More than a third of kids under 1 year old are already swiping away on cellphones and tablets, according to a survey. (iStock)

Smart phone. Dumb idea.

More and more Americans are handing their smartphones to their kids, some as young as 6 months old, according to a new study. Experts warn, however, that the habit could be harmful for a child’s development, despite the promises of cellphone “learning apps.”

More than a third of kids under 1 year old are already swiping away on cellphones and tablets, according to a survey by pediatric researchers at the Einstein Healthcare Network.

Researchers polled 370 parents of children ages 6 months to 4 years old as they visited a pediatric clinic for a low-income, minority community in Philadelphia (74 percent of respondents were African American and 14 percent were Hispanic, according to a summary of the survey). The survey, which was presented on Saturday at an American Academy of Pediatrics conference, consisted of 20 questions on when their child was first exposed to mobile media devices.

The survey found higher — and earlier — use of mobile devices among young children than previous studies.

Among kids younger than 1, 52 percent had watched television on mobile devices, 36 percent had been allowed to scroll the screen, 15 percent used apps and 12 percent played video games. Almost a quarter of the kids under 1 year old had already called someone.

By the time they reached the age of 2, a majority of kids were using cellphones or tablets, according to the summary.

Even the researchers were stunned by how early the kids had been handed cellphones by their parents.

“We didn’t expect children were using the devices from the age of 6 months,” said Hilda Kabali, a third-year resident at Einstein who led the survey. “Some children were on the screen for as long as 30 minutes.”

While not a comprehensive scientific study, the survey backs up an alarming trend seen in other polls: Kids are using cellphones and tablets at an ever-decreasing age. In 2013, an Internet survey of 1,463 parents found that, among kids under 2, 38 percent had used smartphones or tablets. That was the same percentage as among kids 8 and younger during a similar survey in 2011.

The survey is alarming, given growing concerns about the effect that such screen time has on young children. The British government warned in 2013 that too much on-screen time causes emotional problems for kids. The American Academy of Pediatrics discourages the use of screen devices among children under age 2.

A 2014 study found that preteens who were stripped of their digital devices and forced to spend five days at an outdoor camp almost immediately showed an improved ability to read “nonverbal emotion cues.” In other words, in being human.

While lazy parenting and the sheer ubiquity of phones is part of the problem, some advocates also blame companies for pushing the idea that cellphone and tablet apps are just as good as real, in-person interaction with a child.

“In addition to persuading parents to waste money on useless products, marketing products for babies as teaching numbers and letters sends a troubling and potentially harmful message to parents about learning and how babies should spend their time,” said Susan Linn, director for the Campaign for a Commercial-Free Childhood, last year. Instead of handing a child a tablet, parents should engage in “hands-on creative play, active play, and active engagement with the adults who love them,” she said.

Fisher-Price and other “baby genius” apps often promise to help kids learn fundamental skills, like numbers and the alphabet. But a number of child development and educational experts have said such promises are misleading.

“Based on scientific evidence on how infants learn, I believe that claims that a two-dimensional touch screen app can teach alphabet letters, numbers, and counting from 1 to 10 to babies (including those as young as 6 months) are inaccurate, seriously misleading to parents and potentially detrimental to infant development,” said Laura Berk, a psychology professor at Illinois State University.

“Advertising claims that touch screen devices can successfully teach number concepts and counting to babies as young as 6 months are deceptive,” wrote Herbert Ginsburg, a psychology professor at Columbia University.

So while there may be an app for everything, screens are still no substitute for spending time with your kid.