WASHINGTON — A University of Maryland researcher has a message for parents who fret about how much time their preteen children spend on computers: Worry not.
In what researchers describe as one of the first long-term looks at the effects of media use during childhood, a study released Wednesday linked hours at the computer with achievement test scores and behavior and found little sign of harm for children ages 6 to 12 as they increased their screen time over a six-year period.
Moreover, the study found benefits for girls and African-American boys.
"Generally, adolescent achievement and adjustment showed benefits from the use of the computer, and it didn't have to be studying. It could be playing games," said Sandra Hofferth, a family science professor and director of the Maryland Population Research Center.
Hofferth's results, published in the journal Child Development, showed that African-American boys' reading scores improved by four points, considered significant, as they increasingly logged more time on the computer.
Girls' achievement test scores for reading and math notched upward by a point. Socially, there was another positive effect: White girls were less likely to be withdrawn as they played more on the computer.
In 2008, children ages 10 to 12 were messaging, playing games, studying and surfing Web sites an average of 3.4 hours a week. Those ages 16 to 18 spent 6.3 hours a week at the keyboard that year.
The greatest increases in the six-year period of the study, which predated the rise of social networking among adolescents, were in time spent playing computer games. But computer use overall "involves problem-solving. It involves reading; it involves communication, and these are skills that help children," Hofferth said.
With children becoming computer-literate at increasingly younger ages, Hofferth said, she set out to learn whether screen time leaves children more isolated and withdrawn and whether it leads to declines in achievement because it replaces time that could be spent studying, reading, taking part in sports and playing outdoors.
"Parents are seeing the increase in their children's screen time and they always ask, 'Well, how much time should they be spending?' " she said. "I was trying to find out, 'Is this really terrible for children?' " She said she expected to document negative effects but concluded that increasing time on the computer did not mean less reading and studying.
Only white boys showed a decline in test scores — small but statistically significant — that Hofferth interpreted as resulting from too much surfing the Web. "Too much just random surfing isn't necessarily good," she said. "However, playing games and studying are more focused, and they have a positive effect."
Sandra Calvert, a psychology professor at Georgetown University and director of the Children's Digital Media Center, said the findings about improved scores for African-American boys are important. "I think these data are promising in terms of what computers can do for kids," she said.
One message of the study, Hofferth said, is that not all forms of media are equal "in terms of consequences for kids."
Hofferth's study found that video game play on systems such as PlayStation, Wii and Xbox is linked to less time reading and studying. Still, "the reduction wasn't associated with a decline in achievement, and that was a surprise," Hofferth said.
Her research found that boys who increased their video game hours the most over the six-year period also had the biggest increase in aggressive behavior. Even so, she said, the increase was small for most children.
Some parents were not entirely soothed by the findings.
"It's a relief that it's not harming them academically, but that's only part of the picture," said Mimsy Pangilinan, a mother of two in suburban Manassas, Va.
"They never have an opportunity to be bored," she said. "Or know what their own thoughts are, because there's not much time to be introspective."
Hofferth's study was nationally representative and included 1,000 children who were ages 6 to 12 in 1997 and ages 12 to 18 in 2003. She relied on time-use diaries, parent surveys and achievement test results, and recently updated her work with 2008 data from comparable children.
Hofferth said the most dominant screen in U.S. households remains the most familiar: television.
The study found a decline in TV hours, but television still outpaced other screen time: about 13 hours a week in 2008 for children of all ages, compared with six to 10 hours a week for computers and gaming systems combined.