London: Violent films and video games numb teenagers` brains, with repeated viewing making them less sensitive to aggression.
Researchers say their brain scans are among the first hard physiological evidence for the theory that on-screen violence leads to real world aggression.
For years campaigners have argued that watching violent films and playing games like Grand Theft Auto, Mortal Kombat and Modern Warfare makes youngsters more prone to violence, reports the Telegraph.
In the Grand Theft Auto series, players become characters who win points for car-jacking, killing prostitutes and running over pedestrians, according to the journal Social Cognitive and Affective Neuroscience.
Summarising his findings, Jordan Grafman, of the National Institute of Neurological Disorders and Stroke in Bethesda, US, said: `Continued exposure to violent videos will make an adolescent less sensitive to violence, more accepting of violence, and more likely to commit aggressive acts since the emotional component associated with aggression is reduced.`
For the study, Grafman and his team recruited a group of boys aged 14-17.
They were asked to watch a series of 60 four-second video clips, arranged randomly in three lots of 20 clips.
The degree of violence and aggression in each scene was low, mild or moderate. There were no extreme scenes.
The boys were asked to rate the aggression of each scene compared to the last by pressing one of two response buttons. As they watched, their brain activities were monitored using MRI scans.
In particular, the area of the brain known as the lateral orbitofrontal cortex (lOFC), which is thought to be involved in emotions and emotional responses, became increasingly desensitised over time.
This was most marked after watching the most aggressive clips, the study showed.