By Keiran Hardy

Researchers in terrorism studies frequently ask questions about radicalisation – what is it, how does it happen, who is most susceptible, and how it can be reversed. Generally speaking, radicalisation is a process in which an individual internalises an extremist ideology and moves towards violent action. Beyond this broad consensus, there is ongoing confusion as to the ‘end-point’ of the process (Neumann, 2013) and when it has sufficiently reversed to consider a program or intervention successful. This creates obstacles to effective programs and policy.

Cognitive vs behavioural radicalisation

On one view, a person radicalises when they adopt and believe in extremist ideas; on another, they only radicalise when they act on those beliefs. This distinction between cognitive and behavioural radicalisation is the ‘principal conceptual fault line’ in the field (Neumann, 2013).

There is no necessary connection between cognitive and behavioural radicalisation – someone can be a ‘cognitive extremist’ without necessarily being a behavioural one, and vice versa (Guhl, 2018). Influential radicalisation models describe stairways, pathways or conveyor belts to terrorism (Mogghadam, 2005; Silber & Bhatt, 2007), but these can be misleading as there is no necessary progression from the first stage to the last.

Controversial groups like Hizb-ut-Tahrir have many extreme views but do not engage in terrorism, and polling has shown that up to 100 million people worldwide sympathise with the aspirations of terrorist groups (Borum, 2011). The vast majority of those people will never go on to commit an act of violence. Conversely, many behavioural terrorists do not display strong evidence of cognitive radicalisation. Many young recruits to Islamic State were driven primarily by an underdeveloped sense of identity, resulting in a violent ‘quest for significance’, with only a rudimentary understanding of terrorist ideology (Silverman, 2017).

Deradicalisation vs disengagement

Debates between deradicalisation and disengagement have also taken ‘centre stage within the literature’ (Weeks, 2018). These terms refer to when the radicalisation process has sufficiently reversed to consider a program or intervention successful. For example, a growing number of empirical studies examine the effectiveness of prison rehabilitation programs for terrorist offenders (Cherney, 2018). These can be designed to achieve either disengagement or deradicalisation.

Deradicalisation typically means a complete reversal of the radicalisation process, to the point where the person no longer believes in an extremist worldview. By contrast, disengagement refers to the point at which they stop acting on their beliefs. As Schuurman and Bakker (2016) explain, ‘[w]hereas disengagement is primarily a process of behavioral change, deradicalization seeks cognitive adaptations’. In other words, like there is cognitive and behavioural radicalisation, there is cognitive and behavioural deradicalisation – with behavioural deradicalisation typically called disengagement.

In criminology, disengagement is usually called desistance: when someone ceases their involvement in criminal behaviour. However, terrorism researchers have been reluctant to use that term because terrorists typically desist for reasons that are different to other offenders (Horgan, 2014b). As many terrorism researchers come from a political science background, fewer criminological concepts are used to understand the behaviour, even though there can be significant overlap in the ideas and approach.

As with cognitive and behavioural radicalisation, the relationship between deradicalisation and disengagement is thought to be relatively independent. At least, disengagement is possible without deradicalisation and is not a necessary precursor to it (Schmid, 2013). However, there remains an ‘imperfect understanding’ of both these processes (Schuurman & Bakker, 2016). Each has ‘unique underlying mechanisms’ in need of further study (Windisch et al, 2016).


There are different ways to define when someone has radicalises and deradicalises. The resulting confusion represents a major obstacle to terrorism research and practice. As Horgan (2014a) has written, ‘[t]hat we do not know precisely what we are preventing … does not make for a bright future’. In particular, it makes program evaluation difficult, as it is not clear how to measure success in preventing extremism and radicalisation.

Favouring different definitions also leads to ‘strikingly different policy approaches’ (Neumann, 2013). One country’s programs can focus on countering the ideological threat of extremism, while others target violent and criminal behaviour (Hardy, 2018). This may undermine multilateral efforts to combat terrorism as a threat to global security.

The way forward for terrorism researchers is not necessarily to agree on any single definition of radicalisation or deradicalisation. Cognitive and behavioural approaches can both be studied empirically to inform valuable research. However, the terms should at least be used consistently, and researchers should be clear as which definition they use to frame their analysis and evaluations. In addition, studies into radicalisation and deradicalisation should further interrogate the relationship between the cognitive and behavioural aspects of these processes.


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Borum, R. (2011). Radicalization into violent extremism I: A review of social science theories. Journal of Strategic Security, 4(4), 7-36.

Cherney, A. (2018). The release and community supervision of radicalised offenders: Issues and challenges that can influence reintegration. Terrorism and Political Violence, DOI: 10.1080/09546553.2018.1530661.

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Hardy, K. (2018). Comparing theories of radicalisation with countering violent extremism policy. Journal for Deradicalization, 15, 76-110.

Horgan, J. (2014a). Countering violent extremism as a field of practice. United States Institute of Peace Insights, 1, 2-3.

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Schmid, A.P. (2013). Radicalisation, de-radicalisation, counter-radicalisation: A conceptual discussion and literature review. The Hague: International Centre for Counter-Terrorism.

Schuurman, B., & Baker, E. (2016). Reintegrating jihadist extremists: evaluating a Dutch initiative, 2013-2014. Behavioral Sciences of Terrorism and Political Aggression, 8(1), 66-85.

Silber, M., & Bhatt, A. (2007). Radicalization in the West: The homegrown threat. New York: New York City Police Department.

Silverman, T. (2017). U.K. foreign fighters to Syria and Iraq: The need for a real community engagement approach. Studies in Conflict & Terrorism, 40(12), 1091-1107.

Weeks, D. (2018). Doing derad: An analysis of the UK system. Studies in Conflict & Terrorism, 41(7), 523-540.

Windisch, S., Simi, P., Ligon, G.S., & McNeel, H. (2016). Disengagement from ideologically-based and violent organizations. Journal for Deradicalization, 9, 1-38.