Violent extremism is a costly, global problem, yet research has yet to come to a consensus on the psychological underpinnings of violent extremism. The aim of this dissertation was to contribute to a more nuanced understanding of the psychological underpinnings of violent extremism and group-based violence by (1): moving beyond the traditional focus on disadvantaged groups, Islamist extremism, and first-hand experience of victimisation or disadvantage; (2): moving past the long-standing person-situation dichotomy; and (3) attempting to integrate the role of personality and social psychological factors in susceptibility to violent extremism.

In Study I we tested a social psychological model of Islamist extremism amongst Muslims living in the West, and Muslims living in countries which have first-hand experience of Western military intervention. We found that the model applies across contexts, suggesting that a sense of muslim identity based on a sense of victimisation, cuts across borders, and victimisation can be experienced vicariously.

In Study II I found that both personality (honesty-humility) and team identification predict violent intentions amongst soccer supporters, and that collective narcissism partially mediated these associations. 

Study III identified common personality and social psychological predictors of group-based violence across three studies sampling from Black Lives Matters supporters, an immigration-critical group (Swedes), and soccer supporters. Across all contexts, with group-based relative deprivation positively and honesty-humility negatively predicting support for violence. Further, amongst BLM supporters and the immigration-critical group, emotionality negatively predicted support for violence, violent intentions, and self-reported aggression/violence. 

In Study IV I predicted that modesty would be negatively associated with group-based relative deprivation amongst members of advantaged but not disadvantaged groups. Across two studies amongst White and Black Americans, and amongst men and women, I found that modesty interacted with group membership. Specifically, modesty was negatively related to group-based relative deprivation amongst White Americans but not Black Americans, and amongst men, but not women. An implication of these findings is that individuals espousing the rhetoric of far-right and men’s right’s movements, are low in modesty, predisposing them to feel a greater sense of entitlement, and hence violation of entitlement.

Overall, the findings across these studies suggest that both personality and social psychological variables need to be considered when examining why individuals endorse violent extremism. Furthermore, the findings demonstrate that there are common personality and social psychological factors underpinning different forms of group-based violence, including identity processes, feelings of group-based disadvantage and injustice, and personality characterised by low honesty-humility and emotionality.

Furthermore, feelings of injustice and group-based relative deprivation can be experienced in the absence of direct experience of victimisation, in non-political contexts, and even when one belongs to a structurally advantaged group. Although many groups perceive that their group is disadvantaged relative to other groups, personality (e.g., low modesty) may predispose members of structurally advantaged groups to perceive that their group is not getting what they are entitled to.