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—some even say the ancients read silently just as much as they read aloud—but there is one scene in literature they agree is crucial. In St. Augustine’s Confessions, the titular professor describes the reading habits of Ambrose, the bishop of Milan:

But when Ambrose used to read, his eyes were drawn through the pages, while his heart searched for its meaning; however, his voice and tongue were quiet. Often when we were present—for anyone could approach him and it was not his habit that visitors be announced to him—we saw him reading in this fashion, silently and never otherwise.

The fact that this was so remarkable to Augustine, some scholars argue, is because in the 400s, silent reading wasn’t really a thing.

Other researchers say that this passage is meant more to point out Ambrose’s rudeness. “It’s really that Ambrose would go on reading silently while he was there, like someone going on texting while you’re trying to talk to them,” says D. Vance Smith, a medievalist in the Princeton English department. “[Augustine is] surprised by his rudeness at not reading out loud to share with him.”

“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.”

If silent reading was in fact rare or rude in ancient times, then at some point the expectation of readers in society 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.”

But by the time Marcel Proust was writing in the late 1800s, his narrator hoping for time to read and think alone in his bed, reading privately had become more of a norm for wealthy, educated people who could afford books and idle bedroom rumination.

This came with the spreading of literacy and diverse kinds of reading material. Writes Darnton, records from until as late as 1750 showed that people who could read had only a few books: perhaps the Bible, an almanac, and some devotionals, that they read and re-read. But by 1800, he writes, people were reading more voraciously—newspapers and periodicals—and by the late century they had branched out into children’s literature and novels.

As reading shifted away from the social, some researchers believe this helped create what we now call an interior life. Writes Alberto Manguel in his 1996 book, A History of Reading:

But with silent reading the reader was at last able to establish an unrestricted relationship with the book and the words. The words no longer needed to occupy the time required to pronounce them. They could exist in interior space, rushing on or barely begun, fully deciphered or only half-said, while the reader’s thoughts inspected them at leisure, drawing new notions from them, allowing comparisons from memory or from other books left open for simultaneous perusal. And the text itself, protected from outsiders by its covers, became the reader’s own possession, the reader’s intimate knowledge,