The pointer to this article came via email from Chris M. who says, “I recommend that this be tested first on government employees who carry guns and on those who give them orders.”

Several areas of the brain have been shown to be implicated with antisocial personality disorder (ASPD), commonly known as psychopathy or sociopathy. The frontal cortex is the large part of your brain that is responsible for higher reasoning and behavioral traits, and is one of the areas that has been looked at. It’s smaller than normal in individuals with ASPD. Although there is a difference in crime rates between men and women, 77 percent of that difference goes away once you control for frontal cortex volume.

Dysfunction or abnormalities in other brain regions have also been associated with higher rates of crime and ASPD. The septum pellucidum is a region of brain tissue that separates the brain’s fluid-filled spaces, called ventricles. During fetal development, there is an opening inside this tissue that usually closes up within the first few months after birth. Individuals for whom this doesn’t happen have higher rates of arrest and conviction, and score higher for ASPD.

A key center of emotion activity in the brain, the amygdala, is another important region, and a study comparing ASPD and normal brains found deformations and a significant reduction in volume in the ASPD cohort. These were centered on the basolateral nucleus, which is responsible for fear conditioning. This suggests that one possible source of differences (or one of several interweaving mechanisms) is that ASPD-affected individuals don’t form the same sort of response to fear as normal people.