Group behaviour in sociology refers to the situations where people interact in large or small groups. The field of group dynamics deals with small groups that may reach consensus and act in a coordinated way. Groups of a large number of people in a given area may act simultaneously to achieve a goal that differs from what individuals would do acting alone (herd behaviour). A large group (a crowd or mob) is likely to show examples of group behaviour when people gathered in a given place and time act in a similar way—for example, joining aprotest or march, participating in a fight or acting patriotically. Special forms of large group behaviour are:
* crowd "hysteria"
* spectators - when a group of people gathered together on purpose to participate in an event like theatre play, cinema movie, football match, a concert, etc. * public - exception to the rule that the group must occupy the same physical place. People watching same channel on television may react in the same way, as they are occupying the same type of place - in front of television - although they may physically be doing this all over the world. Group behaviour differs from mass actions which refers to people behaving similarly on a more global scale (for example, shoppers in different shops), while group behaviour refers usually to people in one place. If the group behaviour is coordinated, then it is called group action. Swarm intelligence is a special case of group behaviour, referring to the interaction between a group of agents in order to fulfil a given task. This type of group dynamics has received much attention by the soft computing community in the form of the particle swarm optimization family of algorithms.