To discern trends in violent extremism research, we present a machine-learning analysis of over 34,000 articles published since the early 1900s. We identify two primary waves of research and, different to previous reviews, a clear diversification in studied groups, contexts, and topics. Less than 20% of articles employ methodologies that are conducive to drawing causal inferences. While more studies are using experimental and longitudinal methods, this increase is outpaced by the rise of methods that preclude the assessment of causality. Nuancing previous reviews, at the broader field level, violent extremism research is profoundly multidisciplinary, with political science, international relations, psychology, history, and law emerging as the “Big Five” contributors. At the study level, contributions from single disciplines remain the norm. While single-author contributions have rapidly declined in favor of team-based research, one-time contributing authors remain consistently high over time. To enhance future violent extremism research, we make five recommendations: (1) prioritizing methodologies that allow for causal inferences; (2) incorporating state-based violent extremism perspectives also in individual-level research; (3) increasing the utilization of big data by interdisciplinary teams; (4) increasing the focus on developmental research to understand early life influences; and (5) initiating more interdisciplinary work at the study level.

The global resurgence of violent extremism punctuated by recent acts of politically motivated violence necessitates a detailed examination of the factors that contribute to the radicalization process. Here, we argue that relative deprivation, or the perception that one’s in-group is unfairly deprived of material or symbolic goods relative to other groups, often elicits support for violent extremism. Because relative deprivation theory emphasizes perceived, rather than actual, experiences of injustice, the concept helps explain why members of both structurally disadvantaged and advantaged groups sometimes turn to violent extremism – especially when they believe that their in-group cannot redress their perceived grievances through normative mechanisms (i.e., when group efficacy is low). After demonstrating that relative deprivation can foster support for extremist violence and introducing an integrative model of group-based relative deprivation and violent extremism, we propose solutions to the growing threat of radicalization including the need to (a) reduce inequality, (b) develop productive ways for the disenfranchised to establish meaning in their life, (c) foster belongingness, and (d) build inclusive democracies that provide legal means to redress real or perceived grievances. By taking such proactive measures, practitioners and policymakers can mitigate the threat of violent extremism and make the world a safer place.

This chapter examines how emotions contribute to the development of violent extremism, drawing on research into emotional drivers of violent intergroup behavior. We first introduce the concept of emotion and explain the role of cognitive appraisals of events in shaping emotions. Then, to position emotions within the context of hostile intergroup relations, we demonstrate how social identities and group processes impact emotional experience. In the main section of this chapter, we consider the roles of several discrete emotions that motivate distinct types of behaviors relevant to violent extremism. Using a broad framework of the radicalization process, we suggest that: (1) humiliation, shame, and anger in response to self- or group-relevant experiences are pertinent pre-radicalization as they create a desire to reestablish a positive self- or group-image and to restore a sense of justice; (2) contempt, disgust, and hatred, as emotions that exclude their targets from moral consideration and motivate their eradication, develop during active radicalization; and (3) positive emotions, such as love, joy, and pride, which increase commitment and motivate others, characterize the engagement stage. We draw out implications of our analysis for policymakers, stressing the importance of responding to the unfulfilled emotional needs that motivate violent extremism.

Historical records and recent events suggest that conspiracy theories and violent extremism are closely associated. However, empirical research examining this link has only recently gained momentum. The present chapter provides an overview of this fast-growing research field. We first discuss theoretical explanations of the link between conspiracy theories and violent extremism, as well as the hypothetical mechanisms underpinning it. Next, we summarize the empirical evidence so far along three main research lines: (a) evidence from radicalized groups and individuals; (b) evidence from general population studies focusing on support for, and intentions to engage in, violent extremism; (c) evidence from the general population focusing on extreme political attitudes. We conclude by formulating recommendations for policy and practice.

Previous research has underscored the significance of intergroup threat perceptions in fostering prejudice and hostility toward out-groups. Nevertheless, the degree to which different types of threats – symbolic, realistic, numerical, existential, and meta-threat – remains insufficiently explored. This chapter provides a theoretically informed review of the role of these diverse threat types and synthesizes recent empirical studies demonstrating that perceptions of threat can precipitate extreme forms of out-group hostility, including violent extremism. The evidence suggests that threat perceptions not only incite violent hostility across various cultural contexts but also provoke violent defensive reactions among both majority and minority groups aiming to protect their valued traditions, scarce resources, and societal status and to avoid the perceived dread of extinction. We further discuss how cultural narratives, media portrayals, and political rhetoric shape these threat perceptions, which may fuel the process of radicalization and lead to a spiral into violent extremism. Our objective is to present a detailed analysis that can lay the groundwork for devising strategies to alleviate perceived threats leading to violent extremism. Accordingly, we propose prevention and intervention strategies designed to diminish perceived threats and curtail their violent ramifications.

This chapter examines the effects that international military interventions and foreign military occupations have on violent extremism with a particular focus on how interventions and occupations foster psychological processes associated with radicalization and patterns of political violence. The chapter begins by providing definitions for the key terms and then surveys the main strands of literature on how international interventions and foreign occupations may provoke violent extremist responses. In particular, the chapter discusses evidence that military interventions and occupations enhance grievances and feelings of national humiliation among affected populations, prompting them to support political violence. International military interventions and occupations can also foster violent extremism by facilitating othering of foreigners, by worsening human rights standards, and by producing a strategic environment conducive to political violence. The chapter also examines how interventions and occupations may foster vicarious radicalization outside of the intervened-in or occupied country, thereby increasing the threat of political violence globally. The discussion of the literature is expanded to acknowledge that certain studies in the literature depict a relationship of greater complexity or nuance. It discusses some key limitations in the literature on international military interventions, foreign occupations, and violent extremism. Finally, it concludes with implications for scholars and practitioners.

Moral beliefs are often proposed as causes of violent extremism, specifically, and political violence more generally. Yet, few empirical studies focus on the general causal links between morality and violent extremism. We review several strands of scholarship that bear directly or indirectly on the morality-extremism link. Several general psychological frameworks that cover morality can be applied to explain extremism, notably the Moral Foundations Theory, the Theory of Honour Culture, moral universalism, and theories of moral dilemmas (the Trolley problem literature). Other approaches, such as Virtuous Violence and Sacred Values Theory, provide more direct morality-based explanations for extremism. Our main contention is that the causal link between moral beliefs and violent extremism remains woefully unexplored and that this presents a sharp contrast with the central role that extremist movements often attribute to moral narratives in their justifications for violence. We highlight the need to incorporate morality-based appeals (linked to the reviewed frameworks) in studies of interventions to combat violent extremism and that policymakers should recognize the potentially significant role of moral beliefs as a driver of extremism.

This chapter characterizes violent extremism as an ideology, and associated communication-based or overt behavior, that protects, promotes, advances, and defines a group’s social identity, and is implicitly or actually violent. It presents a social identity theory and, primarily, an uncertainty-identity theory account of how normal social identity-based group and intergroup behaviors can become violently extreme. Social identity processes are driven by people’s motivation to (a) secure a favorable sense of self though belonging to high status groups, and (b) reduce uncertainty about themselves and who they are through identification with distinctive groups with unambiguously defined identities. In the former case, people strive to protect or improve their group’s status relative to other groups, and when moderate nonviolent strategies are continuously thwarted, they can reconfigure their group’s identity to incorporate and promote violent extremism. In the latter case, people strive to resolve feelings of self-uncertainty by identifying with distinctive groups, and when intergroup distinctiveness is blurred and their group’s social identity becomes fuzzy they are attracted to ethnocentrism, populist ideology, autocratic leaders, and ultimately violent extremism. The chapter ends by identifying warning signs of radicalization and intervention principles.

We offer an integration of temporal approaches to the psychology of violent extremism. Focusing on the role of remembering, we draw attention to how memories and perceptions of the past motivate the use of violence in the present. Reminiscing about a glorious past elicits nostalgia, which, in turn, may increase present-day feelings of relative deprivation, collective angst, and threat. Furthermore, remembering historical perpetrators instills threat perceptions and negative intergroup emotions, whereas remembering past victimization elicits moral entitlement, thereby justifying more extreme means. We explore how different imaginings of the future – for the self and community – function as a double-edged sword either fueling or preventing radicalization in the present. Imagining can stimulate utopian or dystopian visions, which, in turn, may encourage mobilization of more extreme means by instilling a sense of legitimacy and hope in terms of utopias and moral obligation and urgency to prevent dystopias. However, imagining can also elicit a realistic, positive future outlook for the self and wider community, functioning as a protective shield against radicalization into violent extremism instead. We conclude by providing primary, secondary, and tertiary prevention recommendations based on our temporal approach aimed at policymakers and key stakeholders and avenues for future research.

This chapter examines the complex relationship between religious fundamentalism and violent extremism, focusing on the socio-cognitive processes involved in radicalization. In the central part of our analysis, we explore how religious fundamentalism may contribute to violent extremism. Our investigation reveals that the relationship between these two variables is mediated by some group-related factors and ideologies (e.g., out-group hostility, perceived superiority, collective narcissism, ideological extremism, and extremist networks). Importantly, religious fundamentalism does not always lead to violent extremism; it is moderated by some situational and contextual factors (e.g., perceived injustice, perception of threat, and group tightness). We then discuss the implications of these findings for counter-violent extremism programs. We argue for a comprehensive approach, advocating for integrated interventions that combine ideological, psychological, and economic strategies. This assertion stems from the recognition that the drivers of violent extremism extend beyond religious narratives to include psychological factors and subjective and economic deprivation. As such, we caution against an approach that disregard nonideological aspects, as it may weaken the effectiveness of interventions.

The role of poverty in violent extremism is best explained by moving away from reductionism and adopting a “from societies to cells” perspective. We explain terrorism, an important kind of violent extremism, by using the metaphor of a staircase to terrorism, which proposes the conditions in which there is an increased probability of individuals moving up the staircase, and eventually participating in terrorist actions on the final floor. Each floor of the staircase is characterized by particular psychological processes, but common to all these experiences is the primacy of subjectivity. While actual material conditions do not explain individual propensities to climb up the staircase to terrorism, feelings of relative deprivation and injustice increase the probability of this action. Although social class and poverty do not explain individuals moving up the staircase, they do influence the location of terrorist specializations on different levels of the staircase. Terrorist specializations have been ignored, but they are of vital practical importance. Nine different terrorist specializations are identified, and a schematic representation is presented, locating the specializations on the staircase to terrorism. Implications for policymakers and practitioners are discussed.

The current chapter focuses on the relationships of stable, nonpathological individual differences to violent extremism. Traditionally, strong contextual forces have been viewed as overriding personal traits in determining group behavior generally and violent extremism specifically. This chapter challenges such conventional wisdom by emphasizing the role of individual differences. We argue and provide evidence that supports and highlights the interplay and complementary roles of individual psychology and social environments in shaping violent extremism. We review recent research exploring the relationship between violent extremism and individual psychological variables such as mental disorders, cognitive styles, motivational imbalances, group identity needs, ideological orientations, sensation-seeking behaviors, and group-based emotions, as well as the Big Five and HEXACO models of personality. We further discuss common criticisms against individual differences in approaches to violent extremism. Here, we distinguish between historical disputes, often based on researchers speaking past each other, and challenges in contemporary individual difference research. Having highlighted the significance of individual differences in violent extremism, we focus on how these insights can aid practitioners and shape policies that counteract violent extremism.

In this chapter, we discuss the psychological foundations of violent extremism. We consider violent extremism as a specific form of extreme behavior resulting from a radicalization process that involves inflicting a high-severity aggression or violence against people or properties as a means to achieve a political, ideological, or religious goal. Throughout our discussion, we focus on the role of the need for significance (Kruglanski et al., 2022) as a core psychological driver that prompts violent extremism. We review those factors that activate the need for significance, propelling individuals toward violent extremism. Specifically, we posit that when the quest for significance is activated, whether by personal or group-level experiences of significance loss or opportunities for gain, individuals seek avenues to fulfill this need through extreme actions that demonstrate their allegiance to socially esteemed values. In such scenarios, violent extremism emerges as a viable outlet, especially when bolstered by a narrative that promotes it and a supportive social network that endorses the narrative, offering validation and significance to individuals who express their commitment through their actions. Finally, we outline how the theoretical framework centered on the need for significance can inform the development and implementation of deradicalization programs by practitioners.

One of the rapidly emerging consequences of the climate crisis is the increase in frequency and severity of climate catalyst events, such as hurricanes, tsunamis, droughts, and wildfires. Experts increasingly recognize that these developments are likely to precipitate violent extremism; however, a comprehensive overview of this nexus remains absent to date. Against this background, this chapter presents an in-depth framework for analyzing the intersection between climatic catalyst events and violent extremism from a psychological standpoint. Initially, it explores the manner in which the climate crisis exacerbates risk factors linked to violent extremism on a global scale. These factors include heightening feelings of insignificance, diminishing opportunity costs, triggering mass migration and displacement, and provoking defensive responses in conjunction with the rise of ecofascism. Next, the chapter iterates upon the Climate Change and Violence Model, demonstrating how catalyst events can create a cyclical feedback loop of increasing violence and violence-risk factors. To illustrate the role of the psychological processes and risk factors, the chapter discusses two case studies in which climate shock events contributed to violence and extremism. Finally, potential policy solutions focused on preventing the occurrence of climate-related events and their subsequent escalation into violent extremism are proposed.

Terrorism, radicalization, and (violent) extremism are all contested concepts, referring to specific political labels, ideologies, and related actions. The oldest of the three is “terrorism,” which, as a term, has been around since the late eighteenth century. “Radicalization” is derived from “radicalism” which has its roots in the progressive programs of nineteenth-century political parties that fought, inter alia, for secularism and democracy. “Extremism” is a term first associated with totalitarian movements emerging in the twentieth century in the wake of the First World War. “Violent extremism” is a construct that surfaced only at the beginning of the twenty-first century, referring initially to Islamist ideologies but became subsequently extended to acts of violence by secular groups, especially those on the far right as well. The three concepts are sometimes used wrongly interchangeably, as quasi equivalents. In this chapter some of their characteristics and relationships are explained. Practical and policy implications on countering (violent) extremism, based on the opposite of extremism – moderation – are outlined at the end.

This chapter considers the overlaps and divergences between cults and terrorist movements. It begins by considering whether terrorism has entered a new era that increasingly overlaps with apocalyptic religious cults. It then takes into account the historical tension between defining groups that engage in extremist violence for ideological purposes as terrorist groups, as cults, or as a combination of the two. Following this, an analysis of the Islamic State of Iraq and Syria provides a vehicle for drawing out the commonalities and dissimilarities between the two concepts. Finally, the chapter concludes by considering any need to differentiate between terrorism and cults when engaging in risk assessment for individuals at risk of violence, along with strategies for intervention.

There is a growing concern about the evolution of violent extremism in the digital era. This chapter presents historical progression and current state of how extremists have used digital advancements to increase their reach and influence for their own nefarious purposes. This chapter also discusses the challenges due to encryption and the need for a strategic collaboration and comprehensive whole-of-society approach to combat the threats effectively.

Extremism of all types arises from a motivational imbalance wherein one need outweighs all other needs. When such a process occurs, more means to achieving the focal goal, including those considered extreme, become available to the individual. Presently, we focus on the need for significance, an existential social need. When the quest for significance is dominant, an individual may be willing to make extreme sacrifices in order to achieve their goal. The quest for significance can be activated through many different means, one of which is the loss of significance through exclusion. When one perceives that they have been excluded, their motivation to regain respect is activated. When this motivation to restore significance comes to suppress one’s other needs, the individual becomes willing to engage in activities they may have previously considered socially unacceptable, including joining extreme groups and participating in violence, in order to fulfill their quest for significance.