Carl Iver Hovland (June 12, 1912 – April 16, 1961) was a psychologist working primarily at Yale University and for the US Army during World War II who studied attitude change and persuasion. He first reported the sleeper effect after studying the effects of the Frank Capra's propaganda film Why We Fight on soldiers in the Army. In later studies on this subject, Hovland collaborated with Irving Janis who would later become famous for his theory of groupthink. Hovland also developed social judgment theory of attitude change. Carl Hovland thought that the ability of someone to resist persuasion by a certain group depended on your degree of belonging to the group. Biography Carl Iver Hovland was born in Chicago on June 12, 1912. As a child, he had a deep interest in music. Up until college, when psychology became a major part of his life, he was looking into a musical career. In 1938 he married Gertrude Raddatz. He was recruited by Samuel Stouffer, a sociologist who was on leave from University of Chicago. Hovland had the responsibility of leading a team of fifteen researchers. Hovland was involved in a study of the conditions under which people are most likely to change their attitudes in response to persuasive messages. The Yale Group's work was first described in Hovland's book Communication and Persuasion, published in 1953. His major interests in his last few years of life were with concept-formation, which he approached with computer simulation. In his lifetime, Hovlan was a member of the American Philosophical Society, the American Academy of Arts and Sciences, and the National Academy of Sciences. Contributions Psychological research was Hovland's intellectual joy. Especially in his early career, his investigations covered many topics. His papers in psychological journals included a study of test reliability, a major review of the literature on apparent movement, as well as his four classical papers on conditioned generalization from his doctoral dissertation. Hovland began to emphasize micro-level analysis of propaganda and its effects. Hovland's army experiments were the beginnings of that micro-level analysis of an individual. Hovland's "core conceptual variable was attitude". Hovland believed that if he was able to recognize the attitude an individual has towards a trigger, he would be able to predict the behavior and actions of an individual over time. However, there were many studies that argued the contrary and showed that "an attitude toward a person or