About 90 percent of U.S. children under age 2 and as many as 40 percent of infants under three months are regular watchers of television, DVDs and videos, researchers said on Monday.

They said the number of young kids watching TV is much greater than expected.

“We don’t know from the study whether it is good or bad. What we know is that it is big,” said Frederick Zimmerman of the University of Washington, whose research appears in the Archives of Pediatrics and Adolescent Medicine.

The American Academy of Pediatrics estimates that children in the United States watch about four hours of television every day. They recommend that children under age 2 should not watch any and older children should watch no more than 2 hours a day of quality programming.

But 29 percent of parents surveyed by Zimmerman and colleagues believe baby-oriented TV and DVD programs offer educational benefits.

“Parents are getting the message loud and clear from marketers of TV and videos that this is good for their kids. That it will help their brain development ... None of this stuff has ever been proven,” Zimmerman said.

For their study, Zimmerman’s team conducted random telephone surveys of more than 1,000 families with young children in Minnesota and Washington.

They found that at 3 months, children watched less than an hour per day, but by 24 months, they watched more than 1.5 hours per day.

About half of the shows watched were in the educational category, with the remainder split evenly among noneducational children’s content, baby DVDs/videos and adult TV.