Social movement theory is an interdisciplinary study within the social sciences that generally seeks to explain why social mobilization occurs, the forms under which it manifests, as well as potential social, cultural, political, and economic consequences, such as the creation and functioning of social movements. Classical approaches The classical approaches emerged at the turn of the century. These approaches have in common that they rely on the same causal mechanism. The sources of social movements are structural strains. These are structural weaknesses in society that put individuals under a certain subjective psychological pressure, such as unemployment, rapid industrialization or urbanization. When the psychological disturbance reaches a certain threshold, this tension will produce a disposition to participate in unconventional means of political participation, such as protesting. Additionally, these approaches have in common that they view participation in contentious politics as unconventional and irrational, because the protests are the result of an emotional and frustrated reaction to grievances rather than a rational attempt to improve their situation. These psychologically-based theories have largely been rejected by present-day sociologists and political scientists, although many still make a case for the importance (although not centrality) of emotions. See the work of Gustav LeBon, Herbert Blumer, William Kornhauser, and Neil Smelser. Deindividuation model Sociologists during the early and middle-1900s thought that movements were random occurrences of individuals who were trying to emotionally react to situations outside their control. An important writer in this area of research was Gustave LeBon. In his book The Crowd, he studied the collective behavior of crowds. What he concluded was that once an individual submerges in a crowd, his behavior becomes primitive and irrational and he is therefore capable of spontaneous violence. This transformation happens under certain conditions. Once individuals submerge themselves in a crowd, they gain a sense of anonymity and this causes them to believe that they cannot be held accountable for their behavior within the crowd. This is combined with a sense of invisibility by being part of a crowd. Under these conditions, critical reasoning is impossible and an unconscious personality emerges: a personality which is dominated by destructive instincts and primitive beliefs. This theory has been picked up and further developed by other theorists like Herbert Blumer and Neil Smelser. Mass society theory Mass society theory emerged in the wake of the fascist and communist movements in the 1930s and 1940s and can be seen as an