Zimbardo suggested that there are contributing factors towards deindividuation like anonymity such as wearing a uniform, this means a person in a large crowd is faceless and not easily identified, which means social constraints are reduced. Therefore the larger the group, the greater the anonymity and the greater the reduced sense of guilt, leading to an increase in anti-social aggressive behaviour. Another factor which is suggested contributes to deindividuation is altered consciousness through drugs or alcohol. Both anonymity and altered consciousness increase arousal and reduce responsibility, leading to an increase in normally inhibited behaviors.
There is research to support this theory. Watson found that in tribal warfare, warriors who changed their appearance more prior to warfare participated in more killings, mutilations and tortures than those warriors who made minimal alterations to their appearance. Watson’s study demonstrated how the increased anonymity, which here was appearance changing, has the potential to lead to an increase in violent behaviour. This also explains why soldiers are made to wear uniform into battle, as it makes them less identifiable as an individual and therefore more likely to achieve the war objective.
However a meta-analysis by Postmes & Spears refutes parts of the deindividuation theory as a cause of aggression. They found that disinhibiton and anti-social behaviour is not more common in large groups or anonymous settings. As well as this, they found no evidence of deindividuation being associated with reduced self-awareness, or that decreased self-awareness leads to an increase in aggressive behaviour. These findings cast significant doubt on the accuracy of deindividuation theory, demonstrating that some aspects of the theory may not be entirely correct and don’t always apply in real life situations.
The above research and others casts doubts on the accuracy of deindividuation theory. Indeed the theory of a “collective mind” is a determinist concept, as it suggests that people in crowds will always act unanimously, so will all follow the same aggressive behaviour patterns. However research has suggested that in a large group collectively acting aggressively rarely occurs, as many people remain stubbornly individual. This shows that deindividuation may not affect a crowd unanimously, and many people freely chose whether to loose their inhibitions and behave aggressively. This means the accuracy of the concept of a collective mind is highly questionable.
Additionally, research has suggested that there is significant gender bias with in the theory, as it has been found that males and females respond differently under deindividuated settings, as males show increased aggression, but females don’t. This suggests that biological factors may be an influence in aggression, as Dabbs et el found that those with greater testosterone levels, also had a history of violent crime. As males have a higher level of testosterone than females, this goes someway to suggesting why males do react aggressively under deindividuated settings whereas females don’t. It is therefore key to adopt a diathesis stress approach towards explaining aggression, as we may be predisposed to act aggressively e.g. increased testosterone, but the aggression is expressed when exposed to social triggers, such as deindividuation conditions.