raine et al Flashcards
aims
- look at direct measures of both cortical and subcortical brain functioning by using pet scans in people charged with murder who had pleaded by not guilty by reason of insanity (NGRI)
- hypothesized brain scans would show dysfunctions in areas of the brain linked to violence
which areas of the brain are linked to violence
- prefrontal cortex
- amygdala
- corpus callosum
- thalamus
- hippocampus
prefrontal cortex
implicated in planning decision making and moderating social behavior
prefrontal cortex
implicated in planning decision making and moderating soca behavior
amygdala
central role in how humans assess and respond to environmental threats and challenges - important for response and memory of emotions
corpus callosum
- nerve cells physically connecting 2 hemispheres allowing for communication
- critical for contralateral control of body
thalamus
filters information
received information from sense and passes it onto appropriate areas of the cerebral cortex
hippocampus
regulates emotions and is associated with memory, especially long term memory
sample - criminal group
- 41
- 39 male
- 2 female
- all committed manslaughter or murder
- all had been referred for brain scanning to find evidence that they were ngri for =
- schizophrenia (6)
- head injury/brain damage (23)
-epilepsy
non criminal control group
- 41, matched to age and gender to criminal group
- schizophrenic criminals were marched to schizophrenic non criminals
- rest of the control group were screened and showed no history of psychiatric illness
controls before testing
- all offenders were in custody and kept medication free before scanning
- control group kept medication free
- tests were undertaken to make sure being left/right handed had no effect on behavior
- 14 murderers were non white and when compared to white murderers there were no differences on brain scans
- 23 murderers had head injuries which don’t show any different from non head injured murdered except for corpus callosum
procedure
- participants were injected with a radioactive glucose tracer which would show the level of activity in different brain regions
- participants did a continuous performance task (CPT) which tested their pre frontal cortex
- CPT lasted 32 mins
- after ctp participants went to pet scanning room and their brain was scanned
what was the cpt
-involved participants indicating every time the number 0 appeared in the screen
- the numbers visually degraded over time to require more effort of each participants pre frontal cortex
what happened 10 minutes before participants were injected
they were given practice time of the ctp so they knew what to expect
what happened 30 seconds before the cpt task
- they stated the actual task to ensure the novelty of the task didn’t show up on the scan
what happened in the brain scanning room
participants brains were scanned 10 times at 10mm intervals to measure brain activities in cortical and subcortical areas
results
compared to controls ngris showed:
- less activity in pre frontal cortex
- less activity in corpus callosum
- less activity in left side of amygdala
- more activity in right side of amygdala
- more activity in occipital areas
- more activity in right side of thalamus
occipital areas
visual centeres of brain
conclusions
- reduced brain activity in pre frontal cortex could explain impulse behavior and lack of self control
- differences in amygdala could support theory that violence is due to unusual emotional responses and lack of fear
- differences in corpus callosum corresponds to findings from split brain patients who show inappropriate emotional expression and inability in long term planning
generalizability strengths
- large sample size of 82 so anomalies, e.g participants with unusual brain structures / people who disrupted test by not focusing on cpt dont skew results = more representative of wider population
generalizability weaknesses
- ngris aren’t usual offenders so aren’t representative of other criminals so findings can’t be applied to all of them
- only 2 women in both groups limiting generalizability to female offenders
reliability strengths
- pet scans are reliable brain imaging techniques giving objective and replicable results
- same cpt was used for all participants for same length of time, this identical procedure ensured all participants concentrated on the same thing and that similar brain activity was used for all participants
= easy to repeat and check for consistency
application strengths
-can be used to help prevent crimes by intervening in children who could be potential offenders due to genetic influence
- putting health and nutrition programs for pregnant women to help reduce biological risk factors for criminal behaviors, e.g not smoking
application weaknesses
- can’t be applied to people who commit other violent crimes
- can’t be applied to other non violent criminals
validity strengths
- participants were matched on age sex and ethnicity so results can be compared more accurately, increasing internal validity
- use of scientific measures like pet scans and a standardized procedure
validity weaknesses
can’t show cause and effect as it is uncertain when murderers develop brain defects
ethics
- pet scans are harmful as participants have to be injectednwith a radioactive tracer
