Madelyn McKeon has a lot to do. There's the tea cup on the floor that has to be picked up, then a pen to examine. Mom's lap always needs climbing into. And then there are the mice on the TV.

At 11 months, Madelyn can't tell you their names -- Tizzy, Tog and Toot -- but when she hears them start to sing, she turns her head toward the television and starts to sway.

Between napping, eating, being read to, gnawing on her hand and playing with toys, Madelyn watches anywhere from a half-hour to two hours of television a day. This places her among the estimated 43 percent of babies younger than 1 who watch television every day, according to the Kaiser Family Foundation.

Tapping into the diapered demographic are established media players such as the Walt Disney Co. and Sesame Workshop, and newcomers such as BabyFirstTV, a 24-hour cable channel based in Los Angeles. And demand for such programming appears strong, despite an 8-year-old recommendation by the American Academy of Pediatrics of no screen time for children younger than 2.

Less than a year after its debut on the Dish Network and DirecTV, BabyFirst is launching on 10 cable television systems in the next six months. A British-based rival, BabyTV, which has expanded to 45 countries in two years, plans to come to the United States in the fall. Beyond premium channels, videos and DVDs made for infants and toddlers rack up more than $100 million in sales a year.

While almost all marketers of baby media promote their products as beneficial to a baby's development, little is known about the impact of television viewing on very young children.

"We're in the midst of a huge national experiment on the next generation of children," said Dimitri Christakis, a pediatric researcher at the University of Washington. "We don't know the effects and we're letting them watch."

The notion that television can be educational for preschoolers has been around at least since "Sesame Street" debuted in 1969, aimed at kids 2 and older. It wasn't until the 1990s that marketers began promoting programming for those younger than 2.

The company that created Brainy Baby videos was founded in 1995. The Teletubbies, a British show meant for toddlers, premiered Stateside in 1998, after building a daily audience of 2 million at home and generating $50 million in sales of tie-in products. Three years later, Disney bought Baby Einstein, increasing sales of Baby Einstein products from $25 million to $250 million. Today, there are even video games for infants as young as 6 months.

"What people meant by stimulation was talking to your baby and hanging out -- things people naturally do. Somehow the gravitas of having neuroscience tell us we have to have stimulation has been translated into beeping toys and flashing lights and computers and the television," said Susan Gregory Thomas, author of "Buy Buy Baby," a book on marketing to babies due out in May.

Marketers almost always pitch their products as brain food. A Brainy Baby video, for example, promises to "stimulate cognitive development." The Dish TV channel guide lists BabyFirstTV shows only as "developmental programs for baby."

But rarely are educational claims for baby media products backed by clinical trials or other outcome-based research, child development experts said. Rather, their creators are guided by child development principles and feedback from child psychologists.

Some critics of baby media complain that educational claims are false and misleading. "They are hard-wiring dependence on media before babies get a chance to grow and develop," said Susan Linn, co-founder of the Campaign for a Commercial-Free Childhood, a Boston-based advocacy group. The campaign has petitioned the Federal Trade Commission to treat claims made by Baby Einstein and Brainy Baby as deceptive advertising.

Baby media marketers contend they're catering to an existing need and their products are another tool for parents to use to interact with their children.

"We're not putting babies in front of television. We're giving them a cleaner, safer alternative," said BabyFirstTV co-founder Sharon Rechter. The channel, which costs $10 a month, offers slow-paced, five-minute shows with no advertising. Parents are reminded regularly in subtitles and short messages to take the time to point out shapes, colors and objects.

Demand for shows for infants and toddlers isn't limited to the United States. In Israel, BabyTV's first market, the premium channel "sold as well as Playboy," spokeswoman Maya Talit said. BabyTV is now carried in Latin America, Asia, the Middle East, Canada and Europe.

The appeal, it seems, is universal: "It's guilt-free electronic baby sitting," said Michael Rich, a Harvard pediatrics professor and director of the Center on Media and Child Health. In reality, he said, most parents do not interact with their children while watching television.

He and other researchers cite several recent studies that suggest the tube may not be an effective teacher, such as one 2004 experiment that found that infants and toddlers can imitate a task such as removing a mitten after one live demonstration, but need to watch the same demonstration six times on video before they get it.

Watching a screen is "much more difficult for babies than we think," said Rachel Barr, a Georgetown University psychologist and study co-author.

A 2004 analysis by Christakis concluded the more time 1 1/2- and 3 1/2-year-olds spent watching television, the more likely they were to have attention problems at age 7.

"There's no question babies are engaged in the screen . . . but that should not be confused with either the child liking it or the child deriving benefit from it," he said.

Programmers, however, counter that existing studies, including Christakis's 2004 analysis, don't look at content.

Take "Sesame Street." Research has shown regular viewers aged 2 and older learned words more quickly than children who watched less. But one study has also indicated that watching the show may slow language acquisition in those younger than 2.

"Content does matter. Television is not monolithic, and there's no evidence the box is inherently evil," said Rosemarie Truglio, vice president of education and research for Sesame Workshop.

In the absence of more definitive findings, parents are left to weigh claims by marketers -- and their critics -- against the day-to-day realities of living far from extended-family support, spending long hours at work, needing a shower and getting baby to sleep at 3 a.m.

Andrea McKeon of Owings, Md., never considered herself "a big proponent of kids and television." Then, during Mother's Day weekend, she and her mother, Francine Abell, stumbled across BabyFirstTV on DirecTV. Madelyn, then nearly 3 months old, responded almost immediately.

"Her little face had a look of surprise, followed by intense scrutiny," Abell said.

On a recent weekday morning, McKeon and Abell looked on as Madelyn meandered around the living room, stopping occasionally to look at "her stories," as McKeon calls them.

"Who's at the door?" Abell quizzed Madelyn as the sound of someone knocking rang out from the TV speakers.

Madelyn walked up to the screen and banged it, a sign she liked what was on. Another show about squirrels hiding an acorn, however, couldn't compete with a mug on the floor.

In fact, since Madelyn has become mobile, she watches less -- one of several reactions that have convinced her mother that her time in front of the tube has largely been good for her.

"She's very alert. It hasn't affected her activity level. It's not as if where other kids are out running around, she's just sitting there. That's not the case," McKeon said.

By 11 a.m., Madelyn's eyelids were getting a little droopy. In her mother's arms, she left for her morning nap.

"I can see where parents are apprehensive about letting kids go down this road," Abell said. "As long as it teaches her something, I don't see the harm."