Thu-Huong Ha writes:

People think of reading as the introvert’s hobby: A quiet activity for a person who likes quiet, save for the voices in their head. But in the 5,000 or so years humans have been writing, reading as we conceive it, an asocial solo activity with a book, is a relatively new form of leisure.

For centuries, Europeans who could read did so aloud. The ancient Greeks read their texts aloud. So did the monks of Europe’s dark ages. But by the 17th century, reading society in Europe had changed drastically. Text technologies, like moveable type, and the rise of vernacular writing helped usher in the practice we cherish today: taking in words without saying them aloud, letting them build a world in our heads.

Among scholars, there is a surprisingly fierce debate around when European society transitioned from mostly reading aloud to mostly reading silently…

“The default assumption in the classic period, if you were reading around other people, you’d read aloud and share it,” says Smith. “For us, the default is we’ll read silently and keep it to ourselves.”

At some point that expectation shifted. As late as the 1700s, historian Robert Darnton writes, “For the common people in early modern Europe, reading was a social activity. It took place in workshops, barns, and taverns. It was almost always oral but not necessarily edifying.” …

There isn’t much consensus between historians on why people started reading silently. Saenger hypothesizes that a shift in the way words were laid out a page facilitated the change. Latin words once ran all together, makingithardtoparsethem. Saenger argues that Irish monks, translating Latin in the seventh century, added spaces between words to help them understand the language better. This key design change, he argues, facilitated the rise in silent reading.

M. B. Parkes, in his 1992 book, Pause and Effect: Punctuation in the West, argues something similar. He writes that a “grammar of legibility”—the visual changes made to texts, like punctuation and word spaces—changed the way we read. This early book technology was premised on the idea that the scribes, the people writing, didn’t know who their readers would be, or how fluent they might be in reading Latin, and so had to find a standardized way of telling them how to read: Pause here; these are two separate words; this is a long “a.”

This scholarship applies for the most part to the Latin-based writing and reading of Europe. In other major reading cultures of the world like Chinese, whose script doesn’t have spaces between words, and whose literature depends heavily on prosody, silent reading may have developed differently.