The youths were tested with functional magnetic resonance imaging to see how their brains reacted while watching video clips. The clips showed people in pain as a result of accidents — such as when a heavy bowl dropped on their hands. They also showed intentional acts, like stepping on another person’s foot.
When the aggressive youths watched people intentionally inflicting pain on another, the scan showed a response in the part of the brain associated with reward and pleasure. The youths who were not aggressive didn’t show the same brain response.
The study, published in the current issue of the journal Biological Psychology, suggests that the brain’s natural impulse for empathy may be disrupted in the brain of a bully, leading to increased aggression.
“This is the first time that f.M.R.I. scans have been used to study situations that could otherwise provoke empathy,” said Jean Decety, professor of psychology and psychiatry at the University of Chicago, in a press release. “This work will help us better understand ways to work with juveniles inclined to aggression and violence.”
While the study is small, the striking differences shown in the brain scans suggests that bullies may have major differences in how their brains process information compared to non-bullies. Dr. Decety said the aggressive adolescents showed a strong activation of the amygdala and ventral striatum, areas of the brain that respond to feeling rewarded. The finding “suggested that they enjoyed watching pain,” he said. Notably, the control group of youths who weren’t prone to aggressive behavior showed a response in the medial prefrontal cortex and the temporoparietal junction, areas of the brain involved in self regulation.