https://www.sciencedaily.com/releases/2022/02/220207083421.htm

Shortly after lockdown began in early March 2020 across 13 countries, parents were asked to complete an online questionnaire containing questions on the child's age, exposure to different languages, number of siblings and vocabulary development. Parents were then contacted again at the end of the lockdown (for that family or in that area, in general). They were asked about the activities that they undertook with their child during lockdown, the amount of time their child had access to screens both during lockdown and before, as well as questions on how much screen time they typically had themselves and their attitudes towards children's screen time. Parents were also asked to complete a standardized vocabulary checklist indicating the number of words their child understood and/or said at the beginning, and again, at the end of lockdown so that an increase in the number of words gained over lockdown could be calculated.

The studies find that, during lockdown, children who were read to more frequently were reported by their caregivers to have learned more words, relative to their peers who were read to less frequently. However, children with increased exposure to screens learned to say fewer words, relative to their peers with less screen time. In addition, while children were exposed to more screen time during lockdown than before, overall, children were reported to have gained more words than expected during lockdown, relative to pre-pandemic levels. The increase in screen time during lockdown was greater if lockdown was longer, and in families with fewer years of education, and where parents reported using screens for longer themselves.