When I first learned to read, my dad would insist that I do so loudly. In turn, when the boy started to read, I would ask him to do it out loud.
In both cases, we (that is, the boy and I) quickly realised that we read much slower when articulating the words than when reading in our minds.
When I grew up a bit, I also learned that some people who read in their minds were sub-vocalising. In other words, they were mentally pronouncing each word. This meant, of course, that they were reading slowly.
Did it really make a difference, whether one read loudly or quietly? Was subvocalised reading less efficient than speed-reading? Was it important to be an efficient reader?
When my boy read loudly, he sometimes slurred the words. I had to ask him to slow down. I wanted to make sure he pronounced each word correctly - after all, while his vocabulary was growing, he needed to know what the words sounded like.
I noticed that when I was paying attention to the act of reading, I tended to understand less of what I read. That is to say, observing myself reading affected my reading - and comprehension.
One day, when I was about thirteen years old, I decided I would read an entire James Bond book. I was in the library and there were about two hours to closing. I finished it just in time. When I got home, I had forgotten the entire plot of the book - and yet, as I was reading it, I was enjoying it! (The sexy bits, at least.)
When I was little, every time I came across a new word, I'd ask my dad what it meant. He'd direct me to the dictionary, and as it was too much of a hassle to stop reading, pick up the dictionary and look up the word, I stopped asking for meanings. My boy asks me for meanings, as I once did. I don't direct him to the dictionary; I tell him the meanings; but I find that he doesn't always remember what I said. The asking appears to be more important than the hearing.
Historically, reading was a communal affair - at least here in England. Sister-familias would read loudly to the family, mater-familias would knit, pater familias would smoke a pipe, frater-familias would get a kick every time he fidgeted. The family spent some time as a unit, welcomed new worlds into its midst, enjoyed the sonority of the words.
How did reading become a solitary affair? Here is St Augustine, writing about his mentor, St Ambrose:
When he was reading, he drew his eyes along over the leaves, and his heart searched into its sense, but his voice and tongue were silent. Oft-times when we were present... we still saw him reading to himself, and never otherwise... . But with what intent soever he did it, that man certainly had a good meaning to it.
Was Augustine surprised at the silent reading? Did this mean that silent reading at the time (4th century AD) was considered an oddity? Or was he more perturbed by the fact that Ambrose was reading to himself whilst in company? Was reading expected to be a shared experience?
These days, privacy is all and individualism is paramount. The occasions for shared reading are few and circumscribed. An author reads excerpts on a publicity tour. A parent reads to a child. A pastor reads to the congregation. The magic of the written word is now a purely personal thing.