TUESDAY, March 16 (HealthDay News) -- A new study suggests that the brain's reward system, which makes us feel good when we get things we want and need, could hold insight into why some people are psychopaths.

Researchers from Vanderbilt University in Nashville, Tenn., used brain scans to find evidence that the brain reward system is hypersensitive in people who show more latent signs of psychopathic personality disorder.

"By linking traits that suggest impulsivity and the potential for antisocial behavior to an overreactive dopamine system, this study helps explain why aggression may be as rewarding for some people as drugs are for others," Dr. Nora Volkow, director of the U.S. National Institute on Drug Abuse, which funded the study, said in a statement.

Psychopaths are defined as charming, manipulative and sensation-seeking people who lack empathy. Many people who fit into this category become criminals.

In the study, researchers studied the brain's reward system as subjects received low doses of amphetamine and played a game.

The researchers think it's possible that people with hypersensitive reward systems "may become focused on a chance to get a reward, and less able to shift their attention until they get what they're after," said Joshua Buckholtz, doctoral candidate in neuroscience and the lead author of the study, in a statement. "This pattern, along with other traits, could develop into psychopathic personality disorder."

An intense focus on a particular goal could cause psychopathic individuals to shed the fear that often accompanies negative behavior, the team said. They may also have less sensitivity to other's emotions and a reduced capacity to learn from their own mistakes.

The study is published in the March issue of the journal Nature Neuroscience.

More information

The U.S. National Library of Medicine has details on mental health.