16.1.7

Biological Explanations 2

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Genetic Explanations: Aggression and Y Chromosome Studies

There are three main pieces of evidence for the genetic explanation of criminality: adoption studies, genetic influences on aggression and extra Y chromosome studies.

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Genetic influences on aggression

  • The second piece of evidence for the role of genetics in criminal behaviour would be levels of aggression.
  • Psychologists have stated that there is a link between aggression and criminal behaviour.
  • Higher levels of aggression could lead to criminal activity.
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Christiansen (1977)

  • Studies have shown that there is a link between genetics and aggression.
  • Twin studies like Christiansen (1977) found that:
    • Male identical twins had 35% concordance for criminality.
    • Whereas male non-identical twins had only a 12% concordance rate.
    • Females had a 21% concordance for identical.
    • And 8% for non-identical.
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Y chromosomes

  • The final piece of evidence for the role of genetics in criminal behaviour would be studies done on extra Y chromosomes.
  • Males are supposed to have an XY chromosome pattern.
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Jacobs et al. (1965)

  • By examining a prison population, Jacobs et al. (1965) found that there was a higher percentage of prisoners with the atypical chromosome pattern (XYY) compared to non-prisoner population.
  • The study stated that the extra Y chromosome could be linked to increased testosterone production and increased violent behaviour.
  • These could lead to criminal behaviour.
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Other studies

  • Other, later, studies found that the chromosomal pattern results in:
    • Hyperactivity
    • Increased impulsivity
    • Lower IQ
  • These three factors could explain increased criminal behaviour.

Neural Explanations of Criminal Behaviour

Raine et al. (1997) conducted a study to examine the link between brain abnormalities and criminal behaviour. Their findings support the biological explanation of criminality.

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Method:

  • PET scans create 3D images of processes that occur within the brain.
  • PET scans detect differences in glucose metabolism, an important process for neuron conduction.
  • Raine scanned 41 murderers and 41 control participants.
  • The murderers had plead not guilty by reason of insanity.
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Results:

  • There were differences in glucose metabolism in three areas of the brain:
    • Prefrontal cortex.
    • Superior parietal gyrus.
    • The corpus callosum.
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Results cont.:

  • These three areas had reduced glucose metabolism in the murderers as compared to the controls.
  • There was also asymmetric activity in the two hemispheres in the murderers.
  • Overall, some brain processes were dysfunctional in the murderers.
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Conclusions:

  • Raine et al. found evidence of neural differences in murderers compared to controls.
  • The evidence supports a link between brain dysfunction and violent criminal activity like murder.
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Evaluation: Strengths

  • The researchers used a control group who were matched on age and sex, increasing the validity of the results.
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Evaluation: Limitations

  • They found a correlation between brain dysfunction and violent behaviour, however, a causal relationship cannot necessarily be concluded.
  • The reason being that the researchers could not randomly assign the participants into the murderer group and the control group.
  • To study the causality of brain dysfunction on criminal behaviour, a longitudinal study would have to be done.

Jump to other topics

1Social Influence

2Memory

3Attachment

4Psychopathology

5Approaches in Psychology

6Biopsychology

7Research Methods

8Issues & Debates in Psychology (A2 only)

9Option 1: Relationships (A2 only)

10Option 1: Gender (A2 only)

11Option 1: Cognition & Development (A2 only)

12Option 2: Schizophrenia (A2 only)

13Option 2: Eating Behaviour (A2 only)

14Option 2: Stress (A2 only)

15Option 3: Aggression (A2 only)

16Option 3: Forensic Psychology (A2 only)

17Option 3: Addiction (A2 only)

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