Spending too much time in front of the television makes kids think less of themselves. But not if you're a white boy, according to a new study.

Nicole Martins, an assistant professor of telecommunications at Indiana University, and Kristen Harrison, a communications professor at the University of Michigan, surveyed 400 second- through fourth-graders in several Midwestern communities twice, a year apart, asking them to respond to statements like, "There are many things about myself I would like to change." For both white and black girls and black boys, self-esteem decreased in that time, while for white boys it went up.

Despite an increase in diversity in kids' programming, perception gaps still exist, partly because kids this age also watch the less-diverse programming their parents are watching, Martins said.

"No matter what the program, if you're a white boy, things look pretty good for you, but girls and black boys see more limitations in their roles," she said. "For girls, success is based on how they look. Black boys see black characters more likely to be portrayed as criminals or crime victims."

The study concluded that regardless of what they watch, the amount of time they spend doing it may be even more harmful. The white children spent 25 to 30 hours a week watching TV, while the black children spent 32 to 40 hours.

"That's like a full-time job, and it's displacing real-life experiences," Martins said. "Time spent with the TV is time not spent on confidence-building activities like sports, learning to play an instrument or just hanging out with Mom and Dad."