AMES, Iowa -- It's not just American kids who become more aggressive by playing violent video games. A new study -- presented last month at the inaugural seminar sponsored by Iowa State University's Center for the Study of Violence -- showed effects of violent video games on aggression over a 3-6 month period in children from Japan as well as the United States.

ISU Distinguished Professor of Psychology Craig Anderson -- director of the Center for the Study of Violence -- presented the results from the study, which is published in the November issue of Pediatrics, the professional journal of the American Academy of Pediatrics.

The research links an earlier ISU study of 364 American children ages 9-12 with two similar studies of more than 1,200 children between the ages of 12-18 from Japan. It found that exposure to violent video games was a causal risk factor for aggression and violence in those children.