Consensus decision making in human crowds

In groups of animals only a small proportion of individuals may possess particular information, such as a migration route or the direction to a resource. Individuals may differ in preferred direction resulting in conflicts of interest and, therefore, consensus decisions may have to be made to prevent the group from splitting. Recent theoretical work has shown how leadership and consensus decision making can occur without active signalling or individual recognition. Here we test these predictions experimentally using humans. We found that a small informed minority could guide a group of naive individuals to a target without verbal communication or obvious signalling. Both the time to target and deviation from target were decreased by the presence of informed individuals. When conflicting directional information was given to different group members, the time taken to reach the target was not significantly increased; suggesting that consensus decision making in conflict situations is possible, and highly efficient. Where there was imbalance in the number of informed individuals with conflicting information, the majority dictated group direction. Our results also suggest that the spatial starting position of informed individuals influences group motion, which has implications in terms of crowd control and planning for evacuations. (c) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.