Collectivities are groups that exhibit the same behavior. The various types of collectivities that exist are: crowd, mob, fad, riots, panic, mass hysteria, rumour, public opinion, etc. The various types of collectivities differ in the number of people that participate in them and the manner in which their actions are carried out. Three theories have been proposed for collective behaviour, these are contagion theory, emergent norm theory and value added theory.
