You know, not that anyone asked, but I have a theory sort of how mental regression would work out, like, loosely we can comprehend the idea of losing your understanding of language, because we've all seen foreign symbols that are repeating, so not natural, and don't repeat exactly, so presumably they have meaning beyond aesthetics. A very, very small child can work that out even if they have no idea what it means. We don't have a way to compare and process not knowing how many of something there is when you can see them infront of you.
So, from what I understand of neurological development, and processing, you start off with direct comparisons, I have a finger, I can hold up a finger for each thing I see, processing gets difficult after five, and utterly impossible after 10, because you run out of comparisons, you can teach a child to use an abacus but that only expands the number a little. If you learn, and are able to retain, the word FIVE, you know that FIVE means ||||/ many. Like, fifty plus fifty equals one hundred, and one hundred is 10 sets of ten, or 20 sets of five... but if I put it in front of you a sheet of paper with dots on it, you can do five, you can do 10, once you get to 20, visual recognition becomes harder, 30, more difficult, you'll also start to see if you sneak in an extra dot, the brain will have broken the count down to sets of ten, and you will get 30, instead of 31, which is the correct answer. The human brain cannot process anything past 50 reliably, at that point your brain looks at a series of dots and says "a lot", double that? "a whole lot." multiply it by 2, "a heck of a lot", and cube that, "holy cow that's a lot."
So if you snip snip snip out those pesky numbers by removing the words from the vocabulary, and their meaning with them, even basic counting above the number of fingers you have available is impossible.
(I'm a big fan of age regression, and cognitive regression or regressive addling is also something I'm a fan of, but the idea of removing someone's sense of self is gross to me, so, as a writer of stories, I put a little too much thought into things u.u)
You know, not that anyone asked, but I have a theory sort of how mental regression would work out, l
