By Leslie Wade, CNN
(CNN) -- For years, pediatricians have recommended that young children watch no TV, or as little as possible, because it can lead to problems in school and behavior issues. Now a new study concedes children are sitting in front of the TV a lot longer. However, controlling what they watch can improve how they behave.
When preschoolers watch educational programs instead of violent TV shows, they tend to be more compassionate and less aggressive, according to a study published Monday in the journal Pediatrics.
About 600 families were recruited and assigned to one of two groups. Parents in the first group were encouraged to substitute violent shows with educational and pro-social ones - shows that stressed compassion and cooperation.
Families were given monthly TV guides listing educational programming for their area: shows such as "Dora the Explorer," "Super WHY," "Sesame Street" and "It's a Big, Big World." Parents were also encouraged to watch TV with their kids.
The children went from watching a half-hour of violent programming a day to 23 minutes. Parents then increased educational viewing from about 30 to 43 minutes a day.
Families in the second group did not change their viewing habits.
"This is the first study to try to modify the viewing habits of preschool kids," says Dr. Vic Strasburger, spokesperson for the American Academy of Pediatrics. "That's one of the significances of this study."
After a year, researchers found that children watching less violent and more child-appropriate shows scored better on tests that measured cooperation, a willingness to share or compromise. They also had fewer incidents of aggressive behavior such as yelling and hitting.