Book excerpt: This interdisciplinary book extends knowledge by comparing rivalry and rival group behavior in sport within areas outside of sport, such as consumer brands, political discourse, and product/service preferences. It examines how out-group behavior differs among relevant groups. Readers are introduced to the phenomenon of rivalry, using the sport setting as an example. Then, the author offers separate quantitative and qualitative investigations to compare how rivalry and group behavior differ among sport and non-sport settings. Incorporating research from marketing, psychology, political science, and sociology, this book offers researchers in several fields a new understanding of individual and group behavior.