Every day, children get messages about how they should look and act

In addition to pressure from friends, kids also are heavily influenced by the media -- movies, music videos and television. The average child spends three to five hours a day watching television, and they're getting messages about how to dress and how to act from the shows they watch and the ads they see.

Sometimes you can see the impact of media right away, such as when your child watches superheroes fighting and then copies their moves during play. But most of the time the impact is not so immediate or obvious. It occurs slowly as children see and hear certain messages over and over.

Many of these messages are coming from the ads that bombard them on TV, on the Internet and on the radio.

Children are big business, and advertisers know that. American children ages 4 to 12 spent over $35 billion of their own money last year, and they influenced a surprising $500 billion of their parents' purchases. The youth marketing research firm WonderGroup reported that parents are giving their kids greater financial responsibility, partly because parents aren't around to help their children make spending choices.

"They have really taken over the minds of children, and they're good at it," Lamia says of advertisers. "Parents should be teaching their child about what marketers do and how they are trying to influence them."

The advertising industry has funded dozens of studies on children designed to enhance their marketing effectiveness. Some agencies have even hired clinical psychologists and cultural anthropologists to record more than 500 hours of interviews and observations of children.

In some cases, the messages they may get from TV, music videos or video games can be downright dangerous. The programming may be overly violent, or overwhelmingly sexual.

A study by The Rand Corp. found that watching sex on TV predicts and may hasten adolescent sexual initiation. The study also found that reducing the amount of sexual content in entertainment programming or increasing references to possible negative consequences of sexual activity could delay their desire to engage in this kind of activity.

"They begin to think that being seductive is the way to be," Lamia says. "They see that children get attention from other kids from dressing or acting like that."