The state of scientific knowledge regarding factors associated with terrorism.

Abstract

We conducted a systematic review of the contemporary scientific literature to (a) identify consensus, where it exists, regarding factors associated with membership in terrorist organizations and/or perpetration of terrorist attacks; (b) drive future research directions; and (c) inform evidence-based counterterrorism strategies. Systematic searches of 6 databases identified 205 articles that met inclusion criteria. Of these, 50 articles reported on findings of empirical research, 24 reported inferential statistics, and 6 of these compared characteristics of known terrorists to nonterrorists. Across various aspects of terrorism and terrorists (e.g., type of terrorist, attack type), articles rarely specified their focus. When examined factors typically focused on characteristics of the individual. Review of the empirical findings suggest 9 variables with at least some support for their association with terrorism: age, socioeconomic status, prior arrest, education, employment, relationship status, having a grievance, geographic locale, and type of geographic area. However, given the limitations of the research, there is insufficient evidence to conclude that any of these variables are empirically supported risk factors. Findings identified additional characteristics of an individual (i.e., country of birth, Islamic faith, military experience, foreign travel history, family or friend in a terrorist or extremist organization) and their environment (i.e., income inequality, media and government influences) that merit further evaluation. Findings also emphasized the importance of a triggering event. Finally, findings indicate that some widely accepted "risk" factors have limited empirical support for their association with terrorism. A focus on these factors might contribute to discrimination and reduce the effectiveness of counterterrorism strategies.

Visualizing the relationship among indicators for lone actor terrorist attacks: Multidimensional scaling and the TRAP‐18

“…Likewise, uncontrolled descriptive studies of terrorists have yielded to comparative studies, such as ideologically motivated versus non-ideological mass murderers (Horgan, Gill, Bouhana, Silver, & Corner, 2016); individual terrorists versus autonomous cells in Europe (Meloy, Roshdi, et al, 2015); jihadist versus single-issue versus right wing terrorists (Gill, Horgan, & Deckert, 2013); terrorists versus murderers in Iraq (Dhumad, Candilis, Cleary, Dyer, & Khalifa, 2019); and violent versus non-violent extremists in the UK (Knight, Woodward, & Lancaster, 2017). These efforts have all contributed to the disaggregation of the meaning of "terrorist" and "terrorism" (Desmarais, Simons-Rudolph, Brugh, Schilling, & Hoggan, 2017) and the recognition that differences in static (e.g., age, education, history of criminality) and dynamic (e.g., roles, pre-offense behaviors) characteristics yield more operationally relevant data (Borum, 2015) and help to bridge the gap between academia and pragmatic efforts at prevention.…”

The Base Rate Study: Developing Base Rates for Risk Factors and Indicators for Engagement in Violent Extremism

“…Risk factors for violent extremism can serve as markers to inform the detection and disruption of terrorist threats. A systematic review showed that age, socioeconomic status, prior arrest, education, employment, relationship status, having a grievance, geographic locale, and type of geographic area, are factors associated with violent extremism . Other systematic reviews, rapid evidence assessments, and research syntheses report similarly .…”

“…Empiricism in terrorism studies is increasing . One systematic review of factors associated with violent extremism found 50 empirical articles . Studies typically cover areas concerning socio‐demographic characteristics, criminal history, religion and spirituality, work and education, personal experiences, attitudes and beliefs, relationships, mental health, motivation, radicalizing processes, and environmental factors .…”

“…Control group studies are rare in violent extremist research. Desmarais et al’s systematic review found just six. Generalizing results from research designs lacking adequate control or comparison groups likely overpredict violent extremism.…”

How can the literature inform counter-terrorism practice? Recent advances and remaining challenges

“…More recently, others have also noted the need for more empirical research in this area, for primary sources of data to be used and for the gap between academic research and counterterrorism intelligence (in terms of data sharing and the skills needed to make sense of this) to be narrowed (e.g. Borum, 2012;Desmarais, Simons-Rudolph, Brugh, Schilling, & Hoggan, 2017;Ranstorp, 2007;Schmid, 2016;Schuurman, 2018). This longstanding self-reflection by those seeking to understand terrorism demonstrates that researchers are not ignorant to the limitations associated with this field of study, and that serious attempts to address these have been made.…”