classic study: raine Flashcards
what is the aim of raine’s study?
wanted to use brain scanning technology to identify brain impariments in people charged with murder who had pleaded not guilty by reason of instanity
what was the method of raine’s study?
looked at differences between 41 murderers and 41 non-murderers.
- the independant variable was murderer or non-murderer
- ppts were not assigned these conditions and therefore this is not a true experiment
- a matched pairs design was used
- the dependent variable was glucose metabolism in specific brain areas
what were the ppts matched on?
- sex
- age
- ethnicity
what was the procedure of raine’s study?
each ppts underwent a PET scan of their brain. they were injected with a radioactive tracer to light up their brain metabolism under the scanner.
- they each did a continuous performance task for 32 minutes after the injection
- the purpose of the task was to encourage uptake of the tracer in areas of the brain they wished to investigate.
- the PET scan was conducted immediately after
what were the findings in the corticol regions?
murderers had significantly lower glucose metabolism than controls in the following corticol regions: lateral and medial prefrontal areas, left angular gyrus and left and right superior perietal areas
- they showed higher metabolism than controls in the occipital lobe
what was the conclusion?
murderers pleading NGRI have different brain activity from people who are not violent offenders and they had impaired functioning in areas of the brain previously identified as involved with violent behaviour.
what were the findings in the subcorticol regions?
murderers had lower glucose metabolism than controls in the corpus collosum, left amygdala and left medial temporal lobe
- murderers had greater activity in the right amygdala, the right medial temporal lobe and the right thalamus
what is a strength of raine’s study?
there is a high degree of control in the study
- ppts were matched across the experimental and control groups on three potentially confounding variables.
- standerdised procedures were also used to control other variables
- the PET scans followed the same protocol so that the experience of the procedure would be identical for all ppts
this means the study had a high internal validity
what is the competing argument for the strength?
the ppts were not randomly allocated to the experimental or control groups
- matching was used to partly overcome this limitation but the matching was not thorough
- failure to match on some variables may have confounded some of the results
raine et al. acknowledged that a history of head injury may have explained differences in corpus callosum activity between the two groups
what is a weakness?
the PET scanning technique may have given misleading results
- scans the brain in 10mm slices relative to what is known as the canthomeatal line, an imaginary line from the outer corner of the eye to the middle of the ear
- it makes it hard to locate precisely the different brain areas under study
this reduces the internal validity
how can raine’s study be applied?
being cautious of biological evidence
- the research appears to suggest that particular brain structures can be identified that cause aggression and thus aggression can be treated by changing biological structures through medication or surgery
