Irving Lester Janis (26 May 1918 - 15 November 1990) was a research psychologist at Yale University and a professor emeritus at the University of California, Berkeley most famous for his theory of "groupthink" which described the systematic errors made by groups when making collective decisions.
Early years 
During the Second World War, Janis was drafted into the U.S. Army, where he carried out studies of military morale. In 1947, Janis became a faculty member of the Yale University Psychology Department, where he remained for nearly forty years. He collaborated with Carl Hovland on his studies of attitude change, including the sleeper effect.
During his career, Janis studied decisionmaking in areas such as dieting and smoking. This work described how people respond to threats, as well as what conditions give rise to irrational complacency, apathy, hopelessness, rigidity, and panic.
Janis also made important contributions to the study of group dynamics. He did extensive work in the area of “groupthink,” which describes the tendency of some groups to try to minimize conflict and reach consensus without sufficiently testing, analyzing, and evaluating their ideas. His work suggested that pressures for conformity restrict the thinking of the group, bias its analysis, promote simplistic and stereotyped thinking, and stifle individual creative and independent thought.
In 1967, Janis was awarded the Socio-Psychological Prize by the American Association for the Advancement of Science (b). In 1981, he received the Distinguished Scientific Contribution Award of the American Psychological Association. In 1991, he won the Distinguished Scientist Award from the Society of Experimental Social Psychology.
He retired from Yale University in 1985, and in 1986 was appointed Adjunct Professor of Psychology Emeritus at the University of California, Berkeley.
Personal life 
Selected books 
- Hovland, Carl Iver; Janis, Irving L.; Kelley, Harold H. (1953). Communication and persuasion; psychological studies of opinion change. New Haven: Yale University Press. OCLC 187639.
- Janis, Irving L. (1958). Psychological stress; psychoanalytic and behavioral studies of surgical patients. New York: Wiley. OCLC 14620125.
- Janis, Irving L. (1959). Personality and persuasibility. New Haven: Yale University Press. OCLC 224637.
- Janis, Irving L. (1969). Personality: dynamics, development, and assessment. New York: Harcourt, Brace & World. ISBN 0-15-569585-1.
- Janis, Irving L. (1972). Victims of groupthink; a psychological study of foreign-policy decisions and fiascoes. Boston: Houghton, Mifflin. ISBN 0-395-14002-1.
- Janis, Irving L.; Mann, Leon (1977). Decision making: a psychological analysis of conflict, choice, and commitment. New York: Free Press. ISBN 0-02-916160-6.
- Wheeler, Daniel D.; Janis, Irving L. (1980). A practical guide for making decisions. New York: Free Press. ISBN 0-02-934460-3.
- Janis, Irving L. (1982). Counseling on personal decisions: theory and research on short-term helping relationships. New Haven: Yale University Press. ISBN 0-300-02484-3.
- Janis, Irving L. (1982). Groupthink: psychological studies of policy decisions and fiascoes. Boston: Houghton Mifflin. ISBN 0-395-31704-5.
- Janis, Irving L. (1982). Stress, attitudes, and decisions: selected papers. New York: Praeger. ISBN 0-03-059036-1.
- Janis, Irving L. (1989). Crucial decisions: leadership in policymaking and crisis management. New York: Free Press. ISBN 0-02-916161-4.
- "Irving Janis Dies at 72; Coined 'Group Think'". New York Times. November 18, 1990.
- Smith, M. Brewster; Mann, Leon (June 1992). "Irving L. Janis (1918-1990): Obituary". American Psychologist 47 (6): 812–813. doi:10.1037/0003-066X.47.6.812.
- Nemeth, Charlan; Tetlock, Phillip (1991). "University of California: In Memoriam, 1991. Irving L. Janis".