John Sweller, an Australian educational psychologist, has spent three decades studying how our minds process information and, in particular, how we learn. His work illuminates how the Net and other media influence the style and the depth of our thinking. Our brains, he explains, incorporate two very different kinds of memory: short-term and long-term. We hold our immediate impressions, sensations, and thoughts as short-term memories, which tend to last only a matter of seconds.
