I was doing this clinic with this piano player one time and I told her to play this chord prgogression behind me while I demonstrated this technique ( it was a simple chord , I think it was the chords to Knocking on Heavens Door, G D A-)
She looked at me and said"I don't know what those chords are can you write them out". So I had to stop doing what I was doing, dig up some staff paper and write the notes of the chords out on the clef for her.
She was a very talented piano player who could play chopin beatifully note for note....but never took the time or had the instruction to associate what she was reading on the paper to general knowledge. true story.