Neural explanations of aggression a2


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Neural explanations of aggression a2

  1. 1. Biological explanations of aggression Neural and hormonal mechanisms and aggression 1
  2. 2. Essentially the argument is • Low levels of serotonin • High levels of dopamine • High levels of testosterone • Low levels of cortisol ..... are associated with aggression 2
  3. 3. Serotonin AO1 • Thought to inhibit aggressive responses to emotional stimuli • Low levels associated with increased susceptibility to impulsive behaviour, aggression & violent suicide • Drugs which reduced serotonin increased measures of hostility and aggression in males (but not females) 3
  4. 4. Dopamine AO1 • Link less well established than serotonin • Giving amphetamines (which increase dopamine) increases aggressive behaviour • Giving anti-psychotics (which reduce dopamine) reduced aggressive behaviour in violent delinquents 4
  5. 5. Testosterone AO1 • Thought to act on areas of brain which control aggression from young adulthood onwards • Thought to be primary biochemical influence on aggression • Salivary testosterone levels were able to differentiate between violent and non-violent criminals and their crimes • Aggressive behaviour in drunken males also positively correlated with testosterone levels • Castrated male mice showed decreased aggression which then increased when given testosterone again 5
  6. 6. Cortisol AO1 • Cortisol mediates other hormones such as testosterone • High levels of cortisol inhibit testosterone and so inhibit aggression • So low levels of cortisol associated with increased aggression and studies have supported this. • Low levels of cortisol have been found in habitual violent offenders and also in violent schoolchildren 6
  7. 7. AO2 Serotonin • Findings on serotonin replicated in vervet monkeys (Raleigh et al (1991)) But issue of: – extrapolation • Meta-analysis (Scerbo 1993) supports low level of serotonin consistently found in aggressive children and adults but found no dopamine abnormalities • Bond – drugs (anti-depressants) that increase serotonin levels to reduce impulsive aggressive behaviour. 7
  8. 8. AO2 Serotonin • Findings on serotonin also confirmed via studies on anti-depressants • However Lenard (2008) cautions that serotonin not just linked to aggression: also to impulsive behaviour, depression, over-eating, alcohol abuse; violent suicide 8
  9. 9. AO2 Dopamine • Causal role of dopamine unclear • Perhaps high levels of dopamine are an effect rather than a cause because dopamine is released by performing aggressive acts, so aggression could be being rewarded in the brain. 9
  10. 10. AO2 Testosterone • Evidence conflicting on role of testosterone • Studies showing positive correlation small samples and self-report measures • Studies mainly correlational (eg. Wagner) so not possible to conclude that testosterone causes aggression • Also testosterone not always associated with negative characteristics: improved sporting and spatial abilities also been found 10
  11. 11. AO2 issues and debates • 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 • Also cultural bias as most research conducted in western countries 11
  12. 12. AO2 debates • Reductionist to just consider role of biochemistry alone • Also need to consider genetic factors and brain structure • Eg. Phineas Gage suffered brain injury and showed heightened levels of aggression • Also need to consider the contribution of environmental factors such as situational cues, temperature, noise, overcrowding, and the role of learning 12
  13. 13. AO2 application • 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 • If the role of biochemistry can be understood it can perhaps be treated or managed • 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 • Could perhaps be treated more ethically through diet (tryptophan) and exercise 13