Watching violent television programs between the ages of two and five years of age is clearly linked to aggressive and anti-social behaviors in boys when they reach age seven to nine, according to a new study published in the November 2007 issue of Pediatrics. Investigators Dimitri A. Christakis, MD, MPH, and Frederick Zimmerman, PhD, both of Seattle Children's Hospital Research Institute and the University of Washington School of Medicine, add these findings to their growing body of research on the effects of television and media on children and their ability to learn, socialize and develop.

The journal article titled "Violent Television Viewing During Preschool is Associated with Anti-social Behavior During School Age" reviews data from the Panel Study of Income Dynamics, which is a 40-year study of 8,000 US families. The project looked at the types of programming watched by 184 boys and 146 girls between ages two and five, and anti-social behaviors between ages seven and ten. A clear link was found between pre-school age boys who watched violent programs and their later development of anti-social and aggressive behaviors at ages seven to nine. There was no such correlation found for girls.

"This new study provides further evidence of how important and powerful television and media are as young children develop," said Christakis. "However, the news here is not all bad. While we found that shows like violent cartoons or football can make children more aggressive, we found no such effect for other programs such as educational ones. This points out that parents must be informed and very selective when making media choices for their children."

The anti-social and aggressive behaviors noted in this study's data included observations about cheating, being mean to others, feeling no regret, being destructive, disobedience at school and having trouble with teachers.

In the study, television programming such as football, many cartoons and titles like Power Rangers, Star Wars, Space Jam and Spider Man were all classed as violent entertainment because characters fight or flee from violent situations, laugh or cheer as they rejoice in violent acts, and show more violence than would be expected in the everyday life of a child. Even G-rated films intended for children can be filled with violence and classed as violent entertainment, according to this definition. By contrast, shows considered non-violent included programs like Toy Story, Flintstones and Rugrats. A third category of educational programming was also reviewed, such as Barney, Sesame Street, Magic School Bus and Winnie-the-Pooh. Significantly, the correlation to later aggressive and anti-social behaviors in boys only appeared with those shows and programming rated as violent.

It has long been suspected that television, media and entertainment have a great impact on the development of children. "We now recognize that content is key," said Christakis. "Given the media saturated world that young children now inhabit, we need further research and policies to ensure that media exerts a positive influence on children."

In a related companion journal article appearing in the same issue of Pediatrics called "Association Between Content Types of Early Media Exposure and Subsequent Attentional Problems," the same researchers found that for children under age three, each hour per day spent watching violent television was associated with approximately twice the risk of attention problems five years later. There was also significant risk of increased attention problems associated with watching nonviolent television for the same age group, but no risk was associated with viewing educational programming. Older children ages four and five showed no increased risk five years later for attention problems from watching violent or non-violent programs. This second study was based on data collected from parents of 933 children and shows that the effect of violent television content on attention problems is much higher than previously estimated when program content was not identified.

"It would appear both of these studies rule out educational TV as a contributor to either aggression or attention problems among young children," said Zimmerman. "Parents can take some comfort in that, especially since there is some high-quality educational programming available on TV and DVD. Together these studies suggest that by changing the channel, parents may be able to change their children's behavior."

Christakis' and Zimmerman's other recent studies have shown that playing with blocks can improve language acquisition, and that baby DVDs and videos that purport to enhance language development may in fact actually hinder it. Together they are authors of the book The Elephant in the Living Room: Make TV Work for Your Kids, a guide for parents.