Why do some countries succeed while others struggle Why are some firms profitable while rivals fail Why do some marriages thrive and others end in divorce The questions seem unrelated, but societies, companies, and marriages have one important thing in common They involve more than one individual. They thus face the same fundamental challenges. How can people be made to help rather than hurt each other How can they use sacrifice, cooperation, and coercion to promote the common goodbr br In this introductory text, Tore Ellingsen equips readers to answer essential questions around the success and failure of humans in groups, drawing on behavioral game theory, psychology, and sociology. He emphasizes how other-regarding preferences such as altruism and dutifulness matter for societies' prosperity and analyzes the role of culture in the form of shared values and understandings. One lesson is that cooperation is facilitated when people anticipate that they will hold common memories of past