The average toddler is missing out on hearing more than 1,000 words spoken by an adult each day due to screen time, setting back their language skills, a first-of-its kind study has found. The research, published on Tuesday in the Journal of the American Medical Association (Jama) Pediatrics, tracked 220 Australian families over two years to measure the relationship between family screen use and children’s language environment. Families recorded all the audio around their child using advanced speech recognition technology over a 16-hour period on an average day at home. They repeated this process every six months between the ages of 12 and 36 months. The lead researcher, Dr Mary Brushe from the Telethon Kids Institute, said: “The technology we use is essentially like a Fitbit, but instead of counting the number of steps, this device counts the number of words spoken by, to and around the child.” The device also picked up electronic noise, which the researchers analyzed to calculate screen time.

The researchers found young children’s exposure to screens including TVs and phones was interfering with their language opportunities, with the association most pronounced at three years of age. For every extra minute of screen time, the three-year-olds in the study were hearing seven fewer words, speaking five fewer words themselves and engaging in one less conversation. The study found the average three-year-old in the study was exposed to two hours and 52 minutes of screen time a day. Researchers estimated this led to those children being exposed to 1,139 fewer adult words, 843 fewer child words and 194 fewer conversations. Because the study couldn’t capture parents’ silent phone use, including reading emails, texting or quietly scrolling through websites or social media, Brushe said they might have underestimated how much screen usage is affecting children.

A language-rich home environment was critical in supporting infants and toddlers’ language development, Brushe said. While some educational children’s shows were designed to help children’s language skills, very young kids in the age group of the study could struggle to translate television shows into their own life, she said. This study did not differentiate between whether children were watching high- or low-quality screen content.