If a video game is rated “E” for “suitable for everyone,” that is supposed to be a signal to parents that the game is acceptable for their children. But a study by Harvard School of Public Health researchers found that of 55 E-rated games that they surveyed, 64 percent contained intentional violence. The average amount of violent play was more than 30 percent, with one game offering more than 90 percent violent playing time. “We didn’t expect to see as much violence as we did in some of these games,” said the study’s lead author, Assistant Professor Kimberly Thompson, “particularly given their E rating.” She said the health effects of exposure to video-game violence are uncertain and need further study. The goal of the School of Public Health study was to take the first quantitative look at the content of an entire classification of video games. “This study is focused on what’s in the games themselves so that parents, physicians, and policymakers can talk about the nature of the games,” said Thompson. The study was funded by a private gift from Mitchell Dong and Robin LaFoley Dong to the Harvard School of Public Health.