From games inspired by popular TV shows to digital play labeled as educational, children’s apps continue to explode on smartphones and tablets.

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But parents may not realize that while their little ones are learning letters and numbers or enjoying virtual adventures, they’re also likely being targeted by advertisers.

Ninety-five percent of commonly downloaded apps marketed to or played by children 5 and under contain at least one type of advertising, according to a new study led by University of Michigan C.S. Mott Children’s Hospital.

Published in the Journal of Developmental & Behavioral Pediatrics, the study reviewed 135 different apps — and it marks the first effort to examine the prevalence of advertising in children’s apps.

Researchers found play was frequently interrupted by pop-up video ads, persuasion by commercial characters to make in-app purchases to enhance the game experience and overt banner ads that could be distracting, misleading and not always age-appropriate.

“With young children now using mobile devices on an average of one hour a day, it’s important to understand how this type of commercial exposure may impact children’s health and well-being,” says senior author Jenny Radesky, M.D., a developmental behavioral expert and pediatrician at Mott.

Radesky notes that her team found high rates of mobile advertising through manipulative and disruptive methods — with exposure to ads even surpassing time spent playing the game in some cases.

“Our findings show that the early childhood app market is a wild west, with a lot of apps appearing more focused on making money than the child’s play experience," she says. "This has important implications for advertising regulation, the ethics of child app design, as well as how parents discern which children’s apps are worth downloading."

Ads target youngest players

Researchers detailed experiences with advertisements during gameplay of the most popular children’s apps.

Although 100 percent of surveyed free apps contained advertising content (compared to 88 percent of purchased apps), the ads occurred at similar rates in both types of apps categorized as educational.

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Ad videos interrupting play were prevalent in more than a third of all analyzed apps and in more than half of free apps. In-app purchases were also present in a third of all apps, and in 41 percent of all free apps.

This discrepancy worries Radesky. “I’m concerned about digital disparities," she says. "Children from lower-income families are more likely to play free apps, which are packed with more distracting and persuasive ads.”