There are many possible sources of cognitive overload, but two of the most important, according to Sweller, are “extraneous problem-solving” and “divided attention.” Those also happen to be two of the central features of the Net as an informational medium. Using the Net may, as Gary Small suggests, exercise the brain the way solving crossword puzzles does. But such intensive exercise, when it becomes our primary mode of thought, can impede deep learning and thinking. Try reading a book while doing a crossword puzzle; that’s the intellectual environment of the Internet.