The crime rate in the United States is down again and people are looking for reasons why. Here is an interesting possible answer from James Q. Wilson: crime is down because people are exposed to less lead. This is how the reduction in lead would help:

In recent years, neuroscientists have made important progress in identifying the precise mechanisms by which lead exposure reduces impulse control…

While we can’t always control what we feel – many of our urges are ancient drives, embedded deep in the brain – we can control the amount of attention we pay to our feelings. When faced with a tempting treat, we can look away…

The tragedy of lead exposure is that it undermines one of the most essential mental skills we can give our kids, which is the ability to control what they’re thinking about. While the unconscious will always be full of impulses we can’t prevent, and the world will always be full of dangerous temptations, we don’t have to give in. We can choose to direct the spotlight of attention elsewhere, so that instead of thinking about the marshmallow we’re thinking about Sesame Street, or instead of thinking about our anger we’re counting to ten. And so there is no fight. We walk away.

This is an interesting argument. I suspect there is a bigger story that could be told about lead reduction over the years: Wilson hints at the background as the EPA announced a phased-in reduction in the lead in gasoline in late 1973 and lead was banned from paint in 1977. These facts are taken for granted now but I imagine these were public health announcements that created some discussion at the time, particularly from industry lobbying groups.

Is there a way to test the lead hypothesis by looking at a comparison group?

If this turned out to be a primary factor in the reduction of crime, how would public officials, police officers, and the public work with this information?