October 18th, 2010
07:15 PM ET
Watching violence portrayed in movies and other media may make teens more accepting of violence, researchers report in the journal Social Cognitive and Affective Neuroscience.
Previous research has shown a connection between violent media and aggression, as well as violence and desensitization. But this study looks at how teenagers' brains specifically respond to violent media, said Jordan Grafman, senior investigator at the National Institute of Neurological Disorders and Stroke.
Participants in the study were 22 boys ages 14 to 17. For that reason, researchers cannot determine whether the brain patterns they observed would also apply to girls. This is also a small sample size, meaning more research should be done to confirm the results.
Each participant watched clips of violent scenes from 60 different videos, which included movies such as "World's Wildest Street Fights Vol. 1 and 2," Grafman said, and rated the aggression of the scenes. Researchers could observe their brain function because each boy watched these scenes while in a functional magnetic resonance imaging (fMRI) scanner.
These brain images showed that more aggressive violence was associated with desensitization in the lateral orbitofrontal cortex of the brain, which scientists believe has to do with emotions and emotional responses to events. They measured this by looking at the deoxygenation of blood in this area of the brain and how it changes over time.
Participants also wore electrodes on the fingers of one hand to measure the electrical conductance of the skin, which indicates emotion. This was used to look at how desensitized the boys were to different videos, depending on the level of violence. This electrical conductance test showed that the boys appeared to be more desensitized by the mildly and moderately violent videos than the ones with a low-level of violence.
Boys who had the greatest level of exposure to violent media routinely showed the greatest desensitization in this study.
If you already have a predisposition toward violence, based on your home life and genetics, and are exposing yourself to violent media, "the risk would go up for being, first, accepting of violent or aggressive behavior around you, which be often as devastating as actually committing the act, or potentially being more easily provoked," Grafman said.
That assessment does not apply to these individual children in the study, but it's the study's broader message, he said.
"Sometimes people just call these 'games,' but imagine if you're doing this three hours a day, four hours a day; it's not just 'games,' it's your environment, he said."
Although the study did not directly address the issue of violence in video games, previous research found that "emotional desensitization had been associated with children’s exposure to violent video games and adults' self-reported reduced sympathy with victims in violent movie scenes," Grafman's study said.
But there may be a flip side to video games with some degree of violence. A September study in the journal Current Biology found that participants ages 18 to 25 could make faster decisions that were no less accurate after playing action games such as "Call of Duty 2" and "Unreal Tournament," which are first-person shooter games.
The lesson from that is not to carve out as much time for video games as you can, said Alexandre Pouget of the University of Rochester, co-author of the Current Biology paper. Rather, exploring how video games help with quick thinking can translate into educational tools and games that more effectively teach useful skills, he said.
For children over 6 years of age, pediatricians recommend no more than two hours of screen time per day, said Dr. Jennifer Shu, CNNHealth living well expert. But some studies have shown that, in practice, many kids spend about 7 hours a day in front of some kind of screen, including smart phones.
Parents should put limits on-screen time, she said. It's a cause for concern if a child becomes hyperactive, has attention problems, doesn't sleep well or get enough exercise because of things like video games and television.
From around the web
About this blog
Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.