I can believe there is no specific answer to the question. I know I used to have "engage" my brain to be in listening mode to listen to speech when I had my HA. I wouldn't always "get it" when somebody spoke to me at first especially out of the blue. I would have say "I'm sorry but I wasn't paying attention".
After I got my CI, I was able to catch something somebody said right off the bat a lot more often. Nowadays, I'm pretty much automatic about it but I still have my moments especially if I'm deep in thought. This aspect is one of the things I really appreciate about my CI. I don't feel like I'm having to catch up with everybody else (what did I miss type of thing?).
On the other hand, if it were just noises not speech whether with HA or CI, I never had trouble realizing I heard a noise. I would always react appropriately to it (i.e., it was a normal non threatening sound, it was a sound that I needed to investigate, or it sounded like I needed to be on guard and etc).
I guess to answer my own question, some of it can be developmental but there are definite unknowns involved as well.
Thanks...