Public debates about terrorism and radicalisation continue to be shaped by emotions and a lack of factual knowledge. In order to overcome this state of affairs, scholars need to adopt a cross-disciplinary perspective to develop useful tools for threat analysis.
Terrorism in Europe
Post-war Europe has experienced multiple terrorist conflicts, from the troubles in Northern Ireland, to Euskadi Ta Azkatasuna’s (ETA) separatist violence in the Basque Country, to the Rote Armee Fraktion’s (RAF) militant campaign in West Germany. While the number of terrorist incidents and victims worldwide has grown since the early 2010s, it has declined  in the European Union since 2014 according to Europol, the EU’s law-enforcement agency.
At the same time, questions surrounding radicalisation have become more prominent in European public discourses in recent years in light of numerous well-publicised attacks carried out by lone actors and small cells in cities across the continent. One hundred thirty-five of the 142 terrorist victims reported by the EU member states  last year were killed in Islamist attacks, making it the deadliest form of terrorism on the continent.
Whether the perpetrators are foreign to, long-term residents in, or citizens of the countries they attack, establishing what leads them to commit such acts remains challenging, as pathways towards radicalisation are complex and highly idiosyncratic. More often than not, neighbours, friends, and family of attackers describe them as ‘friendly’, ‘ordinary’, and ‘normal’.
When Khalid Masood , a 52-year-old Briton, drove a car into pedestrians on Westminster Bridge in the heart of London in March 2017, his radicalisation was attributed to a number of different factors, many of which apply to millions of Europeans: he was brought up by a single mother; dropped out of school at age 16; had a history of committing crimes and using drugs; and converted to Islam late in life.
But why did Masood become so radicalised that he crossed the threshold into violent action when others who have a similar background do not? How can practitioners use their limited resources effectively to identify individuals who are most likely to commit terrorist attacks?
Research on Terrorist Radicalisation: Hedgehog or Fox?
In a famous 1953 essay , the British philosopher Isaiah Berlin theorised that the intellectual world is inhabited by ‘hedgehogs’ and ‘foxes’: those who attribute everything in life to a single organising principle (the hedgehogs) and those who pursue diffused, unrelated, and often-contradictory visions (the foxes).
Noémie Bouhana , an Associate Professor in Security and Crime Science at University College London and an expert on terrorist radicalisation, argues that this classification applies to the field of terrorism scholarship. Bouhana’s message is clear: the study of terrorist radicalisation is still dominated by the scattered world of foxes, and it doesn’t do terrorism risk analysis any good. Instead, she emphasises the usefulness of adopting ideas developed in other areas of the human sciences (still a rare trait among scholars of terrorism).
Herself a political scientist turned criminologist, Bouhana sees radicalisation essentially as a process of socialisation. Regardless of its ideological basis, radicalisation refers to the development of a propensity (rather than a motivation) for violent action as an alternative political tool, even if it contradicts valid social and legal norms. Perpetrators like Masood are often perceived as ‘normal’ because the factors that shape their path towards radicalisation—relationships with family and friends, cultural and religious values, personal grievances and traumas—are no different from those that shape human socialisation in general.
While scholars agree that there is no single root cause of terrorism, many still proceed from the assumption that radicalisation is best conceptualised as a ‘kaleidoscope of factors’  with ‘infinite individual combinations’ as the EU’s Radicalisation Awareness Network (RAN)  puts it. But if each path towards radicalisation is unique, how can practitioners assess an individual’s readiness to resort to political violence correctly and prevent future attacks?
A Cross-Ideological Model of Radicalisation
Bouhana’s response to this question is the following: if we are to develop useful threat analyses, we need to become hedgehogs and look at the meta-mechanisms of radicalisation rather than foxes who look at the specific manifestations of an endless list of factors that can never be exhaustive. Drawing on evidence from a 3-year EU-funded study of lone-actor terrorists, she argues that three mechanisms matter for risk analysis:
- an individual’s susceptibility to moral change and contact with radicalisation settings;
- his or her uninterrupted cognitive and emotional exposure to terrorism-supportive teachings in such settings; and
- the emergence of radicalised settings in places shaped by specific forms and levels of social cohesion and trust.
Indeed, these are the dynamics that are at stake when we speak of the banlieues in France or the ‘backyard mosques’ in Germany as potential spaces of radicalisation and social media networks as a tool for promoting terrorist violence. Low levels of cohesion in the broader society—a lack of resources, mobility, and opportunity for participation of particular demographic groups—can lead to feelings of frustration, exclusion, and helplessness that make individuals more susceptible to alternative sources of stability and sense-making, including teachings that reject the social and legal norms of the society they live in. Migrant communities are particularly vulnerable to these dynamics as a consequence of their generally lower socioeconomic status compared to the recipient community. Successful terrorist attacks such as the lorry attack in Berlin in December 2016 or the suicide bombing at Ariana Grande’s Manchester concert in May 2017, in turn, negatively affect levels of social cohesion by provoking further backlash against the social group that the perpetrator is believed to represent.
The Future of Terrorism Research: Becoming Hedgehogs
Forty years after the terrorism-studies field began to emerge out of criminology, research into the processes of radicalisation has stagnated. To overcome this stagnation, scholars should return to the criminological roots of studying terrorism as a specific form of violent deviance and develop a willingness to cross disciplinary boundaries. A trans-ideological and -socio-geographical approach to terrorist radicalisation is important not only to police work, but also to tackling the biggest challenge connected to terrorist radicalisation: providing equal life chances and opportunities in multicultural, multi-ethnic, and multi-faith societies.
Josefin Graef is a Research Assistant at the University of Birmingham with an interest in violence, crime, diversity and cohesion. She is also a co-convener of the PSA German Politics Specialist Group.