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This study tested two hypotheses concerning the effects of external rewards on intrinsic motivation: External rewards will undermine intrinsic motivation for highly interesting tasks and enhance intrinsic motivation for uninteresting tasks, and external rewards will undermine intrinsic motivation for unstructured tasks and enhance intrinsic motivation for highly structured tasks. Sixty-four college students worked on puzzle tasks of high or low interest, under high or low task structure, for a reward or no reward. The major dependent variable was intrinsic motivation as measured by the amount of free time spent on the task, questionnaire responses, and willingness to participate in a similar study. Results indicated that external rewards undermined intrinsic motivation for tasks of high interest and/or low structure. Rewards did not affect intrinsic motivation for tasks of low interest. On highly structured tasks, rewards enhanced subjects' willingness to participate in a similar study, but this effect did not occur on the other dependent measures.

Janis' (1972) groupthink formulation was tested in the laboratory by manipulating group cohesiveness and adequacy of decision procedures in a factorial design. Internal analysis, involving redefined cohesiveness categories, provided mixed support for the groupthink hypothesis on measures of decision quality and group processes presumed to underlie the groupthink decisions. Specifically, it was found that: (1) highest quality decisions were produced by groups of intermediate cohesiveness; (2) high cohesive groups without adequate decision procedures (the groupthink condition) tended to make the poorest decisions; and (3) the presence of groupthink was characterized by a lack of disagreement and a high level of confidence in the group's decisions.

Janis (1972) proposed that groupthink is essentially a stress-reduction process. Cohesive groups reduce the stress of decision making by suppressing critical inquiry. Theoretically, groupthink could be prevented in cohesive groups if the stress could be diffused by other factors. We investigated the effects of task structure (decision-making procedures) and an individual factor (dominance) on the quality of group decision making, anxiety, and symptoms of groupthink. Students (n = 112) participated in twenty-eight 4-person, mixed-sex groups. Groups composed of highly dominant members made higher quality decisions, exhibited lower state anxiety, and took more time to reach a decision. They also tended to make more statements of disagreement and agreement, and to report more group influence on the members. Decision-making procedures had little effect on the decision process.

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