- 1961 – Carl Hovland, American psychologist and academic (b. 1912).
Carl Iver Hovland (12 June 1912 to 16 April 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 judgement 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.