Brain abnormalities in murderers (Classic Research)

  • Created by: aemaan786
  • Created on: 11-11-18 17:21


Raine et al used a matched pairs design in his natural/ quasi-experiment. There were 41 criminals (39 males and 2 females) who had committed murder and plead NGRI. Those in the control group were matched by age, sex and diagnosis. A control group was formed by matching a murderer with a normal individual. For example, 6 schizophrenics were matched with 6 schizophrenics from the mental hospital. All participants stopped taking any prescribed medications. 

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On the day of their PET scan, all participants were injected with a glucose tracker (FDG) which is taken by the active areas of the brain and they completed a target-recognition test for 32 minutes. They were given a PET scan to allow researchers to monitor the activity across their brains. After this, they took 10 horizontal slices (pictures) of their brain which was recorded by using the cortical peel and the box techniques. 

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NGRIs were found to have less activity in their prefrontal and parietal areas, more activity in their occipital areas and no difference in their temporal areas. They were also found to have less activity in the Corpus Callosum (the part of the brain that joins 2 hemispheres together). There was an imbalance between the 2 hemispheres in terms of activity in the amygdala (less activity in the left side and more in the right), the hippocampus had less activity in the left side and more in the right and the thalamus had more activity in the right side but no difference in the left side. 

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Raine et al concluded that individuals who had committed murder but plead NGRI did have different levels of activity in different parts of their brains and these areas may be linked to violent behaviour. 

  • The amygdala is important for processing emotions, so the findings could support theories that violence is due to unusual emotional responses (lack of fear) 
  • people with a damaged corpus callosum have been found to have difficulties controlling emotions, which fits with the nature of their violent crimes 
  • the differences in the prefrontal cortex may be important because rational thinking takes place here 
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Raine et al increased the validity of their study by ensuring that they controlled any possible factors that could've changed the participants' violent behaviour, such as individual difference which was controlled by using a matched pairs design and stopped all medications. 

One strength of the study was that they used a biological measurement which cannot be affected by demand characteristics. The participants would not be able to alter their brain activity with what the researchers would've wanted. this increases both validity and reliability. 

The data appears to show that there is a relation with two variables (activity in the brain and violent behaviour). We will never know if the brain activity caused violent behaviour, or if the violent behaviour caused the brain activity. There may have been other variables that were not controlled. Therefore, the results need to be treated with caution.

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Ethical Issues

The medications of all participants were stopped, this could have put them at risk of harm (they had disorders that could've been harmful). A PET scan was used, which is a non-intrusive method of observing the brain activity and carries out a small risk(because of the injection that carries a radioactive substance). It does not involve any surgery and it is helpful in informing our understanding of certain disorders and allowing development of certain treatments. 

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Social Implications

Studies like this raise the possibility that one-day technology will allow us to predict if individuals are likely to commit crimes. For example, Aharoni et al scanned the brains of 96 male prisoners just before their release. They found that those with less activity in some part of the brain called the anterior cingulate cortex were more likely to be arrested. some criminals may be able to argue for diminished responsibility because of their biology, or individuals may be labelled criminals even if they have not committed a crime. 

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