My father, who was trained in engineering at M.I.T. in the slide-rule era, often lamented the way the pocket calculator, for all its convenience, diminished my generation’s math skills. Many of us have discovered that navigating by G.P.S. has undermined our mastery of city streets and perhaps even impaired our innate sense of direction. Typing pretty much killed penmanship. Twitter and YouTube are nibbling away at our attention spans. And what little memory we had not already surrendered to Gutenberg we have relinquished to Google. Why remember what you can look up in seconds?