Wow! This is really funny-- I never really knew what it was, just that I would get teased by my father something horrid for the way I said "kitten". I still don't really hear the difference, but never really realized it was with all tt words.
You're onto something!
I don't think it's an accent, just the way I learned phonemes.
Interesting aside- I had a lisp growing up. Pretty bad one. Went to years of speech therapy and everything. I didn't hear that either. I do a lot of professional work now on literacy and am pretty sure it's because I had chronic ear infections as a child so I learned language without properly hearing it.
Course the Speech Therapy gave me TMJ, but that's just one more link in an interesting chain of events.