Readers didn’t just become more efficient. They also became more attentive. To read a long book silently required an ability to concentrate intently over a long period of time, to “lose oneself” in the pages of a book, as we now say. Developing such mental discipline was not easy. The natural state of the human brain, like that of the brains of most of our relatives in the animal kingdom, is one of distractedness. Our predisposition is to shift our gaze, and hence our attention, from one object to another, to be aware of as much of what’s going on around us as possible.
