Every year, millions of people are unfaithful in their romantic relationship-- risking the integrity of their families, finances, and reputations. In surveys, approximately half of unfaithful individuals report that they were happy with their primary relationships when their affairs began. Why would so many people engage in behavior that's so obviously self-defeating? Unfaithful Minds chronicles the discovery of key hidden brain processes, explains their functions, shows how they interact with other factors, and reveals the specific ways that they influence-- and sometimes hijack-- unfaithful individuals' conscious decisions. Couple therapists and self-help books tell us that infidelity results from familiar factors-- like stress, poor communication, anger, and substance use. Such factors do play a role, but they are, at most, half the story. What these explanations leave out is the human brain-- along with the last few decades of psychological science, which have done nothing less than revolutionize scientists' understanding of the origins, or sources, of a person's behavior. Application of the new paradigm can transform our understanding of infidelity, and it makes a fascinating story. Yet remarkably, to date, no book has told it. Unfaithful Minds is the first book to address the role of hidden brain processes in infidelity; it provides an entirely new understanding of unfaithful behavior-- and even explains why happy people cheat.