When I was listening to some of the samples on the page you linked (pronunciation of “when”), it really seemed to me like the difference they were highlighting was how much the “h” was pronounced. Even knowing what I was listening for, it was very like my brain was just refusing to recognize the vowel sound distinction. So I think you must be right about it being a matter of basic brain chemistry.
In the example of the reverse pen/pin merger (HMS Pinafore) on that page, I couldn’t hear “penafore” to save my life. Fascinating stuff.
I used to think of the movie “Fargo” and think “haha comical upper midwestern accents.” And then at some point I realized that the characters in “No Country for Old Men” probably must sound similarly ridiculous to anyone whose grandparents and great grandparents didn’t all speak with a deep, rural West Texas accent - which mine did, so watching the movie it just seemed completely natural for the place and time at a deeply subconscious level.
In the example of the reverse pen/pin merger (HMS Pinafore) on that page, I couldn’t hear “penafore” to save my life. Fascinating stuff.
I used to think of the movie “Fargo” and think “haha comical upper midwestern accents.” And then at some point I realized that the characters in “No Country for Old Men” probably must sound similarly ridiculous to anyone whose grandparents and great grandparents didn’t all speak with a deep, rural West Texas accent - which mine did, so watching the movie it just seemed completely natural for the place and time at a deeply subconscious level.