Introduction
Political violence has long posed a puzzle for social scientists: Why do some individuals, and not others, come to support or engage in violent extremism? The traditional answers to this question in political science have tended to emphasize structural, ideological, or strategic variables such as grievance, state repression, group mobilization, or instrumental rationality (Goodwin, Reference Goodwin2001; Gurr, Reference Gurr1970; Kalyvas, Reference Kalyvas2006; Tilly, Reference Tilly2003). These explanations are valuable but also incomplete. They struggle to account for the uneven distribution of violence across otherwise similar individuals or the specific psychological pathways by which grievances are converted into lethal action (Ginges & Atran, Reference Ginges and Atran2009; Wood, Reference Wood2003). Meanwhile, scholars in neighboring disciplines—especially psychology and neuroscience—have developed rich literatures on individual and social catalysts of aggression and violence.
Taken together, this broad and expanding set of literatures on the roots of political violence turns on a simple but complex distinction, often popularized in terms of a debate between “bad barrels versus bad apples” (Trevino & Youngblood, Reference Treviño and Youngblood1990; Zimbardo, Reference Zimbardo2007): Do the origins of violent behavior lie primarily in context or character? The bad barrels perspective, exemplified by Zimbardo’s Stanford Prison Experiment and Milgram’s obedience studies (Milgram, Reference Milgram1974), suggests that situational forces—including authority structures, group dynamics, and institutional contexts—can overwhelm individual moral restraints and lead ordinary people to commit harmful acts. From this view, violence emerges not from pathological personalities but from normal psychological responses to abnormal situations. In contrast, the bad apples perspective emphasizes individual differences in personality, biology, and developmental history that make some people more prone to violence than others, even despite similar contexts. This approach, with roots in criminology and personality psychology, focuses on identifying stable personality traits—such as impulsivity or sensation-seeking—that predict aggressive behavior across contexts (Gottfredson & Hirschi, Reference Gottfredson and Hirschi1990; Paulhus & Williams, Reference Paulhus and Williams2002).
Although this debate implies to some that these sets of explanation are mutually exclusive, these perspectives are in fact complimentary levels of analysis. The bad barrels view helps explain why ordinary people can commit extraordinary violence under certain conditions, while the bad apples view helps explain why some individuals but not others act violently when exposed to the same or similar situational pressures. As Palmer (Reference Palmer2012) convincingly argues, the most comprehensive accounts of unethical behavior recognize the interaction between individual predispositions and enabling environments. In this article, I show how we can move beyond truism to demonstrate the actual interplay of these two levels in order to gain a deeper understanding of the roots and mechanisms of violence.
This integrative approach promises theoretical and practical benefits. Theoretically, it moves beyond disciplinary silos by compelling dialogue between two perspectives on violence that do not often interact. Practically, it can inform better-targeted interventions by clarifying whether prevention efforts should focus on group-level conditions, individual risk profiles, or both. Most importantly, the framework avoids two common errors: the assumption that violent extremists are categorically different from ordinary individuals and the opposite assumption that context alone fully determines violent behavior. Instead, it shows how extremist violence arises from the interaction between universal human capacities and individual-specific thresholds.
The framework is elaborated in the following sections. First, I situate Arendt’s banality of evil with an evolutionary framework, illustrating how universal psychological systems can produce violence when activated by particular social conditions. This section then uses three leading theories of political violence—the Devoted Actor Model, The Quest for Significance Model, and the Staircase to Terrorism Model—as illustrations of how the banality perspective is expressed in contemporary psychological research. Section 2 shifts to the complementary perspective of individual catalysts, explaining how biological, psychological, and demographic factors shape variation within this shared human architecture. The third section demonstrates the necessary and dynamic interplay of both dimensions in an integrated model, followed by implications for political science research and policy in the fourth section. The final section concludes with brief suggestions for future work and reflections on the importance of interdisciplinary synthesis.
Universal causes of violence: Species-typical mechanisms
Political violence poses a paradox that has preoccupied scholars since Arendt’s account of the “banality of evil”: how extraordinary harm can arise from ordinary psychological processes. This section revisits that paradox by (1) building an empirical bridge between Arendt’s abstract concept of banality and the material instantiation of universal psychological architecture and (2) identifying three leading and contemporary theories of political violence that, implicitly or explicitly, rest on assumptions of human universality.
Hannah Arendt’s concept of the “banality of evil” provides a compelling conceptual lens for understanding how ordinary individuals can participate in extraordinary violence. Arendt’s observations of Adolf Eichmann during his trial revealed not a monstrous psychopath but rather a bureaucrat who compartmentalized his actions, prioritized career advancement, and abdicated moral responsibility through appeals to duty and authority (Arendt, Reference Arendt1963). Importantly, Arendt’s concept is used here not to equate all forms of political violence with genocidal atrocity; rather, it is to emphasize the ordinariness of the underlying processes. “Banality” refers to the commonplace psychological mechanisms—conformity, loyalty, and routinized duty—through which extraordinary harm can arise. This insight—that evil can emerge from mundane motivations and ordinary psychological processes—has profound implications for our understanding of political violence. Indeed, as Zimbardo later recognized in developing his Heroic Imagination Project (Heroic Imagination Project, n.d.; Zimbardo, Reference Zimbardo2007), the psychological processes that permit ordinary people to commit extraordinary harm also make possible extraordinary prosocial behavior. The same universal capacities for social identity and self-sacrifice can be directed toward either destructive or benevolent ends depending on context.
How do we get from banality to universality? Evolutionary theory provides the empirical bridge from Arendt’s conceptual claim to a universal psychological architecture. Natural selection operates by favoring traits—whether anatomical, cognitive, or motivational—that enhanced survival and reproduction in ancestral environments (Dawkins, Reference Dawkins1982; Maynard Smith, Reference Maynard Smith1958; Williams, Reference Williams1966). Over evolutionary time, this process yields patterned design: functional systems that recur across individuals because they solved common adaptive problems faced by ancestral humans (Buss, Reference Buss1999; Tooby & Cosmides, Reference Tooby, Cosmides, Barkow, Cosmides and Tooby1992). The human mind, like the human hand or eye, reflects this process of cumulative selection. Its information-processing structures are species-typical rather than idiosyncratic, representing shared solutions to recurrent challenges of coordination, defense, and social living (Barrett, Reference Barrett2015; Pinker, Reference Pinker1997; Tooby & Cosmides, Reference Tooby, Cosmides, Barkow, Cosmides and Tooby1992). This logic explains why some psychological capacities, such as loyalty, moral concern, and sensitivity to threat, may be widespread across cultures: they are part of a common architecture shaped by shared selection pressures (Barkow et al., Reference Barkow, Cosmides and Tooby1992). They are, in a word, banal. Evolution thus provides a naturalistic account of Arendt’s “banality of evil”—it provides a material grounding for the ordinariness of the mechanisms through which humans perceive, evaluate, and respond to their social world.
Within this universal architecture, human coalitional psychology is especially relevant to political violence. Research across the social sciences indicates that humans possess specialized mechanisms for encoding and updating coalition membership, regulating loyalty, punishing defection, and orienting toward allies versus rivals (e.g., Hafner-Burton et al., Reference Hafner-Burton, Haggard, Lake and Victor2017; Johnson, Reference Johnson2020; Kertzer & Tingley, Reference Kertzer and Tingley2018; Lopez et al., Reference Lopez, McDermott and Hatemi2011; Pietraszewski, Reference Pietraszewski2016, Reference Pietraszewski2022; Pietraszewski et al., Reference Pietraszewski, Curry, Petersen, Cosmides and Tooby2015; Tooby & Cosmides, Reference Tooby, Cosmides and Høgh-Olesen2010; Wrangham, Reference Wrangham2018). Coalition tracking is cognitively distinct from other forms of categorization and is highly plastic: boundaries can expand from kin and local allies to ideological, religious, or national identities (Gat, Reference Gat2006; Johnson, Reference Johnson2020; Lopez, Reference Lopez and McDermott2012). This plasticity helps explain how modern individuals become deeply invested in symbolic groups and why perceived threats to those identities can elicit disproportionate affect and action. Ordinary, evolutionarily shaped systems—designed for affiliation, coordination, and defense—can, under particular social and ideological conditions, be mobilized toward extraordinary political aggression.
Recent work in evolutionary personality science also illustrates how universal mechanisms may produce individual variability through adaptive calibration. Lukaszewski et al. (Reference Lukaszewski, Lewis, Durkee, Sell, Sznycer and Buss2020) argue that the emotion of anger is a species-typical regulatory system that evolved to negotiate social conflicts and assert entitlements within cooperative groups. Rather than being an idiosyncratic trait, anger represents a functional mechanism whose threshold of activation is tuned to cues about an individual’s bargaining power, social value, and environmental context. Individuals with greater physical formidability or social leverage, for instance, exhibit lower thresholds for anger activation, while those with fewer resources or less status display greater inhibition. These differences are expressed in the personality dimension known as “agreeableness”: variation in agreeableness, they show, reflects systematic individual differences in the activation and output of the common underlying anger program.
This “calibrated differences” perspective builds on a long tradition of evolutionary explanations of personality variation (e.g., Buss, Reference Buss1999; Tooby & Cosmides, Reference Tooby, Cosmides, Barkow, Cosmides and Tooby1992—for an application to political science, see Lopez and McDermott, Reference Lopez and McDermott2012). It shows that while the anger system itself is universal, its parameters can be flexibly adjusted in response to developmental social and ecological inputs—a process Buss (Reference Buss1999) has termed “early experiential calibration.” The resulting individual differences are not deviations from a universal design but expressions of that design’s functional plasticity. This insight clarifies how evolved psychological systems can yield both cross-culturally recurrent patterns and idiosyncratic individual responses.
With this bridge in place—from Arendt’s banality to universal architecture—we can now examine three leading proximate frameworks of political violence: the Devoted Actor Model, Quest for Significance Theory, and the Staircase to Terrorism model. Each of these illustrates how ordinary, species-typical mechanisms may interact with specific contexts and individual history to produce diverse pathways to political violence.
Due to space and scope, however, I do not aim to evaluate the evolutionary origins of each model; rather, these models are meant to serve as illustrations of the operation of ordinary psychological mechanisms in diverse political contexts. Although contemporary research on the contextual factors that precipitate political violence is not always couched explicitly in terms of a universal evolved psychology—or even in Arendt’s articulation of its banality—it is nevertheless logically rooted in the broader question of how otherwise “normal” psychological processes can lead to extreme behavior. These models, therefore, illustrate how ordinary people come to support or engage in political violence and together exemplify the approaches typical of a banality of evil perspective.
The Devoted Actor Model, developed by Scott Atran and colleagues, explains how moral commitment and social identity can override instrumental reasoning in motivating extreme political behavior (Atran & Ginges, Reference Atran and Ginges2015). At its core, the model links two interacting processes: sacred values—objects or beliefs regarded as non-negotiable and immune to material tradeoffs—and identity fusion, a deep sense of oneness between the self and a group (Whitehouse et al., Reference Whitehouse, Jong, Buhrmester, Gómez, Bastian, Kavanagh, Newson, Matthews, Lanman, McKay and Gavrilets2017). When people perceive their personal identity as indistinguishable from that of their group, threats to the group are felt as threats to the self. In these situations, actions that would normally seem irrational—such as risking one’s life or rejecting compromise—become experienced as moral imperatives. The model, therefore, challenges rationalist approaches to political violence by arguing that some forms of commitment are deontic (rules-based and duty-driven) rather than utilitarian.
From the perspective of the devoted actor herself, the process is less about fanaticism than about meaning and belonging. When individuals fuse their identity with a group (e.g., religious community, nation), the group’s cause becomes a personal calling. Violence, in this sense, is not pursued for private gain but to affirm loyalty or moral worth. A fighter who refuses to retreat despite certain death or a nationalist who views territorial loss as spiritual desecration is acting from this fusion of self and cause. The Devoted Actor Model helps explain why material incentives or sanctions often fail to deter such actors: to compromise would not merely surrender an objective but betray one’s own sense of self (Tetlock, Reference Tetlock2003). This dimension of purpose identity and moral duty makes the model powerfully useful for understanding how ordinary people can come to see extraordinary sacrifice as both necessary and just.
The Devoted Actor Model has been supported by lab and field experiments, as well as neuroimaging studies. Pretus et al. (Reference Pretus, Hamid, Sheikh, Ginges, Tobeña, Davis, Vilarroya and Atran2018) find that individuals who endorse sacred values show increased willingness to fight and die for their group and that these values activate brain regions associated with rule-based reasoning and deontic processing rather than deliberative cost–benefit reasoning. Their findings reinforce the notion that sacred values engage deeply rooted cognitive systems, making compromise less likely and increasing the potential for morally motivated violence. Importantly, these neural patterns are not pathological but represent normal variations in how the human brain processes moral commitments and group-based identities. Furthermore, this model has been broadly applied to many contexts of political violence, from ISIS foreign fighters to nationalist militias. Sheikh et al. (Reference Sheikh, Gómez and Atran2016), for example, found that individuals identified as frontline fighters in a conflict zone showed stronger fusion with their group identity and greater endorsement of sacred values related to land than non-fighters drawn from the same population. Similarly, Gómez et al. (Reference Gómez, López-Rodríguez, Sheikh, Ginges, Wilson, Waziri, Vázquez, Davis and Atran2017) demonstrated that identity fusion and commitment to sacred values predicted willingness to make costly sacrifices in culturally diverse contexts—including Libya, Spain, and the United States—providing empirical support for the cross-cultural robustness of devoted actor mechanisms.
A second body of literature—the Quest for Significance Model (QSM)—proposes that the need to feel worthy, respected, and meaningful is a universal human motive (Kruglanski et al., Reference Kruglanski, Gelfand, Bélanger, Sheveland, Hetiarachchi and Gunaratna2014). Fundamentally, people strive for significance—a perceived sense that their lives matter and are valued by others—and respond powerfully when this sense is lost or threatened. Such loss can result from humiliation, injustice, failure, or exclusion, triggering a motivation to restore significance. The process unfolds in three main steps: (1) a precipitating event that diminishes personal significance, (2) exposure to an ideology or narrative that prescribes violence as a legitimate path to restore it, and (3) social validation from a supportive group that reinforces this new moral framework. When these elements converge, individuals may come to view violent action not as deviant but as morally prescribed—indeed as redemptive. QSM thus frames radicalization as an ordinary human process of significance restoration rather than as a symptom of pathology or irrationality.
The central locus of this model is a basic human yearning to matter. In many contexts, a drive to reestablish value or meaning can lead to constructive outlets. But when paired with narratives that cast violence as heroic and group belonging as conditional on sacrifice, the same desire for dignity can take destructive form. This again serves to highlight the “dual-use” function of these universal underlying systems, that is, that they can and are often active in the creation and maintenance of pro-social as well as anti-social dynamics. A disaffected youth who finds affirmation in an online extremist forum, or a former soldier who interprets social marginalization as betrayal and embraces vengeance, is both enacting the same psychological script: to regain lost significance by tethering their identity to a cause that promises redemption.
The QSM is supported by empirical studies showing that perceived loss of personal significance predicts support for radical action (Bélanger et al., Reference Bélanger, Caouette, Sharvit and Dugas2014; Webber et al., Reference Webber, Babush, Schori-Eyal, Vazeou-Nieuwenhuis, Hettiarachchi, Bélanger, Moyano, Trujillo, Gunaratna, Kruglanski and Gelfand2018). More recent work has shown that this motive operates across ideological contexts and is not confined to violent extremism: individuals seeking significance may engage in political activism, prosocial behavior, or radicalization depending on what normative pathways are available (Jasko et al., Reference Jasko, LaFree and Kruglanski2020). QSM is further elaborated through studies examining how different cultural and social contexts channel the significance quest in different directions. Kruglanski et al. (Reference Kruglanski, Bélanger and Gunaratna2019) show how the same psychological need for significance can manifest in dramatically different behavioral outcomes depending on the available ideological narratives and social networks. For example, individuals who lose personal significance through experiences of humiliation or status loss may respond differently depending on the availability of ideological narratives and social networks. In some cases, such individuals may turn toward prosocial activism; in others, they may radicalize. These divergent outcomes often hinge on exposure to charismatic leaders, identity reinforcing peer groups, or propaganda emphasizing moral absolutes. Consistent with the banality of evil framework, and similar to the Devoted Actor Model, the QSM interprets violent extremism not as a product of pathological minds but as one potential outcome of an otherwise universal human architecture.
Lastly, the “Staircase to Terrorism” model (Moghaddam, Reference Moghaddam2005) offers another influential contribution that finds resonance within the banality of evil framework. In this model, radicalization is depicted as progression along a psychological staircase, where each level or “floor” represents an increasingly constrained set of choices in response to perceived injustice, blocked pathways to significance, and growing ideological commitment. On the ground floor, individuals experience everyday frustrations or perceptions of injustice but still believe they can address them through normal social or political channels. Next, on the first floor, feelings of relative deprivation (Gurr, Reference Gurr1970) and unfair treatment intensify as individuals begin to compare their own group’s disadvantage with the privilege of others. On the second floor, we observe displacement of blame onto perceived outgroups or institutions, accompanied by moral disengagement and acceptance of categorical thinking. The model’s third and fourth floors are characterized by increasing isolation from moderating influences, finding validation in extremist narratives, and redefining violence as morally justified or even obligatory. The top floor, however, is distinguished by the fact that all psychological space for alternative action has largely disappeared, and violence is no longer one option among many; rather, it is the only coherent response that remains. The Staircase Model is predicated on the operation of ordinary cognitive and motivational processes: frustration, fairness concerns, and group identification. What changes is not human nature, but a specific and powerful situational narrowing of perceived choice.
This is a tragic blend of mind and place that is invariably human. Perhaps, one poignant and defining feature of this model is that each step along the staircase feels, in the moment, like a reasonable response to escalating wrongs. Ordinary people, motivated by ordinary concerns about fairness and respect, can climb toward extraordinary acts of violence—not because they are deranged but because each step upward appears, at the time, to make moral sense.
Subsequent work within this tradition has identified how institutional, social, and even digital environments shape the progression from non-violent grievance to violent extremism. Moghaddam (Reference Moghaddam2006) identifies the role of perceived procedural injustice, where individuals judge that they are denied fair treatment or voice in decision-making processes. This perception of injustice creates fertile ground for radicalization, particularly when combined with categorical thinking that divides the world into rigid us-versus-them categories. Additional, empirical support for the staircase model has come from diverse methodological approaches. Qualitative studies of radicalization pathways, such as those conducted by Horgan (Reference Horgan2008), have documented the gradual progression from grievance to violence that many extremists experience. Similarly, network analyses by Sageman (Reference Sageman2008) have shown how social bonds and group dynamics facilitate movement up the metaphorical staircase, with peer influence playing a crucial role in normalizing extreme beliefs and behaviors. More recently, Vergani et al. (Reference Vergani, Iqbal, Ilbahar and Barton2020) have integrated the staircase model with other theoretical frameworks to develop a comprehensive “Three Ps” approach to radicalization that emphasizes push factors (grievances), pull factors (group attractions), and personal factors (individual vulnerabilities).
These three models—the Devoted Actor, Quest for Significance, and Staircase to Terrorism—share a common emphasis on how ordinary psychological processes can lead to extraordinary violence under specific conditions. They differ in their emphasis (identity and sacred values, significance restoration, or progressive constraint), but all reject the notion that violent extremists are fundamentally different from ordinary individuals. Instead, they highlight how universal human capacities—for group loyalty, meaning-making, and justice sensitivity—can be channeled toward violence through social, ideological, and situational factors.
The banality of evil perspective offers a powerful—but on its own, incomplete—framework for understanding how individuals can engage in extraordinary violence. By focusing on universal psychological mechanisms, it provides a more comprehensive and empirically grounded account of political violence. However, a full accounting of the capacity and distribution of political violence must complement this perspective by also examining the individual-level factors that influence susceptibility to political violence, thereby helping to address the question of why only some individuals act on the universal potentials described here. At the same time, it is important to recognize that this interactionist account does not preclude rare cases in which either side of the equation predominates—situations so overwhelming that they override individual dispositions or individuals whose individual traits enable violence even in the absence of strong situational pressures.
Nevertheless, the implications of the banality of evil perspective are profound. If violent extremism emerges from ordinary psychological processes rather than pathological ones, then prevention efforts must focus on the conditions that channel these processes toward violence rather than attempting to identify and isolate “dangerous” individuals based on psychological profiles alone. This perspective also suggests that the capacity for extreme violence lies dormant in most individuals, activated only under specific conditions of threat, identity fusion, moral outrage, or perceived injustice. Understanding these conditions—and how they interact with individual differences—is essential for developing effective prevention and intervention strategies.
Individual catalysts: Biological and personality-based variability
While universal psychological mechanisms provide the capacity for violence, they may not explain why only some individuals carry it out. In many radical movements, the gap between belief and violent action is substantial. This raises a second explanatory layer: the broad and varied set of individual propensities that differentiate more violence-prone individuals from their peers, to which I now turn.
Demographic and personality factors
Demographic patterns in violent extremism have been well-documented across a broad range of contexts. Young males are consistently overrepresented among violent extremists, a pattern that holds across ideological orientations, cultural contexts, and historical periods (Horgan, Reference Horgan2014; Silke, Reference Silke2008). This gender and age gap likely reflects both biological factors—such as the effect of testosterone on risk-taking and status-seeking behavior—and social factors, including gendered expectations about masculinity and violence (Inoue et al., Reference Inoue, Burriss, Hasegawa and Kiyonari2023; Kimmel, Reference Kimmel2018; Vermeer et al., Reference Vermeer, Krol, Gausterer, Wagner, Eisenegger and Lamm2020). While demographic patterns provide important insights into risk factors, they are clearly insufficient for explaining individual variation in violent behavior, as the vast majority of young men never engage in political violence despite sharing these demographic characteristics.
Personality traits offer another perspective on individual variation in susceptibility to violent extremism. Several traits have been found to correlate with support for or engagement in political violence. For example, Doosje et al. (Reference Doosje, Moghaddam, Kruglanski, de Wolf, Mann and Feddes2016) summarize evidence showing that traits such as sensation-seeking and need for cognitive closure are associated with increased vulnerability to radicalization. Relatedly, Zmigrod et al. (Reference Zmigrod, Rentfrow and Robbins2019) found that individuals with lower cognitive flexibility—measured through behavioral tasks—were more likely to endorse extremist attitudes, including a willingness to support violence or make sacrifices for their ideological group. These findings suggest that inflexible cognitive styles may increase susceptibility to absolutist ideologies and reduce inhibitions against violent action in defense of the group.
The Dark Triad personality traits—narcissism, Machiavellianism, and psychopathy—are likely linked to support for political violence, though in complex ways. Narcissism, characterized by grandiosity and entitlement, may increase vulnerability to radicalization by heightening sensitivity to perceived slights against one’s identity or group. Psychopathic traits, including callousness and lack of empathy, may reduce moral barriers to violence, particularly when combined with ideological justifications (Međedović & Knežević, Reference Međedović and Knežević2019). However, it is important to note that most violent extremists do not exhibit clinical levels of these traits; rather, subclinical variations may interact with situational factors to increase risk.
Neurobiological and genetic factors
Advances in neuroscience have provided new insights into the biological bases of aggression and moral decision-making, with implications for understanding violent extremism. Neuroimaging studies have identified several brain regions and circuits that play key roles in regulating aggressive behavior and moral judgment, including the ventromedial prefrontal cortex (vmPFC), amygdala, and anterior cingulate cortex (ACC).
The ventromedial prefrontal cortex (vmPFC) plays a critical role in integrating emotional and cognitive inputs during moral decision-making and in regulating impulsive behavior. Individuals with damage or dysfunction in this region often show impaired moral judgment, including greater permissiveness toward harm in moral dilemma tasks (Koenigs et al., Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007). Neuroimaging studies of violent offenders have identified structural abnormalities and reduced gray matter volume in the vmPFC and adjacent regions, suggesting deficits in moral reasoning and impulse control (Raine et al., Reference Raine, Lencz, Bihrle, LaCasse and Colletti2000). While few studies have directly examined the neural correlates of violent extremism, these findings support the hypothesis that variations in prefrontal function may influence susceptibility to radicalization by undermining behavioral inhibition and moral evaluation.
The amygdala, a key structure in threat detection and emotional processing, also contributes to aggression and moral intuitions by modulating responses to emotionally salient stimuli. Blair (Reference Blair2007) demonstrated that psychopathy is associated with amygdala dysfunction, particularly reduced responsiveness to others’ distress cues. This may help explain why some individuals are less inhibited by the suffering of outgroup members, especially when such suffering is ideologically justified. Neuroimaging studies by Bruneau et al. (Reference Bruneau, Jacoby and Saxe2017) found that when participants evaluated outgroup members, brain regions involved in mentalizing—such as the medial prefrontal cortex and temporoparietal junction—were less active, suggesting a neural correlate of dehumanization. Together, these findings suggest that neurobiological variations in empathy and social cognition may increase susceptibility to extremist narratives that legitimize violence against outgroups.Footnote 1
Research on the neurobiology of sacred values provides further insight into individual variation in commitment to ideological causes. Berns et al. (Reference Berns, Emily Bell, Capra, Prietula, Moore, Anderson, Ginges and Atran2012) found that sacred values—beliefs perceived as absolute and non-negotiable—activate brain regions associated with rule-based, deontological reasoning rather than cost–benefit analysis. These include the temporoparietal junction and ventrolateral prefrontal cortex. This distinct neural signature suggests that sacred values are processed differently from ordinary preferences. Individual differences in the strength of these neural responses may help explain why some individuals are more willing than others to make costly sacrifices in defense of ideological commitments.
Genetic research has identified several polymorphisms associated with aggression and antisocial behavior, with potential implications for understanding violent extremism. One of the most extensively studied is the monoamine oxidase A (MAOA) gene, which regulates the breakdown of neurotransmitters such as serotonin and dopamine. McDermott et al. (Reference McDermott, Tingley, Cowden, Frazzetto and Johnson2009) found that the low-activity variant of MAOA, combined with provocation, predicted increased aggression in laboratory settings. Importantly, this effect was moderated by early-life adversity, suggesting a gene–environment interaction where genetic predispositions are expressed only under specific environmental conditions. Supporting evidence also comes from Sawyer (Reference Sawyer2022), who examined genetic variance in susceptibility to political violence within the Basque population. Her findings indicate that individuals carrying low-activity MAO-A variants were more likely to engage in political violence when exposed to sustained political repression, highlighting the moderating role of social context in the expression of genetic predispositions.
Additionally, gene–environment interactions have been observed for polymorphisms related to serotonin and dopamine function. Caspi et al. (Reference Caspi, McClay, Moffitt, Jonathan Mill, Craig, Taylor and Poulton2002) found that a functional variant of the monoamine oxidase A (MAOA) gene moderated the relationship between childhood maltreatment and adult antisocial behavior. Separately, research suggests that genetic variation influencing dopamine signaling is associated with sensation-seeking and risk-taking behavior, traits that may increase vulnerability to violent radicalization under certain conditions (Harden et al., Reference Harden, Quinn and Tucker-Drob2012).
Developmental pathways and early-life experiences
Developmental factors and early-life experiences play a critical role in shaping individual vulnerability to violent extremism. Childhood trauma, abuse, and neglect have been linked to increased risk of aggression and antisocial behavior in adulthood, effects that are mediated by alterations in stress response systems, emotion regulation, and social cognition (Raine, Reference Raine2013). These developmental pathways may increase vulnerability to violent extremism by lowering thresholds for aggressive behavior and reducing capacity for empathy and moral reasoning.
Several studies have found elevated rates of childhood adversity among violent extremists. Simi et al. (Reference Simi, Sporer and Bubolz2016) documented high rates of childhood trauma, family dysfunction, and early exposure to violence among former white supremacists in the United States. Similarly, Speckhard and Akhmedova (Reference Speckhard and Akhmedova2006) found that many Chechen terrorists had experienced significant trauma, including witnessing violence against family members. These experiences may create psychological vulnerabilities that increase receptivity to extremist narratives offering meaning, identity, and opportunities for revenge. Attachment patterns formed in early childhood also influence vulnerability to extremist recruitment. Secure attachment promotes healthy identity development, empathy, and resilience to stress, while insecure attachment patterns may increase vulnerability to groups offering surrogate family relationships and clear identity markers (Borum, Reference Borum2014). Extremist groups often exploit these attachment needs by positioning themselves as substitute families for alienated individuals seeking belonging and protection.
Educational experiences and cognitive development also shape vulnerability to extremism. Poor educational outcomes, limited critical thinking skills, and exposure to authoritarian teaching methods have been associated with increased support for extremist ideologies (Davies, Reference Davies2009). Conversely, education that promotes critical thinking, perspective-taking, and tolerance for ambiguity may build resilience against extremist narratives that offer simplistic, black-and-white worldviews.
The individual differences described above do not operate in isolation; rather, they interact dynamically with species-typical capacities for coalitional behavior, moral outrage, and identity fusion. This interaction between universal capacities and individual differences helps explain the uneven distribution of violent extremism across populations. While most humans possess the psychological architecture necessary for intergroup violence, individual variations in personality, neurobiology, and developmental history influence the threshold at which these capacities are expressed as violent action. Some individuals require extreme provocation or intense socialization to cross this threshold, while others may do so more readily due to pre-existing vulnerabilities. Understanding this interplay is essential for developing comprehensive explanations of violent extremism and designing effective prevention and intervention strategies. The next section will integrate these two levels of analysis into a coherent explanatory framework that accounts for both the universality and the unevenness of violent extremism.
Toward an integrated framework
The two perspectives outlined above—species-typical mechanisms and individual catalysts—are often discussed in isolation. Yet, a full explanation of violent extremism requires their integration. This section unites the two perspectives in a comprehensive dynamic framework, demonstrating how they interact to produce the patterns of political violence observed across contexts.
This framework proposes that acts of political violence emerge when universal predispositions are activated (such as—but not limited to—threat perception, group loyalty, sacred values) and individual thresholds for violent action are low. These two levels are not mutually exclusive but interact dynamically in at least two important ways.
Individual differences can moderate the impact of universal mechanisms
For example, individuals with high trait aggression or low impulse control may be more responsive to coalitional threats, converting these perceptions into violent action more readily than others (Chester & DeWall, Reference Chester, DeWall, Vazsonyi, Flannery and DeLisi2018). Similarly, individuals with strong identity fusion may be more susceptible to appeals based on group loyalty and sacred values, increasing their willingness to engage in costly pro-group behavior (Swann et al., Reference Swann, Gómez, Huici, Morales and Hixon2012). These individual differences do not create the capacity for violence but rather lower the threshold at which universal mechanisms translate into violent action.
Universal mechanisms can amplify or attenuate individual predispositions
For instance, strong group identification can override individual inhibitions against violence through processes such as diffusion of responsibility, deindividuation, and moral disengagement (Bandura, Reference Bandura2016). Conversely, positive group norms and leadership can channel individual aggressive tendencies toward constructive rather than destructive ends (Atran, Reference Atran2016). This bidirectional relationship helps explain why individual risk factors for violence are not deterministic but context-dependent.
The interplay of these dynamics can be seen in empirical research on ISIS foreign fighters, which dramatically underscores how broad psychological appeals combined with personal susceptibilities drive recruitment. Many ISIS recruits from Western nations seem to have been motivated by a desire for moral purpose, identity, and group belonging—universal psychological needs that ISIS explicitly targeted in its propaganda (Coolsaet, Reference Coolsaet2016; Kruglanski et al., Reference Kruglanski, Bélanger and Gunaratna2019; Speckhard et al., Reference Speckhard, Shajkovci and Yayla2017a, Reference Speckhard, Shajkovci and Yayla2017b). The organization portrayed itself as both spiritual community and revolutionary vanguard, offering recruits not only a sense of mission but also a path to significance, consistent with QSM models. Through this narrative, ISIS activated human psychological mechanisms such as identity fusion and sacralization of group values. As Atran et al. (Reference Atran, Sheikh and Gómez2014) and Gómez et al. (Reference Gómez, López-Rodríguez, Sheikh, Ginges, Wilson, Waziri, Vázquez, Davis and Atran2017) demonstrate, personal and group identities merged in a process of fusion that was central to many fighters’ willingness to undertake extreme sacrifices on behalf of the group. Sacred values, understood as moral convictions that resist trade-offs, were also activated: Pretus et al. (Reference Pretus, Hamid, Sheikh, Ginges, Tobeña, Davis, Vilarroya and Atran2018) show that ISIS sympathizers who endorsed sacred values exhibited distinct neural and behavioral responses, including an increased willingness to fight and die for their cause. Together, these mechanisms helped create a powerful sense of solidarity and devotion among recruits, transforming alienated individuals into devoted actors—those who prioritize group values over material costs or survival (Atran, Reference Atran2016). That ISIS was able to attract thousands of foreign fighters from diverse cultural backgrounds points to the cross-cultural resonance of these underlying psychological appeals.
Crucially, however, not all who were exposed to ISIS’s message or grievances actually joined its ranks. The selective nature of recruitment highlights the role of individual vulnerabilities in turning ideology into action. Those who did become foreign fighters frequently exhibited specific risk factors that made them more susceptible to violent mobilization. Many had turbulent or fractured life histories—for instance, experiencing childhood trauma, war-zone displacement, or personal loss—leaving them hungry for identity and revenge. Others showed patterns of thrill-seeking and impulsivity, evident in prior criminal behavior or trouble with authorities, which made the militant adventure of jihad appealing as an outlet (Kruglanski et al., Reference Kruglanski, Bélanger and Gunaratna2019; Vergani et al., Reference Vergani, Iqbal, Ilbahar and Barton2020). Demographic studies have noted an overrepresentation of young males (including second-generation immigrants or recent converts) among Western ISIS recruits, a group prone to identity crises and feelings of marginalization in their societies. Such personal instabilities created a psychological opening for ISIS’s universal appeals to take root. In line with broader radicalization research, many foreign fighters embody a convergence of push factors (like grievance, trauma, or social alienation) and pull factors (like ideological purpose, adventure, and camaraderie). A systematic review of violent extremism found that individual-level traits—from mental health issues to personality profiles marked by impulsiveness and sensation-seeking—distinguish those who radicalize behaviorally from peers who, despite sharing the same propaganda or grievances, do not turn to violence (Wolfowicz et al., Reference Wolfowicz, Litmanovitz, Weisburd and Hasisi2021).
This interplay between universal motives and individual vulnerabilities in the ISIS case illustrates the explanatory power of an integrated framework. ISIS’s narrative of sacred cause and belonging held broad appeal across dozens of countries, but actual enlistment was largely limited to those with the requisite personal susceptibility to embrace violent extremism. Notably, similar dynamics appear in other contexts of political violence: for example, researchers find that many Chechen and Boko Haram volunteers were driven by collective grievances or ideology while only those undergoing acute personal turmoil or social dislocation actually took up arms (Speckhard & Akhmedova, Reference Speckhard and Akhmedova2006; Vergani et al., Reference Vergani, Iqbal, Ilbahar and Barton2020). By accounting for both the cross-cultural pull of compelling group narratives and the personal risk factors that govern who responds to those narratives, we gain a more nuanced understanding of why only a subset of individuals progress from sympathizing with extremist causes to actively participating in violence. The case of ISIS foreign fighters thus reinforces the importance of integrating universal psychological mechanisms (e.g., significance-seeking, identity fusion, and in-group solidarity) with individual-level vulnerability factors in explaining involvement in political violence.
Research on right-wing extremism in Europe and North America reveals similar patterns. Blee (Reference Blee2002) found that white supremacist movements appeal to universal motives such as identity protection, status concerns, and moral outrage. However, those who join such movements often display individual risk factors such as childhood trauma, substance abuse, or sensation-seeking tendencies (Simi et al., Reference Simi, Sporer and Bubolz2016). The combination of universal mechanisms (activated by perceived demographic threats or status anxiety) and individual vulnerabilities (shaped by developmental experiences and personality traits) produces the observed patterns of radicalization and violence.
Left-wing militant groups provide another instructive case. Looking at cases of terrorism in Italy and Germany, della Porta’s (Reference della Porta2013) shows how universal mechanisms of moral outrage, group solidarity, and ideological commitment drive radicalization. While individual factors such as biographical availability, personal connections to movement members, and specific personality traits helped to influence who crossed the threshold into clandestine violence, the interaction between structural conditions (state repression, political exclusion), universal psychological mechanisms (moral outrage, group loyalty), and individual differences (risk tolerance, social networks) ultimately shaped trajectories toward violence. A similar pattern emerges in Tezcür’s Reference Tezcür2020 study of Kurdish women’s participation in insurgency, where individual experiences of patriarchal constraint and lack of autonomy intensified the appeal of a collective movement that framed insurgent violence as a morally righteous path to dignity and empowerment. Tezcür effectively demonstrates how personal grievances—rooted in gendered subordination—interacted with a sacralized political narrative, making violence intelligible and even desirable as a form of redemptive agency. In other words, we see further support for the core premise of the integrated framework: political violence emerges from the interplay between universal psychological motives and individual-level catalysts.
These brief examples dynamically illustrate that neither universal mechanisms nor individual differences alone can fully explain patterns of violent extremism. Instead, it is their interaction—along with structural and situational factors—that determines who engages in political violence, when, and how.
Gains for theory and policy
This integrated framework offers several theoretical advantages over single-level explanations of violent extremism. First, it avoids the reductionism of purely individualistic accounts that attribute violence solely to personality traits, psychopathology, or biological factors. Such accounts may help explain why some individuals are more prone to violence than others, but may struggle to explain why violent extremism clusters in particular times and places, or why it often follows predictable patterns across diverse cultural contexts. By incorporating universal mechanisms and structural conditions, the integrated framework provides a more contextually sensitive explanation.
Second, the framework avoids the determinism of purely structural or cultural accounts that treat individuals as passive products of their environment. Such accounts struggle to explain why only some individuals within a given context engage in violence, or why individuals with similar backgrounds often follow different trajectories. By incorporating individual differences, the integrated framework acknowledges human agency and variation while still recognizing the powerful influence of social and structural factors.
Third, the framework bridges the gap between proximate and ultimate explanations of violent behavior. Proximate explanations focus on immediate mechanisms (the “how” of violence), while ultimate explanations address evolutionary functions (the “why” of violence). By integrating species-typical mechanisms (which have evolutionary origins) with individual differences (which reflect developmental and biological variation), the framework provides a more complete causal account that spans multiple levels of analysis.
Finally, the integrated framework helps resolve the apparent contradiction between the banality and exceptionality of evil. From one perspective, the capacity for violence is banal—a universal potential embedded in human psychology. From another perspective, actual violence is exceptional—limited to specific individuals under specific conditions. The integrated framework reconciles these views by showing how universal capacities interact with individual differences to produce the observed patterns of violence: widespread in potential but uneven in expression.
Policy insights
Although there is a strong case for the integration of these the two levels when approaching questions of political violence, there are also compelling implications for policy designed to prevent and counter violent extremism. By recognizing both universal mechanisms and individual catalysts, several insights are yielded for policymakers seeking to develop more targeted and effective interventions. I discuss several of these before concluding with broader implications for the study of violence.
First, prevention efforts should address both levels of the framework. Programs that focus exclusively on individual risk factors without addressing group dynamics, ideological narratives, or structural conditions are likely to be ineffective. Similarly, approaches that target only structural or ideological factors without considering individual vulnerabilities may miss opportunities for targeted intervention. Comprehensive prevention requires a multi-level approach that addresses both universal mechanisms and individual catalysts.
For example, community-level interventions might focus on providing alternative narratives that satisfy universal needs for meaning, identity, and justice without requiring violence (Kruglanski et al., Reference Kruglanski, Gelfand, Bélanger, Sheveland, Hetiarachchi and Gunaratna2014). At the same time, individual-level interventions might target specific vulnerabilities such as impulsivity, trauma, or sensation-seeking through counseling, skills training, or mentorship (Williams et al., Reference Williams, Horgan and Evans2016). The most effective programs would integrate these approaches, addressing both levels simultaneously.
Second, counter-radicalization efforts should recognize the diversity of pathways to violent extremism. The integrated framework suggests that there is no single profile of a violent extremist or universal trajectory toward violence. Instead, radicalization emerges from the interaction between universal mechanisms, individual differences, and contextual factors, producing multiple pathways that vary across individuals and contexts.
This diversity of pathways implies that counter-radicalization programs should be flexible and tailored to specific contexts and individuals rather than applying one-size-fits-all approaches. For instance, interventions targeting individuals primarily motivated by sensation-seeking or status concerns might differ from those addressing individuals driven by moral outrage or identity fusion (Barrelle, Reference Barrelle2015). Similarly, programs addressing religious extremism might differ from those targeting ethnonationalist or ideological violence, reflecting different configurations of universal mechanisms and individual catalysts.
Third, policymakers should avoid pathologizing or stigmatizing individuals based on demographic or psychological characteristics alone. The integrated framework emphasizes that violent extremism emerges from the interaction between universal human capacities and individual differences, not from inherent pathology or categorical difference. Prevention efforts that target entire communities based on demographic characteristics or that treat radicalization as a form of mental illness may be both ineffective and counterproductive, potentially increasing grievances and reinforcing extremist narratives.
Instead, prevention efforts should focus on specific risk factors and behaviors while respecting individual dignity and community autonomy. For example, programs might target impulsivity or poor emotion regulation—traits associated with violent behavior across contexts—rather than religious beliefs or cultural practices that may be conflated with extremism (Weine et al., Reference Weine, Eisenman, Kinsler, Glik and Polutnik2017). This approach reduces stigmatization while still addressing genuine risk factors.
Fourth, policymakers should recognize the importance of providing alternative pathways to significance, identity, and moral purpose. The integrated framework suggests that many individuals are drawn to violent extremism not because of inherent violent tendencies but because extremist groups offer compelling narratives that satisfy universal psychological needs. By providing alternative means of fulfilling these needs—through civic engagement, positive social identity, or constructive activism—prevention efforts can reduce the appeal of violent extremism without suppressing legitimate grievances or aspirations.
For example, programs might create opportunities for meaningful civic participation, foster positive group identities based on shared values rather than opposition to outgroups, or channel moral outrage toward constructive activism rather than destructive violence (Kruglanski et al., Reference Kruglanski, Bélanger and Gunaratna2019). These approaches address the universal mechanisms that underlie radicalization while providing healthier outlets for individual needs and motivations.
Finally, policy approaches should balance security concerns with respect for civil liberties and democratic values. The integrated framework suggests that repressive measures that increase grievances, restrict legitimate political expression, or violate community rights may inadvertently strengthen the universal mechanisms that drive radicalization, such as moral outrage, group solidarity, and perceptions of injustice. Effective prevention requires addressing legitimate grievances and ensuring that counter-extremism efforts do not undermine the very values they aim to protect.
This balanced approach might include ensuring procedural justice in counter-terrorism operations, protecting civil liberties while targeting specific violent behaviors and addressing structural conditions, such as discrimination or political exclusion, that fuel extremist narratives (LaFree & Dugan, Reference LaFree, Dugan and Deflem2004). Indeed, research in moral psychology shows that many people perceive violence as virtuous or morally justified when it protects the ingroup or upholds sacred values (Slovic et al., Reference Slovic, Vastfjall, Erlandsson and Gregory2022). By combining security measures with efforts to address root causes and protect democratic values, policymakers can develop more sustainable and effective approaches to preventing violent extremism.
Conclusion
Distinguishing clearly between species-typical mechanisms and individual catalysts in order to map their interplay helps explain both the ubiquity and the unevenness of political violence—why the capacity for extremist violence is widespread but its expression is limited to specific individuals under specific conditions. Indeed, individual uniqueness despite human universality is not a puzzle—it is an irreducible starting point.
The first level of this framework focuses on species-typical mechanisms: species-typical psychological systems for coalitional thinking, moralized violence, and ingroup loyalty that are widely shared across the human population. These mechanisms include coalitional psychology, which facilitates the categorization of individuals into “us” versus “them”; sacred values, which render certain beliefs or commitments non-negotiable; and identity fusion, which blurs the boundary between personal and group identity. Together, these mechanisms create the psychological foundation for intergroup conflict and sacrificial violence.
The second level focuses on individual catalysts: biologically and psychologically variable traits that predispose some individuals to cross the threshold into violent action. These catalysts include personality traits such as sensation-seeking, impulsivity, and narcissism; neurobiological factors such as variations in prefrontal function and emotional processing; genetic polymorphisms that influence aggression and impulse control; and developmental pathways shaped by early-life experiences and trauma. These individual differences help explain why only some individuals act on the universal potentials described in the first level.
The integrated framework emphasizes that these two levels interact dynamically. Individual differences can moderate the impact of universal mechanisms, making some individuals more responsive to coalitional threats or moral violations. Universal mechanisms can amplify or attenuate individual predispositions, overriding inhibitions against violence through processes such as diffusion of responsibility or moral disengagement. Both levels interact with environmental and situational factors, creating complex pathways to violent extremism that vary across individuals and contexts.
By embracing an integrative framework over single-level explanations, scholars avoid the reductionism of purely individualistic accounts as well as reject the determinism of purely structural or cultural explanations. Such an approach bridges proximate and ultimate explanations, providing a more complete causal account that spans multiple levels of analysis, and resolves the apparent contradiction between the banality and exceptionality of evil. We are left with complete and dynamic account how universal capacities interact with individual differences to produce patterns of violence that are widespread in potential but uneven in expression.
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