Stuart Brown, a psychiatrist, clinical researcher, and the founder of the National Institute for Play, has spent his career studying animal behavior and conducting more than six thousand "play histories" of humans from all walks of life — from serial murderers to Nobel Prize winners. This book explains why play is essential to our social skills, adaptability, intelligence, creativity, ability to problem solve, and more. Co-author Christopher Vaughan, a communications officer at Stanford University, says the message of the book is that the urge to play is a basic biological drive that nature uses play to promote brain development and social integration as well as prepare for the unexpected — which is why all higher juvenile animals do it.