A new study on brain activity shows that the brains of aggressive youths may be wired to feel pleasure when they witness pain in someone else. For the study, professors at the University of Chicago used fMRI scans to compare brain activity in eight unusually aggressive 16- to 18-year-old males to those of eight normal adolescent males while they watched videos of people getting hurt. The participants had histories of lying, stealing, committing vandalism, and bullying.

The results showed activity in the brain’s pain centers for both groups, but the aggressive youths also showed activity in the brain’s pleasure center, suggesting they were not indifferent to the pain, they actually enjoyed what they were seeing.

What researchers were expecting to see was an emotional indifferent response from people with conduct disorder, but fMRI scans showed a strong "pleasure" response to the image of people experiencing pain. "They're responding to others being hurt, but in a way that's self-reinforcing," said Dr. Benjamin Lahey, co-author of the study and professor of epidemiology and psychiatry at the University of Chicago.

It appears that bullies lack a mechanism that helps regulate emotion when, for example, they see someone getting hurt accidentally or intentionally. Instead of responding with negative emotions, they respond positively, Lahey said.

"We will have to develop therapies to either treat or compensate for this lack of self-regulation that we think is there and the fact that it may be positively reinforcing every time they hurt somebody," he added.

The study was published in the journal Biological Psychology.

Scientists hope they’ll begin to understand more about the unique ways in which the brain works. This study is just the beginning.