Biological Explanations for Aggression

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  • Created by: Amy
  • Created on: 03-01-13 19:04

Case Study of Charles Whitman

Although happily married, 25-year-old Charles Whitman was a worried man. He knew that he was in the grip of a terrible compulsion and on the verge of doing something appalling.

Finally, on 31st July 1966 his self-control snapped and after killing his wife and mother so that they would be spared the shame, he climbed the white granite tower of the University of Texas administration building, and started shooting at anyone who moved below.

Fifteen people died and thirty were injured before police assault teams got close enough to gun him down.  His psychiatrist, Dr. Heatly, came under intense scrutiny, when his records revealed the fantasy killing spree that Whitman had outlined during their session, but he was never held accountable for his failure to act.  

Interestingly, when Whitman’s body was autopsied, doctors did indeed discover a small tumour in his brain, as he had feared, but experts concluded that this was unlikely to have caused his subsequent actions. Given that brain science was not as advanced in the mid-sixties, it would be interesting to know if today’s specialists would have drawn the same conclusions.

Do you think Charles Whitman committed these crimes because of his nature or nurture?  Explain your answer

From what this passage says, I believe that he committed these crimes because of his nature. However, it does not say what his social life was like.

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Neural Mechanisms in Aggression

Davidson, Putnam and Larson have suggested that the neurotransmitter serotonin may serve to inhibit aggression. So high levels of serotonin (linked to happiness) make us less aggressive, whereas low levels makes us more aggressive.

An amino acid called tryptophan has been found to be essential for the production of serotionin (high levels of T = high levels of S = low levels of A)

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Evaluation

Strengths:

  • David, Putnam and Larson: they compared violent and non-violent prisoners and found levels of serotonin to be markedly lower in violent prisoners
  • Reducing levels of serotonin in Vervet monkeys increases aggression
  • Tryptophan has traditionally been given to juvenile delinquents to successfully reduce their aggression (Morand et al)
  • Silver foxes have been tamed by humans for pets in Russia. Research has shown they have higher than normal levels of serotonin and tryptophan which leads to lower levels of an enzyme called monoamine oxidase that removed serotonin from the synapse between neurons  (low levels of MAO = high levels of S = low levels of A)

Weaknesses:

Low serotonin levels could be an effect rather than a cause of aggression. However, deliberately increasing levels in animals does reduce aggression

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Brain Structure

  • Brain structures have also been implicated in aggression. Animal research suggests that the hypothalamus and amygdala initiate aggression.
  • The prefrontal cortex is closely connected to the functioning of the hypothalamus in terms of inhibiting aggression.
  • Prefrontal cortex damage is associated with a change in personality – impulsiveness, irritability and easily provoked.
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Evaluation

Strengths:

  • Electrical stimulation of the hypothalamus produces attack behaviour in cats (Flynn), whilst lesioning of the amygdale has a taming effect.
  • Autopsy revealed that Charles Whitman’s tumour was pressing against his amygdale
  • Any amydalectomy (surgical removal amygdale) reduces violent behaviour in animals and humans
  • In 1884, Phineus Gage, a railway worker,sustained prefrontal cortex damage when a tamping iron was accidentally blasted through his head while clearing rocks for a railway track.
  • He survived 11 years but his personality changed dramatically – impulsive and heightened aggressive behaviour and he was unable to sustain a job for very long.

Weaknesses:

  • Animal research: generalisability, ethics
  • Deterministic: low serotonin/brain damage will cause aggressive behaviour. Ignores the role of free will and environmental factors. What about social psychological theories?
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Hormonal Mechanisms in Aggression

  • Aggression is linked to male sex hormones called androgens e.g. testosterone. Androgens are produced by Leydig cells in male testes
  • The basal model of testosterone states that increased testosterone makes a male more competitive and dominant – therefore this could mean they are more likely to engage in aggressive behaviour such as fighting.
  • However, the reciprocal model of testosterone states that testosterone levels are an effect of the male’s dominance.
  • PMT has been successfully used to reduce murder charges to manslaughter – higher androgen levels
  • In addition, younger males in all species tend to be more aggressive than older males – androgen levels are higher, especially during puberty. 
  • Nelson found a positive correlation between androgen levels and aggression in male and female prisoners.
  • Wagner et al found that if a male mouse is castrated, overall levels of aggression tend to reduce. If the castrated mouse receives testosterone, aggression levels increase.
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Continued

  • Harrison et al noted that after giving testosterone to 56 men aged 20-50, when given a frustration-inducing computer game, aggressive responses were significantly increased. But this effect was not the same for the entire sample. If anything, the changes were largely psychological and few had any noticeable physical effect on behaviour
  • Pillay took saliva samples from 94 athletes (males and females) and found that testosterone levels were linked to the aggressiveness of the sport they played – testosterone was higher in those who did wrestling as opposed to swimming. But there could be positive aspects of higher testosterone – increased competitiveness, so is not always aggressive behaviour
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Evaluation

  • Deterministic
  • Nature side of nature-nurture debated, although the reciprocal model of testosterone does take into account environmental factors
  • Reductionist
  • Gender bias – research sampling bias in favour of males
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Genetic Factors in Aggression

Sandberg first identified what is known as 47 XYY Karotype. It is possible for some males to have the additional Y chromosome.

Evaluation:

  • Court-Brown 1965-1967 believed that XYY males should be hospitalised due to an increased risk of aggression, however, further research into the XYY Karotype has revealed that although XYY people are on average taller than the general population, there is no evidence of aggression (Milunksy) or higher than average testosterone levels (Ratcliffe)
  • Despite this, Theilgard did find that XYY males have more aggressive interpretation of images during Thematic Apperception Testing. Low external validity – artificial task, will not reflect real life
  • Rutter er al carried out a meta-analysis of twins studies on criminality: dizygotic twins have concordance rates between 13-22%, while monozygotic twins have concordance rates between 26-51%. Supports the genetic explanation as MZ twins have higher concordance rate, as expected, because they have 100% of the same genetic makeup. However, it’s not 100%, therefore must be environment factors playing some role. Moreover, not all criminal acts involve aggression. Therefore, this study provides weak support for the genetic theory
  • Selective breeding experiments can lead to more aggressive animals. Cairns created a highly aggressive strain of mice using selective breeding, this suggests there is a genetic transmission of aggression. However, it is difficult to reflect this to humans
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Evaluation of the Theory

Approaches/Comparisons:

Alternative: social learning theory, environment

Issues and Debates:

Reductionist – uses a simple theory to determine aggression

Deterministic – too deterministic, a person may not be aggressive if their parent is

Psychology as a science – you can test it empirically 

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Evaluation of the Theory

Approaches/Comparisons:

Alternative: social learning theory, environment

Issues and Debates:

Reductionist – uses a simple theory to determine aggression

Deterministic – too deterministic, a person may not be aggressive if their parent is

Psychology as a science – you can test it empirically 

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Comments

MrsMacLean

LOADs and loads of really useful material.  Thank you!

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