Raine et al classic study (pack 3) Flashcards
aim
find out which brain areas were dysfunctional in violent offenders, using PET scans
sample
41 individuals
39 males and 2 females
who had been tried in California for murder or manslaughter
trying to plead NGRIs
what was the control group like?
matched to the experimental group on variables such as age and sex and psychiatric illnesses such as schizophrenia
what was the experimental design
matched pairs
research method
lab experiment using matched pairs design
IV?
whether the ppt had committed murder/manslaughter or not
DV
the results of the PET scans
what were 4 steps in the procedure?
- had to do a continuous performance task, where they had to stare at a screen whilst blurred symbols appeared
- PPT had to press a button when a particular symbol appeared
(task done for ten mins before beginning as a control) - radioactive glucose tracer then injected
- after 32 mins of task, subjects brains were PET scanned to determine glucose metabolic rate in brain to determine level of activity in certain areas of the brain
results to do with cortical areas of the brain?
- lower levels of activity in both hemispheres compared to control in the PFC + parietal cortex
results to do with subcortical areas of the brain?
- lower levels of activity compared to control in both hemispheres in the corpus callosum
- abnormal uneven levels of limbic system activity compared to controls in the:
thalamus, amygdala and hippocampus - NO overall difference in activity levels in AMYGDALA
conclusions
reduced activity in PFC and Corpus callosum as well as abnormal asymmetries of activity in limbic system such as amygdala and hippocampus
COULD
predispose a person towards violent behaviour
What are 2 reasons Raine gave for his findings?
- lack of functioning in PFC results in reduced ability to regulate activity in limbic system and cannot control impulsiveness
- abnormal functioning of amygdala, which is responsible for emotional processing, results in murderers being fearless
generalisability
S- large sample so more representative (41 violent offenders)
W-
mainly men, not representative of females
HOWEVER - most extremely violent offenders are men, so may give results of brain dysfunction in this small group
reliability
S- standardised procedures and equipment used
all ppt used the same brain scanner
+ same performative task for 32 mins
quantitative data about glucose levels increases replicability
application
S- suggest predispositions could be identifies with PET scans and so would prevent crimes as PET scans showed abnormal activity in the PFC
W- cause and effect is not established in this study
Caution is needed… it cannot be used as a definite
validity
S- some variables are controlled
increases the validity by reducing confounding variables
for example having no medication 2 weeks before study
and control was matched to the experimental group based on age, sex etc.
HOWEVER, did not have control over all confounding variables such as upbringing of sample
W- reductionist as it focuses on brain structure and function
BUT
valuable as it makes it more scientifically credible
PET scans resolution lower that FMRI, lowers validity as accuracy is lowered
ethics
approved by ethics committee
consent given- possible ppt may not be fully aware of implications of consent as they have schizophrenia
Convicts did it as they may have been under pressure to gain evidence for a NGRI
W-
although ethics followed, were not always protected from harm as they had to come off their medication as well as been given radioactive tracers
however these problems may have been outweighed as their hope to have a NGRI accepted and escape death penalty
