Attention moms and dads; "Arthur" and "Barney" are OK but you may want to skip allowing the little ones to watch "Rugrats" and "Power Rangers."

A new study of early TV-watching and future attention problems found for every hour per day that kids under 3 watched violent child-oriented entertainment their risk doubled for attention problems five years later. Even nonviolent kids' shows like "Rugrats" and "The Flintstones" carried a still substantial risk for attention problems, though slightly lower.

On the other hand, educational shows, including "Arthur," "Barney" and "Sesame Street" had no association with future attention problems

Interestingly, the risks only occurred in children younger than age 3, perhaps because that is a particularly crucial period of brain development. Those results echo a different study last month that suggested TV watching has less impact on older children's behavior than on toddlers