THE COMMON KNOWLEDGE EFFECT - INFORMATION SHARING AND GROUP JUDGMENT

The hypothesis that the influence of an item of information on a group judgment is directly related to the number of group members who hold that information before group discussion was tested. Three-member grou ps read short descriptions of students and were asked to make individu al and then group consensus judgments about those students' grades in the course. Information held by all members before group discussion ha d more influence on the group judgments than information held by only 1 member. However, no effect of information distribution was found whe n controlling for member judgments, suggesting that the impact of the information, and hence the effects of distribution across members, was mediated by its impact on individual-member prediscussion judgments. The group judgments were no more accurate than the average of the memb er judgments. Group members were not aware of the common knowledge eff ect's influence on their use of information.