A study published in Biological Psychology, concerning the brain’s response to videos showing people inflicting pain on others, suggests that bullies actually take pleasure in watching someone else get hurt.

The United States brain imaging research showed that when known as aggressive teenage boys watched those videos, an area of their brain, which is usually associated with reward, registered increased activity.

Moreover, it revealed that accidentally inflicted pain was the one to trigger the response in the brain, while scanning of boys who had no history of having been particularly aggressive showed their reward-associated area in the brain did not light up when exposed to the video clips.

The study looked at 16 teenage boys aged 16 to 18, of whom half had a behavioral disorder that made them prone to aggression, while the other half had no such tendency.

Participants from the first group had a history of starting fights, stealing and even using a weapon.

Researchers scanned their brain with a Magnetic Resonance Imaging (MRI) machine that registered brain activity while the 16 teenagers were watching videos of people accidentally having a heavy bowl drop on their hands or being intentionally stepped on their foot by another person.

Activity in the aggressive boys’ brains showed activation of the amygdala and ventral striatum, which are connected to feelings of reward, while the medial prefrontal cortex and the temporoparietal junction, areas linked to self-regulation and empathy, remained inactive.

On the other hand, where the control group of the study was concerned, these parts of the brain registered increased activity.