Genes link criminality and intelligence

Data collected from over one million Swedish men shows that sons whose fathers have criminal records tend to have lower intelligence than sons whose fathers have no criminal history.

The research, conducted by scientists in Sweden and Finland, indicates that the link is not directly caused by fathers' behaviour but is instead explained by genetic factors that are shared by father and son.

"The findings are important because cognitive ability is among the most important psychological predictors of many important life outcomes, including socio-economic success and health," said lead researcher Antti Latvala from the Karolinska Institute in Sweden and the University of Helsinki in Finland.

Looking at the extensive data, the researchers found that men whose fathers had any criminal convictions tended to have lower cognitive-ability scores than men whose fathers had no such history.

And this association seemed to be influenced by the severity of the fathers' criminal history.

"The more severe crimes the father had committed, the poorer was the sons' cognitive performance," Latvala added.

But did fathers' antisocial behaviour have a direct causal effect on sons' cognitive ability or could the link be explained by shared genetic factors?

To find out, the researchers compared the link between fathers' criminal history and sons' cognitive ability across cousins whose fathers had varying relationships to each other.

When the researchers took the varying genetic relationships into account, the association between fathers' criminality and sons' cognitive ability gradually diminished.

"Our results, thus, indicate that despite the adversities related to parental criminality, having a father who has been convicted of crime is unlikely to influence cognitive development in the offspring when the effects of other factors associated with parental antisocial behaviour, including genetic risks, are taken into account," the authors said.

The study appeared in the journal Psychological Science.