Cheryl Olson is a researcher and co-author of the book Grand Theft Childhood: The Surprising Truth About Violent Video Games And What Parents Can Do.

Olson has conducted research on violent video games and examined other studies in detail. She says no one has done the type of study needed to determine the true links between violent games and violent behavior.

"The games are changing all the time. One of the things you would like to do in research is follow people over time, what you call a longitudinal study. Because that's the only way you can really tease out cause and effect," she said. "And it's very hard to do that because of the constantly changing games."

Olson also discusses some misconceptions about violent video games and explains how eighth graders in one of her studies described "killing" people on screen.