A new study of brain activity reveals that aggressive boys and men may enjoy seeing others in pain.

Benjamin Lahey of the University of Chicago and colleagues looked at the reactions of a group of youngsters with or without a history of violent behaviors while they were watching videos of people inflicting pain.

As stated by Lahey, psychologist at the University of Chicago and co-author of the study, the study’s results were startling. Researchers didn’t expect to learn that seeing people intentionally causing harm to others through verbal harassment or physical assault could actually please the teenagers. "It just dumbfounded us," Lahey said.

A small study of 16-18 year olds was carried out. Eight of the male participants had aggressive conduct disorder and eight had any unusual signs of aggression. Using functional Magnetic Resonance Imaging (fMRI), the team of researchers was able to compare the teens’ brain activity.

It appears that, while all in the study showed some activity in the brain’s pain centers, the brains of males with aggressive tendency also showed activity in a different area - the brain's pleasure centers. Participants without a history of unusual aggression showed no such activity, the journal Biological Psychology wrote.

According to lead author Jean Decety, professor of psychology and psychiatry at Chicago University, the research was aimed to better understand how to work with teenagers “inclined to aggression and violence.”

Researchers now think of developing therapies to treat or compensate for this deficiency of self-regulation “that we think is there and the fact that it may be positively reinforcing every time they hurt somebody," said Lahey. "I am not surprised that scientists who are working on this and doing brain imaging are finding more and more," asserted Marlene Snyder of Clemson University's Institute on Family and Neighborhood Life and the Olweus Bullying Prevention Program.