Quinn Marvin, 14, in his room at his home in Washington. He built his own computer. (Matt McClain/FOR THE WASHINGTON POST)

Before she became a parent, Claire Harvey was firm on the subject of screen time.

“I wasn’t allowed to watch a lot of TV when I was younger, and I wanted my kids to have the same sort of innocent childhood,” Harvey says. “I am the mother who said to herself, ‘My kids will never watch TV!’ ”

Today, however, as she and her husband juggle the demands of family and jobs, Harvey acknowledges turning to the television, or her iPhone, to entertain her two young children. Against her pediatrician’s advice, Harvey, 32, of Bethesda, allows her 2-year-old, Jace, to watch “This Old House.” “He could watch five episodes in a row, if I let him,” Harvey says. Occasionally, she also lets him use an educational app on her iPhone.

Harvey doesn’t think the screen time is harmful. Still, she says she feels guilty every time she turns on a device — particularly when her 1-year-old, Haisley, is in the room.

“It’s one of my constant everyday struggles and worries,” Harvey says. “I wish there were more guidelines out there.”

Based on research linking too much television to language delays and disrupted sleep patterns, the American Academy of Pediatrics strongly discourages television viewing for any child younger than 2, and recommends that older children watch no more than an hour or two per day. But for parents seeking advice on managing their kids’ screen time beyond television, the recommendations go no further than the obvious: Limit it, and monitor content.

In part, that’s because the definition of screen time has grown far beyond television to include laptops, smartphones and tablets. It has become harder to measure how long our kids are exposed to various screens.

A 2011 study by Common Sense Media, a San Francisco-based think tank focused on children and media use, found that half of children younger than 8 had access to a mobile device and that TV still accounts for the largest share of their screen time. Half of children younger than 2 watch TV or DVDs on a typical day, and among all children younger than 2, the average is 53 minutes a day. About 12 percent of children 2 to 4 use computers daily, and 24 percent at least once a week.

“All screen time is not equal,” says Michael Rich, director of the Center on Media and Child Health at Boston Children’s Hospital. “What a kid does on an iPad is totally different from what they are doing when they are watching TV. It’s different psychologically, neurologically, educationally — so we can’t just lump all screens together.”

Further complicating efforts to draft new guidelines for screen time is the breakneck pace of technology. Almost as soon as scientists begin to study a new device, the gadget-of-the-moment becomes a thing of the past. Research into the developing brain and the impact of new technology is still in its infancy.

And much of what we are learning is contradictory. A Common Sense media survey of teachers about the role at-home media use plays in the classroom found that most teachers believe technology harms academic performance. Yet the teachers also said media use is helping students develop quick, efficient research skills.

But as parents teetering anxiously on the digital divide, how do we know if the decisions we make are hurting our children? The fact is, it’s too soon to say what the neurological impact is on a toddler given an iPhone to ward off a tantrum or on a preschooler watching a few hours of movies on a long car ride.

We do know that when our kids are engaging in screen time, they are missing out on time-tested activities that contribute to their emotional, cognitive and physical growth. But we also know that a digital world is one in which they will need to be adept.

“Media are so ubiquitous that we need to start thinking about them not as something good or evil, but part of the environment in which we raise our kids,” Rich says. “We need to think about it like the air we breathe or the water we drink.” And then he delivers a more pointed criticism: “We need to get involved and stop using it as a babysitter.”

Get involved? For many parents, screen time means the opposite — it’s a chance to step back from the demands of our children. But Rich says understanding your child’s media choices can turn technology into a learning opportunity.

That’s what happened when Collette Loll Marvin, who teaches at Duke Ellington School of the Arts, and is a mother of two, stopped imposing limits on screen time for her son, Quinn, 14.

“Quinn has always been drawn to screens and technology — ever since he was 3 years old,” she says.

Marvin and her husband, a technology executive, spent years questioning their parenting when it came to Quinn’s television or computer time. It was not until they loosened the reins on at-home media, she says, that they saw its potential.

“I saw that for him it was an interest like sports or music, and that he was using technology as a tool for creativity,” Marvin explains.

Now a freshman at the Lab School, a school for kids with learning difficulties, Quinn is thriving. Marvin says increased screen time has helped him academically and socially. He has turned technology into a serious pursuit, building his own computer.

But at what age do we begin to experiment with technology as an educational tool? That’s where the early research gets thorny.

At Georgetown University’s Children’s Digital Media Center, director Sandra Calvert, a psychology professor, oversees studies into the “video deficit,” the hypothesis that toddlers learn better from observing behaviors in real life than on a screen.

In one study, researchers showed 21-month-old children a video of the familiar “Sesame Street” character Elmo nesting plastic cups. They showed another group the same video featuring an unfamiliar character called DoDo nesting the cups. Finally, they gave the cups to a control group of toddlers who had not watched any videos. The children who watched Elmo nest the cups outperformed those in the other two groups, evidence that toddlers can learn conceptual information from videos featuring familiar characters like Elmo.

In a similar, ongoing study, the center is using iPads to measure the strength of “parasocial” (or intimate, one-sided) relationships children have with on-screen characters and how we can leverage these in education.

“Twenty-first-century literacy is dependent on screens, and our early findings are promising,” Calvert says. “Tuning it out is a missed opportunity to open up a wonderful world of exploration that involves learning with your child.”

Maybe so, but there remain many informed parents who choose to cut out media entirely. For some, it’s out of fear that research might someday show new technology damages nascent brains.

For others, it’s a personal choice. Daniel Willingham, a psychology professor at the University of Virginia, doesn’t allow his children — 5 and 7 — any at-home screen time. Willingham says that as a result, his children play well together and are quick to entertain themselves.

That said, Willingham, a cognitive neuroscientist, is not sounding any alarm bells. He notes that his family’s stance on screen time was not inspired by research.

“We made this decision because we like a peaceful house,” Willingham says.

Until research offers clarity, experts agree the best thing we can do is find a way to manage screen time that works best for our families, and ensure it’s being used judiciously. And we need to be mindful that when our children are in front of a screen, they are not climbing trees, painting pictures, caring for baby dolls or building towers with blocks.

“For every hour our kids spend on the screen, they should spend at least one squeezing mud between their toes in the back yard,” Rich says. “An iPad can’t dig a hole in the sand or build a fort out of sticks and mud.”

Molly Knight Raskin is a freelance writer.