The principle of majority rule is a major decision-making strategy widely used in human and animal society. While majority rule yields highly accurate performance compared to individuals in the same situation, its performance is strongly undermined by a small correlation among individual judgments. We focus on the alternative, the selected majority rule, which is the majority rule by a small number of comities selected from the large group. The present study investigated relative advantages of a smaller group of selected majority rule with computer simulation, systematically controlling 4 parameters—group size, distribution of individual performance (mean and variance), and correlation among decisions. The result showed that compared to simple majority rule and the single expert, the selected majority rule robustly yields higher performance against changes in these parameter values. Further, the absolute number of committee members contributes to robustness against the influence of group size. This robustness is undermined if the number of committee members increases proportionally to the number of total members, even though the committee members are a minority. Thus, absolute number of group size is more critical than the proportion of selected members. This study indicates that the rationale for the majority decision of smaller committees is often fixed against the total number of members in the organization in terms of decision accuracy.
Instantaneous areal population density of entire Atlantic cod and herring spawning groups and group size distribution relative to total spawning population
