Pain May Be Pleasurable for Some Bullies

On top of that, subjects with conduct disorder showed no activity in the prefrontal cortex, which could have controlled those pleasurable emotions. The study results suggest that young people with conduct disorder enjoy seeing others in pain and lack the ability to control potentially inappropriate emotions.

"They're not only indifferent to the pain, they love it -- maybe," Lahey said. "They're responding to others being hurt, but in a way that's self-reinforcing."

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While the study proposed an exciting new hypothesis about how young people with conduct disorder may respond to certain stimuli, experts caution that it may not be appropriate to extrapolate the results to the garden-variety bully roaming elementary and junior high school hallways.

"CD at a young age is associated with very poor psychosocial outcomes," said Dr. Paul Sagerman, assistant professor of pediatrics at Wake Forest University School of Medicine in Winston-Salem, N.C.

These outcomes include poor relationships, incarceration, depression and suicide.

And conduct disorder is not very common, affecting 1 to 4 percent of 9- to 17-year-olds in the United States, according to the U.S. Department of Health and Human Services. The disorder is also far more common among boys than girls.

Bully for You

Sagerman, who was not associated with the study, pointed out that bullying typically peaks in young adolescence, between the sixth and eighth grades, and may serve to impress peers.

Using aggressiveness to gain something tangible such as social approval versus personal reward is an important distinction between a regular bully and someone with conduct disorder. Indeed, aggressiveness can be channeled constructively to allow a neurotypical person to excel later in life, in business or athletics, for example.

Although the study is not large enough to draw firm conclusions, it does lead to some new hypotheses and questions.

"The question is what's the chicken and what's the egg?" Sagerman said.

Is bullying a learned behavior, creating pathways in the brain that lead to conduct disorder, or is conduct disorder inherent and results in aggressive behavior?