The average American boy spends more than seven hours a week playing video games. An Iowa State University study finds violent video games may be hurting more than characters on-screen.Playing violent video games is a hazard and a risk for kids and adults, according to Dr. Craig Anderson, chair of I-S-U’s Department of Psychology. He reviewed 35 other studies of thousands of video game players, and concludes violent shoot-em-up games boost aggression levels.He says playing such games causes a decrease in “helping” behavior, and an increase in aggressive behavior and thoughts. Dr. Anderson says parents need to know what their kids are playing. He says one study found up to 80-percent of kids admit they have video games on their computers which their parents don’t know about and wouldn’t let them play, if they knew about them. Anderson endorses a better ratings system for video games.Anderson points out the young gunmen in the high-profile high school killings in Columbine, Colorado, were big fans of the video game “Doom.”