Cookie White Stephan and Walter G. Stephan This is a book about the two social psychologies-psychological social psychology and sociological social psychology--written by social psychologists from both disciplines. It focuses on the benefits and costs of interchange between psychological social psychology and sociological social psychology, with the ultimate goal of encouraging interaction among scholars in the two disciplines. The primary questions addressed are: What do the two disciplines have to offer each other? What are the barriers to fruitful interchange? How can these barriers be overcome? In this introductory chapter we will first examine some historical reasons for the lack of interchange between the two social psychologies. Then we will provide a brief preview of the chapters to follow. The Development of the Two Social Psychologies The beginning of concern with the social animal can be traced to the ancient Greeks. However, social psychology's formal beginning is usually dated from Norman Triplett's 1897 publication of his findings on the effects of competition or from the publication in 1908 of two books including the words Social Psychology in their titles, one by the psychologist William McDougall and the other by the sociologist Edward Alsworth Ross. Thus, from its inception, social psychology was already divided into two distinct academic units, housed in the disciplines of sociology and psychology.