Leon Festinger

Leon Festinger (8 May 1919 – 11 February 1989) was an American social psychologist, perhaps best known for cognitive dissonance and social comparison theory. His theories and research are credited with repudiating the previously dominant behaviorist view of social psychology by demonstrating the inadequacy of stimulus-response conditioning accounts of human behavior. Festinger is also credited with advancing the use of laboratory experimentation in social psychology, although he simultaneously stressed the importance of studying real-life situations, a principle he perhaps most famously practiced when personally infiltrating a doomsday cult. He is also known in social network theory for the proximity effect (or propinquity).

Festinger studied psychology under Kurt Lewin, an important figure in modern social psychology, at the University of Iowa, graduating in 1941, but was not interested in social psychology at the time, focusing instead on level of aspiration research and statistics. He became a social psychologist "by fiat" when he joined the faculty at Lewin’s Research Center for Group Dynamics at the Massachusetts Institute of Technology in 1945. Despite his preeminence in social psychology, he turned to visual perception research in 1964 and then archaeology and history in 1979 until his death in 1989.