Discuss Hormonal Explanations of Human Aggression

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AO1 - Testosterone Hypothesis

  • Testosterone is a hormone, a chemical that control and regulate bodily functions, in the androgen class. In males, testosterone levels are on average 10x higher than in females and across many cultures males are seen to be more aggressive than females.
  • Therefore, testosterone could be linked to aggression in humans.
  • The testosterone hypothesis's core idea is based on our levels of aggression fluctuating according to our hormone levels.
  • Evidence suggests that testosterone acts at the synapse and reduces the metabolism of the neurotransmitter serotonin. S
  • Many studies on testosterone activity have shown a relationship between high levels of testosterone and a tendency towards aggression. It is thought that the interaction between the low serotonin and high testosterone levels in the central nervous system have a significant effect on the neural mechanisms involved in the expresion of anger. 
  • It would seem that testosterone modulates serotonergic receptor activity in a way that directly affects aggression, fear and anxiety.
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Differences in TS levels in violent criminals

  • There are 3 main research approaches to investigate the role of testosterone (TS) in aggressive behaviour. (AB)
  • Dabbs et al  (1995)
    • Measured the TS levels in the saliva of 692 adult male prisoners
    • Found that those who had committed crimes involing AB such as sex and violence had higher TS levels than those involved in crimes like burgalry and theft.
    • The high TS males were more likely to be involved in AB in the prisons. 
      • This supports the TS hypothesis theory and the idea that increased TS levels cause AB
      • Problems with the research include:
        • Sample size: All pps were prisoners, there was no comparison w/ non-prisoners - therefore not generalisable to the public.
        • Cause & Effect: Correlational analysis means that we cant safely say that there is a causal relationship between increased levels of TS and increased AB. It could be equally true that aggression causes the high levels of TS.
      • These issues reduce the extent to which the study can support the testosterone hypotheis theory.
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Relationship between TS levels and AB in non-crims

  • Dabbs & Morris (1990)
    • Reviewed the records of 4000 male military veterans (400 high TS, 3600 normal TS) and compared males in the upper 10% of the TS levels with the rest.
      • They found that the high TS group had been in more trouble with authority+peers, had more frequent assaults on other adults and more drug use.
      • Effects were found to be greater if they were from low socioeconomic backgrounds
    • This supports the theory and the idea that high levels of TS increase the frequency of AB occuring.
      • Problems with this research include:
      • The sample is not representative; Therefore we cannot generalise the findings to a wider audience.
      • Correlational analysis; we cant draw a causal relationship, other factors may influence AB such as drug use or socioeconomic background.
    • These issues undermine the support the study lends to the theory that high levels of TS causes AB.
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The Effect of Hormone Manipulation on AB

  • Pope at al (2000)
    • Used a double-blind procedure to give men aged 20-50 a placebo or testosterone, over a 6 week period. After the 6 weeks, pps were paired with a fiction pp and either member of the pair could reduce the amount of mney received by the other person by pushing a button. They were told the other person was reducing their cash.
      • Found that pps who had received the TS pushed the button more times than those who had taken the placebo.
    • This provides good causal evidence for the theory that TS causing aggression
      • Problems with this study include:
      • The measure of aggression: pressing a button does not reflect IRL aggression and is unrealistic.
    • This issue reduces the extent to which this research demonstrates that high TS causes IRL AB.
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Other Explanations

Apart from the flaws with the supporting research, the TS hypothesis of AB has also suffered due to the large amount of contradictory findings. There is a wealth of evidence which finds little or no effect.

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The RLSHIP between TS+AB may be indirect

  • TS may only affect other variables that then lead to AB. For example, a personality characteristic may be altered by TS, which then could affect AB.
  • Schalling (1987)
    • Gave a series of personality scales and questionnaires to adolescent delinquent boys.
      • Found that TS levels were significantly correlated with a preference for physical sport, sociability, extraversion, nonconformity and verbal AB.
      • This finding gives support to the idea that TS affects personality factors, which can also lead to AB.
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The RLSHIP between TS+AB may be bi-directional

  • It may be the case that increased AB leads to the increase in TS levels and not the other way around. Furthermore, the high aggression leading to high TS could then increase the A response.
  • Elias (1981) 
    • Found that college wrestlers who had won competitive matches demonstrated a greater increase in TS than the losers of such matches.
      • This suggests that the aggression is causing the increase in TS, and so supports the bi-directional relationship theory of TS and AB.
      • This theory could also explain the findings by Dabbs (1995) and Dabbs&Morris (1990): The crimes that theycommitted may have increased their TS levels, and the military veterans are generally aggressive in their job (but also ion the other factors) and so may have increased TS and more AB because of this.
      • These findings however are challenged by Pope (2000) as his findings show a causal relationship between TS and AB, the high TS caused the AB.
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The influence of TS may only be small

  • A large amount of researchers believe that there may only be a small influence os TS onto AB.
  • Kreuz & Rose (1972)
    • Studied the relationships between TS and AB in a prison sample
      • Found that levels of TS only became a factor of AB when other social factors were taken into account, especially family background and learning history.
      • This supports the idea that hormonal theories of AB are reductionist  because they are overly simplistic and do not consider the role of other factors such as environment (family background.
    • Hormonal + social psychological theories could work together in explaining AB;
      • High TS, combined with for example, the Frustration A Hypothesis or Social Learning Theory, could lead to higher levels of AB.
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  • The theory that low levels of the neurotransmitter TS cause AB clealry supports the nativist approach to explaining human behaviour, in other words aggression is caused by biological factors only.
  • Although such an approach enables good causal evidence to be produced, e.g an increase in TS causes AB, it is limited by the fact that it fails to consider any environmental influences on AB.
  • A more valid explanation would be that AB is caused by an interaction between nature+nurture (refer to previous slide)
  • Theories such as the TS hypothesis can only be described as biologically determinist, which means causes of AB are biological and outside control of the individuals.
  •  Positives of this approach are that some individuals can understand where their A tendencys come from, but issues are raised such as can a person then be held responsible for their behaviours.  
  • An alternate explanation would be that we all have free will over our behaviour, and therefore we make choices about the way that we behave; we can control our behaviour.
  • In many legal causes in which individuals have commited violent acts, they are assumed to have free will over their actions.
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