“POVERTY”, wrote Aristotle, “is the parent of crime.” But was he right? Certainly, poverty and crime are associated. And the idea that a lack of income might drive someone to misdeeds sounds plausible. But research by Amir Sariaslan of the Karolinska Institute, in Stockholm, and his colleagues, just published in the British Journal of Psychiatry, casts doubt on the chain of causation—at least as far as violent crime and the misuse of drugs are concerned.

Using the rich troves of personal data which Scandinavian governments collect about their citizens, Mr Sariaslan and his team were able to study more than half a million children born in Sweden between 1989 and 1993. The records they consulted contained information about these people’s educational attainments, annual family incomes and criminal convictions. They also enabled the researchers to identify everybody’s siblings.

In Sweden the age of criminal responsibility is 15, so Mr Sariaslan tracked his subjects from the dates of their 15th birthdays onwards, for an average of three-and-a-half years. He found, to no one’s surprise, that teenagers who had grown up in families whose earnings were among the bottom fifth were seven times more likely to be convicted of violent crimes, and twice as likely to be convicted of drug offences, as those whose family incomes were in the top fifth.

What did surprise him was that when he looked at families which had started poor and got richer, the younger children—those born into relative affluence—were just as likely to misbehave when they were teenagers as their elder siblings had been. Family income was not, per se, the determining factor.

That suggests two, not mutually exclusive, possibilities. One is that a family’s culture, once established, is “sticky”—that you can, to put it crudely, take the kid out of the neighbourhood, but not the neighbourhood out of the kid. Given, for example, children’s propensity to emulate elder siblings whom they admire, that sounds perfectly plausible. The other possibility is that genes which predispose to criminal behaviour (several studies suggest such genes exist) are more common at the bottom of society than at the top, perhaps because the lack of impulse-control they engender also tends to reduce someone’s earning capacity.

Neither of these conclusions is likely to be welcome to social reformers. The first suggests that merely topping up people’s incomes, though it may well be a good idea for other reasons, will not by itself address questions of bad behaviour. The second raises the possibility that the problem of intergenerational poverty may be self-reinforcing, particularly in rich countries like Sweden where the winnowing effects of education and the need for high levels of skill in many jobs will favour those who can control their behaviour, and not those who rely on too many chemical crutches to get them through the day.

This is only one study, of course. Such conclusions will need to be tested by others. But if they are confirmed, the fact that they are uncomfortable will be no excuse for ignoring them.