"'There is tons of research on this,' says Joanne Cantor, professor emerita of communications at the University of Wisconsin, and an expert on the effect of violent movies and video games. 'Watching violence makes kids feel they can use violence to solve a problem. It brings increased feelings of hostility. It increases desensitization.' Every parent understands this instinctively, of course, but those instincts are backed by decades of solid research."

Read more: Joe Nocera, New York Times