“Too much television will rot your brain” has been a cultural refrain dating back to the days when screen time options were limited to a handful of broadcast networks and Super Mario Bros. While not technically accurate, a new study in the Journal of Pediatrics does indicate that limiting screen time improves toddlers’ executive functioning. In other words, TV might not “rot” a little one's brain, but it sure hurts their ability to pay attention, remember, and stay on task.

First of all, what exactly is executive function? For kids, it’s everything. “Executive function underlies your ability to engage in goal-directed behaviors,” Naiman Kahn, Ph.D. said in a release. The University of Illinois Urbana-Champaign kinesiology and community health professor led the study which is part of the STRONG KIDS 2 cohort at the university. “It includes abilities such as inhibitory control, which allows you to regulate your thoughts, emotions and behavior; working memory, by which you are able to hold information in mind long enough to accomplish a task; and cognitive flexibility, the adeptness with which you switch your attention between tasks or competing demands.”

If that sounds like a laundry list of things kids struggle with at any time on any given day, you’re onto something. Previous studies have linked too much screen time — as well as unhealthy diet and weight trajectory — with lowered executive function in school-aged children, and this most recent study examined how early those connections start. The impetus for the study was to explore find out whether a toddler’s executive function is improved by following the American Academy of Pediatrics guidelines for screen time, diet, and physical activity.

The study followed 356 toddlers from birth to five, looking at the dietary habits and weight trajectories using parental surveys and hard data (like weight) on the children gathered at eight points during that timeframe. They asked about physical activity, whether their diet included at least five servings of fruits and vegetables each day, whether they consumed sugar-sweetened beverages. For screen time, they simply asked parents how much time their kids spent looking at screens.

To evaluate executive function, parents were then asked about their child’s ability to plan and organize their thoughts, regulate their emotional responses, inhibit impulses, remember information and shift attention between tasks.

The connection between weight, diet, and executive function overall weren’t significant, although toddlers who got at least 60 minutes of daily physical activity also did better on tests measuring working memory compared to less active kids. But when it came to screen time, the connection was crystal clear — and worrisome.

“We found that toddlers who engaged in less than 60 minutes of screen time per day had significantly greater ability to actively control their own cognition than those who spent more time staring at phones, tablets, televisions and computers,” said Arden McMath, a graduate student who helped author the study. “They had greater inhibitory control, working memory and overall executive function.”

There are of course limitations to a study like this. For one, surveys are not the most accurate way of measuring ones habits, and when it comes to the habits of our children, hopes and fears and best intentions might skew the data coming from parents. Furthermore, executive function is a broad thing to measure — and as such this study can’t tell us how specifically diet, weight, and screens are impacting our kid’s development.

But one thing is broadly clear: Emphasizing screen time limits is beneficial for kids and parents should feel empowered to just say no. Otherwise, you can expect an inattentive emotional mess on your hands —or at least more of a mess than you would without that Bluey marathon.

American Academy of Pediatrics Screen Time Guidelines for Toddlers

It might not be practical or easy to follow screen time limits for toddlers all day every day, but it’s important to remind ourselves of the strict limits set by the AAP, which are:

• Until 18 months of age, limit screen use to video chatting along with an adult (for example, with a parent who is out of town).

• Between 18 and 24 months, screen time should be limited to watching educational programming with a caregiver.

• For children 2-5, limit non-educational screen time to about 1 hour per weekday and 3 hours on weekend days.