Collective behaviour encompasses activities of people and social groups that typically emerge spontaneously (such as crowds, riots, and so on) rather than arising from established processes of socialisation leading to conformity to social rules and norms. These behaviours often occur in response to a shared situation or stimulus and can involve large numbers of people acting in relatively unstructured ways. Examples of collective behaviour include panics, fads, rumors, social movements, and disasters. Sociologists study collective behaviour to understand the dynamics of group actions that are not governed by typical social structures or institutions. Factors such as anonymity, suggestibility, and the rapid spread of information can play a significant role in shaping collective behaviour.