I understand the process experientially. I was a good student, a teacher's pet, the one who always had to have the correct answer. In childhood I talked like a book. (When my son, John Paul, was a small child talking in sentences, my mother called him "the pocket edition.") It was not long before I was gratuitously correcting other people's grammar and usage, and by the time I was a graduate student in English, I was a proper prig about language and usage.