Deindividuation, one of the most recognised consequences of crowd behaviour (Postmes & Spears, 1998), has traditionally been defined as a state where individuals in a crowd are ‘able to indulge in forms of behavior in which, when alone, they would not indulge,’ (Festinger et al., 1952). Researchers in Social Psychology have identified a number of variables that contribute to deindividuation (Guerin, 2003). However, which of these variables is responsible is a widely debated issue, with no conclusive findings to date. The following essay explores the concept of deindividuation according to the leading deindividuation theories. Gustave Le Bon, one of the first to analyse crowd behavior (Li, 2010), was a French social psychologist who read accounts about crowds in the French revolution of 1848, and Paris commune of 1871 (Douglas & Sutton, 2013). Appalled by the atrocious actions of the crowds, Le Bon sought to explain why crowds behave in such barbaric ways in his 1896 writings ‘The Crowd: A Study Of The Popular Mind,’ which gave rise to the mass politics of the twentieth century as stated by Mosciovici (1981) (Reicher, 2001). The social psychologist claimed that ‘under certain circumstances, and only under those circumstances, an agglomeration of men presents new characteristics very different from those of the individual composing it,’ (Reicher, 2001). Le Bon outlined three processes that occur in crowds, causing them to act a destructive manner. Firstly, ‘submergence’ occurs, whereby individuals lose all sense of self and personal responsibility for their actions, as they are shielded by anonymity (Reicher, 2001). Through ‘contagion,’ individuals follow the ideas and emotions of the crowd, which spread rapidly (Douglas & Sutton, 2013). Lastly, through the process of ‘suggestion,’ individual antisocial motives are released from the unconscious (Douglas & Sutton, 2013). Thus, a ‘group mind,’ develops, as eventually the crowd develops shared beliefs (Postmes, 2001), and individuals become deindividuated and undergo ‘savage, destructive instincts,’ (Li, 2010). Festinger, Pepitone, and Newcomb (1952) developed Le Bon’s theory further, and argued in their Deindividuation theory that the crowd behavior described by Le Bon was due to ‘deindividuation,’ which they defined as a state characterized by reduced self- awareness, and is commonly associated with involvement in a crowd (Festinger et al., 1952). The theorists claimed that a loss of individuality leads to a loss of control over ones actions, which causes different and more impulsive behaviour when in a group (Postmes & Spears, 1998). Administering a study to test their theory, Festinger et al. (1952) asked participants to discuss, in a group, a study read to them by an experimenter (Reicher, 2001). As expected, all participants showed aggressive emotions towards their parents, which, like Le Bon, Festinger et al. claimed was due to individuals sharing the ideas and emotions of their fellow group members (Reicher, 2001), with a reduction of their inner restraints and self- awareness and increased attention to the group instead (Chang, 2008). Furthermore, Zimbardo (1970), adding to the notion of deindividuation, conducted experiments to investigate the effects of the ‘cloak of anonymity’ that shielded an individual when part of a crowd (Douglas & Sutton, 2013). Zimbardo (1969) proposed that input variables such as sensory overload, group size, anonymity, diffused responsibility and arousal, lessen self-awareness, leading to deindividuated behaviours (Innes, Mann & Newton, 1982). However, like Le Bon (1896), Zimbardo argued for anonymity as the main contributor to deindividuation (Postmes & Spears, 1998), claiming that, by being anonymous, individuals lose all sense of personal identity and responsibility for their actions and concern for self- evaluation, reducing one’s guilt