The boys were attached to brain-scanning machines and shown a series of short videos portraying painful situations - some accidental, such as a hammer dropped on a toe; others intentional, such as a piano lid closed on a player's fingers. The scans showed that the pain centers of the brains of both groups of boys lit up when viewing the videos, indicating a response of empathy with the hurt people.
But the bully group showed a surge of activity in the amygdala and ventral striatum, areas of the brain sometimes associated with reward and pleasure. "We think it means that they like seeing people in pain," said Benjamin Lahey, a psychologist at the University of Chicago and co-author of the study. Jean Decety, a University of Chicago neuroscientist, is lead author of the study. "If that is true," added Lahey, "they are getting positively reinforced every time they bully and are aggressive to other people."
The researchers didn't expect the results. They thought the bullies would be unresponsive when they witnessed pain in other people - merely emotionally cold and remorseless. The scans also revealed that a region of bullies' brains that assists in regulating emotion is inactive.
Thus, they lack a mechanism to control themselves when provoked. "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," Lahey said.
"I am not surprised that scientists who are working on this and doing brain imaging are finding more and more," said Marlene Snyder of Clemson University's Institute on Family and Neighborhood Life and the Olweus Bullying Prevention Program. "I think we're just at the beginning of pioneering understanding of how the brain works," she said. "The more we know about this, the more hopeful we can all be in finding meaningful interventions."