Language learning in the context of a global pandemic: proximal and distal factors matter.

Background: Public health measures implemented during the COVID-19 pandemic fundamentally altered the socioecological context in which children were developing.

Methods: Using Bronfenbrenner's socioecological theory, we investigate language acquisition among 2-year-old children (n = 4037) born during the pandemic. We focus on "late talkers", defined as children below the 10th percentile on the MacArthur-Bates Communicative Development Inventories-III.

Results: Overall, the proportion of late talkers declined as a function of pandemic wave, with 13.0% of those born during the first wave classified as late talkers compared to 10.4% born in wave two, and 8.0% born during wave three. In sex-based analysis, we observed a 15.9% prevalence of late talking among female toddlers, which was significantly different from the norming sample. In contrast, the prevalence of late talking among male toddlers was 9.1%. Using hierarchical logistic regression to identify both proximal and distal factors associated with being a late talker, we found that male sex, lower socioeconomic status, greater screen time, receiving childcare at home, disruptions to childcare, and experiencing greater exposure to public health restrictions were associated with increased odds for being a late talker.

Conclusion: We interpret the findings in relation to the need to consider the special needs of young children in disaster preparation and response.

Impact: Two-year-old children acquiring language in the context of the COVID-19 pandemic have vocabulary size similar to historical norms. A higher-than-expected prevalence of late talkers (below the 10th percentile) was observed among females and children born during the first wave of the pandemic. Motivated by Bronfenbrenner's socioecological theory, we show that both proximal and distal environmental factors are associated with vocabulary size. Infants exposed to stricter public measures had reduced vocabulary size. The findings suggest a need to recognize the developmental needs of children as part of the public health response to emergencies.