Stop the educational YouTube videos! Well, maybe not those, but if you really want to improve your kids’ cognitive abilities, you should actually limit the amount of time they spend in front of televisions, computers, tablets, and smartphones, and make sure they get ample sleep, according to a study by Canadian researchers.
In looking at more than 4,500 children in the U.S. between the ages of 8 and 11, researchers found that the average American child gets 3.6 hours of screen time a day, an amount associated with inferior cognitive development and academic performance.
The team used the Canadian 24-Hour Movement Guidelines for Children and Youth for the study, which recommend that children get between 9 and 11 hours of uninterrupted sleep, less than 2 hours of screen time, and at least 1 hour of physical activity a day. Youngsters who met those guidelines scored highest on tests for assessing language abilities, memory, executive function, attention, and processing speed.
In the U.S., 19 out of 20 children failed to reach all of the benchmarks for sleep, screen time, and physical activity. Approximately half got the daily recommended amount of sleep; however, just 37% met the guideline for limited screen time, and a paltry 18% met the guideline for physical activity.
The researchers also accounted for other factors that can influence cognition, including: 
- Household income
- Body mass index (BMI)
- Traumatic brain injury
- Parental and child education levels
- Pubertal development in mind
How the Data was Collected
As part of the project, researchers across the U.S. interviewed children and their parents about the amount of time they spent being physically active, sleeping, and using screens on the average day. Additionally, the children were given questionnaires, provided spit samples, and completed puzzles that allowed the researchers to measure their cognitive abilities. 
The more benchmarks a child met, the more improvements in cognition the researchers were able to track, though limiting screen time and sleep were found to have the biggest impacts. No association was found between the physical activity guideline and cognition, which may suggest that the researchers weren’t specific enough in how they measured physical activity. 
Dr. Jeremy Walsh, the study’s lead author and a postdoctoral fellow at the University of British Columbia, said in a press release:
“Evidence suggests that good sleep and physical activity are associated with improved academic performance, while physical activity is also linked to better reaction time, attention, memory, and inhibition.”
Walsh pointed out that the relationship between recreational screen time and cognitive development has been murky, and this type of research is still in its infancy.
How Much Screen Time?
He said: 
“Behaviors and day-to-day activities contribute to brain and cognitive development in children, and physical activity, sedentary behavior, and sleep might independently and collectively affect cognition.
We found that more than 2 hours of recreational screen time in children was associated with poorer cognitive development. More research into the links between screen time and cognition is now needed, including studying the effect of different types of screen time, whether content is education or entertainment, and whether it requires focus or involves multitasking.”
When it comes to screen time, the American Academy of Pediatrics (AAP) recommends the following:
- When children less than 1-2 to 2 years old watch TV or use electronic devices, parents should watch and play with them.
- Children ages 2-5 years old should have no more than 1 hour of screen time. Again, parents should watch and play with them.
- There is no specific limit on screen time for older children, but families are encouraged to develop their own daily media limits with the help of the AAP’s online planning tool.
What About Sleep
When it comes to sleep, this is how much the AAP says children need, according to age:
- Infants 4 to 12 months – 12 to 16 hours of sleep every 24 hours (including naps).
- Children 1 to 2 years – 11 to 14 hours of sleep every 24 hours (including naps).
- Children 3 to 5 years – 10 to 13 hours of sleep every 24 hours (including naps).
- Children 6 to 12 years – 9 to 12 hours of sleep every 24 hours.
- Teens 13 to 18 years – 8 to 10 hours of sleep every 24 hours.
Smartphones, tablets, and other screens should be removed from kids’ bedrooms, as research shows that just knowing the devices are in the room can disrupt a child’s sleep.
 ABC News
 Consumer Affairs