This definitive work—now extensively revised with virtually all new chapters—has introduced generations of researchers to the psychological processes that underlie social behavior. What sets the book apart is its unique focus on the basic principles that guide theory building and research. Since work in the field increasingly transcends such boundaries as biological versus cultural or cognitive versus motivational systems, the third edition has a new organizational framework. Leading scholars identify and explain the principles that govern intrapersonal, interpersonal, intragroup, and intergroup processes, in chapters that range over multiple levels of analysis. The book's concluding section illustrates how social psychology principles come into play in specific contexts, including politics, organizational life, the legal arena, sports, and negotiation.