Also, as an adult, you have to provide for yourself. Without language, that virtually becomes impossible. Therefore, you have to keep using a language you already know, which reduces immersion. As a 2-5 year-old, everything is provided for you, so you don't have to use a language you already know. You can just be there messing up language all you want in trial-and-error until you get it.

To make a real quasi-experimental study (random assignment is impossible because age cannot be assigned), we'd have to ensure that adults are given the same amount of support with activities of daily living as children. We'd also have to give them the same understanding, compassion, and forgiveness for mistakes, and also encouragement and esteem support.

After thinking it through to write this comment, I think the original microblog post is based af.