Great decision accuracy can be achieved by groups through individuals having local interactions without communication


Animals in moving groups must agree on a direction if they are to stay together. In many cases such as schools of fish individuals only have limited information about others due to crowding and limited vision. It remains a mystery quite how these large groups manage to coordinate their direction of travel as well as they do, because they can’t agree in advance where to go and they cannot verbally lead one another. It is also unlikely that many animals are clever enough to deliberately try to lead others.


We made a model of behaviour in which each individual moves according to 3 rules: (1) avoid getting too close to others, (2) align direction of travel with neighbours, (3) follow a preferred direction if they have information. We assume that only a few individuals have any information, the others only have rules (1) and (2). Even those these rules are very simple, only a few individuals are able to lead the group in the correct direction almost all the time. The large the group the smaller the proportion of informed individuals are needed to guide the group. Groups can make consensus decisions if even knowledgeable individuals do not know whether they prefer the same option as the majority or not, just by following simple rules that at the group level enable a decision between competing options.


Information can be transmitted through a group even if group members do not know who has information, by each individual following simple rules and just responding to their neighbours. There is no need to search for explicit signals or communication among social animals to explain their apparently clever group behaviour. Leadership just emerges from local interactions too, with knowledgeable individuals ending up at the front of groups, without having to communicate that they should lead.


Social behaviour

Subject Group

Zoology and Ecology







Posted by


on Fri Nov 10 2017

Article ID


Details of original research article:

Couzin ID, Krause J, Franks NR, Levin SA. Effective leadership and decision-making in animal groups on the move. Nature. 2005;433:513-516.

Preceded by:

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