In family rooms across America, millions of children and teenagers are playing video games, such as Call of Duty, Halo, and Grand Theft Auto, roaming violent virtual worlds—with virtual guns in their hands. 

In what sometimes seems like an increasingly violent world, it's only natural to worry about the effects of all this pixelated gore. But is that concern misplaced? Authors and psychologists Patrick M. Markey and Christopher J. Ferguson say it is.