By the time children are two years old, 90 per cent of them regularly spend time watching TV, DVDs and videos, U.S. researchers have found.

The American Pediatric Society recommends children under two should not watch any TV, and previous studies suggest less viewing time may be important in developing vocabulary. The Canadian Pediatric Society also warns that too much TV is linked to problems with attention, learning and aggressive behaviour.

"For the kids under the age of three, the biggest thing is that they should be interacting verbally," said Dr. Sarah Shea, head of the child development clinic at the IWK Children's Health Centre in Halifax, commenting on the study.

"When the TV is on, people don't talk to each other in a meaningful way. They don't look at each other when they do talk, except to say things like, 'Be quiet.'"

At 29 per cent, the top reason parents gave for putting their babies in front of TVs was they believed the programs they chose were good for the child's brain.

The second most cited reason, at 23 per cent, was that parents believed their baby enjoyed watching or it was relaxing for them. Another 21 per cent of parents said it gave them time to get things done while the child was entertained.

For the study in the May issue of the Archives of Pediatrics & Adolescent Medicine, Frederick Zimmerman of the University of Washington in Seattle and his colleagues surveyed 1,009 parents of children aged two to 24 months by telephone. They were mostly well-educated, upper-income families.

"These results suggest that the widespread notion that parents turn to television only as an electronic babysitter is a misconception," the researchers concluded. More than half of the time, parents said they watched with their children.

"Parents are clearly hungry for truly educational content for children younger than two years. More research is urgently required to determine whether it is realistic to produce genuinely educational content for children younger than two years, and, if so, what it would be."

About 40 per cent of infants by the age of three months regularly watched TV, DVDs and videos, according to the study. At the age of two, 90 per cent of children were watching, averaging more than 1.5 hours a day.

Parents 'suckered in' to educational value: pediatrician

There is no evidence that infants enjoy or benefit from educational or entertainment programming, Shea said. "It's not credible, in my opinion, but it's really good marketing and parents have been suckered in."

For children under three, the best ways to help develop their brain is by talking, reading and playing with them — activities that are less passive than watching TV, she suggested.

Scott Rose of Halifax said he bought a Baby Einstein DVD for his 13-month-old daughter, Sienna, thinking it would be educational for her.

Rose said Sienna likes the colours and sounds on the DVD, and that he believes it is helping her make associations with objects around her. He also makes sure she enjoys lots of real-life play time to help her development as well.

Viewing tied to learning problems in teens

The detrimental effects of TV time on learning may be long lasting, a second study appearing in the same issue of the Archives of Pediatrics & Adolescent Medicine suggests.

Jeffrey Johnson of the Columbia University College of Physicians and Surgeons and his team found teens who watched three to four hours of TV a day were more likely to show attention or learning problems and were less likely to earn a degree.

At age 14, 33 per cent of teens from the 678 families surveyed reported watching three or more hours a day.

The researchers found TV time was linked to a higher risk of:

• Frequent attention difficulties.
• Frequent failure to complete homework.
• Frequent boredom at school.
• Failure to complete high school.
• Poor grades.
• Academic failure at the post-secondary level.

Results were the same regardless of socio-economic status.

The findings "suggest that by encouraging youths to spend less than three hours per day watching television, parents, teachers and health-care professionals may be able to help reduce the likelihood that at-risk adolescents will develop persistent attention and learning difficulties," the study's authors concluded.

It could be that TV shortens teens' attention spans, and future studies should look at whether promoting other activities like athletics, music or arts helps reduce the risk of learning problems, they added.