It should come as no surprise that advertisers want you to watch their ads. It may, however, irk you to discover that apps for kids aged five and under are also packed with ads that researchers describe as manipulative, disruptive, and not at all age-appropriate.A new study, published in the Journal of Developmental & Behavioral Pediatrics, reviewed 135 different apps aimed at children—including many from the “5 And Under” category at the Google Play store—and found that 100% of free apps and 88% of paid apps included ads. The frequency of advertisements was the same whether an app was classified as “educational” or not.

“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,” said senior author Jenny Radesky, a developmental behavioral expert and pediatrician at the University of Michigan C.S. Mott Children’s Hospital.

Children under 8 now spend about one hour a day using mobile devices. While many researchers are studying the impact of screens on children’s sleep, as well as their broader development, this study is the first to examine the prevalence of advertising in children’s apps, many of which are labeled as “educational.”

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TV advertising in the US aimed at young children has been regulated by the Federal Communication Commission since the 1970s, based on research that showed children under 8 were not able to differentiate between programming and advertising. But as kids have become digital natives, little effort has been made to assess the impact of ads in the worlds they now inhabit. “Digital-based advertising is more personalized, on-demand and embedded within interactive mobile devices, and children may think it’s just part of the game,” says Radesky.

Researchers found that play in the apps was frequently interrupted by pop-up video ads, commercial characters persuading kids to make in-app purchases, and banner ads they labelled as “distracting, misleading and not always age-appropriate.” They also documented instances where the apps asked the user to share information on social media sites. Also, 17 of the apps requested permission to access phone functionality, 11 asked for microphone permission, nine asked for camera permission, and six requested location access.

This could be in violation of the US Children’s Online Privacy Protection Act, designed to protect the privacy of children under 13. Child consumer advocacy groups, led by the Campaign for Commercial-Free Childhood (CCFC) and Center for Digital Democracy, plan to file a complaint with the Federal Trade Commission about the study’s findings.

“This groundbreaking study demonstrates that popular apps for preschoolers are rife with commercialism that takes unfair advantage of children’s developmental vulnerabilities,” Josh Golin, the CCFC’s executive director, said in a release accompanying the study. He added that the practices are “not only unethical, but illegal.”

Radesky is particularly concerned about how ads negatively impact lower-income children, since in-app purchases were present in a third of all apps studied in the report, and 41% of all free apps. “My lower-income patients play free apps, and my interview participants have described relying on free apps to entertain their child when they have no money for real toys or other outings,” she told Quartz.

Here’s what she said needs to be done:

Ad content regulators should get the inappropriate and sometimes disturbing content out of kids’ in-app ads, or even better eliminate ads in apps for kids;

App designers shouldn’t let ads take up more time than gameplay

App stores like Google Play should do more vetting before apps are offered in a section deemed “designed for families”

“When playing these apps, we felt like advertisers were using a model developed for adult users, and transferring it into kids’ tech,” she said. “It felt totally inappropriate.”