I can’t see any way that mask-wearing won’t affect some children’s social and language development tbh. Anecdotally friends who work in Early Years and SALT (I’m an ex-primary school teacher) are saying that there has already been an uptick in young children presenting with speech and language delay, but it’s a difficult one as the Covid restrictions have been so extensive and multi-faceted that it will be difficult to separate out the impact of mask-wearing vs social distancing for example. So, to what extent are masks causing poor socialisation in kids, and to what extent is it simply lack of exposure to a range of people and places?
For each specific element of development/socialisation in babies and toddlers there is often a fairly brief window, and if these skills are missed they can’t always be easily caught up on without external intervention. Many aspects of child development are cumulative, with each new skill building on pre-existing ones, and if the basic ‘building blocks’ aren’t in place there can be issues further along the line.
Most children will probably adapt to their circumstances and turn out broadly fine, but some clearly won’t. In many cases it may be that those who are predisposed to have issues anyway will have more severe problems than they would otherwise have done; some children who were borderline in terms of normal development may also tip over into having issues. Many of these, I imagine, will only be picked up once these cohorts start formal schooling. I certainly don’t envy the Reception/KS1 teachers of the next few years.
My own DD is 3 and seems fine, but I have minimised mask-wearing as far as possible within the guidelines, continued to take her into public spaces (shops, on public transport) throughout lockdown, encouraged verbal interaction with as many people are possible and made the most of every opportunity on offer during periods of lesser restrictions.
Also imo it isn’t just the fact that babies can’t read masked expressions that is the only factor. I’ve attended lots of toddler classes with DD both pre- and post-pandemic, and have noticed a huge difference between how parents/caregivers interact with children in masks and without - there’s much less interaction generally when adults are wearing masks, lots of people seem to retreat into their phones rather than attempting to chat etc. It is literally a barrier to communication, and also to community cohesion.
I’d also add that it isn’t just the youngest children who are being impacted by prolonged mask-wearing. I have several close friends whose teens have gone from outgoing, chatty, high achieving students to being withdrawn, totally silent in lessons, grades slipping etc. Masks have been cited as the probable reason in each case by both parents and school.