I knew someone who could type 80 WPM while holding a conversation with me on the phone. I concluded that reading->typing could use an entirely different part of the brain than hearing->thinking->speaking, and she agreed. I'm not sure if what would happen if both tasks required thinking about the words.
I can do that. I think about the typing just long enough to put it in a buffer and then switch my focus back to the conversation (whose thread I'm holding in my head). I do this very quickly but at no point would I say my conscious focus or effort are on both things. When I was younger and my brain's processing and scheduler were both faster, I could chat in person and online, but it was a lot more effort and it was just a lot of quickly switching back and forth.
I don't really think it is much different than reading ahead in a book. Your eyes and brain are reading a few words ahead while you're thinking about the words "where you are".
> my conscious focus or effort are on both things.
If this switcheroo is really fast and allows you to switch between two different thoughts so quickly while keeping a pointer to the position of the thought (so you can continue it with every switch), this is indistinguishable from doing it in parallel — and it still seems it's mostly blocking on your verbal, language apparatus, not on your thought process.
Reminds me of the early days of multithreading on a single core CPU and using the TSS (Task Switch Segment IIRC) on Intel CPUs to (re)store the context quickly.
Certainly from the outside it is indistinguishable, but that's not the conscious experience of it. I can type the words in the buffer without thinking about them at all. It is possible that at that point they are no longer language, depending on how my brain actually does this. However, the conscious experience of it is that "I" need to decide what to say in both conversations and I can only experience that decision a conversation at a time, even if the thoughts themselves are generated and/or in parallel.
A similar effect occurs when playing music. I can only consciously work on improving a single thing at a time. What does happen over time is that what a "single thing" is can become more encompassing. For instance, with the piano I had to first concentrate on what the chord I wanted was, then concentrate on hitting each note of the chord. Now I can just play that chord, without thinking consciously about the notes involved or how to hit them. So if a song calls for a C chord, I can just focus on "hit a C chord" rather than "hit the notes C, E, and G". Then the C chord itself grows into its various inversions, major/minor, arpeggiation, etc.
But at no point in my entire life have I ever had the conscious experience of multiple conscious experiences in parallel.
I've noticed myself being able to do this, but modulo the thinking part. I can think about at most one thing at once, but I can think about what I want to type and start my fingers on their dance to get it out, while switching to a conversation that I'm in, replaying the last few seconds of what the other party said, formulating a response, and queuing that up for speech.
I strongly believe that the vast majority of people are also only able to basically do that - I've never met someone who is simultaneously form more than one "word stream" at once.
Yeah I agree, my brain works in that rapid switching kinda way. I feel you can set up the subconscious one to do a task while your conscious brain works on something else. Trying to output two conscious 'word streams' simultaneously as you said, feels impossible.