocampal functioning.
              • Unrepresentative sample - all prisoners
              • Correlative - cannot establish causation
      • Amygdala
        • Responsible for determining an emotional response
          • Pardini et al.
            • Connection between low amygdala volume in boys and later aggressive character traits in adulthood
              • Gender bias - all male sample could lead to androcentrism
          • Has been shown to work with the OFC - which is not part of the limbic system. This shows the theory may be incomplete.
            • OFC - Orbitofrontal Cortex
          • Removing the amygdala in monkeys results in loss of status in the group
            • Animal model, cannot be extrapolated
          • Gospic et al.
            • Pps playing the Ultimate Game (a bidding game involving rejection) had fewer aggressive responses when the amygdala was suppressed using a drug
              • Used fMRI (functional magnetic resonance imaging) to directly study inactivity - increasing validity
              • Drug also suppressed the entire ANS (autonomic nervous system) - which could have lead to another responsible region being suppressed
      • Hypothalamus
        • Responsible for regulating the release of hormones in response to aggressive stimuli
    • Neurotransmitters
      • Serotonin is thought to play an inhibitory role in the response to stimuli
        • Virkkunen
          • Compared the amount of serotonin breakdown fluid in the cerebrospinal fluid of impulsive non-violent offender and impulsive violent offenders.
            • Violent offenders had a lower concentration of serotonin breakdown fluid that non-violent
              • Correlative - cannot establish causation
        • Berman
          • Drugs that increased serotonin activity decreased frequency and severity of electric shocks in a Milgram-esque game
            • Use of a control group increases internal validity, allowing for a comparison
            • Ethics - protection from harm infringed due to electric shocks
    • Deterministic
      • Aggression is the result of biological factors beyond the control of the individual
    • Hormones
      • Testosterone is associated with high levels of aggression
        • Mehta and Joseph
          • Measured testosterone in men before and after they lost a competitive game
            • Pps were allowed to re-challenge the opponent. Those whose T had increased were more likely (73%) to re-challenge than those whose T had decreased (22%)
    • Genes
      • Twins
        • Coccaro et al.
          • In adult male twins, the concordance for direct physical aggression was 50% for MZ (monozygotic) twins and 19% for DZ (dizygotic) twins
            • Not 100% - other factors must be in play
            • Adult model - there is significant evidence to suggest that the genome changes over the course of someone's life, meaning at birth concordance of genes could have been higher
            • Environmental factors - MZ twins tend to be treated the same way due to being identical whereas DZ twins are distinguishable and will be treated differently
      • MAOA
        • The MAOA gene codes for the creation of an enzyme that breaks down neurotransmitters after impulses are fired.
        • A variant of this gene lowers the activity of the MAOA enzyme, which is associated with aggression
          • Brunner
            • 28 men in a large Dutch family with a history of violent, impulsive crime all had the gene variant
              • One family, cannot generalise
              • Correlation not causation
          • Frazetto et al.
            • Diathesis-Stress may play more of a role
            • Found that the MAOA variant must be accompanied by trauma in the first 15 years of life in order to create aggression

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