In (rec.radio.amateur.misc), Cmd Buzz Corey wrote:

I used to teach Novice classes, and I always assumed that anyone could
learn the code if they really wanted to. I found that some people had
difficulty telling the difference between a dit from a dah unless it was
sent very slowy and the dah made a lot longer than the dit, but when
sending a character that contained several dits or dahs or combinations,
they simply could not tell one from the other. It wasn't that they
lacked the skill to learn the code, I could right out characters in dits
and dahs on the board and they could recoginize them, it was an
interpertation problem with the brain of telling the sound of a dit from
the sound of a dah. People with hearing aids often had a difficult time.

You hit that part right on the head. My XYL has a deep notch in her hearing
response curve, from about 400 Hz to about 2 KHz, due to playing viola in
a symphony orchestra for 15 years, sitting right in front of the brass
section[1]. She's having the very devil of a time with Morse, mostly
because she has problems distinguishing between dit and dah. She has
learned not to trust her ears, and now she's trying to learn to read with
them. The deep notch right where most people tune to read CW and where the
various tapes, CDs, and tutor programs all put the tone, also makes it very
difficult for her.

When she passes Element 1, I have to go learn American Sign Language and
pass a proficiency test.

[1] I'll bet most people don't think much about hearing damage in people
playing in symphony orchestras. It's fairly common.

--
Mike Andrews W5EGO 5WPM
Extra
Tired old sysadmin working on his code speed