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Genetic Confounds and the Causes of Crime

Criminologist Brian Boutwell on the genetic influences on behavior, including criminal behavior:

Variety in our gene pool matters when we seek to understand why some people can dunk a basketball or compose a sonnet, and why some people persistently break the law. The effects of genetic differences make some people more impulsive and shortsighted than others, some people more healthy or infirm than others, and, despite how uncomfortable it might be to admit, genes also make some folks more likely to break the law than others.

...Imagine that you’re curious whether certain parenting styles influence self-control in children. It’s not hard to find evidence that the way parents treat their children is associated with the child’s level of self-control later in life. But parents don’t just pass on life lessons for learning self-control to their kids, they also pass along their genetic material. Half of your genetic material was inherited from Mom and half came from Dad. If you ignore the element of genetic transmission, you might falsely attribute any correlation between parent and child as being due to social transmission.

The way parents treat children is, in part, a product of their own personality and temperament. Personality is partly heritable, so the observation that parents and children tend to have similar levels of self-control could be due to social transmission, genetic transmission, or both.

Most of the evidence about the causes of crime overlooks genetic transmission. Yet, some research has found that once you account for genetic influences on self-control, previously identified social transmission effects (read: parenting) on the child’s self-control become unstable. In other words, when you control for genetic transmission (the alternative explanation that most criminologists overlook), the effect of parenting on self-control diminishes or goes away entirely.

Consider another type of parenting effect — one that shows up in the news frequently — spanking. Not long ago, we examined the relationship between spanking and behavioral problems in children. Once we controlled for genetic transmission, there was no spanking effect in the way that most scholars think about spanking effects. Put another way, our evidence did not support the conclusion that spanking causes behavioral problems in the sense that most psychologists would argue.

The conundrum of heritability transcends parenting. For instance, it’s obvious that crime isn’t randomly distributed across neighborhoods. It seems to be a relatively stable factor that defines an area over many generations. Equally nonrandom, though, is the process by which people sort themselves into neighborhoods. People cluster into areas based on a host of factors, including the primary factor of income. Here’s the kicker, if any of the traits that affect residential choices are heritable and you ignore that influence, your findings regarding the impact of neighborhood factors on crime could be in jeopardy.

A remarkable study in Sweden recently found that highly disadvantaged neighborhoods had more crime. Yet that neighborhood effect disappeared when risk factors concentrated within certain families were taken into account. Once again, social transmission effects weakened (and, in this case disappeared) when other factors like genetic transmission were controlled for. Does this finding guarantee that similar results will emerge in other samples around the world? No. But criminologists rarely consider the possibility that their own studies could be polluted by hidden genetic effects.

The more technical term for this phenomenon is genetic confounding, and there is reason to believe that it is endemic to much of the research coming out of the social sciences in general, and criminology in particular. Our own research into the issue suggests that even a modest amount of unmeasured genetic influence can pollute and infect your findings. As a result, much of what we think we know about the causes of crime could be overstated or just flat wrong.

I first became interested in genetic influences on behavior and opinion when I was writing my book on the death penalty. I wanted to know what kinds of argument and information change peoples' views on capital punishment, and found that the answer was, basically, none. The typical arguments people use against capital punishment are human rights, cost, reliability, deterrence, possibility of executing the innocent. And study after study showed that these arguments usually only changed a small percentage of peoples' minds, and that the changes were often temporary.

One reason for that is that your views on capital punishment are influenced by your genes. Since the sequencing of the human genome in 2003 -- the most important scientific achievement of the past 20 years -- researchers have been able to tease out the genetic influences on all sorts of behavior and personality traits. There's no reason that should exclude crime -- in fact, the kinds of personality traits which lead to a higher likelihood of crime are well-known to be heritable.

Every time you read about a social-science survey on the effects of education, parenting, or environment on this or that human trait, you should scan the report for any signs that the authors took genetic confounds into account. If they didn't the report is worthless. It's that simple.

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