doesn't/don't: first-hand experience

[RonButters at AOL.COM]

My first really memorable introduction to practical linguistics came when I
was 18 years old and went off to the University of Iowa as a freshman. I had
been an honors student in high school English in Cedar Rapids, Iowa, and I
participated in high-school speech contests (mostly in extemporaneous speaking). No
one ever called me on any aspect of my grammar.

I was not conscious that "He don't" (and, in general, the use of "don't" with
singual subjects) was a part of my speech until college friends--graduate
students--pointed it out to me. I have no idea whether or not I had unconsciously
shifted to "He doesn't" in speech contests, but I doubt it. Perhaps the
construction never came up in those formal situations. It does seem impossible that
I could have gone through high-school and never written "he don't" unless I
unconsciously style-shifted to "doesn't" in writing.

I would NEVER have written or said "He do" or "It do" or "John do," however.

A similar experience fifteen years later: a friend pointed out to me that, in
speech, I regularly did not use a linking /n/ between the indefinite article
"a" and a word beginning with a vowel. I tended to use a glottal stop instead:
"a?apple"rather than "an apple," etc. She found this very amusing, especially
because I was by that time a tenured member of the Duke English Department,
specialing in English linguistics. Ever since then, my tongue invariably flaps
against my alveolar ridge betweeen the word "a" and a word beginning with a
vowel.