It seems intuitive that children’s schoolwork will suffer if they spend too much time gazing at their phones instead of getting to bed or getting some exercise. And that is broadly what a recent study has found. But should parents be panicked into pulling the plug on their kids’ electronic devices.

Jeremy Walsh at the Children’s Hospital of Eastern Ontario Research Institute in Ottowa, Canada, and his colleagues evaluated the lifestyle data  of 4520 US children, 8 to 11, and how far they  met various Canadian government guidelines on cognition.   These suggest limiting screen time to 2 hours a day, sleeping for 9 to 11 hours a night and spending at least an hour being physically active.

More than a third – 1655 children – met the guideline for limiting screen time, and their average performance in the cognitive tests was 4.5 per cent higher than that of the 1330 children who met none of the guidelines. The gain was even higher, at 5.2 per cent, for those meeting both the screen-time and sleep recommendations (The Lancet Child & Adolescent Health, doi.org/ct95).  The US study is running for a further 10 years, and will enable researchers to track whether the children change their behaviour over time, and whether screen time depletes cognitive performance.

Two caveats:  What the the survey didn’t reveal was what the children were doing on their screens, which could be either educational or trivial. To truly understand the impact of digital media on children, researchers must understand not only how much, but also how, what, where and with whom they’re watching.  Secondly, the answers were self- reported by the children .  Can 8 to 11-year-old children reliably report their own screen and physical activity behaviour?

More research will make the data more reliable.   So far the lessons are sensible: parents should try to set some limits on screen time, especially prior to bedtime . Screen time before bed is doubly problematic because it keeps kids up later, and exposure to light impairs sleep quality, cognition and the general working of he brain..  (Andy Coghlan. New Scientist , 23 Oct 2018).

So now I am off to the gym, where I will find numerous young adults staring fixedly at their phones or treadmill screens – with exercising an incidental.  Epicurus never opined about exercise, as far as I know, but then there were the Olympics and the near- worship of physical fitness.  Add to that sunset and the difficulty of reading after sun-down, and I guess the ancient Greeks must have been psychologically well- adjusted.  They certainly produced some smart philosophers.