Signal-detection analysis of group decision making

How effectively can groups of people make yes-or-no decisions? To answer th is question. we used signal-detection theory to model the behavior of group s of human participants in a visual detection task. The detection model spe cifies how performance depends on the group's size, the competence of the m embers, the correlation among members' judgments, the constraints on member interaction, and the group's decision rule. The model also allows specific ation of performance efficiency, which is a measure of how closely a group' s performance matches the statistically optimal group. The performance of o ur groups was consistent with the theoretical predictions, but efficiency d ecreased as group size increased. This result was attributable to a decreas e in the effort that members gave to their individual tasks rather than to an inefficiency in combining the information in the members' judgments.