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- Murderers pleading NGRI characterised by reduced glucose metabolism in prefrontal cortex, pariateial cortex and corpus callosum - abnormal asymmetrics of activitity (left hemisphere lower than right) in amygdala, thalamus, hippocampus.
- Violent behaviour can be explained by the disruption of a network of interacting brain mechanisms rather than any single structure. Such disruption would not cause behaviour to be violent but would predispose an individual to violent behaviour.
- Confounding variables - Head injury, IQ.
- Neural processes underlying violence - complex and cannot be reduced to single brain mechanism causing violence in a direct way.
- Violent behaviour probably involves the disruption of a network of multiple interacting brain areas that predispose people to violence in the presence of other social, environmental and psychological predispositions.
- Issue of cause and effect, all we know is that brain dysfunction is related to violence. Maybe that a violent lifestyle causes changes in the brain rather than the other way around.
- Issue of assessor of PET scans possible lack of concentration and other variable factors.
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- Results do not show that violent behaviour determined by biology alone, clearly social, psychological, cultural, and situational factors play important roles in predisposition to violence.
- Results do not show that murderers pleading NGRI are not responsible for actions, nor that PET cam be used as means of diagnosing violent individuals.
- Results do not show that brain dysfunction causes violence. May even be that brain dysfunction is an effect of violence.
- Results do not show that evidence can be explained by the results, relate only to criminal behaviour.
- Findings do suggest a link between brain dysfunction and a predisposition towards violence in specific groups - further investigation required.
- Raine made clear that this study does not mean that murderers can not be held accountable for their actions, nor that we can use a PET scan to diagnose criminals.
- Also acknowledged that he could not rule out head injury and IQ as factors that may have contributed to the results.
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- Methodology and Procedures - Findings do not show that violent behaviour is determined by biology alone. Limitation of method - no casual conclusions drawn. Danger readers misinterpret findings and assume that criminal behaviour is predetermined and inescapable.
- Research Technique - Data collected in study using PET scans. Techniques permitted researchers to study brain in a way not possible until recently. In past, researchers relied on post-mortem exams where brain physiology could not be linked to behaviour. PET scans permit researchers to study detailed regions of the brain. Enable brain in action to be examined. Could see how brains of different individuals differed in ways they processed info.
- Ethical Issues & Social Implications - main group of participants - murders, suggests may not have been mentally competent to provide valid consent. Participants may not have fully understood what they would be required to do. e.g. may have found performance task difficult - potential to lower self-esteem - psychological harm. May not have realised what would be involved in a PET scan and may have found distressing. May not have fully understood their right to withdraw at any time, especially as they were prisoners. May not have felt they couldn't simply say they no longer wished to take part.
- Socially sensitive research - any research that has consequences for larger groups which participants are members. e.g. research on drug addiction or homosexuality. If the research indicates that murderers are born rather than made may have consequences that would be disadvantageous for people with similar brain abnormalities. Might be imprisoned without any trial or any reference to their social circumstances.
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- Sample - Murderers not typical of all violent individuals. Findings do not show that all violent offenders have such brain dysfunctions - study can only draw conclusions about murderous offenders. Individual with some recognised form of mental impairness. Many violent crimes do not involve murder. Conclusions restricted to a very particular group.
- Alternative Evidence - Yang & Raine 2009 - meta-analysis of 43 imaging studies considered both antisocial and violent behaviour. Conclusions -significantly reduced prefrontal activity in antisocial and/or violent individuals. Supported by genetic studies that indicate a 'criminal gene'. Maoa gene causes abnormally high levels of dopamine.
- Tiihonen et al. 2015 analysed genes of 895 Finnish prisoners - found association between gene and an increased likelihood of committing a violent crime. 1 neuroscientist researching this - James Fallon, analysed his own genes and found that he had the genetic and brain characteristics of a violent criminal but he wasn't.
- Diathesis - stress explanation - genetic predisposition only manifested if certain stressors triggered it. e.g. difficult childhood.
- Biologically reductionist - ignores the many other possible reasons why a person may act violently. Social background, role models, psychological predispositions, learned responses etc. Ignoring those other factors is unethical as it places the blame for the criminal behaviour solely inside the criminal, absolves society as a whole for any blame.
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