This is the VOA Special English Economics Report.

American children and teenagers have increased their use of entertainment media by more than one hour a day in the last five years. On an average day they now spend seven and a half hours using media.

These are the findings of a new survey. It included devices like TVs, computers, mobile phones and MP3 players, but also media like books and magazines. It did not count media use for school.

Vicky Rideout at the Kaiser Family Foundation, a health research group, wrote the report. She was surprised that kids could fit even more media time into their day.

She found that they spent ten hours and forty-five minutes if you counted each device individually. But children multi-task a lot, and Vicky Rideout says this is not necessarily a good thing.

VICKY RIDEOUT: "People who study the brain will tell you that you can't actually multi-task in that way. You're really switching back and forth sequentially from different tasks, just doing it rapidly, and that you don't really do either task as well as you would do them if you did them one at a time."

The study suggests a link between heavy media use and lower performance in school. About one-fourth of those who used media the least reported that their grades were mostly average or below. But that was true of half the heavy media users.

So where are the parents? Children who had any rule limiting the use of any kind of media were exposed to an average of about three hours less media a day. But only one-third of children had to follow any rules.

Girls spent more time than boys on social networking sites, listening to music and reading. Boys spent more time on video games -- an average of forty-eight minutes more a day than girls.

VICKY RIDEOUT: "It looks like the girls just sort of lose interest in the games and they drop off and start doing other things, whereas the boys' interest remains strong."

Some other findings: Time spent reading books has not dropped in the last five years. But time with newspapers and magazines has, though some reading now takes place online.

Blacks and Hispanics use media over four hours more a day than other groups. And for all children, media use appears to reach its highest point between the ages of eleven and fourteen. Vicky Rideout will try to explain these findings in future research.

The report is based on more than two thousand students ages eight to eighteen. They took a written survey in class through May of last year.

And that's the VOA Special English Economics Report, written by Mario Ritter. How much media use do you think is enough for children? Post your comments at voaspecialenglish.com, and you can find transcripts and captioned videos of our reports. I'm Mario Ritter.