I learned Morse code almost 50 years ago. I distinctly remember how learning progressed through stages

- hear di-dah (sound), think dot-dash (printed symbols), in the table that's an A

- hear di-dah, think "A"

- hear dah, di-di-di-dit, dit, hear the word "the"

- add more and more words

Along with that progression, the mental buffer got bigger, as it has to in order for you to recognize whole words. If I was having a conversation near my speed limit, a good way to break me was to send a long unusual word