The study of attitudes and persuasion can be traced back to the earliest years of the twentieth century (Allport, 1935). This early research focused on issues such as discrimination, the attitude-behavior relationship, and persuasion (McGuire, 1985). However, the emergence of the social scientific study of persuasion can be traced to the middle of the twentieth century. In particular, World War II played a critical role in bringing together scholars from several different disciplines to focus on the war effort, including scholars from social psychology, sociology, and communication within the United States (Rogers, 1994). But research on persuasion emerged as a major area of study in the social sciences in the mid1950s (McGuire, 1985).