scienceblogs.com - When Jimmy was around 18 months old, Greta and I were both in graduate school. I attended classes at night and Greta taught and worked in the lab during the day. In the late afternoon I'd drive into the city with Jimmy in the car seat, and we'd swap -- she'd drive back home and I'd go to class, taking the train back home when I was done.

At this point, Greta was extremely pregnant with Nora. She was exhausted at the end of her workday, but Jimmy had usually taken a nap in the car, so he was rearing to go. All Greta wanted to do was lie down and take a rest, and fortunately, there was one way to get Jimmy to sit still long enough for her do that: Barney the Dinosaur. She turned on the TV and reclined on the couch while Jim sat entranced by Barney's soothing antics with his friend Baby Bop. After the thirty minute break, Greta was refreshed enough to make dinner, and after dinner and a bath, Jimmy was ready for bed. So you could say that Barney helped both Greta and me make it through graduate school by "taking care" of Jimmy for a half-hour a day.

But was Barney being helpful to Jimmy? By using Barney as a surrogate parent, were we teaching Jim that he should expect to be perfectly entertained at all times, instead of exploring the world on his own or spending time with his parents? And what about other TV shows and movies, like those featuring violence or non-educational content? Could it be possible that early exposure to TV ruins kids by shortening their attention spans and making it harder to focus on tasks like reading and schoolwork?

In 1997, a long-term NSF-sponsored study of 4,800 families added new questions about children's daily activities, including TV watching. The same families were re-surveyed in 2002, offering an excellent opportunity to take a look at the long-term effects of TV watching. The 1997 survey asked parents to keep a diary of activities for one weekday and one weekend day. Since the respondents reported on the TV programs their kids watched, researchers could assess not only the impact of TV-watching, but also the impact of specific TV programs. Is Barney better than Power Rangers?

Frederick Zimmerman and Dimitri Christakis classified programs into three categories: Educational (Barney, Sesame Street), Nonviolent entertainment (Rugrats, Babe), and Violent entertainment (Power Rangers, America's Funniest Home Videos). The researchers analyzed the responses of 542 parents of 0- to 36-month-olds, as well as 391 parents 4- to 5-year-olds. The 1997 responses gave them the TV-viewing data, and the 2002 responses allowed them to identify children who later developed attention problems. This graph shows the results:

The results are expressed in terms of an odds ratio -- in this case, the chance of developing attention problems compared to not developing those problems five years later. An odds ratio of 1 signifies that there is no relationship between the two items compared. For toddlers age 0 to 36 months, those who watched either nonviolent or violent TV were significantly more likely to develop attentional problems later. There was no significant relationship between watching educational TV and attentional problems.

For 4-5 year-olds, none of the results were significant. Although it appears from this graph that watching educational TV might lead to attentional problems in this group, the results weren't actually significant because there was a very large range of responses (for the statistics-inclined, the 95 percent confidence interval for this group ranged from 0.8 to 3.5).

So these results suggest that it's not a good idea to have your toddler watch non-educational TV, including such kid-oriented programs as Looney Tunes cartoons, The Lion King, and even Bambi. For older kids, these shows appear to pose less of a problem. I should point out, however that an odds ratio of 2 is fairly low, so we're not talking about an especially dramatic result. Only about ten percent of all the kids in the study actually developed attentional problems, and these results suggest just a slightly higher risk of attentional problems for toddlers watching entertainment TV shows.

F. J. Zimmerman, D. A. Christakis (2007). Associations Between Content Types of Early Media Exposure and Subsequent Attentional Problems PEDIATRICS, 120 (5), 986-992 DOI: 10.1542/peds.2006-3322