Classic Study: Raine (1997) Flashcards
Overview
He studied American prisoners who pleaded Not Guilty By Reasons By Insanity (NGRI’s) by using brain scanning techniques. He found that the NGRI’s had a lower percentage of glucose metabolism in the prefrontal cortex when doing a continuous performance task
Reliability Point
- High reliability as there was a standardised procedure
- This is because the same CPT was used for a standard time of 32 minutes. Therefore ensuring all ppts had similar types of brain activity and so makes it more reliable
- It is further increased through the use of PET scans as they produce objective results which can be analysed by more than one researcher
- Therefore, this experiment is easily replicable
- This is a strength for the theory overall because it adds more credibility to the results
Validity Point
- Brain scans used in the study lack validity
- PET scans are not always easy to interpret
- They work by injecting a small amount of a radiotracer such as glucose, as the brain starts working the glucose will be used up and the radioactive atoms start to break down emitting positrons. During this process, gamma rays are produced, and this is what the scanner picks up. High activity is shown by the colour red and ow activity is blue.
- Therefore, the precise location of active areas in relation to the brain structure is often difficult to pinpoint and consequently the accuracy and credibility of findings is reduced
- This weakens Raines overall validity of the study meaning the results may not be accurately applied and interpreted
Generalisability
- Although the sample size could be considered large under the circumstances as NGRI’s are unusual offenders, this makes it ungeneralisable as the results are therefore not representative of typical murderers. Consequently, the results cannot be generalised to typically aggressive murderers or non-violent criminals.
- Furthermore, sample is predominantly male as 39 men and 2 women were used
- overall, limits results
Application
- Results at face value suggest that deficits in glucose metabolism in particular brain structures cause aggression
- Therefore can be treated with medication
- However, application is limited because the study simply identifies brain structures as a partial explanation and not the cause meaning the data is only correlational and so can’t make medical applications
- overall, opens up the need for more research into what causes aggressive behaviour
Aims
- To show that the brains of murderers who pleaded not guilty by reason of insanity were different from the brains of non-murderers
- To investigate if this abnormality makes them more aggressive and so reduces accountability
- 41 murderers pleading NGRI
- 41 non-murderers
Who were used in the sample?
What participant design was used?
Matched pairs on sex and age, 6 non-murderers having schizophrenia to match the 6 murderers with schizophrenia.
What type of method was used?
Lab
Briefly describe the procedure of this classic study.
- 10 mins before being given a FDG injection for the PET scan subjects were given practice trials on the continuous performance task
- 30 secs before the injection, the real CPT task started and were monitored for 32 mins in the PET scan
- The CPT involved spotting targets on a screen and pressing a button to indicate the target had been recognised
- Their brains were scanned 10 times at 10 minute intervals to pick up differences in glucose metabolism in the cerebral cortex and sub-cortical layers
What were the results of Raine’s study?
- Parietal lobes of murderers had lower activity in both hemispheres than controls with a difference of 0.05 in the left and 0.04 in the right
- Frontal lobs of murderers had lower activity in both hemispheres than controls with a difference of 0.03 for both
- Amygdala of murderers had lower activity in left (0.94) compared to 0.97 of non-murderers and greater activity in right (0.88) compared to 0.83 of non-murders
Describe the conclusion based on the parietal lobes.
The parietal lobes are responsible for speech and so if there is low activity in this region someone wouldn’t be able to articulate their feelings such as anger and so it gets differed to aggressive acts
Describe the conclusion based on the frontal lobes.
The frontal lobes are responsible for personality and self-control and so damage to the frontal lobes can result in impulsivity, lack of self control and the inability to modify behaviour which in turn can facilitate aggressive acts
Describe the conclusion based on the amygdala.
The amygdala plays a role in the recognition of affective and social significant stimuli and so abnormalities could be relevant to a theory of violence based on the findings of reduced autonomic arousal (fight or flight) and lack of fear in offenders
Describe the overall conclusion of this experiment.
Violent behaviour is controlled by areas of the brain and that abnormalities to these areas can affect behaviour, even though we can’t be certain that their violent behaviour was caused by these abnormalities.
