classic study: brain abnormalities in murderers indicated by PET (Raine, A. et al., 1997) Flashcards
1
Q
what did Raine look at in this study?
A
- people charged with murder and pleading not guilty by reason of insanity to see if there were brain differences that might link to their aggressions
2
Q
what scanning technique was used in this study?
A
- PET scanning
- used to look for differences in brain functioning between murders who pleaded NGRI and control group
3
Q
how is this research useful?
A
- when considering looking at brain structure and function in relation to aggression
4
Q
what was the aim of the study?
A
- to see whether there was different brain functioning in a group of murderers to control ppts
5
Q
what was the expectation of the study?
A
- the murderers would show evidence of brain differences in their prefrontal cortex as well as in other areas that are thought to be linked to violent behaviour
6
Q
where did the expectation come from?
A
- from previous research which suggested:
- violent offenders had poorer brain functioning
- damage to the prefrontal cortex was linked to aggression
- abnormal function of the hemispheres in violent offenders
- possible dysfunction to the corpus colosseum in violent offenders
- the limbic structures (amygdala and hippocampus) are linked to aggression
7
Q
what did the study use and who did they examine?
A
- PET scans
- examined brains of 41 people (39 males and 2 females) who were charged with murder and pleading NGRI
- compared them to 41 controls
8
Q
where were the NGRIs referred to?
A
- imaging centre for legal reasons eg to obtain evidence for the defence
9
Q
what were the reasons for referrals?
A
- 6 cases of schizophrenia
- 23 cases of head injury or organic damage
- 3 cases of drug abuse
- 2 cases of affective disorder
- 2 cases of epilepsy
- 3 cases of hyperactivity or learning difficulties
- 2 cases of personality disorder
10
Q
how were the ppts matched?
A
- matched by age and sex to a control group of ppts
- independent groups design
11
Q
what was the mean age of the NGRIs?
A
- 31.7 years
12
Q
who were the ppts with schizophrenia matched with?
A
- other people with the same diagnosis but no history of murder
13
Q
what were all offenders in?
A
- in custody
- kept medication free for two weeks before scanning
- control group were also medication free
14
Q
what were all the ppts injected with?
A
- glucose tracer (fluorodeoxyglucose)
15
Q
what were the ppts required to do after being injected with the tracer?
A
- work at a continuous performance task based around target recognition for 32 minutes
- then given a PET scan
16
Q
what were the NGRIs compared with?
A
- compared with the controls on the level of activity (glucose metabolism) independent right and left hemispheres of the brain in 14 selected areas
17
Q
what activity did the researchers look at?
A
- looked at activity in six cortical areas (part of the cerebral cortex which is the outermost layer of nerve tissues of the cerebral hemisphere)
- eight subcortical areas (brain structures below the cortex)
18
Q
did the findings support the hypothesis?
A
- yes
- brain dysfunction in the NGRI group was in areas previously implicated in violent behaviour
19
Q
what were the results showing?
A
- cerebral cortex is commonly described in terms of four areas/lobes: prefrontal, parietal, temporal and occipital
- compared to controls, NGRIs were found to have less activity in prefrontal and parietal areas, more activity in occipital areas, and no difference in temporal areas
- raine et al argue that difference in activity in amygdala can be seen to support theories of violence that suggest it’s due to unusual emotional responses eg lack of fear
- differences in corpus callous activity between NGRIs and controls suggest it can be matched up to evidence of people with severed corpus callosum which show they can have inappropriate emotional expression and inability to grasp long term implications of situations
20
Q
‘NGRIs had less activity in prefrontal brain regions’ what is the possible role of this brain region?
A
- difference in activity in prefrontal cortex can be linked to research which found that damage to region results in aggressive acts through impulsive behaviour, loss of self control, immaturity, altered emotional reactions and inability to change behaviour
21
Q
‘NGRIs had less activity in parietal brain regions’ what is the possible role of this brain region?
A
- difference in activity in parietal regions may be linked with deficits in learning, eg low verbal ability
- could contribute to problems with processing social and cognitive info
- could ultimately predispose individual to educational and difficulties in employment which could predispose someone to criminal behaviour
22
Q
‘NGRIs had an imbalance of activity between two hemispheres in amygdala, hippocampus and thalamus’ what was the imbalance and what is the possible role of this brain region?
A
- less activity in left side and more activity in right side of amygdala and hippocampus
- more activity in right side of thalamus, though no difference in left side
- difference in activity in amygdala can be seen to support theories of violence that suggest it’s due to unusual emotional responses eg lack of fear
23
Q
‘NGRIs has less activity in the corpus callosum’ what is the possible role of this brain region?
A
- difference in corpus callosum can be matched up to evidence of people with severed corpus callosum which show they can have inappropriate emotional expressions and inability to grasp long term implications of a situation
24
Q
what is the conclusion of the research?
A
- supports previous findings about role of certain brain structures in ** iolent behaviour**
- they suggest that difference in activity in amygdala (part of limbic system) can be seen to support theories of violence that suggest it’s due to unusual emotional responses eg lack of fear
- differences in corpus callosum activity between NGRIs and controls suggest this can be matched up to evidence of people with severed corpus’s callosum which show they can have inappropriate emotional expression** and inability to grasp long term implications of a situation
25
Q
what did Raine et al conclude?
A
- violent behaviour can’t be attributed to a single brain region and multiple regions are involved as well as environmental factors
- it’s clear from the findings that violent behaviour can’t be attributed to a single brain region and multiple areas are involved
- it’s speculated that the differences in brain function don’t directly cause violent behaviour but *(predispose those with dysfunction** when combined with other social, psychological and environmental predispositions to violent or aggressive behaviour
26
Q
what implications of the findings were Raine et al cautious about?
A
- findings can’t be taken to show that violence is only caused by behaviour
- don’t show that NGRIs are not responsible for their actions
- don’t say anything about the causes of the brain differences
- can’t be generalised from NGRIs to other type of violent offenders
- can’t be generalised to other types of crime
27
Q
what did Raine further suggest?
A
- an individual may have increased risk of having biological predispositions to anticosial behaviour from:
- birth complications
- poor parents
- physical abuse
- malnutrition
- smoking and drinking during pregnancy
28
Q
strength: generalisability
A
- used large sample (82), which is largest at the time for this sort of study
- anomalies, eg ppts with unusual brain structure/people who disrupted the test by not focusing on continuous performance task, shouldn’t skew data too much
- makes the results representative of wider population
29
Q
weakness: generalisability
A
- NGRIs are unusual offenders
- people who have killed someone, but eke they don’t remember doing it or are too confused to stand trial
- these people are not representative of “typical” murderers, still less of typical violent individuals
- as Raine points out, not all of NGRIs killed victims violently
30
Q
strengths: reliability
A
- PET scans are a reliable brain imaging technique that’s been used with growing success since 1970s. it produces objective and replicable results and it can be tested and re-tested to check its reliability
- CPT ensures that all ppts were concentrating on same thing, which should ensure they all had similar types of brain activity. this is a standardised procedure that also adds to reliability
31
Q
weakness: reliability
A
- Raine admits that were were still problems with reliability of PET scanning in the 1990#. the results were sometimes unclear and has to be interpreted, which introduces subjectivity and low reliability
32
Q
strengths: application
A
- Raine suggests that if the damage that causes brain deficits can be prevented, people might be prevented from becoming murderers; they will not develop a murderous predisposition. this involves early intervention with at-risk children in school, programmes to steer young people away from drugs and monitoring people who have received brain injury
- might be possible to treat people who suffer from brain deficits. if the deficient parts of brain can be stimulated (through drug therapy or counselling), then they might be less likely to engage in impulsive, aggressive behaviour
33
Q
strength: validity
A
- Bufkin and Littrell
- carried out meta-analysis
- analysed results of 17 studies that use brain imaging to study aggression in humans (Raine et al was one used)
- found that all studies point to similar conclusions: impulsivity is linked to deficits in prefrontal cortex or amygdala and such people have difficulty coping with negative emotions
- adds to the construct validity of Raine’s study, since it shows the results tie in with findings of other studies
34
Q
weaknesses: validity
A
- CPT used by Raine could be criticised for being artificial and unconnected to violent or provocation. ppts were all doing unusual task and in unusual state of mind when PET scan was carried out. this lowers ecological validity of study.
- as natural experiment, this study can’t show cause and effect. eg, NGRIs might have developed their brain deficits **after&* killing, because of stress of event, their arrest and imprisonment and coming trial
- similar idea is that there’s another explanation for aggression: learned behaviour, shown in Bobo doll studies by Bandura. if people learn aggressive behaviours, their brains might change because of it. this means that brain deficits aren’t cause of aggressive behaviour; they’re the result
- study only looks at brain activity and this could be a very reductionist view of human behaviour: an explanation from one narrow perspective that doesn’t take in the big picture. to be fair, Raine makes a point of explaining that personal, social and cultural influences might be at work as well as brain deficits. another study that looks at genetic and environmental factors behind aggression is Brendgen et al
35
Q
strength: ethics
A
- NGRIs agrees to have PET scans because it would help their court case, either by showing they were not fit to stand trial or acting as evidence that they weren’t in control of themselves when committing the crime
- controls all gave their prior consent to be tested and for imaging data to be used in study
- University of California approved study
- if NGRIs or schizophrenic controls were not competent to consent, then presumptive consent was given by lawyer or carer
36
Q
weaknesses: ethics
A
- PET scans are an invasive procedure, because ppts have to be injected with radioactive tracer. the NGRIs were having this procedure carried out anyway, for legal reasons, but for controls this was a medical procedure they wouldn’t otherwise have undergone. it’s not a serious or dangerous procedure, but any unnecessary medical procedure increases risk of research
- there are ethical concerns with conclusions for study like this. it seems to suggest that some people are driven to kill by brain structure and that their violence is out of their control. it invites us to “screen” prospective job candidates, perhaps even potential partners, to check they don’t have a “murderer’s brain”. Raine and his colleagues make it clear they are not drawing these conclusions themselves, but once a study like this is known to public its conclusions may be misinterpreted. this would go against social responsibility of ethical research
