| Summary: | 碩士 === 中原大學 === 心理學研究所 === 92 === The common knowledge effect refers to the phenomenon that decision-making groups are much more likely to discuss information that members shared before discussion than to discuss information that is held by individual members. Thus, group decisions are much more impacted by the shared information than by the unshared information. When unshared information is critical to identifying the superior decision option, such as, in hidden profiles, group performance would be biased by focusing on discussing the shared information. Most studies on the common knowledge effect have been conducted in laboratories. However, ecological decision groups usually are groups with members knowing each other, even had some experiences of joint decision making. Thus, the effectiveness of group decision making with various degree of group familiarity deserves more investigation.
The effects of group familiarity on common knowledge effect still are uncertain. When members do not know one another well, they may establish credibility and evaluates themselves through the communication of shared information. Thus, they intend to mention and repeat shared information, leading to the common knowledge effect. However, the members of familiar groups have already known one another, they may not need to establish credibility and evaluates themselves through the communication of shared information. Therefore, groups composed of familiar members would be less likely to exhibit the common knowledge effect and more likely to reach the correct group decision than groups composed of strangers (Wittenbaum, Hubbell, & Zuckerman, 1999). But from the perspective of cohesion, familiar groups have greater cohesion and conformity than stranger groups. Hence, members in familiar groups will consider harmonious relations are more important than decision quality. Therefore, groups composed of familiar members are likely to suppress conflicts and dismiss information that could incite them, and their decisions will be much more affected by the common knowledge than groups composed of strangers (Hogg, 1992). In the present study, it was proposed that task type might clarify the inconsistent effects of group familiarity on common knowledge effect.
The present study adopted a 2 (information distribution: full information profile/ hidden profile) × 2 (group familiarity: familiar group/ stranger group) × 2 (task type: intellective/ judgmental) between-subjects factorial <a href="http://www.ntsearch.com/search.php?q=design&v=56">design</a>. Dependent variables were the amount of total discussion, discussion focus, and the correctness of group choice. A total of 89 valid groups (three <a href="http://www.ntsearch.com/search.php?q=university&v=56">university</a> students with the same gender as a group) were randomly assigned to eight experimental conditions. Each participant read a murder mystery, and then each group discussed the case to indicate a suspect.
Experimental results showed that, in the full information profile, regardless of task type, the amount of total discussion and the proportion of group choice correctness were identical between the familiar group and the stranger group. Furthermore, regardless of group familiarity, the amount of total discussion and the proportion of group choice correctness were the same between the intellective task and the judgmental task. In hidden profiles, regardless of group familiarity, groups with intellective tasks focused more on unshared information than groups with judgmental tasks. In the same profile condition, the stranger group with the intellective task chose the correct suspect more often than the stranger group with the judgmental task; the proportions of choice correctness were identical between the intellective task and the judgmental task for the familiar groups. Furthermore, in the hidden profile, regardless of task type, familiar groups focus more on the unshared information than stranger groups, but familiar groups failed to choose the correct suspect more often than stranger groups.
In sum, familiar groups focused more on the unshared information than stranger groups, familiar groups thus showed less discussion bias of the common knowledge effect. Nevertheless, familiar groups did not choose the correct suspect more often than stranger groups. The inconsistent findings in the discussion focus and choice correctness could be explained by considering decision strategies adopted by the groups. In hidden profiles, familiar groups preferred employing the majority rule to make decisions, whereas stranger groups preferred exploiting the information pooling strategy to make decisions. A model reconciling the above findings was developed and explicitly discussed.
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