Are criminals wired differently than the rest of us? Many psychologists have theorised about criminals having brain abnormalities, especially those who have committed the most heinous crimes, such as Raine et al. (1997). These abnormalities are the potential source of behavioural dysfunction. Those who claim they are not guilty by reason of insanity (NGRI) lean heavily on the idea of biological causes for their criminal behaviours.
- First, we'll introduce the context behind the study of Raine et al. 1997 psychology.
- Next, we'll outline the Raine et al. 1997 methodology.
- Then, we'll consider the brain abnormalities in murderers found in Raine et al. (1977).
- Moving along, we'll provide Raine et al. 1997 summary and explore the meaning of the findings.
- Finally, we'll discuss the Raine et al. 1997 evaluation, including the strengths and weaknesses of Raine et al. (1997).
Fig. 1 - Is there an objective way to determine the validity of the not guilty by reason of insanity claim? This is what Raine et al. (1997) set out to investigate.
Raine et al. 1997 Psychology
Raine et al. (1997)1 sought to shed light on this claim by analysing a group of 41 murderers who had pleaded NGRI. Using a positron emission tomography (PET) scan, they investigated the brains of these murderers and found some interesting and revealing results.
A PET scan is a neuroimaging technique involving using a radioactive substance to measure changes in the brain.
Many areas of the brain are associated with specific functions, but truly identifying the regions and confidently saying they are responsible for said functions is not an easy task.
For instance, the amygdala is heavily associated with aggressive and violent behaviours and is involved in analysing the facial features of others, especially when they are also experiencing these emotions.
Many psychologists have acknowledged the localisation of function within the brain and have attempted to establish the areas responsible for specific behaviours and actions.
This topic in psychology is known as functional connectivity.
Psychologists have also argued that dysfunction in these areas results in violence and sometimes criminal behaviours in psychology.
Like the amygdala, prefrontal cortex dysfunction has also been associated with issues regulating aggression.
Raine et al. (1997) sought to identify these potential areas of abnormalities in the brain. They hypothesised that violent offenders who plead NGRI would have dysfunction in the prefrontal cortex, angular gyrus, amygdala, hippocampus, thalamus, and corpus callosum.
Raine et al. 1997 Methodology.
Raine et al. (1997) carried out their experiment using a quasi-experimental design. The independent variable was whether the participant was a murderer who had pled NGRI or a normal person, and the dependent variable was the areas of brain dysfunction.
The participants consisted of 41 subjects who had been tried in California (US) - thirty-nine men and two women charged with murder or manslaughter.
They were referred to the University of California for imaging services due to their plea of insanity/incompetence. During this period, all of the participants were in custody. The referrals were based on diagnosed conditions like schizophrenia, brain injury, epilepsy and other disorders.
In seven of these cases, unusual circumstances were noted in the crime, which alluded to considerations of diminished capability or mental impairment.
To ensure the subjects being tested were indeed showing abnormalities, each was matched with a normal subject of the same age. The controls were also tested with a PET scan localised to the same location.
The exception was the six participants with schizophrenia were matched with six people with schizophrenia who had not murdered anyone.
Raine et al. 1977: Procedure
Raine et al. (1997) used fluorodeoxyglucose (FDG), a tracer that gives off radiation when injected into the body. A PET scan can detect the radiation, producing an image of areas of high activity (usually indicated by red/yellow colours) and low activity (usually indicated by blue/green).
Build up of FDG usually indicates activity in that area of the body.
FDG was injected and taken up by the brain (a brain metabolic rate of 32 minutes), during which Raine et al. (1997) had the subjects complete a continuous performance task (CPT), to test the patterns of brain activation in subjects.
In the task, each participant wore earphones and pressed a button every time they heard a beep; this task involves concentration and should, in theory, activate the prefrontal cortex.
The subjects completed a practice trial of the CPT 10 minutes before their FDG injection and started the task 30 seconds before the injection.
After the uptake period had ended (32 minutes), the subjects were taken to the PET scanner, and scans were taken at 10mm intervals.
Brain Abnormalities in Murderers: Raine et al. (1977) Results
Results of Raine et al. (1997) indicated differences in brain activity in both the cortical and subcortical regions in murderers compared to controls.
Cortical regions |
|---|
Cortical region | Brain activity in murders compared to controls |
| Prefrontal areas | The lateral and medial prefrontal cortical areas showed lower activity in murderers. |
| Parietal areas | There was lower glucose metabolism (indicating lower activity) in murders in the parietal regions. This was more apparent in the left angular gyrus and the bilateral superior parietal regions. |
| Temporal areas | Murderers had the same glucose metabolism in the lateral temporal lobes. |
| Occipital areas | Murderers had significantly higher glucose metabolism in their occipital lobes. |
| Subcortical regions |
|---|
Subcortical region | Brain activity in murders compared to controls |
| Corpus callosum | Murderers showed lower glucose metabolism in the corpus callosum. |
| Amygdala | The murderers showed asymmetrical abnormalities, as they had reduced left amygdala activity but greater right amygdala activity, which was different to the controls. |
| Medial temporal lobe | Murderers showed asymmetrical levels of activity in these regions. Specifically, there was lower activity in the left medial temporal lobe and hippocampus but higher activity on the right side of this area. Murderers had lower left activity than right. |
| Thalamus | Asymmetrical levels of activity were found in murderers. The right thalamus showed higher activity levels and lower left levels of activity in the thalamus. |
| Caudate, putamen, globus pallidus, midbrain and cerebellum | Murderers showed slightly higher activity levels than controls in cerebellar glucose metabolic levels. |
Overall, there were no significant differences between the groups in their performance on the task.
Fig 2. PET scan example of a normal, healthy brain.
Raine et al. (1997) Summary
Overall, considering the above results, we can say that murderers have lower glucose metabolism in the following brain area:
They also show asymmetrical levels of activity in their left and right hemispheres in the following brain regions:
Amygdala
Thalamus
Medial temporal gyrus
Hippocampus
These results support the notion of there being a biological difference in murderers when they are compared to healthy people.
Areas of the limbic system specifically (e.g. the amygdala) aid in the control of emotion and modulation of aggression. Impairment in these areas could lead to inappropriate responses to threats.
The amygdala and the prefrontal cortex are associated with aggression and self-control, so it is not surprising that dysfunction in these areas could be related to aggressive behaviours, more impulsive actions, and a lack of self-control.
Raine et al. (1997) stress that the results of this study do not indicate that:
- Violence is caused solely by biology.
- Murderers who plead NGRI are not responsible for their actions.
- These results generalise to other offenders claiming NGRI.
- Brain dysfunction predisposes individuals to crime.
Raine et al. (1997): Evaluation
Let's consider its strengths and weaknesses.
Raine et al. (1997): Strengths
Raine et al. (1997) established the largest sample size for an experiment of this type. They collected a sample of violent offenders, accounting for variabilities and ruling out issues such as ethnicity and head injuries whilst analysing behaviour during the entire process.
Overall, this increases the generalisability of the results, although this doesn't account for murderers who did not plead NGRI.
Their results provided an important base for future research.
Specific areas of abnormal function were identified in actual cases of murderers and violent offenders, expanding knowledge on the subject and providing critical areas of interest for future endeavours.
Their results are quite reliable, considering the technique they used.
PET scans are replicable, and the methodology can be used for future research, including the CPT.
Using strict procedures, like matching the murderers with similar controls, means that the results found and associations made could be considered highly valid.
Raine et al. (1997): Weaknesses
Although the controls could consent to the experiment, the murderers were not fully able to consent. This is due to a potential inability to understand what the experiment entails, as well as how the results may impact their plea for NGRI.
This raises ethical issues with the study.
Despite Raine et al. (1997) insistence that the results do not mean that these dysfunctions cause people to commit violent or murderous acts, they may still be misconstrued and interpreted as such.
The justice system may then use evidence like this to convict people of murder based on biological evidence, which has a ripple effect on the judicial system as a whole.
The study can also promote a deterministic view of behaviour. It suggests that violent behaviours are due to biological dysfunction and ignores the idea of free will and personal responsibility.
Can we imprison offenders for something they were predetermined to do? Or is this theory too deterministic?
The study does not provide much information about other violent offences, reducing generalizability and utility.
Although Raine et al. (1997) had a large sample size, the sample consisted of murderers vs non-murderers and did not account for other types of violent crimes.
Raine et al 1997 - Key takeaways
- Raine et al. (1997) hypothesised that violent offenders who plead NGRI would have dysfunction in various brain regions.
- Raine et al. (1997) tested this hypothesis by analysing 41 subjects convicted of murder or manslaughter and pleaded not guilty by reason of insanity (NGRI).
- The subjects completed a continuous performance task and underwent a positron emission tomography (PET) scan.
- Results indicated that murderers had lower glucose metabolism than normal, healthy controls in the bilateral prefrontal cortex, the posterior parietal cortex, and the corpus callosum.
- They also show asymmetrical activity levels in their left and right hemispheres in the limbic system areas.
References
- Raine, A., Buchsbaum, M., & LaCasse, L. (1997). Brain abnormalities in murderers indicated by positron emission tomography. Biological psychiatry, 42(6), 495-508.
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