1. When monks and statesmen, from Mesopotamia to Rome to Medieval Europe, were reading and writing texts, transcribing and memorizing, we they saying what they were reading aloud, or were they able to read in their heads like most of us today?

2. Is this something which has ever been mentioned in old texts, e.g. does the bible ever discuss "the voice in our head" as the voice of god, the voice of our conscience, or mention "crazy people" and prophets who heard voices similar to those with Schizoid disorders experience in modern times?

3. Are there any groups currently which have reading and writing, without internal voice when reading and writing? Do adults whom have recently learnt to read/write find it difficult to not make mouth movements?

4. [More anthropological] Do we believe that for as long as humans have had language, we have had voices in our heads? Is it believed that mental-voice could have predated language, in the sense that I feel I am able to have "wordless thoughts", such as "that's a cool rock" when my attention is captured?

This question is predicated on a few assumptions, so correct me if these are misleading me:

1. The modern world is much more abstract and cognitively stimulating than ancient societies[not pre-agrarian!] and thus more conducive to the acquisition of mental skills like reading internally.
2. Western Humans only really started subvocalising text, "reading in their head", shortly after the invention of the printing press and widespread dissemination of books. However, I'm not sure how this fits in with bibles and torah(s).
3. Pre-printing-press Humans learnt to read much later in life than we do now, closer to adulthood.
4. Learning to read, especially with a mental voice, is quite difficult and complex.
5. The original pronunciation of YHWH, as the "name of God" is believed to be lost. AFAIK vowels are written with small dots, so Hebrew isn't an Abugida where omission of vowels would be customary for most words.
6. Jews wouldn't say YHWH aloud and with vowels, at least not when reading the scripture(s), as it is similar enough to "saying God's name in vain".
7. The Jewish or Yiddish word for "Meditation" means "To mutter to oneself". If this is correct, is it in the context of an Indian Mantra, or Descartes' "philosophical meditation" whereby one inquires into an idea and thinks for a long time, rather than the silencing of inner chatter like most Westerners aim for when we're meditating. [I'm not entirely sure but supposedly meditation can grant us mental-silence by reducing activity in the Default Mode Network https://en.wikipedia.org/wiki/Default_mode_network , which also occurs during the experience of Flow https://en.wikipedia.org/wiki/Flow_(psychology)

My armchair-historian conspiracy is that "YHWH" was never written with the vowels, not since writing god's name was as bad as saying it, but that it couldn't be written without being spoken.

P.S. A psychiatrist has discussed with me there is speculation that some children with ADHD and Asperger's may have delayed development of their "mental narrator". I have friends that claim they can remember the precise moment they "figured out" how to read in their heads as a child. Is it plausible that if we learnt to read as adults, and in a world with far less abstraction[simpler means of production, smaller vocabularies], then this leap wouldn't be accessible to most of us?