The study included 70 university students in France who were assigned to play a violent or nonviolent video game for 20 minutes a day over three consecutive days.
Those who played violent games, such as "Call of Duty 4" and "Condemned 2," showed increases in hostile expectations and aggressive behaviour each day they played. This did not occur in the people who played nonviolent games such as "Dirt2," according to the study, published online ahead of print in the March 2013 issue of the Journal of Experimental Social Psychology.
The study offers evidence that the negative effects of playing violent video games can accumulate over time and cause people to view the world as a hostile and violent place, said study co-author Brad Bushman, a professor of communication and psychology at Ohio State University.
How the study was done
"After playing a violent video game, we found that people expect others to behave aggressively," Bushman said in a university news release. "That expectation may make them more defensive and more likely to respond with aggression themselves, as we saw in this study and in other studies we have conducted."
Because so many young people regularly play video games, it's important to know the long-term effects of violent games, Bushman said.
"Playing video games could be compared to smoking cigarettes," he said. "A single cigarette won't cause lung cancer, but smoking over weeks or months or years greatly increases the risk. In the same way, repeated exposure to violent video games may have a cumulative effect on aggression," he explained.
It's impossible to know exactly how much aggression may increase among people who play violent video games for months or years, Bushman said. "We would know more if we could test players for longer periods of time, but that isn't practical or ethical," he noted.
"I would expect that the increase in aggression would accumulate for more than three days. It may eventually level off. However, there is no theoretical reason to think that aggression would decrease over time, as long as players are still playing the violent games," Bushman said.
Although the study found an association between violent video games and aggression, it did not establish a direct cause-and-effect relationship.
The American Psychological Association has more about violent video games.
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