Group display of aggression (behaviour with intent to harm) in ancestors has been seen as an adaptive response, promoting inter-group harmony and mutual defence. Lynch mobs have been explained by social transition and the need for conformity, for example, Myrdal (1944) found that black lynchings in the USA were due to fear of negroes and white mobs turned to ‘lynch law’ as a means of social control to maintain white supremacy. Mobs are often most active at a time of major social transition, such as after the collapse of slavery, thus when the community is at risk, group survival becomes more important, producing hostility towards outsiders. The Social Power-Threat hypothesis claims that lynching atrocity increases with the proportion of blacks in the community, for example, as the minority poses a greater perceived threat to the majority, resulting in violent discrimination. However, the Self-Attention theory argues that atrocity increases with the proportion of mob members, Freud claimed that aggression is a manifestation of our natural death instinct (Thanatos), thus lynch mobs are a collective release of innate energy of pent-up thanatos which is displaced onto others.
As for religious rituals, self-inflicted aggression as an initiation rite has been explained by the costly signalling theory, as the inherent costs of religious rituals contribute to the success of religion. By engaging in painful rituals, the individual signals commitment to a group and its values, promoting the adaptive benefit of inter-group co-operation. Zahavi (1997) claims that the costs also serve as deterrents to those who do not believe in a group’s teaching but wish to take advantages of its benefits. Sports events and xenophobia have been explained similarly. Shaw and Wong (1989) claim that natural selection favours altruism towards the ingroup but intolerance of outsiders, as the overperception of threat is less costly than underperception, thus avoiding attack and increasing survival. Xenophobia in football crowds is influenced by extreme right wing groups, as racist chants strengthen the cultural identity of supporters by stressing the differences between the two groups. Competitive sport also fuels our psychological need to belong to an ingroup, and membership is shown by group clothing, chants and aggressive actions. This belief is upheld in matches against other teams. Human aggressive displays are thus a demonstration of power (processions of military might) or of intimidation (sport), which act as a warning to other hostile groups.
Crowd behaviour has been explained by many different theories. Deindividuation claims that it is due to the loss of individual identity and the gaining of a group’s collective identity which is caused by anonymity (thus unaccountability for actions), diffusion of responsibility and a large group size. Bystander Apathy explains the lack of altruistic behaviour, although not necessarily aggression, in terms of pluralistic ignorance. In ambiguous situations people look to others for guidance, but if other bystanders are uncertain of what to do in an emergency, looking to others produces the wrong guidance resulting in no action. In a large group, there is also a diffusion of responsibility, thus the more bystanders that are present, the less likely that one of them will intervene and help. Contagion theory states that group norms occur due to the hypnotic effect of members coming together as a group (Le Bon, 1995), not due to pre-existing tendencies, although in real life, most group behaviour is not irrational or mob-like. Convergence theory differs in that group behaviour is explained in terms of like-minded (for example violent) individuals coming together in a crowd. However, this does not explain the fact...