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Empirical findings and meta-analysis

Park (1990) found that "only 16 empirical studies have been published on groupthink", and concluded that they "resulted in only partial support of his hypotheses".: 230 Park concludes, "despite Janis' claim that group cohesiveness is the major necessary antecedent factor, no research has shown a significant main effect of cohesiveness on groupthink.": 230 Park also concludes that research does not support Janis' claim that cohesion and leadership style interact to produce groupthink symptoms. Park presents a summary of the results of the studies analyzed. According to Park, a study by Huseman and Drive (1979) indicates groupthink occurs in both small and large decision-making groups within businesses. This results partly from group isolation within the business. Manz and Sims (1982) conducted a study showing that autonomous work groups are susceptible to groupthink symptoms in the same manner as decisions making groups within businesses. Fodor and Smith (1982) produced a study revealing that group leaders with high power motivation create atmospheres more susceptible to groupthink. Leaders with high power motivation possess characteristics similar to leaders with a "closed" leadership style—an unwillingness to respect dissenting opinion. The same study indicates that level of group cohesiveness is insignificant in predicting groupthink occurrence. Park summarizes a study performed by Callaway, Marriott, and Esser (1985) in which groups with highly dominant members "made higher quality decisions, exhibited lowered state of anxiety, took more time to reach a decision, and made more statements of disagreement/agreement".: 232 Overall, groups with highly dominant members expressed characteristics inhibitory to groupthink. If highly dominant members are considered equivalent to leaders with high power motivation, the results of Callaway, Marriott, and Esser contradict the results of Fodor and Smith. A study by Leana (1985) indicates the interaction between level of group cohesion and leadership style is completely insignificant in predicting groupthink. This finding refutes Janis' claim that the factors of cohesion and leadership style interact to produce groupthink. Park summarizes a study by McCauley (1989) in which structural conditions of the group were found to predict groupthink while situational conditions did not. The structural conditions included group insulation, group homogeneity, and promotional leadership. The situational conditions included group cohesion. These findings refute Janis' claim about group cohesiveness predicting groupthink.