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Research finds that children who play violent video games or watch violent TV can become violent themselves, but what drives this change? Are they kids simply mimicking what they see on the screen, or could gaming have a more profound effect on their brains, affecting behavior?
To explore that question, Dr. Vincent Matthews and his colleagues at Indiana University, who have long studied media violence, looked at what happened in the brain in 28 students who were randomly assigned to play either a violent, first-person shooter game or a non-violent one every day for a week. None of the participants had much previous gaming experience.
At the start of the study, researchers used functional MRI to scan brain activity in the participants, all young adult men, while they completed lab-based tasks involving either emotional or non-emotional content. The participants were then scanned again while they repeated the same tasks, after a week of playing the video games.
Researchers found that those who played the violent video games showed less activity in areas that involved emotions, attention and inhibition of our impulses. "Behavioral studies have shown an increase in aggressive behavior after violent video games, and what we show is the physiological explanation for what the behavioral studies are showing," says Matthews. "We're showing that there are changes in brain function that are likely related to that behavior."
It's not clear how long-lasting the changes may be. When Matthews brought the participants back after a week of not playing video games, their brain activity had changed again, reverting to more normal reactions, but their brain functions still weren't quite the same as before they were exposed to the violent games.
One task the participants completed while being scanned assessed their response to violent versus non-violent words. The participants were presented with violent words such as hit, harm and kill and non-violent words like run, walk and talk, each in different colors. Participants were asked to identify the color of each word, rather than the word itself, a variation of a common psychological test known as the Stroop effect: normally, there is a delay in identifying the color, since we tend to process the meaning of the word we read first, before noting the color of the letters.
Researchers found that those who played the non-violent video games showed the normal delay, but also showed increases in activity in the emotional parts of the brain when faced with the violent words. The violent-game players, meanwhile, showed similar brain activity in the baseline tests, but after a week of playing violent games, they revealed significantly less activation of their emotional brain centers.
Another task designed to test participants' attention and concentration showed declines in the violent-game group after a week of play. The men were presented with a numeral — 1, 2 or 3 — repeated various numbers of times, and were asked to press a button indicating not the numeral itself, but how many times it appeared. The violent-game players showed decreased activity in the parts of the brain that regulate attention and concentration.
The brain changes don't appear to be permanent, but documenting that the brain does change in response to playing a violent game — even just for two hours a day for a week — is a significant advance in understanding how young players may be affected by these games. The brain changes that Matthews' group saw were similar to those seen in teens with destructive sociopathic disorders, and his results, along with those from previous studies showing shorter-term effects, have been used in court cases by parents and others hoping to limit violent game play among young children. "Individuals and parents of children who choose to play games need to be aware that there are changes in brain function and they need to consider that when they decide whether or not to play these games," says Matthews.
Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME's Facebook page and on Twitter at @TIME.
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