Biological expl of aggression


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Biological expl of aggression

  1. 1. Biological explanations of aggression<br />Neural and hormonal mechanisms and aggression<br />1<br />
  2. 2. Neural and Hormonal Mechanisms in Aggression<br />BATs<br />A01 -Outline biochemical influences on aggressive behaviour (hormones and neurotransmitters)<br /> - Outline how brain structure can affect aggressive behaviour<br />A02/3 Evaluate the effectiveness of biological explanations of the cause of aggression<br />P66-67<br />
  3. 3. Essentially the argument is<br />Low levels of serotonin<br />High levels of dopamine<br />High levels of testosterone<br />Low levels of cortisol<br />..... are associated with aggression<br />3<br />Neurotransmitters<br />hormones<br />
  4. 4. Serotonin AO1 <br />Thought to inhibit aggressive responses to emotional stimuli<br />Low levels associated with increased susceptibility to impulsive behaviour, aggression & violent suicide<br />Mann et al (1990) – drugs which reduced serotonin increased measures of hostility and aggression in males (but not females)<br />Scerbo & Raine (1993) – meta-analysis supports low level of serotonin but found no dopamine abnormalities<br />4<br />
  5. 5. Dopamine AO1 <br />Link less well established than serotonin<br />Lavine (1997) – giving amphetamines (which increase dopamine) increases aggressive behaviour<br />Buitelaar (2003) – giving anti-psychotics (which reduce dopamine) reduced aggressive behaviour in violent delinquents<br />5<br />
  6. 6. Testosterone AO1<br />Thought to act on areas of brain which control aggression from young adulthood onwards<br />Thought to be primary biochemical influence on aggression<br />Dabbs et al (1987) – salivary testosterone levels were able to differentiate between violent and non-violent crimes<br />Lindman et al (1987) – aggressive behaviour in drunk males positively correlated with testosterone levels<br />Wagner et al (1979) castrated male mice showed decreased aggression which then increased when given testosterone again<br />Archer (1991) and Book et al (2001) – meta analyses with weak but positive correlation between testosterone and aggression<br />Wingfield et al (1990) – argue that testosterone levels rise in monogamous species in response to social challenges<br />6<br />
  7. 7. Cortisol AO1 <br />Cortisol mediates other hormones such as testosterone<br />High levels of cortisol inhibit testosterone and so inhibit aggression<br />So low levels of cortisol associated with increased aggression<br />Virkuunen (1985) found low levels of cortisol in habitual violent offenders;<br />Tennes & Kreye (1985) same in violent schoolchildren<br />7<br />
  8. 8. AO2 / AO3<br />Findings on serotonin replicated in vervet monkeys (Raleigh et al (1991))<br />Tryptophan - increases serotonin levels in brain<br />Monkeys given high amounts of tryptophan – less aggressive, and vice versa<br />But issues of: <br />extrapolation<br />Ethics<br />8<br />
  9. 9. AO2<br />Findings on serotonin also confirmed via studies on anti-depressants<br />Bond (2005) – anti-depressant drugs that elevate Serotonin – reduce irritability and impulsive aggression<br />However Lenard (2008) cautions that serotonin not just linked to aggression: also to impulsive behaviour, depression, over-eating, alcohol abuse; violent suicide<br />9<br />
  10. 10. AO2<br />Causal role of dopamine unclear<br />Perhaps high levels of dopamine are an effect rather than a cause?<br />Couppis and Kennedy (2008) – mice - reward pathway in brain activated in response to an aggressive event – dopamine acts as a positive reinforcer.<br />Seek out aggressive encounter because they get a rewarding sensation from it.<br />10<br />
  11. 11. AO2 / AO3<br />Evidence conflicting on role of testosterone<br />Studies showing positive correlation - small samples, mostly males in prisons and self-report measures.<br />Studies mainly correlational (eg. Wagner) so not possible to conclude that testosterone causes aggression<br />Also testosterone not always associated with negative characteristics: improved sporting and spatial abilities also been found<br />11<br />
  12. 12. AO2 clarification needed<br />Mazur (1985) - Need to distinguish between aggression & dominance<br />Issue relates to the internal validity if the research as studies may be measuring different things, making comparison of results difficult<br />12<br />
  13. 13. AO2 issues<br />Gender bias evident as most research done on males (animals and humans) whereas it is known that there are differences between the genders in androgens<br />Also cultural bias as most research conducted in western countries<br />Animal research – can’t generalise to humans, ethics<br />13<br />
  14. 14. AO2 debates<br />Physiologically reductionistic to just consider role of biochemistry alone<br />Also need to consider genetic factors and brain structure <br />Eg. Phineas Gage suffered brain injury and showed heightened levels of aggression<br />Also need to consider the contribution of environmental factors such as situational cues, temperature, noise, overcrowding, and the role of learning<br />14<br />
  15. 15. AO2 application<br /><ul><li>Clearly a very important & useful area of biopsychological research and theory as aggression associated with many anti-social phenomena in society, eg. numerous forms of crime, violence
  16. 16. If the role of biochemistry can be understood it can perhaps be treated or managed
  17. 17. Although there would be ethical issues associated with giving people drugs simply to alleviate aggression (ie. for social control) , or male castration, even if it may be in the interests of multiple parties
  18. 18. Could perhaps be treated more ethically through diet (tryptophan) and exercise</li></ul>15<br />
  19. 19. Brain Structure and Aggression – A01<br />The amygdala is a seat of basic emotions<br />Stimulation with electrical impulses provokes rage<br />Lesioning (removing all or part of amygdala) provokes passivity<br />The prefrontal cortex is the seat of higher thinking and is linked to the amygdala<br />Damage causes impulsivity, immaturity – linked to aggression<br />
  20. 20. Animal Studies – 1930’s - removal of amygdala in aggressive animals – taming effect<br />LeDoux 1996 – sustained stimulation of amygdala in lab animals resulted in fear and rage<br />Human studies – Narabayashi et al (1972) – 43/51 patients who hd amygdala removed showed reduced aggression, Heimberger (1978) 48/58 patients showed improvement in aggressive behaviour<br />Temporal lobe epilepsy – Ashford (1980) – become aggressive to people close by<br />Parts of amygdala ‘wired’ to produce aggression, whereas prefontal cortex offers control of aggression<br />Brain Structure and Aggression – A02<br />
  21. 21. Case Study – Phineas Gage<br />Use the internet to investigate the case of Phineas Gage.<br />Describe what actually happened to him<br />Critically analyse the extent to which Gage’s case provides evidence for the argument that brain structure influences aggressive behaviour.<br />Explain your answer<br />
  22. 22. Brain Structure and Aggression – A03<br />Phineas Gage - case study – relying on notes made by Dr Harlow. Can’t generalise.<br />Animal research – can’t generalise. Humans more complex<br />Synoptic Points – <br />Animal Research - Does the end result of animal research justify the means?<br /><ul><li> Bateson 1986 – need to maintain a balance between advancing psychological understanding and keeping suffering to a minimum.</li>