Scientists in the US examining brain scans of teenage boys with and without a history of aggressive conduct disorder found that their brains responded differently while they watched scenes of people in pain and suggested that bullies may enjoy watching people in pain.

The study was the work of professor Jean Decety who holds posts in the Departments of Psychology and Psychiatry at the University of Chicago, and other colleagues from the University, and is published in the journal Biological Psychology.

Decety and colleagues were interested in finding out if adolescents with aggressive conduct disorder (CD) showed different empathic responses to seeing others in pain.

Using a type of brain scan called fMRI (functional magnetic resonance imaging), they studied the brain activity of 8 teenagers with aggressive CD and another 8 matched controls that did not show symptoms of CD, while they watched animated scenes showing people in pain and not in pain. All the boys were aged between 16 and 18.

Scenes of people in pain were of two types: deliberately inflicted and accidentally inflicted by another person.

After the scan the participants filled in questionnaires and rated how painful the scenes were.

The results showed that:
  • Brain scans of both the CD and the non-CD group linked perception of pain in others to activation of the pain matrix (anterior cingulate cortex, insula, somatosensory cortex, supplementary motor area and periaqueductal gray).

  • The pain matrix showed a particular level of activation in the CD group, and this was accompanied by significantly greater activation of areas of the brain associated with reward (the amygdala, striatal, and temporal pole).

  • Watching intentionally inflicted pain was linked to increased activity of the medial prefrontal cortex, lateral orbitofrontal cortex, and right temporo-parietal junction in the non-CD group (the controls). This are of the brain is linked to self-regulation.

  • The CD group on the other hand only showed activation of the insula and precentral gyrus (involved with basic motor pathways).

  • Analysis of connectivity showed less amygdala/prefrontal coupling in the CD group compared to the non-CD group when they watched people inflicting pain on others.
The researchers concluded that:

"These preliminary findings suggest that youth with aggressive CD exhibit an atypical pattern of neural response to viewing others in pain that should be explored in further studies."

Decety said in a statement reported by UPI that:

"This is the first time that functional magnetic resonance imaging scans have been used to study situations that could otherwise provoke empathy."

"This work will help us better understand ways to work with juveniles inclined to aggression and violence," he added.

Decety said that the brain scans of the CD group, the boys with a history of aggressive and bullying behaviour, showed their reward centres lit up when they watched pain being inflicted on others, suggesting that they enjoyed watching pain.

"Atypical empathic responses in adolescents with aggressive conduct disorder: A functional MRI investigation."
Jean Decety, Kalina J. Michalska, Yuko Akitsuki, Benjamin B. Lahey.
Biological Psychology, First published online 30 September 2008, Corrected proof in press 7 November 2008.

DOI: 10.1016/j.biopsycho.2008.09.004

Click here for Abstract (via DOI).

Sources: Journal Abstract, UPI.

Written by: Catharine Paddock, PhD.