Describe and Evaluate biological explanations for aggression

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Psychology Unit 3

Describe and Evaluate biological explanations for aggression


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Biological explanations

  • Many studies over the last 30 years have reported high levels of testosterone in violent criminals
  • Advances in Neuroscience have resulted in attention to the infleunce of neural mechanisms
  • Two neurotransmitters that are believed to be particularly important in connection to aggression are low levels of serotonin and high levels of dopamine


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Serotonin exerts a calming effect in the brain.

  • Low levels of serotonin removes this effect which causes an individual to be less able to control their impulsive responses.
  • The influenceon serotonin may be important in explaining the relationship between alcohol and aggression.
    • Alcohol consumption has been found to cause major disturbances in the metabolism of brain serotonin.
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Serotonin Study

Mann et al administered 35 healthy adults which depletes levels of Serotonin

  • The researchers used a questionnaire to assess hostility and aggression levels
    • It was found that among males, but not females, hostility and aggression levels increased

This supports the discovery that Serotonin levels influence aggressive behaviour

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There is a less established link between dopamine and aggression

  • Some evidence shows the use of dopamine antagonists, which resduce dopamine activity, have successfully reduced aggressive behaviours.

Couppis et al found evidence that dopamine plays an important reinforcing role in aggression

  • Their research suggests that some individuals intentionally seek aggressive encounters because of the rewarding sensations caused by an increase in dopamine
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For some large amounts of testosterone correlate with low aggressiveness and for others low amounts of testosterone correlated with high aggressiveness

  • Olweus et al compared samles of institutionalised delinquent boys and non-deliquent male students
    • The results were not statistically significant
    • They also found adolescents with higher levels of testosteone were more likely to respond more vigorously in response to challenges from teachers and peers
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There appears to be inconsistent evidence on the relationship between testosterone and aggression

    • A number of studies have found that high testosterone levels correlated positively with high levels ofaggression but others have found no such relationship

In Kouri et al gave young men doses of either testosterone or placebo

  • They were paired with a ficitious participant and told each member that by pushing a button they could reduce the amount of cash the other received
  • Paricipants who recieved testosterone pushed the button significantly more
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Low levels of cortisol are associated with higher levels of aggressive behaviour.

McBurnett et al evaluated 30 boys age 7-12 who had been referred to a clinic for problem behaviours

  • Their behaviour were evaluated annually for 4 years and salivary cortisol measurements were taken in the 2nd and 4th year
    • They found that boys with lower cortisol concentrations exhibited 3 times the number of aggressive symptoms compared to those with fluctuating or high levels
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Gender Bias:

  • Most research on aggression and testosterone is done using men as they produce more. This causes a great number of gender bias studies.
  • Althought it is easier to clearly see testosterone's effects in men there is little evidence for the link in women
  • Evidence has been found for high testosterone in women and dominating behaviour.


  • Many studies don't take any psychological explanations for aggression into consideration


  • Many studies are an oversimplification of human aggression
  • They don't consider the complexity of human beings
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