團體熟悉性與作業類型對共同知識效果的影響

Effects of Group Familiarity and Task Type on Common Knowledge Effect

李宛珍(Wan-Chen Lee)

指導教授 ： 李玉惠 Yuh-Huev Lee

中原大學/理學院/心理學研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400550

摘要

共同知識效果（common knowledge effect）是指，團體在討論中過於重視成員們先前共同擁有的知識，並使得團體決策偏向共同知識的現象。當團體決策需要交換成員獨有的訊息才能確認正確選項時（如在隱藏式檔案情境時），共同知識效果的出現會使得決策表現產生偏誤。以往有關共同知識效果的研究大部分是使用隨機分配的方式組成受試團體，基本上這些非自然形成的團體，成員間彼此互不認識，相當於陌生團體，但實際上，許多決策團體中的成員之前已經有過互動，甚至有過幾次共同決策的經驗，因此熟悉團體的決策表現值得我們進一步去探討。

有關團體熟悉性對共同知識效果的影響目前尚不明確。過去文獻指出，陌生團體中的成員會藉由討論共有訊息來建立信任感和提高自己的評價，導致共同知識效果的產生，而無法有效的進行非共有訊息的交換，使得團體決策正確性降低；而熟悉團體中的成員已經彼此認識，不再需要藉由討論共有訊息來提升自我評價，因此，熟悉團體較不會受到共同知識效果的影響，而較能有效的進行訊息交換以達成正確決策（Wittenbaum, Hubbell, & Zuckerman, 1999）。但從凝聚力的角度來看，熟悉團體的高凝聚力會導致從眾壓力的提高，使得熟悉團體中的成員因害怕破壞自己與團體的和諧關係，而避免提出與團體共識相抵觸的非共有訊息，反而是在熟悉團體中較容易產生共同知識效果（Hogg, 1992）。筆者預期團體成員對其決策作業類型的知覺不同，或許可以解釋上述團體熟悉性在共同知識效果上的結果之不一致。

本研究採用一個2（訊息分配：完整訊息檔案/隱藏式檔案） × 2（團體熟悉性：熟悉/陌生） × 2（作業類型：智力性作業/判斷性作業）的三因子受試者間實驗設計。受試者為中原大學學生，以同性別的三人為一團體，來進行「商人死亡案件」的決策作業，共有89組有效團體參與實驗。依變項為團體討論中的整體訊息討論量、非共有訊息交換量和團體決策正確性。
研究結果顯示，在完整訊息檔案情境中的團體，不論其作業類型和團體熟悉性為何，整體訊息討論量和決策正確性都大致相同。在隱藏式檔案情境中的團體，不論其熟悉性如何，在智力性作業上的非共有訊息交換量皆會大於判斷性作業，但只有陌生團體在智力性作業上的決策正確性會高於判斷性作業，熟悉團體在智力性作業上的決策正確性則與判斷性作業沒有差異。另一方面，在隱藏式檔案中的團體，不論其作業類型為何，熟悉團體的非共有訊息交換量皆會比陌生團體多，但熟悉團體的決策正確性卻都沒有比陌生團體高。

整體而言，熟悉團體的非共有訊息交換量大於陌生團體，即熟悉團體比較不會有共同知識效果的討論偏誤，但是熟悉團體的團體決策正確性卻不高於陌生團體。筆者以大多數法則使用的情形來解釋團體決策正確性上的結果，發現在隱藏式檔案中，熟悉團體傾向使用大多數法則來達成決策，因而導致團體決策偏向共同知識所支持的選項；陌生團體則是傾向使用訊息收集法則來達成決策，因此若有進行充分的非共有訊息交換，陌生團體的決策正確性有可能會比熟悉團體高。

關鍵字

團體熟悉性 ； 共同知識效果 ； 作業類型

並列摘要

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 design. Dependent variables were the amount of total discussion, discussion focus, and the correctness of group choice. A total of 89 valid groups (three university 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.

並列關鍵字

Group Familiarity ； Task Type ； Common Knowledge Effect

參考文獻

Broadbeck, F. C., Kerschreiter, R., Mojzisch, A., Fery, D., & Schulz-Hardt, S. (2002). The dissemination of critical, unshared information in decision-making groups: The effects of pre-discussion dissent. European Journal of Social Psychology, 32, 35-56.

De Dreu, C. K. W., & West, M. A. (2001). Minority dissent and team innovation: The importance of participation in decision making. Journal of Applied Psychology, 86, 1191-1201.

Festinger, L. (1954). A theory of social comparison. Human Relations, 1, 117-140.

Flowers, M. L. (1977). A laboratory test of some implication of Janis’ groupthink hypothesis. Journal of Personality and Social Psychology, 35, 888-896

Gigone, D., & Hastie, R. (1993). The common knowledge effect: Information sharing and group judgment. Journal of Personality and Social Psychology, 65, 959-974.