Bruce Bartholow of the University of Missouri says the study involved 70 young adult participants randomly assigned to play either a non-violent or a violent video game for 25 minutes. After the playing, the researchers measured brain responses as participants viewed a series of neutral photos, such as a man on a bike, and violent photos, such as a man holding a gun in another man's mouth.
Participants the competed against an opponent in a task that allowed them to give that person a controllable blast of loud noise. The level of noise blast the participants set for their opponent was the measure of aggression.
The study, scheduled to be published in the Journal of Experimental Social Psychology, found participants who played one of several popular violent games, such as "Hitman," "Killzone" and "Grand Theft Auto," set louder noise blasts for their opponents during the competitive task -- that is, they were more aggressive -- than participants who played a non-violent game.
"From a psychological perspective, video games are excellent teaching tools because they reward players for engaging in certain types of behavior," Bartholow says in a statement. "Unfortunately, in many popular video games, the behavior is violence."