November 7, 2008

Study Shows Bullies Relish Inflicting Pain

Abnormally aggressive teens may in fact take pleasure in causing pain in others, investigations using brain scans at the University of Chicago indicate.

"This is the first time that MRI scans have been used to study situations that could otherwise provoke empathy," said Jean Decety, Professor in Psychology and Psychiatry at the University of Chicago. "This work will help us better understand ways to work with juveniles inclined to aggression and violence."

This may not be too shocking to those who have been the target of bullying, but it is not what the researchers were expecting.

"The reason we were surprised is the prevailing view is these kids are cold and unemotional in their aggression," said Lahey, whose study appears in the journal Biological Psychology.

Scans of the violent youth's brains indicated that an area of the brain connected to rewards was highlighted when the youth viewed a violent video clip an individual imposing pain on another. Youths that had no previous history of unusually aggressive behavior did not share that response, the study said.

"This is looking like maybe they care very much," said Lahey of the bullies, who also worked on the study with Decety.

The investigation compared eight 16- to 18-year-old boys with a history of aggressive behavior to a group of adolescents without abnormal signs of hostility.

The youths were scanned with MRI while viewing several video clips where people suffered pain by accident, like when a weighty bowl was dropped on their hands, and deliberately, such as when a person stomped on another's foot.

In the violent teens, parts of the brain connected with feeling rewarded, the amygdala and ventral striatum, increased in activity when viewed pain being exacted on others.

"The aggressive youth activated the neural circuits underpinning pain processing to the same extent, and in some cases, even more so than the control participants without conduct disorder," Decety said.

However, they had very little activity in part of the brain occupied in self-regulation, the medial prefrontal cortex and the temporoparietal junction, as compared to the control group.

"Aggressive adolescents showed a specific and very strong activation of the amygdala and ventral striatum (an area that responds to feeling rewarded) when watching pain inflicted on others, which suggested that they enjoyed watching pain," he continued.

Lahey said the divergence between the groups was important and remarkable, but warned that the study was diminutive and needs to be established by a much larger study.


Image 1: In the study, researchers compared eight 16- to 18-year-old boys with aggressive conduct disorder to a control group of adolescent boys with no unusual signs of aggression. The boys with the conduct disorder had exhibited disruptive behavior such as starting a fight, using a weapon and stealing after confronting a victim. (Photo: 2008 Jupiter Images Corporation)

Image 2: When youth with aggressive conduct disorder watch an individual intentionally hurting another (like closing a piano lead), regions of the brain that process painful information are activated, as well as the amygdala and ventral striatum (part of the neural circuit involved in reward processing. These adolescents seem to enjoy seeing people in pain. (Photo: Jean Decety, University of Chicago)


On the Net:

University of Chicago

Biological Psychology: Atypical Empathetic Responses in Adolescents with Aggressive Conduct Disorder: A functional MRI Investigation (PDF)