A recent meta-analysis supported this conclusion, revealing a positive relationship between right-wing ideology and aggressive attitudes and behaviors ( 16).

Finally, according to various conceptualizations and operationalizations of right-wing authoritarianism (RWA 13– 15), aggressive tendencies constitute an inherent component of this construct, with people high in RWA being more hostile toward others who violate norms than those low in RWA. In line with this reasoning, some studies have demonstrated an empathy gap between liberal and conservative individuals ( 12). They are also less likely to support social dominance ( 11), which could lead to their overall lower likelihood to use violence against adversaries. In contrast, in comparison to their right-wing counterparts, left-wing individuals score higher on openness to new experiences, cognitive complexity, and tolerance of uncertainty ( 5). Because such characteristics have been found to increase in-group bias and lead to greater out-group hostility ( 10), violence for a cause may be more likely among proponents of right-wing ideologies. In comparison to left-wing supporters, right-wing individuals are more often characterized by closed-mindedness and dogmatism ( 9) and a heightened need for order, structure, and cognitive closure ( 5). Much of this research suggests that compared to left-wing extremists, right-wing extremists may be more likely to engage in politically motivated violence. Of these three ideologies, most prior research has contrasted those committed to right-wing and left-wing causes. In this research we address this gap by comparing the use of political violence by left-wing, right-wing, and Islamist extremists in the United States and worldwide using two unique datasets that cover real-world examples of politically motivated, violent behaviors. However, despite the growing interest in research on political ideology ( 8), very few studies have directly examined patterns of violent behavior across the ideological spectrum. Given that these factors may predispose individuals to aggression, one might expect similar differences between ideologies with regard to the use of political violence. At the same time, individuals espousing different ideological views have been found to differ with regard to personality profiles ( 3), cognitive functioning ( 4), social motives ( 5), values ( 6), and moral beliefs ( 7). This could suggest that the willingness to use violence for a cause is independent of the ideological content and can be expected across the ideological spectrum given sufficiently high levels of conflict. Historically speaking, political violence has been perpetrated on behalf of a wide range of political ideologies ( 1, 2). However, differences in violence emerge on the global level, with Islamist extremists being more likely than right-wing extremists to engage in more violent acts. In the United States, we find no difference between the level of violence perpetrated by right-wing and Islamist extremists. Across both datasets, we find that radical acts perpetrated by individuals associated with left-wing causes are less likely to be violent. In this research we address these gaps by comparing the use of political violence by left-wing, right-wing, and Islamist extremists in the United States and worldwide using two unique datasets that cover real-world examples of politically motivated, violent behaviors. Moreover, it has generally focused on respondents in Western countries and has been limited to either comparisons of the supporters of left-wing and right-wing causes or examinations of only Islamist extremism. Prior research on this topic is scarce and mostly restricted to self-reported measures or less extreme forms of political aggression.

Although political violence has been perpetrated on behalf of a wide range of political ideologies, it is unclear whether there are systematic differences between ideologies in the use of violence to pursue a political cause.

Efforts root out farright extremism