Did scientists just confirm the horseshoe theory of politics? Extremism fuels protest across ideological lines

People are more likely to take part in protests and other forms of collective action when the cause aligns with their political values. However, new research suggests that political extremism itself—regardless of ideology—also drives activism. A study published in Political Psychology found that individuals with extreme political beliefs, whether on the left or the right, are more likely to engage in collective action, even if the movement does not align with their ideology. The findings suggest that emotions, particularly anger, play a central role in this relationship.

“Both societal and fundamental interests inspired this research. At the societal level, there is a longstanding debate about the role of political extremes in social movements. In France, this question became particularly salient during the Yellow Vest movement, with analysts attempting to categorize the movement as left-wing, right-wing, or simply extreme,” explained Gaëlle Marinthe, an associate professor at Clermont Auvergne University.

“On the fundamental side, I am deeply interested in the similarities and differences between groups with ideologically opposing viewpoints. My colleagues and I wanted to examine the influence of both ideological values and a more cognitive feature of one’s ideological position (i.e., extremism) in political investment and, in this study, collective action. Our research is based on the premise that values and beliefs indeed play a major role in political behavior. However, structural features of ideology or belief (and in this case, extremism) may operate similarly across different ideological groups and may sometimes lead to counterintuitive outcomes—potentially even undermining the group’s long-term objectives.”

The researchers hypothesized an asymmetric U-shaped relationship between political ideology and activism. This means those at the far ends of the political spectrum—on either the left or the right—are more likely to participate in activism. The researchers also examined the role of emotions, particularly anger, fear, and hope, to understand how they influence the relationship between ideology, extremism, and activism. To examine this, they conducted two studies.

The first study focused on a real-world protest movement in France that opposed government-imposed COVID-19 restrictions. This movement was largely aligned with right-wing values, emphasizing personal freedoms and skepticism toward government interventions.

A total of 1,386 participants completed surveys during the protests. Participants reported their political ideology on a scale from left to right and were also assessed for political extremism, meaning how strongly they identified with the far ends of the spectrum. The researchers measured their intentions to participate in the protests and their levels of anger, fear, and hope.

The results supported the researchers’ hypothesis. As expected, those with right-wing political views were more likely to express intentions to participate in the protests. However, political extremism, whether right-wing or left-wing, was also associated with a greater likelihood of joining the protests. This confirms the asymmetric U-shaped relationship—those at the ideological extremes were more likely to engage in collective action, even if they did not completely align with the movement’s specific values.

Anger played a significant role in explaining this effect. Political extremism was linked to higher levels of anger, which in turn increased people’s willingness to participate in protests. Fear and hope had less consistent effects. Right-wing ideology was associated with lower levels of fear, which further encouraged participation. Meanwhile, higher levels of political extremism were linked to lower levels of hope, but the role of hope in motivating activism was unclear.

To see if these findings would hold in a left-wing movement, the researchers conducted a second study focused on protests against pension reform in France. This movement was largely supported by left-wing individuals who opposed the government’s plans to raise the retirement age.

A total of 418 participants completed surveys during the protests. The study measured the same variables as in Study 1, including political ideology, political extremism, anger, fear, hope, and both intentions and actual participation in collective action.

The findings mirrored those of the first study. Left-wing ideology was strongly associated with participation in the pension reform protests. However, political extremism, regardless of whether it was left-wing or right-wing, was also linked to higher levels of engagement. This again confirmed the asymmetric U-shaped relationship between ideology and collective action.

Anger once again played a central role. Both political ideology and political extremism were associated with higher levels of anger, which in turn increased participation in protests. However, fear showed a different pattern compared to Study 1. While right-wing individuals showed less fear in Study 1, left-wing individuals in Study 2 reported higher levels of fear, and fear was unexpectedly linked to greater intentions to participate in the pension reform protests.

“We examined two real-life social movements in France: one advocating right-wing values (opposing COVID-19 restrictions) and one supporting left-wing values (protesting pension reform),” Marinthe told PsyPost. “Our findings revealed an asymmetrical U-shaped relationship between political ideology and collective action.”

“In other words, people engage in collective action that aligns with their ideology (left or right), but those at the political extremes are also more likely to participate in collective action, even when it does not align with their ideological values. This is partly (but not solely) driven by heightened anger at both extremes of the political spectrum, which can fuel activism.”

“Beyond anger, we also explored the roles of fear and hope, but our results were inconsistent,” Marinthe explained. “This suggests that the impact of these emotions is more complex than we initially expected. Based on these inconsistencies, we speculate that fear and hope may have contradictory relationships with both political ideology and collective action, depending on how they are framed.”

The findings are in line with the horseshoe theory of politics, a political concept that suggests the far-left and the far-right, rather than being at opposite ends of a straight ideological spectrum, actually resemble the two ends of a horseshoe—curving toward each other and sharing certain similarities despite their apparent differences.

The study’s findings show that extremism itself, rather than just ideological content, plays a key role in mobilizing people for collective action. Whether protesting COVID-19 restrictions or pension reform, extremists were more likely to take part, driven by strong emotional responses. This suggests that beyond traditional left-right divides, political engagement at the extremes may be fueled by similar psychological tendencies.

However, it is important to note the study does not suggest that extreme leftists and extreme rightists are ideologically similar or that they frequently participate in each other’s movements. While both extremes show heightened engagement, they still tend to mobilize for causes that at least partially align with their values. The findings suggest that political extremism fuels activism across ideological lines, but they do not necessarily indicate that far-left and far-right politics “meet” in terms of ideology.

The findings are also based on two specific protest movements in France. France has a strong tradition of public demonstrations, and the results might not generalize to other countries where protesting is less common or carries greater risks. “Since our studies were conducted in France, replication in other countries is necessary to assess the generalizability of our results,” Marinthe said.

Additionally, both studies focused on anti-government protests. It is possible that political extremism is particularly relevant for activism that opposes those in power. Future research could examine whether political extremism also predicts participation in movements that support government policies or advocate for broader social changes.

“This research aligns with my broader interest in group and political dynamics,” Marinthe said, “particularly in understanding: 1.) how groups with divergent objectives may function in similar ways and 2.) how groups sometimes act or make decisions in ways that counter their primary interests or could be detrimental in the long run.”

“I would like to emphasize that this research, as well as other studies we conduct, does not equate different groups in terms of their values or impact,” she added. “Our goal is to understand political and group dynamics that may operate similarly across groups with drastically different objectives.”

The study, “Collective action among the extremes? Relations between political ideology, political extremism, emotions, and collective action,” was authored by Gaëlle Marinthe, Alice Kasper, Romain Veillé, and Fanny Lalot.