 It became a must-have part of our lives. Then it trickled down to children. Today, 42% of 10-year-olds have smartphones. But according to Haidt, there's an additional devil hidden in the smartphone. Social media, which Haidt says companies like Meta designed to addict you. Smartphone use among kids was supposed to be just one chapter in Haidt's book. But it rapidly expanded into a book of its own, Haidt's new book, The Anxious Generation.