Some children's television shows may be bad for young kid's brains according to a new study about watching cartoons. It appears that children may not concentrate and focus very well after watching fast-paced programming.

Researchers from the University of Virginia showed 60 4-year olds a 9-minute chunk of what they call an "animated kitchen sponge" cartoon. The experts then tested the children's memory and thinking skills and compared their scores to other youngsters, who had watched a slow-paced educational cartoon or drew pictures with crayons and markers.

The pre-schoolers who watched the fast-paced shows did much worse on the thinking tests than those in the two other groups, who scored about the same. The researchers suspect that the brain gets overtaxed or tired from all of the stimulation from the fast-paced cartoons leading to lower scores.

But what this means for children long term is still an open question. Several other studies have found a link between heavy television viewing and problems with children's attention spans, especially in young children, while others have not. Some researchers are concerned, however, because the ability to concentrate and not get distracted often shapes how well children do in school. Preschoolers watch at least 90 minutes of TV a day, according to the study, but other researchers estimate young kids watch between two and five hours of TV daily.

The American Academy of Pediatrics (AAP) recommends parents "limit children's total media time (with entertainment media) to no more than 1 to 2 hours of quality programming per day" and "discourage television viewing for children younger than 2 years" entirely.

This new study is published in the journal Pediatrics, which is a publication of the AAP.

"We can't tell you definitively from a scientific standpoint what the long-term effects are, but this one small study – if it's confirmed – is suggestive that this could be a real problem," explains Dr. Dimitri Christakis, director of the Center for Child Health, Behavior and Development at the University of Washington in Seattle and author of an editorial in Pediatrics.

Christakis and other researchers say, that when children's brains, which are still developing, are bombarded with too much stimulation, it can interfere with their ability to learn to focus properly. He suggests that parents keep an eye on what their children are watching.

"The point of this study and a lot of other research in media is that what your kids watch is as important as how much they watch. It's not just about turning off the television, it's about changing the channel," says Christakis.

Nickelodeon, owned by Viacom International, which produces the cartoon "SpongeBob SquarePants," released the following statement to CNN when asked about the study. "Having 60 non-diverse kids, who are not part of the show's targeted demo, watch 9 minutes of programming is questionable methodology. It could not possibly provide the basis for any valid findings that parents could trust." It pointed out that the SpongeBob cartoon is designed for 6- to 11-year-olds, not 4-year olds, like the children used in the new study.

But Christakis says the research methodology is solid and though the study is small, its design is stronger than previous research and the findings are significant.

"The important take home message here is that the content of viewing actually matters. Many, many parents have rules about the quantity of programming their children watch but far fewer have restrictions on what they watch," says Christakis.

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