According to the American Academy of Pediatrics, parents should not let their children watch any TV until they are at least 2 years old—not even if the tired mommy really wants to take a shower. That's why my oldest daughter, Fiona, didn't even know the word for TV until her second birthday, when she promptly became a "Sesame Street" and "Blues Clues" junkie.

However, I conveniently forgot about the AAP recommendation when my second daughter, Molly, came along—it seemed too hard to cut TV out altogether. Is that bad?

I certainly wasn't alone in letting my baby watch TV. American children spend two to five hours a day watching television, on average. And 59 percent of children younger than 2—who aren't supposed to be watching any—watch an average of 1.3 hours of television daily.

It turns out that a very large number of studies have reported harmful effects from children's television viewing, including worse performance in school, obesity, attention-span problems, aggression, sleep deprivation, requests for advertised foods, and eating fewer fruits and vegetables and more pizza, snack food, soda, and high-fat foods.

Even videos that claim to be beneficial—like the "Baby Einstein" series—aren't good and may be bad. In one study, for example, for every hour per day spent watching such videos, children understood an average of six to eight fewer words than did those of the same age who did not watch them—a 17-percentile drop in vocabulary.

On the other hand, video games don't necessarily deserve their bad rap. They can be a great way to socialize and connect with friends (especially for boys). And video games can actually facilitate, rather than discourage, physical play. Boys who play sports video games, for example, are actually much more likely to play those games in real life—they use the video games to master new moves, and then they go out and practice in real life.

Seven things to keep in mind when the electronic babysitter is getting a lot of play

  1. Television brings little or no benefits, and it replaces activities that do make kids happier, healthier, and smarter. The more kids watch TV, the less time they tend to spend with their parents and siblings, the less time they spend doing homework (for 7- to 12-year-olds), and the less time they spend in creative play (especially in children younger than 5). For very young children (younger than 3), time spent watching TV replaces activities they need for proper brain development, particularly interaction with their caregivers.
  2. On the other hand, research has shown that playing video games doesn't usually take time away from sports or other active pursuits, and that game-playing teens spend the same amount of time with family and friends as nongamers.
  3. Those pediatricians are right: Infants and toddlers under 2 years old should not have any screen time. Early television exposure is associated with problems like ADD and ADHD, and decreased intelligence later in childhood.
  4. Computer use by children under the age of 3 is also not recommended. However, some research shows that computer programs, when combined with activities that facilitate what the programs are trying to teach, can help 3- to 4-year-olds develop a range of skills, including long-term memory, manual dexterity and verbal skills.
  5. Not all screen time is equal. Research shows a strong link between violent video game play and aggressive feelings and behaviors; violent video games trigger a part of the brain that drives people to act aggressively. And violent video game play measurably decreases helpful behaviors. Similarly, watching violent programming on TV is associated with a decrease in fantasy play among preschoolers and an increase in children's aggressiveness.
  6. Parents who watch television with their children and reinforce the educational aspects of shows can improve the quality of the learning experience for their children. Unfortunately, most kids usually don't watch educational television with their parents. They watch general audience programs targeted to adults rather than children.
  7. Although 68 percent of American kids do have televisions in their rooms, children with a TV in their bedroom are 1.3 times more likely to be overweight (even when they are physically active and/or participate in team sports).

We all have friends who watched TV every waking moment of their childhood but still managed to become smart, physically active, contributing members of society free from attention disorders. But research shows that as parents, we probably need to think of these people as the exception, not the rule. Our best bet is to turn off the boob tube and send the kids out to play.

Video: Screen time

Today's kids spend a lot of time in front of television and computer screens. How much is too much? Should parents be concerned? Watch it now!

Republished with permission from Christine Carter and the Greater Good Science Center.

Published on Oct. 31, 2008; updated on May 7, 2014.

Dr. Christine Carter

Dr. Christine Carter, a sociologist at UC Berkeley's Greater Good Science Center, is the author of "Raising Happiness: 10 Simple Steps for More Joyful Kids and Happier Parents." She also writes a blog for Greater Good, which is syndicated on the Huffington Post and Dr. Carter has been quoted in Women's Health and Parenting magazines, The New York Times, Los Angeles Times, USA Today and dozens of other publications. She has appeared on the "Oprah Winfrey Show," the "Rachael Ray Morning Show," "The Daily Show with Jon Stewart," "CBS Sunday Morning," "ABC World News with Diane Sawyer" and NPR. Dr. Carter teaches parenting classes online throughout the year to a global audience on her website.