It may not be lack of empathy or fear of consequences, as previously postulated, but rather a hyper-active attraction to reward and risk. Researchers suspect this heightened draw may be the result of an exaggerated dopamine responses produced by an overactive nucleus accumbens.

In the first portion of the experiment, the researchers gave the volunteers a dose of amphetamine, or speed, and then scanned their brains using PET to view dopamine release in response to the stimulant. Substance abuse has been shown in the past to be associated with alterations in dopamine responses. Psychopathy is strongly associated with substance abuse.“Our hypothesis was that psychopathic traits are also linked to dysfunction in dopamine reward circuitry,” Buckholtz said. “Consistent with what we thought, we found people with high levels of psychopathic traits had almost four times the amount of dopamine released in response to amphetamine.”

In the second portion of the experiment, the research subjects were told they would receive a monetary reward for completing a simple task. Their brains were scanned with fMRI while they were performing the task. The researchers found in those individuals with elevated psychopathic traits the dopamine reward area of the brain, the nucleus accumbens, was much more active while they were anticipating the monetary reward than in the other volunteers.

“It may be that because of these exaggerated dopamine responses, once they focus on the chance to get a reward, psychopaths are unable to alter their attention until they get what they’re after,” Buckholtz said. Added Zald, “It’s not just that they don’t appreciate the potential threat, but that the anticipation or motivation for reward overwhelms those concerns.”