Two teen boys play Time Crisis II at an arcade.

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An Apparent Connection

Video games and killers have been connected in the media since the 1990s. In 1997, 16-year-old Evan Ramsey brought a shotgun to his Alaska high school and shot four people, killing two. He played a lot of the sci-fi horror game "Doom," in which you have to shoot a character many times before he dies. Ramsey later explained he was surprised to find that rule did not apply in real life [source: Jaccarino].

Also in 1997, a 14-year-old killed multiple people at his high school in Paducah, Ky. He'd played a lot of "Doom," too, along with the fight-to-the-death game "Mortal Kombat," two favorites of the Columbine teens, as well [source:Jaccarino]. Anders Breivik, who killed 77 people at a summer camp in Norway 2011, said he trained for his attack using the war game "Call of Duty," one also favored by Adam Lanza, the shooter at Sandy Hook Elementary[source: Jaccarino].

An even more direct case happened in 2006. Alabama teen Devin Moore was arrested on suspicion of car theft. The police officers easily brought him into the station and had started booking him when Moore suddenly attacked one police officer, stole his gun, shot him and another officer, and then fled down the hall and shot a 911 dispatcher in the head. He then grabbed a set of car keys on his way out the back door, got in a police car and drove away. Moore, who had no criminal history, had reportedly been playing a lot of "Grand Theft Auto" before the killings [source: CBS News]. In "Grand Theft Auto," players steal cars and kill cops.

In many ways, it's the same argument we've heard for decades about violence on TV, and science has come to a general consensus that under certain conditions, TV does have some effect on kids' behavior. For instance, there's evidence linking high exposure to TV sex with younger involvement in sexual activity; and kids who watch more than five hours of TV every day are more likely to smoke cigarettes [source: Kids Health]. Some believe video games are even more likely to affect behavior because they're immersive. People don't just watch video games; they interact with them. The games are also repetitive and based on a rewards system, primary components of classical conditioning, a proven psychological concept in which behavioral learning takes place as a result of rewarding (or punishing) particular behaviors [source: Jaccarino].

Many of these claims seem logical, but proof of a link between virtual and actual violence is tough to come by. A handful of studies, though, have produced some interesting results.