Publication Date


Document Type


First Advisor

Miller, Charles E.

Degree Name

M.A. (Master of Arts)

Legacy Department

Department of Psychology


Group decision making; Social groups


The primary purpose of the present study was to investigate the effects of two independent variables—group cohesiveness and the assigned group decision rule—on group decision making and the phenomenon of groupthink. Janis <1972) hypothesized that the presence of a number of antecedent conditions, including a highly cohesive group and a directive leader, may dispose a group to engage in extreme concurrence seeking behavior which may result in instances of faulty decision making. Cohesiveness was investigated because it has been described by Janis as the principal antecedent condition for groupthink. Additionally, four different decision rule conditions were employed: unanimity rule, majority rule, best-performing dictator, and worst-performing dictator. The dictatorship conditions were intended to create a situation not unlike that involving a directive leader. Janis argues that the presence of the antecedent conditions may well result in the presence of a number of symptoms which are evidence of groupthink. Results of the present study provided mixed support for Janis-' notion of groupthink. Results supported the presence of a number of the symptoms described by Janis. such as an illusion of unanimity, but failed to provide evidence of others, such as pressure to conform. Additionally, the results did not reveal any significant performance differences across the various conditions. Results of analysis of the performance data with regard to the dictatorship conditions revealed that, particularly in the worst-performing dictator condition, the leaders did not behave in a manner analogous to the directive leader described by Janis. Rather, it appeared that the leaders used the information provided by the better-performing members when reaching a group decision. It was mentioned that a number of factors should be considered to strengthen the dictator manipulation.


Includes bibliographical references (pages 81-83)


vi, 156 pages




Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type