"A significant contribution to understanding the interaction among teachers, students, the environment, and the content of learning" (Herbert Kohl, education advocate and author). What is at work in the mind of a five-year-old explaining the game of tag to a new friend? What is going on in the head of a thirty-five-year-old parent showing a first-grader how to button a coat? And what exactly is happening in the brain of a sixty-five-year-old...