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Causes of Crime - Nature AND Nurture

One of the issues that inevitably arises in any discussion of crime and sentencing, and that also must be considered when discussing rehabilitation, is that of the causes and origins of criminal behaviour. It is safe to say there is no one cause for criminality, or even for one particular type of offence. The causes are complex, and will vary from offender to offender. Not only that, but in most cases, there will be more than one cause for any particular offender's behaviour.

Not only many forms of criminal behaviour, but many forms of behaviour generally have some genetic component, in some cases overwhelmingly so. For instance, the body of evidence for over 90% of causation of sexual orientation being genetic continues to mount up. And IQ now looks to be 60-80% heritable, and so on it goes. However, please note that there is no one "criminal gene", and that neither genes nor environment are exclusive causative factors.

Recent findings indicate that genes and environmental factors often interact and one can amplify the effects of the other. It must also be remembered that whatever one's genetic inheritance, people still have the ability to make choices, and must still be held accountable and responsible for those choices. All people have a choice about how they treat others - and a few consistently make the wrong choice...

There is the odd case of a person who commits a single serious offence with one clear cause, but most serious violent offenders have a long track record of a variety of offences, and these are the offenders we are most interested in dealing with. The first thing we need to get out of the way is the old nature/nurture argument - in reality it is not either/or, but a bit of both, with the proportions varying from offender to offender. It would be rare to find an offender for whom their background or environment provided an explanation for all their offending, and likewise it would be fairly unusual to find one for whom all their offending was down to purely genetic causes.

Probably the most insidious misconception in recent years, however, has been the former - the idea that by "fixing society", i.e. eliminating poverty, along with extensive social engineering, we can eliminate violent crime. That does not work, based as it is on the misconception that "nurture" (i.e. society, background, and environment) alone is responsible. Certainly some cultural factors can worsen things, as can changes in such things as the drinking age, as we are now finding out.

This misconception is now thankfully on its way out, as it is eroded by swathes of new research findings, some from right here in New Zealand. For a start there is the following quote from "Mental Health in New Zealand; a Public Health Perspective" by Ministry of Health 1997 (requires Adobe Acrobat PDF Reader)

B I O L O G I C A L

The evidence that biological variables contribute to personality-disordered behaviours comes from three areas of research. The first is genetic studies. Measurable aspects of normal personality are at least moderately heritable, with most studies suggesting that genes account for approximately half the variation found in normally distributed behavioural traits (Holden 1987). Because of problems in classification, it is more difficult to be certain about personality disorders, but a recent survey of the literature reported that there is consistent evidence of a genetic contribution to several categories of abnormal personality (McGuffin and Thapar 1993). The pattern of inheritance is probably polygenic. The second area of research is studies on temperament. Temperament may be defined as simple, non-motivational, non-cognitive behavioural characteristics. Temperamental variables (eg, sociability, activity, impulsivity) can be reliably identified by the time a child is two.

There is now overwhelming evidence that children differ markedly from one another in a host of ways, that these differences are reasonably stable and persistent and that they matter in terms of implications for later development, including abnormal personality traits (Rutter 1987). There is also considerable evidence that these manifest differences are linked with neurobiological variables including autonomic reactivity, cortisol evels and neurotransmitters (Mulder 1992).The third area is neurochemistry. Certain behaviours appear to be related to abnormal neurotransmitter states. The most consistent finding is that low levels of central nervous system (CNS) serotonin are linked with impulsive, violent and disinhibited behaviour in both man and animals (Dolan 1994).Other research links disturbances in CNS dopamine with conduct disorder in boys (Galvin et al 1991).

E N V I R O N M E N TA L

Although clinical experience and personality theories indicate that environment plays a major role in the development of personality disorders, there is remarkably little evidence to support such a view. Vaillant, for example, found very little correlation between a bleak early childhood and the adult use of immature defence mechanisms commonly associated with personality disorders (Vaillant 1977).

And then there are these reports on an excellent study done over 26 years on 442 Dunedin men, demonstrating that both genetic factors and background act in conjunction. Reports on this are here, and here, from the Economist, and here from CBS News and here from the Canadian Broadcast Corporation

Further evidence from overseas research on genetic influences on aggressiveness and some forms of anti-social behaviour from the BBC Science and Technology site and from these reports in the Herald a while back, firstly this very interesting one on research being done with brain scans and violent aggression. Far more controversial is this piece that puts forward the theory that abortion has actually played a part in lowering the crime rate in the US of late. This does have some far reaching implications. However it should also be borne in mind that the US prison population increased markedly over the last 10-15 years and crime figures dropped in line with that. Graphs of these two sets of data are like mirror images...

All of this has a number of implications for crime and justice policy. For a start, we need to recognise that rehabilitation is not always going to work, and we need to look seriously at locking up the substantial proportion of offenders that we cannot realistically hope to rehabilitate, so as to protect the public. This is particularly important when it comes to paedophiles, some of which fall into this category, as this research report shows. This report is also interesting, as it shows that paedophilia seems likely to have a physiological/neurobiological cause.

These two quotes, one from this document;

"Traditionally, psychopathic behavior has been blamed on familial or sociological factors. Increasing evidence indicates, however, that psychopathic behavior stems not from bad parenting or a poor environment, but from fundamental differences in the psychopathic brain."

...and this from Robert D. Hare's book "Without Conscience", reviewed elsewhere on this site;

"To many people the very idea of psychopathy in childhood is inconceivable. Yet, we have learned that elements of this personality disorder first become evident at a very early age."

...leave no doubt, that at least for psychopathy, a common condition amongst serious repeat violent offenders, the evidence demonstrates that genes are a significant, perhaps overriding causative factor. More recent research indicates that brain scans show abnormalities in psychopaths, which no doubt accounts for the poor success rate in treatment of psychopathy. Further evidence has more recently come to light for this in a study of blood flows in the brains of psychopaths indicating that it is indeed a biological defect.

One question that will be asked by many is - "why have violent crime rates gone up so much in the last 50 years - surely genes and human nature do not change that rapidly!" That is a good question - and no, human nature has not changed. What has changed is justice and imprisonment policies, along with society. Many of the social changes of the last fifty years have been desirable and good, but some have not, and have served to amplify rather than rein in the effects of pre-existing neurobiological conditions such as psychopathy in a small percentage of the population. We would suggest that we should perhaps revisit some of the policies and ideas that worked back in the early fifties, and ask ourselves why they were so effective in dealing with pathological variations in human nature than more recent policies....

Further information can be found at these links

• The Biological basis of crime from Edith Cowan University in Perth, Australia.
• Sociological and Environmental Factors of Criminal Behavior a paper from the University of Delaware
• The Neuropsychopharmacology of Criminality and Aggression from the Canadian Psychiatric Association (multi page document)
• Biology of Violence A Princeton University article
• UBC researcher finds genetic link to aggression from University of British Columbia
• A genetic basis for aggression and anger Eureka Alert article
• Evolution, Males, and Violence from the Chronicle of Higher Education
• Finally, a trawl around www.crimetimes.org will yield many more articles relevant to this subject

We'd also strongly recommend reading "The Blank Slate" by Steven Pinker for a really in depth insight into this subject. It demonstrates the clear case that nature (that's genes) plays just as large a part, and in some cases a larger part in behavioural tendencies than nuture (that's environment, upbringing, "society" etc). It's available here and its a damn good read. It might challenge a few people's preconceptions though There's lots more links from this page

Also recommended is "The Demonic Males" by Richard Wrangham and Dale Peterson, an excellent study of the origins of human violence. See this link for more - Are our genes wired for violence? - Expert thinks it's a primal instinct. Copies of this can be picked up from the Icon bookstore in Ponsonby for five bucks, a real steal at the price.

This article is by Peter Jenkins (the webmaster here). If you wish to use it in your own work, go right ahead, help yourself. Some acknowledgement of the source i.e. Sensible Sentencing Trust would be appreciated.