About 12 percent of American children between the ages of 2 and 4 use computers every day.
Fifty percent of children younger than 8 have access to a mobile device like a smartphone, a video iPod or tablet.
And television is still the elephant in the children's media room, accounting for the largest share of screen time. Among all children younger than the age of 2, the average is 53 minutes a day of television or DVDs — more than twice the 23 minutes a day children are read to.
Statistics such as these, compiled in a study by the Kaiser Family Foundation, have caused the American Academy of Pediatrics to reissue their long-standing recommendation that children should spend less time in front of a screen.
Earlier this month, the AAP advised parents - again - to limit or eliminate the amount of time children watch television, play video games and use mobile devices, citing concerns about language delays, disrupted sleep and behavioral problems.
The academy's new report drew on numerous studies that show such devices interfere with talk time between parent and child, which is crucial to language development.
Sedentary activity also contributes to obesity, high blood pressure and other health problems among children, AAP noted.
The association revisited the issue, said Dr. Ari Brown, the lead author of the academy's policy, because video screens are everywhere now and the message is more relevant today than it was a decade ago.
While some people treat electronic devices as digital baby-sitters and others think of them as educational tools, the academy recommends that children younger than the age of 2 years have no screen time at all and those older than 2 years spend no more than two hours of screen time daily.
There also is concern about the use of the latest technology, including apps for babies that are flooding the market. Some promise to develop hand-eye coordination while others focus on teaching fine motor skills to infants.
But even apps that simulate conventional toys - like building blocks or Legos - don't teach children the crucial skills that come from physically engaging in the world around them, the academy said.
Although many parents monitor the time their children spend watching television, playing video games or using mobile devices, Dr. Michael Colli, a pediatrician with Keystone Pediatrics in Chambersburg, Pa., believes "most parents have little idea how much actual screen time their children have each day.
"In fact," he said, "if they set a timer to accurately measure their children's screen time, I bet most parents would be shocked.
"As busy as most parents' lives are, it is easy and convenient for the television, computer or video game system to mindlessly occupy our children's down time," Colli noted.
But you only have to look at the results of recent studies to understand the hazards, he said.
"First of all, weight gain is a balance between caloric intake and expenditure. Sedentary screen time results in less caloric expenditure, which inevitably leads to weight gain and the potential for obesity," he said.
According to Colli, there also is a recent study that compared the executive function of 4-year-olds immediately after watching either an episode of "SpongeBob SquarePants" or "Sesame Street," versus not watching television at all and coloring, instead.
"Executive function is a higher brain activity that allows us to organize tasks and process information and thoughts," Colli explained. "The study showed that the children in the 'SpongeBob' subgroup faired much worse on the executive function task than either of the other subgroups. Why? The theory is that shows like 'SpongeBob,' that are fast-moving and have rapidly changing scenes, fill the child's brain with so much information that executive function becomes impaired immediately afterward."
Colli said it's difficult to know the long-term implications, "but it wouldn't be a stretch to link ADHD (attention deficit hyperactivity disorder) or certain learning disabilities to certain types of video games or television shows."
The Kaiser Family Foundation study found that nearly half of 5- to 8-year olds have televisions, computers and game systems in their bedrooms. Colli agrees with AAP that it's a bad idea.
"It becomes difficult, if not impossible, to keep track of the child's screen time and content," he said. "The AAP strongly recommends taking all viewing items out of the bedroom."
While changes need to be made in the amount of time children spend in front of a screen, Colli said parents need to lead by example.
"This is the key, actually," he said. "Getting the whole family to make lifestyle changes makes it easier for the child to become more active. In fact, I would argue that parents who are more active themselves will be more successful in getting their children to be more active. This holds true for dietary changes, as well. There has to be a whole-family buy-in."