Uninformed Individuals Promote Democratic Consensus in Animal Groups

Abstract

Conflicting interests among group members are common when making collective decisions, yet failure to achieve consensus can be costly. Under these circumstances individuals may be susceptible to manipulation by a strongly opinionated, or extremist, minority. It has previously been argued, for humans and animals, that social groups containing individuals who are uninformed, or exhibit weak preferences, are particularly vulnerable to such manipulative agents. Here, we use theory and experiment to demonstrate that, for a wide range of conditions, a strongly opinionated minority can dictate group choice, but the presence of uninformed individuals spontaneously inhibits this process, returning control to the numerical majority. Our results emphasize the role of uninformed individuals in achieving democratic consensus amid internal group conflict and informational constraints. S ocial organisms must often achieve a consensus to obtain the benefits of group living and to avoid the costs of indecision (1 12). In some societies, notably those of eu social insects, making consensus decisions is often a unitary, conflict free process because the close relatedness among individuals means that they typically share preferences (11). However, in other social animals, such as schooling fub, flocking birds, herding ungulates, and humans, individual groop members may be oflow relatedness; thus, self interest can play an important role in group decisions. Reaching a consensus decision, there fore, frequently depends on individuals resolving complex conilicts of interest (1 11, 13, 14).There are several means of achieving groop consensus. In some cases, decisions made by one or only a small proportion of the group dictate the behavior of the entire group ( 4 6, 13, 14). There fore, a minority, or even a single individual, has the potential to control or exploit the majority, achieving substantial gains at the expense of other group members (1 6,9,10,14). In contrast, consensus can also be reached throogh demo cratic means, with fuir representation and an out come determined by a plurality. Democratic decisions tend to be more moderate, rninimiz ing group consensus costs, particularly in large animal groops (3). However, in the absence of established procedures such as voting ( 8), it is IDlclear how equal representation is enforced Consequently, for both human socwtJes (1,2,6,9,10,14) and group living animals ( 6, 13), it has been afb'lted that group decisions can be subject to manipulation by a self interested and opinionated minority. In particular, previoos work suggests that groups containing individu als who are uninformed, or naive, about the de cision being made are particularly vulnerable to such manipulation (2,9,10,13). Under this view, IDlinformed individuals destabilize the capacity for collective intelligence in groups (J 0, 14), with poorly informed individuals potentially facilitat ing the establishment of extremist opinions in populations (9,14).Here, we address the question of whether and, if so, under which condit...

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