A new study conducted in part by the Harvard Medical School finds that, of 12-14 year-olds who report frequent video game play, the majority of them play some games with Mature (ages 17+) ratings.
While I'm sure this study will be cited in the weeks and months to come as an indictment of the ESRB, parents, or both, I feel like I should point out that letting your kids play M-rated games is not per se bad parenting. The Mature rating is indicative of where the game buyer no longer requires parental guidance -- not an indication that anyone younger should not be allowed near it.
Factors Correlated With Violent Video Game Use [Science Direct, via Ars Technica]
