Is Crime Genetic? Scientists Don’t Know Because They’re Afraid to Ask

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Social scientists generally, and criminologists especially, often lack the ability (usually due to both ethical and practical concerns) to perform randomized controlled trials, the gold standard of research. We might expect, for instance, that having low levels of self-control is a cause of criminal behavior. In fact, some of the most powerful explanations of crime have been built on this idea, and there is much evidence to support it. We might also hypothesize that bad parenting causes children to develop low levels of self-control. Yet we can’t randomly assign people to have different levels of self-control, and we most assuredly can’t randomly assign kids to parents. All of this is to say that criminologists may never know for sure whether parenting causes self-control and whether, in turn, self-control causes crime.

While criminologists typically can’t use randomized trials, they do use a variety of statistical methods to study parenting and self-control, and self-control and crime. They attempt to rule out the most likely alternative explanations for why bad parenting leads to less self-control and why less self-control leads to criminal behavior. This research has consistently revealed that parenting styles correlate with self-control development in children, and self-control in childhood predicts a variety of important outcomes, including criminal behavior. {snip}

Yet these studies will never achieve the accuracy of a randomized controlled trial, because all of those factors, like self-control, delinquent peer affiliation, etc., are also, to some degree, heritable.

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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.

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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.

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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.

Our goal here is not to pick on social scientists; after all, we are social scientists. But social scientists in general, and criminologists in particular, should embrace research designs that allow one to account for genetic confounding. To do so, it will be necessary to adopt designs capable of pulling apart genetic and environmental factors. This translates into a need to analyze data from relatives.

Sampling one child, from one family–as social scientists typically do–is similar to performing a weak drug trial. For decades, behavior geneticists have been analyzing sibling data (mostly twins), which is one of the most powerful methods for probing the relationship between two variables.

Yet most criminologists do not utilize these designs. Not for any good methodological reason, at least none of which we are aware. Instead, it seems that the word “gene” makes social scientists nauseated. Not long ago, in fact, the top journal in the field of criminology published an article calling for an end to twin studies. Let that resonate a moment. {snip}

If criminology and the social sciences wish to continue maturing into powerful scientific enterprises, we must stop conducting studies like they are bad drug trials.