This study used the Group Dynamics Q sort (GDQS) to explore the empirical underpinnings and theoretical logic of the groupthink model. Examination of 10 decision-making episodes revealed considerable historical support for Janis's (1982) classification of groups into groupthink and vigilant decision-making episodes. LISREL analysis, however, revealed less support for Janis's (1982) causal model of groupthink. Neither group cohesiveness nor situational stress emerged as independent predictors of symptoms of groupthink. Structural and procedural faults of the organization did, however, emerge as a potent predictor. Little support was found for Janis's (1982) suggestion that the ill-fated Mayaguez and Iran rescue decisions were the product of groupthink. The results illustrate the symbiotic relationship between social psychology and history. Historical case studies allow for testing theories of group dynamics; social-psychological concepts and research methods can inform interpretations of historical events.

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Previous research has shown that preferences for options, such as gambles, can reverse depending on the response mode. These preference reversals have been demonstrated when tasks were performed sequenfially. That is, subjects completed one task before beginning another. In an attempt to eliminate preference reversals, we asked subjects to perform tasks simulfaneously. That is, subjects made two types of responses for each pair of gambles before evaluating the next pair. In the condition with no financial incentives, preference reversal rates were slightly reduced. In another condition, subjects were paid for their participation and they were allowed to play a gamble with real monetary compensation. A gamble pair was randomly selected, and if a subject's responses in the two tasks were consistent for that pair, he or she was allowed to play the 'preferred' gamble. Otherwise, the experimenter selected the gamble from the pair. With these financial incentives, systematic preference reversals were eliminated for two of the three task combinations. Preference reversals continued to occur for attractiveness ratings versus selling prices, although, even for that pair of tasks, the reversal rate was significantly reduced. For all three task pairs, preference orders from the two tasks appeared to merge into more consistent orders. KEY WORDS preference reversals; violations of expected utility theory; change-ofprocess theory; strength of preference judgmentsDuring the past forty years, psychologists and economists have demonstrated numerous violations of expected utility theory, such as the Allais paradox (Allais, 1953), Ellsberg's paradox (Ellsberg, 1961), and framing effects (Tversky and Kahneman, 1986). Lichtenstein and Slovic (1971) discovered another violation of expected utility theory that they called the preference reversal phenomenon. They presented subjects with pairs of gambles matched on expected value. For each pair, subjects chose the gamble they preferred and then stated a selling price for each gamble separately. When asked, 'Which do you prefer?' in the choice task and 'Which do you value more?' in the pricing task, subjects shouldgive the same answer. But a surprising result occurred: stated preferences reversed depending on the response mode. That is, subjects frequently chose the gamble with the larger probability of winning (referred to as the P bet) over the gamble with the larger amount to win (referred to as the ! $ bet), but they assigned a higher selling price to the $ bet than the P bet. If both choices and selling prices reflect