Biological Theories for Aggression

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  • Biological Theories for Aggression
    • Hormonal Factors
      • Hormones are chemicals that regulate & control bodily functions, they interact with each other & with the nervous system to regulate short term processes such as responses to an external threat eg agg.
        • Testosterone is an androgen so called as it provides  male characteristics. The nature of the link between test & agg is not a simple bio 'cause & effect' mechanism, rather test makes it more likely that a particular behaviour willbe expressed.
          • High levels of test are associated with increased physical agg & this link is found in many species (rats, monkeys, fish & humans.
      • Wagner et al: shows if a male mouse is castrated agg tends to reduce, if the mouse then recieves testosterone agg increases.
      • Men have higher levels of test than women & tend to show more physical agg. Females tend to use indirect agg eg insults & isolating others.
        • The highest levels of violence are by men 15-25yrs, when test levels are highest.
        • Anderson & Bushman: found male murderers out number female murderers by 10:1.
        • Harisson et al: noted after giving test to 56 men aged 20-50, when giving a frustration inducing game, ag responses were significantly increased but this was not the same for entire sample.
      • Link between test & agg is complex, high levels of test can be more associated with competetiveness, sporty types & dominance (which may require agg)
        • Huston et al: found men with high test often perform well in competetive tasks but poorly in co-operative tasks.
      • Research supports a link with agg & test. But it is only correlation, there is a cause & effect issue.
    • Brain Systems
      • The limbic system is linked to the control of emotion. The amygdala in perticular is thought to influence agg.
      • There are studies to support this idea.
        • Potegal et al: stated when the amygdala is stimulated directly in hamsters, they show signs of preparing to attack.
        • Gage: had a tamping iron go through his left jaw, up behind his eye & into his brain. He survived but became agg after the incident & couldnt hold down a job.
          • Agg may be due to his anger for the acident happening to him, may think it is unfair to have happened.
          • Case study so it is a specific case meaning there is a generalisation issue.
        • Raine et al: used PET scans to compare brain activity of 41 convicted male murderers & 41 normal males, found that murderers had reduced activity in the prefrontal cortex & abnormal activity in the amygdala compared to control group.
      • The amygdal has be found to reduce agg behavour at the cost of losing emotion, the amygdala controls all emotion not just agg so ind diff occurs.
    • Neural Factors
      • Neurotransmitters are chemicals that allow impulses in 1 area of the brain to be transmitted to another area :. all behaviours are influenced by the actions of neur trans, 2 of which are believed to be particularly important in the control of agg.
        • The neur trans serotonin is involved in maintainign moods & suppressing impulsive behaviour. Low levels are associated with agg behaviour as people are less able to control agg impulses.
        • Dopamine is released in response to rewarding stimuli such as food. It has been thought that if agg behaviour is rewarding it increases levels of dop which makes the individual want to repeat behaviour.
      • There are many studies to support this factor.
        • Virkkunen et al: showed people with a history of criminal behaviour tend to have low levels of sero.
        • Bruner et al: found a particularly agg family had low levels of sero due to low level of an enzyme that breaks it down.
          • This is unrepresentative as it is just 1 family. Environmental factors may be what is effecting agg levels.
        • Davidson et al: found mice with nonfunctioning sero receptors showed increased agg.
        • Buitelaar: found that the use of dop antagonists have been used successfully to reduce agg.
      • The link between neural factors and agg is not clearly explained, especially with dop. Evidence supports a link but there is a cause & effect issue.
        • Davidson et al: stated that it may be that people who are frequently violent do not have strong urges to be agg but rather have weaker mechanisms for inhibiting agg.
      • There is great ind diff, people prone to depression often become depressed when sero levels are suddenly & temporarily lowered rather than becoming agg.
      • Differences in brain systems may be down to neural factors. Or the neural link may be down to the brain system.
        • Brain Systems
          • The limbic system is linked to the control of emotion. The amygdala in perticular is thought to influence agg.
          • There are studies to support this idea.
            • Potegal et al: stated when the amygdala is stimulated directly in hamsters, they show signs of preparing to attack.
            • Gage: had a tamping iron go through his left jaw, up behind his eye & into his brain. He survived but became agg after the incident & couldnt hold down a job.
              • Agg may be due to his anger for the acident happening to him, may think it is unfair to have happened.
              • Case study so it is a specific case meaning there is a generalisation issue.
            • Raine et al: used PET scans to compare brain activity of 41 convicted male murderers & 41 normal males, found that murderers had reduced activity in the prefrontal cortex & abnormal activity in the amygdala compared to control group.
          • The amygdal has be found to reduce agg behavour at the cost of losing emotion, the amygdala controls all emotion not just agg so ind diff occurs.
    • Genetic Factors
      • The relationship between genes & behaviour is a complex one. A substantial proportion of the human genone is dedicated to behaviour & more genes are expressed in the brain than any other organ.
      • Research into behavioural genetics has shown that most aspects of behaviour are influenced by heredity to some degree.
        • This info can be used for good eg improving psychiatric giagnosis but it can also be used to discriminate against people or provide 'qucik fixes' to social problems of violence in our society.
        • Research has tried to establish whether agg is down to inherited characteristics (nature) or environmental influences (nurtue) but it is still unclear.
      • Specific genes have been found which are involved in reducing the ability to control impulse behaviour leading to agg.
      • Selective breeding has enabled us to produce more agg strains eg dogs.
        • This has good P.A.
      • Mouse studies have manipulated specific genes for serotonin & found increased agg.
        • Animl studies have generalisation issues.
      • Mason & Frick: found MZ twins resemble each other more than DZ twins in agg & criminal behaviour. Adopted children resemble their bio parents in agg & criminal behaviour more than adoptive parents.
      • Cases et al: found some dutch family males with rare MAOA gene mutation had highagg however this could be affected by culture or gender.
      • Genes are only poorly associated with agg & there is an issue with the interaction between genes & environment.
  • Animals in research: generalisation issue.
  • Reductionist to biology & deterministic :. no free will.
    • Ethical issues & various implications of bio explanation eg coud or should we treat agg with drugs/surgery?
  • Social explanation contradicts.
  • Complex idea, cannot pinpoint 1 factor for bio factors & social plays a role.
    • Social explanation contradicts.

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