Raine et al 1997

Many psychologists have theorised the possibility of criminals, especially those who have committed the most heinous of crimes, having brain abnormalities. These abnormalities are the potential source of dysfunction, and those who claim they are not guilty by reason of insanity (NGRI) lean heavily on the idea of biological causes for their behaviours.

Raine et al. (1997) 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.

Murder, flaticon.com/Freepik

Raine et al. (1997) Psychology: Brain Abnormalities in Murderers Indicated by Positron Emission Tomography

Many areas of the brain are associated with specific functions, but truly identifying the areas and confidently saying they are responsible for said functions is not an easy task.

So, many psychologists have acknowledged the localisation of function within the brain, and have attempted to establish the areas responsible for specific behaviours and actions. They have also argued that dysfunction of these areas results in violence and sometimes criminal behaviours in psychology. Like the amygdala, dysfunction of the prefrontal cortex has also been associated with issues in regulating aggression.

Raine et al. (1997) sought to identify these potential areas of abnormalities in the brain. They hypothesized 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 the following methodology:

Design

This was a quasi-experiment. The independent variable was whether the participant was a murderer who had pled NGRI or a normal person. The dependent variable was areas of brain dysfunction.

Participants

The participants consisted of 41 subjects who had been tried in California (US), comprised of 39 men and 2 women. They had been charged with murder or manslaughter, although for this experiment Raine et al. (1997) refers to all participants as 'murderers' for consistency's sake.

• Their mean age was 34.3 years.

They were referred to the University of California for imaging services due to their plea of insanity/incompetence, or because they were believed to have diminished capacity by those overseeing them (which may help their cases in the sentencing phase). They were all in custody during this time period.

These referrals were made for the following reasons:

• 6 cases of schizophrenia
• 23 cases of head/organic brain injury
• 3 cases of psychoactive substance abuse
• 2 cases of affective disorder
• 2 cases of epilepsy
• 3 cases of a history of hyperactivity/learning disabilities
• 2 cases of passive-aggressive/paranoid personality disorder

In 7 of these cases, unusual circumstances were noted in the crime, which alluded to the idea of there being diminished capability or mental impairment.

During their PET scan, the subjects were not taking any regulated psychoactive medications and were asked to remain drug-free for at least two weeks leading up to the scan. Raine et al. (1997) collected urine samples to ensure, whilst undergoing a PET scan, the subjects had tested negative for any medications.

Controls

To ensure the subjects being tested were indeed showing abnormalities, they were each matched with a normal subject of the same age, who had also been tested with a PET scan at the same location.

The exception was the 6 schizophrenic subjects (all of which were men) who were matched with 6 schizophrenics. Overall, there were 41 controls (39 men and 2 women).

• Their mean age was 31.7 years.

Just like the murderers, the controls were medication-free. The controls consented to the experiment, and those with any history of mental disorders in themselves or first-degree relatives were excluded. Those with a history of seizures, head trauma and substance abuse were also excluded.

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 as it gives off positrons, which then allows it to produce an image of areas of high activity (usually indicated by red/yellow colours) and low activity (usually indicated by blue/green colours).

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).

• Various versions of the CPT were used, including a degraded stimulus version for the frontal challenge task as it has an effect on the glucose-metabolic rate in the frontal lobe, and increases in the right temporal and parietal lobes of the controls.

The subjects completed a practice trial of the CPT 10 minutes before their FDG injection, and they 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. Overall, ten slices were obtained.

The slices depicted by Adrian Raine, Raine et al. (1997): Brain Abnormalities in Murderers

They identified brain regions using:

• Cortical Peel Technique (lateral areas)
• Box Technique (medial areas)

They used a MANOVA approach (two-way group repeated-measures multivariate analyses of variance) and a three-way MANOVA when necessary.

Results

For Raine et al. (1997), the results indicate differences in both the cortical and subcortical regions in the brain in glucose metabolic activity in murders compared to controls.

The Cortical Regions

For the prefrontal areas:

• The lateral and medial prefrontal cortical areas showed lower glucose metabolism in murderers in Raine et al. (1997) compared to controls.
• Murderers had significantly lower glucose metabolism in their left and right medial superior frontal cortex, left anterior medial cortex, right orbitofrontal cortex, and the gyri of both hemispheres in the lateral middle frontal.

For the parietal areas:

• There was lower glucose metabolism in murders in the parietal regions than control groups. This was more apparent in the left angular gyrus and the bilateral superior parietal regions.
• Murderers had significantly lower glucose in the left and right superior parietal gyri.

For the temporal areas:

• Surprisingly, murderers had the same glucose metabolism in the lateral temporal lobe when compared to controls.

For the occipital areas:

• Murders had significantly higher glucose metabolism in their occipital lobes when compared to controls.

The Subcortical Regions:

For the corpus callosum:

• Murderers showed lower glucose metabolism in the corpus callosum when compared to the controls.

For the amygdala:

• Murders showed lower and greater activity in their amygdala, specifically the left and right areas respectively when compared to controls. Essentially, the murderers showed asymmetrical abnormalities, as they had reduced left amygdala activity but greater right amygdala activity, which was different to the controls.

For the medial temporal lobe (including the hippocampus):

• Similar to the amygdala, 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 in the right side of this area. Murderers had lower left activity than right when compared to controls.

For the thalamus:

• Again, asymmetrical levels of activity were found in murderers when compared to the controls.
• Specifically, the right thalamus showed higher levels of activity, and lower left levels of activity in the thalamus.

For the cingulate:

• There was no difference here in glucose metabolism in murderers.

For the caudate, putamen, globus pallidus, midbrain and cerebellum:

• Murderers showed slightly higher levels of activity than controls in cerebellar glucose metabolic levels.

CPT and behavioural performance results in murderers

Overall, there were no significant differences between the groups on their performance on the CPT.

Ethnicity, handedness, and head injury effects

They found that left-handed murderers had higher levels of medial prefrontal activity, and less abnormal amygdala asymmetry than right-handed murderers.

Overall, ethnicity appears to have no significant influence on their findings, as white murderers and non-white murderers had no significant differences.

In regards to head injuries, 23 murderers reported such issues. They found no differences in these murderers when compared to murderers without head injuries, apart from one who showed lower activity in the corpus callosum.

Lower Glucose Metabolism and Murderers: Raine et al. (1997)

Overall, considering the above results we can say that murderers have lower glucose metabolism in the brain than normal, healthy controls. Specifically, the areas of lower glucose metabolism are:

• The bilateral prefrontal cortex
• The posterior parietal cortex
• The corpus callosum

They also show asymmetrical levels of activity in their left and right hemispheres in different regions of the brain, specifically:

• The amygdala
• The thalamus
• The medial temporal gyrus and hippocampus

These results support the notion of there being a biological difference in murderers when they are compared to healthy people, and could even suggest that these biological differences may be the cause of the abnormal, violent behaviours; they predispose the murderers into committing violent crimes.

As some of these brain areas, specifically the amygdala, are associated with aggression and self-control, it is not surprising that dysfunction of these areas may result in aggressive behaviours, more impulsive actions, and a lack of self-control.

Areas of the limbic system specifically aid in the control of emotion and modulation of aggression, supporting the inhibition of impulsive behaviours. When confronted by stimulating situations, especially those that may evoke hostile or malicious emotions, these murderers would not be able to form an appropriate response due to the apparent dysfunction, and then would struggle to learn from the consequences of their actions.

This also relates to the fearlessness theory, referring to the amygdala, as reduced activity in the amygdala results in a lack of fear.

PET scan example of a normal, healthy brain, commons.wikimedia.org

Raine et al. (1997) stress that the results of this study do not indicate that:

• Violence is caused solely due to biology, there are other factors such as social and cultural factors that also play a role.
• These results do not indicate that murderers who plead NGRI are not responsible for their actions, or that the PET is a diagnostic technique.
• The results cannot indicate the cause of the brain dysfunctions or establish a causal relationship between brain dysfunction and violence.
• The results cannot be generalised from those pleading NGRI to other violent offenders.
• The results cannot show as to whether these brain dysfunctions indicate a predisposition to specifically violence or crime.

Raine et al. (1997): Evaluation determinism

Let's consider the strengths and weaknesses of Raine et al. (1997).

Strengths

• Raine et al. (1997) established the largest sample size for their experiment that had not yet been conducted to such a scale on this many participants before. They collected a sample of violent offenders, accounting for variabilities and ruling out issues such as ethnicity and heady injuries, whilst analysing behaviour during the entire process. Overall, this increases the generalisability of the results, although this does not 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, which allows further research into these areas, expanding knowledge on the subject and providing critical areas of interest for future endeavours.
• The results also provided support for previous findings, such as the amygdala's association with aggression, and the prefrontal areas association with impulsivity.
• Raine et al. (1997) acknowledged other variables outside of a biological context in their paper, highlighting that although their results indicate there are biological differences in murderers, external factors cannot be ignored.
• Their results are quite reliable considering the technique they used. PET scans are replicable, and the methodology can be used for future research, such as including the CPT. They also provide a highly scientific basis of results, and can thus be trusted over other research that does not employ such rigorous techniques of testing.
• The use of strict procedures, for instance, matching the murderers with similar controls, meant that the results drawn and associations made had high validity.

Weaknesses

• Although the controls were able to consent to the experiment, the murderers were not fully able to consent. This is due to a potential inability to understand the experiment and what it entails, as well as what the results may mean when we consider their plea of NGRI. This raises ethical issues with the study.
• The results, despite Raine et al. (1997) insistence that the results do not mean that these dysfunctions are the cause of people committing violent of murderous acts, 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 also has issues with determinism. It ignores the concept of free will somewhat, as suggesting violent and murderous behaviours are due to biological dysfunction ignores the idea of people being able to make decisions for themselves. This also reduces the degree of personal responsibility in the offenders, as they can claim they did it because they were biologically predetermined to. Can we then imprison them for something they cannot control?
• 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. It, therefore, does not provide much information about any other type of violent offences, which reduces generalisability, as we touched upon earlier.
• The results can only indicate correlations between the abnormalities and the behaviours, not a cause-and-effect relationship. Only further research into external factors would be able to identify this.
• The PET scan had issues with clarity, specifically its resolution, which affected the interpretation of the results, especially when individual variability of brain structure was accounted for. Raine et al. (1997) also highlighted issues with standardised diagnostic testing.

Raine, A., Buchsbaum, M., & LaCasse, L. (1997). Brain abnormalities in murderers indicated by positron emission tomography. Biological psychiatry, 42(6), 495-508.