In recent years, neuroscientists have uncovered the countless ways our brain trips us up in day-to-day life, from its propensity toward irrational thought to how our intuitions deceive us. The latest research on sleep, however, points in the opposite direction. Where old wives tales have long advised to "sleep on a problem," today scientists are discovering the truth behind these folk sayings, and how the busy brain radically improves our minds through sleep and dreams. In The Secret World of Sleep , neuroscientist Penny Lewis explores the latest research into the nighttime brain to...