Biological explanations of        aggressionNeural and hormonal mechanisms and             aggression                     ...
Essentially the argument is• Low levels of serotonin• High levels of dopamine• High levels of testosterone• Low levels of ...
Serotonin AO1• Thought to inhibit aggressive responses to  emotional stimuli• Low levels associated with increased  suscep...
Dopamine AO1• Link less well established than serotonin• Lavine (1997) – giving amphetamines (which  increase dopamine) in...
Testosterone AO1• Thought to act on areas of brain which control aggression  from young adulthood onwards• Thought to be p...
Cortisol AO1• Cortisol mediates other hormones such as  testosterone• High levels of cortisol inhibit testosterone and  so...
AO2 / AO3• Findings on serotonin replicated in vervet  monkeys (Raleigh et al (1991))• But issues of:  – extrapolation  – ...
AO2• Findings on serotonin also confirmed via  studies on anti-depressants• However Lenard (2008) cautions that  serotonin...
AO2• Causal role of dopamine unclear• Perhaps high levels of dopamine are an effect  rather than a cause?                 ...
AO2 / AO3• Evidence conflicting on role of testosterone• Studies showing positive correlation small  samples and self-repo...
AO2 clarification needed• Need to distinguish between aggression &  dominance• Issue relates to the internal validity if t...
AO2 issues• Gender bias evident as most research done on  males (animals and humans) whereas it is  known that there are d...
AO2 debates• Physiologically reductionistic to just consider  role of biochemistry alone• Also need to consider genetic fa...
AO2 application• Clearly a very important & useful area of  biopsychological research and theory as aggression  associated...
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Aggression monday

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Aggression monday

  1. 1. Biological explanations of aggressionNeural 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• Mann et al (1990) – drugs which reduced serotonin increased measures of hostility and aggression in males (but not females)• Scerbo & Raine (1993) – meta-analysis supports low level of serotonin but found no dopamine abnormalities 3
  4. 4. Dopamine AO1• Link less well established than serotonin• Lavine (1997) – giving amphetamines (which increase dopamine) increases aggressive behaviour• Buitelaar 2003) – 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• Dabbs et al (1987) – salivary testosterone levels were able to differentiate between violent and non-violent crimes• Lindman et al (1987) – aggressive behaviour in drunk males positively correlated with testosterone levels• Wagner et al (1979) castrated male mice showed decreased aggression which then increased when given testosterone again• Archer (1991) and Book et al (2001) – meta analyses with slightly different results• Wingfield et al (1990) – argue that testosterone levels rise in monogamous species in response to social challenges 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• Virkuunen (1985) found low levels of cortisol in habitual violent offenders; Tennes & Kreye (1985) same in violent schoolchildren 6
  7. 7. AO2 / AO3• Findings on serotonin replicated in vervet monkeys (Raleigh et al (1991))• But issues of: – extrapolation – Ethics 7
  8. 8. AO2• 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• Causal role of dopamine unclear• Perhaps high levels of dopamine are an effect rather than a cause? 9
  10. 10. AO2 / AO3• 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 clarification needed• Need to distinguish between aggression & dominance• Issue relates to the internal validity if the research as studies may be measuring different things, making comparison of results difficult 11
  12. 12. AO2 issues• 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 12
  13. 13. AO2 debates• Physiologically reductionistic 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 13
  14. 14. 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 14

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