Gender composition and group confidence judgment: The perils of all-male groups

We explore the joint effects of group decision making and group gender composition on the calibration of confidence judgments. Participants in two laboratory experiments, individually and in groups of three, stated confidence interval estimates for general-knowledge questions and for financial forecasts. Across both studies, our results reveal that groups with at least one female member are significantly better calibrated than all-male groups. This effect is mediated by the extent to which group members share opinions and information during the group discussion. Moreover, we find that compared to a statistical aggregation of individual confidence intervals, group discussions have a neutral or positive effect on the quality of confidence judgments for groups with at least one female group member; in contrast, group discussion actually harms confidence calibration for all-male groups. Overall, our findings indicate that compared to all-male groups, even the inclusion of a small proportion of female members can have a strong effect on the quality of group confidence judgment.