LENA itself conducted one of the studies, which analyzed recordings of over 600 babies aged zero to nine months. Babies born during the pandemic, the study found, are vocalizing less and experiencing fewer conversational turns.

Independently, another study from Brown University’s Advanced Baby Imaging Lab found similar results. The lab has been tracking over 1700 families with young children since 2010. One year into the pandemic, researchers found that children’s average cognitive performance was the lowest it had been since the study began. A separate analysis of infants found a dramatic decline in verbal functioning in 2021, apparently because adults were initiating fewer conversational turns…

The reasons for the decline in vocalizations and conversational turns aren’t entirely clear from the data, but the Brown study concluded that factors related to the pandemic had “by far the greatest impact on infant and toddler neurodevelopment.” It seems likely that a combination of stressed caregivers and social isolation is to blame. (Neither study addressed the question of whether masks might interfere with language development, since both were conducted in homes rather than daycare or preschool settings.)