This book presents the wealth of scientific evidence that our personality emerges from evolved primary emotions shared by all mammals. Yes, your dog feels love—and many other things too. These subcortically generated emotions bias our actions, alter our perceptions, guide our learning, provide the basis for our thoughts and memories, and become regulated over the course of our lives. Understanding personality development from the perspective of mammals is a groundbreaking approach and one that sheds new light on the ways in which we as humans respond to life events, both good and bad. Jaak Panksepp, famous for discovering laughter in rats and for creating the field of affective neuroscience, died in April 2017. This book forms part of his lasting legacy and impact on a wide range of scientific and humanistic disciplines. It will be essential reading for anyone trying to understand how we act in the world and the world's impact on us.