The 3 Ps of radicalisation: push, pull and personal. A systematic scoping review of the
scientific evidence about radicalisation into violent extremism
Matteo Vergani* email@example.com – corresponding author
Muhammad Iqbal* firstname.lastname@example.org
Ekin Ilbahar* email@example.com
Greg Barton* firstname.lastname@example.org
* Alfred Deakin Institute for Citizenship and Globalisation, Deakin University, Melbourne
Burwood Campus, 221 Burwood Highway, Burwood, VIC 3125
In this article, we present the findings of the first systematic scoping review of scientific
literature on radicalisation into violent extremism since the al-Qaeda 9/11 attacks in 2001.
We selected and categorised all scholarly, peer-reviewed, English-language articles published
between 2001 and 2015 that empirically investigated the factors of radicalisation into violent
extremism (N = 148). In the analysis we consider two main dependent variables (behavioural
and cognitive radicalisation) and three main independent variables (push, pull and personal
factors). ‘Push’ and ‘pull’ factors of radicalisation emerge as the main factors of
radicalisation across studies focused on different geographical areas and ideologies. This
article points to the need to focus more on personal factors, especially in developing
Radicalisation, violent extremism, literature review, push, pull, personal
The reasons why people participate in violent extremism, and engage with movements
employing the violent methods of terrorism, remain a matter of contention, with scholars
struggling to arrive at a consensus about the basic mechanisms of radicalisation. A substantial
body of research has been published on the issue since the 9/11 attacks in 2001, but only a
small number of systematic reviews of the substantive knowledge on the topic have so far
been attempted in books,1 and research reports. 2 And even then, despite representing
important steps towards the understanding of the field, those reviews generally do not meet
the standards for methodological transparency and replicability. For example, in many
reviews coding occurred with no mention of inter-coder reliability, and the reported findings
tended to be cherry-picked without sufficiently transparent criteria.
Remarkably, given the volume of scholarly articles published, only a handful of
systematic review articles about the factors of radicalisation into violent extremism and
terrorism have been published in scientific journals, where they have undergone a more
formal peer-review process to meet scientific standards. Relevant among these are the
excellent (although technically unsystematic) narrative reviews of specific subfields like
suicide bombing and domestic terrorism, and Borum’s and Victoroff’s reviews of the existing
theories that explain radicalisation into violent extremism.3 To our knowledge, the only
articles that provide a truly systematic quantitative overview of the scientific knowledge
about the causes of terrorism are Campana and Lapointe’s systematic scoping review of the
literature about root causes of non-suicide terrorism, 4 and Jacques and Taylor’s review of the
literature about female terrorism.5 To date, there has been no comprehensive systematic
review of the scientific studies that looked at radicalisation into violent extremism.
One main obstacle to conducting systematic reviews of this issue is the ambiguity of
key terms such as radicalisation and extremism, which by their very nature identify a relative
position on a continuum of opinions and behaviours. Depending on the context, the line that
defines an extremist/radical opinion or behaviour from a moderate/legitimate opinion or
behaviour can be drawn at different points in the continuum. Moreover, structural and
circumstantial factors (such as the agendas of governments and security agencies) influence
the definition of those terms in different circumstances and for different institutions,
potentially creating conflicting classifications. Ultimately, radicalisation and extremism
remain ambiguous and contested concepts and sources of confusion,6 to the point that some
scholars even deny that radicalisation exists.7
At the same time, however, it needs to be remembered that the definitions of virtually
all phenomena of political significance are problematic and contested, including such
fundamental concepts as nationalism, revolution, empire, colonialism.8 Just as it is possible,
and indeed, necessary, to research these issues despite their problematic nature, so too
‘radicalisation’ and ‘extremism’ represent phenomena too important to ignore. And, as this
paper sets out to demonstrate, some significant lines of consensus and important findings
have emerged in the scientific literature of the past decade and a half since the 9/11 attacks
made terrorism a central issue of our times.
As Sedgwick and Neumann noted, common usage of the term radicalisation in the
academic literature emerged following the 9/11 terrorist attacks, but the term became only
widely used after 2005. 9 This period corresponds to what Pape defined as the second wave of
terrorism studies, which has been characterized by more sophisticated methodologies, more
complex theories and more attention to the causes and the consequences of the terrorism.10 At
the same time, the second wave, for all its promise, has also been criticized for having been
unable, as yet, to fully develop as a mature scientific approach.11
This article reviews and consolidates the scientific knowledge produced between 2001
and 2015 regarding radicalisation into violent extremism, and it aims to address very basic
descriptive questions such as: which areas are most under-researched and why? What factors
are universal in predicting radicalisation into violent extremism across ideologies and
geographical contexts? What are the main methodological biases that researchers should be
aware of? This article is intended to be a systematic scoping review,12 in that it addresses a
broad topic (the causes of radicalisation into violent extremism), and a comprehensive range
of publications, including diverse study designs of varying quality and methodological
transparency. This diversity and methodological flexibility poses important challenges to the
achievement of an objective review of the field. This will be discussed at some length in the
methods and limitation sections of this article.
At a time where numerous studies of various quality are published each month, this
review is a valuable exercise to map this field of research. It provides a general picture of the
progress made, the knowledge aggregated and consolidated so far, the main pitfalls and the
Scope and structure of the review
This review study focusses exclusively on the radicalisation into violent extremism, a matter
of immediate concern to states and communities. The definition of radicalisation into violent
extremism generally refers to the path that leads an individual to endorse or commit a
politically motivated act of violence (e.g. terrorism, kidnappings, assassinations, etc.).13
This article distinguishes between two different types of radicalisation into violent
extremism. Specifically, it conceptually separates the studies that focus on behavioural
radicalisation (which focuses on an individual’s engagement in violent action) and cognitive
radicalisation (which focuses on an individual’s adoption and internalisation of violent and
extremist beliefs). The two generally go together but many people behaviourally radicalise
without a correspondingly significant degree of cognitive radicalisation and vice-versa.
We considered a wide range of factors as predictors of radicalisation, which, in order
to make analytical comparisons possible, we grouped in three broad categories: push, pull
and personal factors. ‘Push factors’ overlap with the structural root causes of terrorism that
drive people towards resorting to violence,14 and include, for example, state repression,
relative deprivation, poverty, and injustice (please see the methods section for a more
comprehensive list). ‘Pull factors’ capture the aspects that make extremist groups and
lifestyles appealing to some people, and include, for example, ideology, group belonging,
group mechanisms and other incentives. ‘Personal factors’ include related but more
specifically individual characteristics that make certain individuals more vulnerable than their
circumstantially comparable peers to radicalisation. This includes for example psychological
disorders, personality traits and traumatic life experiences. We acknowledge that certain
psychological disorders (such as depression) can certainly develop in conjunction with, or
even as a result of, the radicalisation process (for example because of the isolation from
primary ties), but the studies that focus on personal factors generally look at those disorders
preceding radicalisation and often in conjunction with other structural and group-level
In reality, push, pull and personal factors are all closely inter-related. Push factors,
which identify contextual and structural conditions, can be often the root cause of both pull
and personal factors. For example, structural conditions (such as poverty) could contribute
substantially to personal conditions (such as depression and low self-esteem) whilst
simultaneously boosting the appeal of pull factors (like material incentives or the need to
belong to a group). Moreover, we acknowledge that radicalisation, for the most part, takes
place in social settings, with “three-fourths of those who join the Islamic State or al-Qaeda”
doing so in groups that “involve pre-existing social networks and typically cluster in
particular towns and neighbourhoods.”15 This means that factors such as the consumption of
propaganda, narratives or political grievances do not operate by themselves but rather have
effect within specific social settings.
Notwithstanding the fact that they rarely occur in isolation, we also see the need to
attempt a clear theoretical distinction between push, pull and personal factors because they
capture different levels of explanation of radicalisation into violent extremism: push factors
largely focus on structural, political and sociological explanations, pull factors tend to focus
on group-level socio-cognitive explanations, and personal factors are concerned primarily
with individual psychological and biographical explanations. Each of those levels is then
associated with a different set of preventative measures and policies, which, in turn, tap into
the political, socio-ideological and psychological-medical spheres. This theoretical distinction
between the three levels of analysis (macro, meso and micro) is used in established
theoretical approaches to analysis in the field of political violence and in cognate fields such
as collective action studies. Examples include Kleinmann’s distinction between individual-
level, group-level and mass-level factors of radicalisation16, and Duncan’s distinction
between perceived injustice, identity and efficacy, and personality and life experiences as
predictors of collective action.17 We think Duncan’s model of collective action is also a
relevant benchmark because radicalisation into violent extremism can been seen as a form of
In April 2016 we searched for the key-words “radicali*ation” (in order to allow both
American and English spelling) or “extremis*” in title, abstract and keywords sections in the
following databases: PsycINFO, PubMed, Sociological Abstracts, Web of Science,
Worldwide Political Science Abstracts, EconLit, Embase, PAIS Index, Scopus. We restricted
the data range from 2001 to 2015, and we searched for articles in English language. After
eliminating the duplicates, we had an initial set of 6,335 items.
The first criterion for including articles in our review was relevance. We included
only the articles that looked at the factors that explain why an actor (either individual or
group) would support or engage in violent extremism. For example, we excluded the articles
that focused on the polarisation of opinions if not explicitly referring to support for violent
ideas,18 as well as mathematical models of opinion and behaviour polarisation. We also
excluded articles that looked at the predictors of voting for extremist parties (i.e. at the
extreme left and right of a country’s political spectrum). This is because even though some
political parties such as, for example, Greece’s Golden Dawn have been associated with
violent militancy, voting and electoral participation belong in the domain of legitimate
activities, and the focus of this review article is exclusively on the illegitimate activity of
politically motivated violence. Moreover, descriptive articles that describe violent extremist
ideas and behaviours without investigating the predictive factors were excluded from the
review.19 In short, we exclusively included the articles that focused on explaining the factors
that predict the dependent variables of interest: cognitive and behavioural radicalisation into
The second criterion was being published in peer-reviewed scientific journals. We
searched exclusively for journal articles that have undergone a formal review process. We
therefore excluded books, book chapters, reports, theses, and other so-called “grey area”
literature. We acknowledge that in doing this we have undoubtedly overlooked relevant work,
but we are also confident that the articles that we have included meet standard criteria of
quality and transparency that is not consistently found in grey area literature.
The third criterion was availability. We excluded articles that were in languages other
than English and that were not publicly accessible from our university library access.
The fourth inclusion criterion was empirical evidence. We included all articles that
presented empirical evidence about the radicalisation factors, including original interviews,
fieldwork, content analysis, original analyses of existing databases and other open source
data. We excluded theoretical articles that were based on literature review and research
published elsewhere.20 We also excluded articles that referred to empirical data from
secondary sources that were collected unsystematically, without consistent transparency with
respect to methodology for data collection and data analysis.21 Nevertheless, some articles
that analysed primary sources (such as YouTube videos published by extremist groups) were
included, even though the methodology of analysis was not completely transparent.22
To ensure that the exclusion/inclusion of the articles was done in a replicable way,
three independent reviewers separately coded 50 articles. The results were then compared and
any disagreements were discussed. We repeated the process until we obtained an agreement
Our independent variables are comprised of three non-exclusive categories: push,
pull, and personal. Push factors include: loss of legitimacy, geopolitical factors, state
repression, relative deprivation, inequality, intergroup contact (e.g. the presence of different
religious or ethnic group in the same space), violence (e.g. high level of violence such as a
war). In our coding, push factors also include variables such as unemployment and education,
because they capture the consequences of structural conditions on the individual.
Pull factors include: cognitive factors (e.g. consumption of propaganda, cultural
congruence, perceived efficacy and morality of a group, search for adventure), social
mechanisms and group processes (e.g. identity fusion and identification, group dynamics,
recruitment and leadership), emotional and material incentives. We coded individual level
variables that refer to ideology and attitudes in this category: for example, the individual’s
consumption of the extremist group’s propaganda was coded as a pull factor.
Personal factors include: individual psychological vulnerabilities independent of push
and pull factors (e.g. mental health conditions, depression, trauma), personality traits (such as
narcissism and impulsivity) and individually specific demographic characteristics (e.g. age,
gender, country of birth) that constitute subjective states that make the individual more
vulnerable to extremism.
The inter-connectedness between push, pull and personal factors poses an
“operationalisation challenge”: for example, unemployment could be seen as both a push and
a personal factor, depending on whether the level of analysis is macro (looking at structural
factors) or micro (looking at biographical availability or frustration). We coded as push
factors all the factors that have been identified in the literature as “root causes” of terrorism,
such as unemployment or poverty, even when they were investigated at a micro-level of
analysis. Only demographic (age, gender), biographical (substance abuse, criminal record)
and psychological characteristics (like disorders and personality characteristics) have been
coded as personal factors. We believe that this coding strategy represents a practicable
approach to accurately reflecting the difference between researching the causes of
radicalisation in sociological forces versus psychological and individual paths, which
although possibly related to structural forces, tend to express unique biographical journeys.
Our dependent variables are comprised of two categories: cognitive and behavioural
radicalisation. Cognitive radicalisation refers to studies that focus on an individual expressing
support for violent extremist acts (e.g., terrorist attacks), people (e.g., Anders Breivik) and
groups (e.g., Al Qaeda) that committed acts of violent extremism (e.g., terrorism).
Behavioural radicalisation refers to studies that focus on an individual committing an act of
violent extremism (e.g., terrorism) or joining a violent extremist group (e.g., ISIL or Al
Three independent reviewers coded each article’s dependent and independent
variables. To ensure the replicability of this process, each reviewer separately coded 50
articles, and the results were discussed and compared until reaching a satisfactory agreement
(all Kappas > .70).
Finally, a more straightforward process of data extraction was conducted to identify
unambiguous information such as the methodology used (i.e. qualitative, quantitative, mixed
methods, social network analysis, and the use of control groups), the data sources (i.e.
existing datasets like the Gallup poll or the Global Terrorism Database (GDT), original
databases compiled with open sources, text analyses, original interviews, ethnographies), the
focus on group versus individual radicalisation, sample sizes and composition, geographical
focus, focus on ‘lone wolves’ and ideology (i.e. jihadism, far-right or other ideologies).
Firstly, we present a quantitative descriptive overview of the information coded and
extracted from the articles considered. Secondly, we provide a comprehensive qualitative
description of the factors of radicalisation that we encountered in each of the push, pull and
personal categories. Thirdly, we conduct cross-tabulations and chi-square tests to examine
whether there are significant differences in the proportions of different types of radicalisation
factors across articles that focus on different geographical areas, ideologies and research
Data analysis and results
Of the initial 6,335 articles, 79.1% (N=5013) were coded as not relevant, 3.1%
(N=198) were found not to be peer-reviewed journal articles, 1.4% (N=91) were in a foreign
language, 2.7% (N=173) were not accessible, and 6.7% (N=422) were not empirically based.
The remaining 2.4% (N=148) were included in this review. Figure 1 shows the distribution
over time of the articles included in this review.
Figure 1. Distribution of the empirical articles over time (frequency of articles per year)
As for the dependent variables, 77.7%% (N=115) of the articles focused on
behavioural radicalisation, and 22.3% (N=33) on cognitive radicalisation. As for the
independent variables, the articles were distributed as follows:
• 25.0% (N=37) had a combination of push and pull factors;
• 21.6% (N=32) only pull factors;
• 17.6% (N=26) a combination of pull and personal factors;
• 14.2% (N=21) had a combination of push, pull and personal factors;
• 14.2% (N=21) only push factors;
• 4.1% (N=6) a combination of push and personal factors;
• 3.4% (N=5) only personal factors.
Overall, pull factors are cited as a driver of radicalisation in 78.4% of the articles
(N=116), push factors in 57.4% of the articles (N=85), and personal factors in 39.2% of the
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Number of Articles
Additionally, we extracted the following information:
• Focus on group (32.4%, N=48) versus individual (67.6%, N=100) radicalisation;
• Methodology, i.e. qualitative (53.4%, N=79), quantitative (39.9%, N=59), mixed
methods (6.1%, N=9), social network analysis (0.7%, N=1);
• Use of control groups (12.8%, N=19);
• Data source (non-mutually exclusive), i.e. existing datasets (12.8%, N=19), original
database compiled from open sources (12.8%, N=19), text analysis (23.6%, N=35),
original interviews (54.1%, N=80), ethnography (2%, N=3);
• Sample size (only reported in some studies, N=64), with a minimum of 1 and a
maximum of 6,020 (M=577.53, SD=1,385.27);
• Sample composition (non-mutually exclusive): extremists (16.9%, N=25), general
population (23.6%, N=35), experts (6.1%, N=9);
• Geographical scope, i.e. Europe, North America and Australia (46.6%, N=69), Middle
East and Central Asia (12.8%, N=19), Africa (5.4%, N=8), Other (18.2%, N=27), and
multiple countries in a comparative perspective (16.9%, N=25);
• Lone wolves (5.4%, N=8);
• Ideological focus, i.e. jihadism (53.4%, N=79), far-right (18.9%, N=28), other
ideology (6.8%, N=10), and multiple ideologies (20.9%, N=31).
The push factors of radicalisation
Within the 85 articles mentioning at least one push factor as a cause of radicalisation,
a variety of push factors were identified. The push factor that appears most often in the
literature is the relative deprivation of a social group,23 which has been also framed in terms
of injustice,24 inequality,25 marginalisation,26 grievance,27 social exclusion,28 frustration,29
victimisation,30 stigmatisation.31 In the case of jihadist radicalisation, numerous articles
mention as a push factor the increasing frustration and sense of injustice derived from the
aggressive foreign policies of Western states in Muslim majority countries, such as the
Global War On Terror,32 the war in Afghanistan,33 Western attacks against the ummah ,34
Western colonisation of Muslim-majority countries,35 and more generally the perception of
Western dominance in world politics.36 The perceived threat to a group is mentioned as a
push factor of radicalisation in the context of right-wing extremism where the threat is
couched in primarily racial terms37 but some articles also mentioned threat perception as a
push factor in the context of jihadist radicalisation38 and Jewish extremism.39
State repression is another push factor that is often cited, especially beyond Europe
and North America in places such as India,40 Israel,41 Middle East and North Africa,42 Russia
and post-communist countries,43 Indonesia and Tanzania.44 In Western countries, the only
articles that see state repression as a cause of radicalisation are focused on left-wing anarchist
groups in Denmark,45 and jihadist radicalisation in prisons in France,46 and Britain.47
Poverty is cited as a push factor of radicalisation exclusively in qualitative articles
that look at radicalisation in Africa,48 with the exception of one article that finds an
association between low income and right-wing extremism in Russia.49 The articles that
focus on African radicalisation also tend to mention corruption as a push factor of
One of the most frequently cited push factors of radicalisation is unemployment.51
The relationship between unemployment and radicalisation is usually explained in two ways:
firstly, unemployment can be a source of frustration that triggers individual’s anger in
combination with other factors.52 Secondly, unemployment can be a factor indicating a
biographical availability, i.e. more free time and more practical availability to recruitment
into violent extremism.53
Level and type of education is another variable connected with push factor that is
often cited as being a predictor of radicalisation.54 Education can be a predictor of radical
opinions because lower levels of education are usually associated with less sophisticated and
more black-and-white worldviews, which are a predictor of cognitive radicalisation.55 Being
located within the educational system (and therefore having a higher level of education),
however, is in some instances seen as a marker of biographical availability to terrorist
We tested whether push factors were more cited in articles that focused on one
specific dependent variable. We found no statistically significant differences, with push
factors being mentioned in 60.6% of the articles focused on cognitive radicalisation, and in
56.5% of the articles focused on behavioural radicalisation. Push factors are comparatively
more cited as a driver of group radicalisation than individual radicalisation, even though they
are also mentioned in about half of the articles about individual radicalisation. Specifically,
push factors alone are most frequently cited to explain group radicalisation, and push factors
in combination with pull and personal factors to explain individual radicalisation (Table I).
The differences between groups were statistically significant, X2 (2, N = 148) = 9.97, p = .01.
Table I. Push factors by group/individual focus (frequencies and column percentages).
No push factors
Push factors in combination
Push factors alone
X2 (2, N = 148) = 9.97, p = .01
The pull factors of radicalisation
In the 116 articles that discuss pull factors, the one that appears most is the
consumption of extremist propaganda. This particular pull factor is mentioned as a cause for
radicalisation in about two-thirds (66.9%) of the articles included in this review. In the
scientific literature, extremist propaganda is examined at a group level in terms of
propaganda,57 but also in terms of culture,58 and myths,59 and also at the individual level in
terms of individual beliefs60, and views.61 The fundamental characteristic of a propaganda
that predicts radicalisation into violent extremism is justification of violence, which is
generally done through mechanisms of moral disengagement and de-humanization.62 Three
articles also found traits such as Right-Wing Authoritarianism and Social Dominance
Orientation to be associated with radicalisation, but not necessarily within the right-wing
context.63 It is important to note that, in the context of jihadist extremism, knowledge of
Islam and religiosity are often negatively associated with radicalisation, with extremists
generally being less religious and having lower knowledge of religious texts before their
radicalisation into violent extremism.64 Given that religiously framed extremism generally
involves religious fundamentalism this is not particularly surprising, because a key
characteristic of religious fundamentalism is the rejection of established, mainstream,
religious scholarly tradition and learning, in the name of (hubristically) going ‘back to
scripture’ untainted by tradition and interpretation.
The second most cited pull factor is group dynamics, which appears in more than one-
third (36.5%) of the articles reviewed. The group dynamics that are relevant to radicalisation
into violent extremism are described in terms of peer pressure,65 the formation of strong
bonds with like-minded people,66 the fulfilment of belonging and identity needs and the total
identification of the individual with the group,67 the influence of family and kinship ties.68
Empirical research on right-wing extremist homicides for example found that in most cases
they happen in group settings.69 Some articles establish a connection between group
dynamics and ideology, because in group settings (especially small groups), individuals are
socialised to violent ideologies.70 Online groups can also fulfil this role.71
A special role is attributed to charismatic leaders and recruiters, who inspire and
sometimes even coach violent extremists throughout their radicalisation path, creating a
special relationship with the recruits. This relationship is described in the literature in terms
of traditional recruitment networks,72 but also in more loose terms of charismatic authority,73
and religious leadership in the context of jihadist radicalisation.74
Other pull factors of radicalisation are related to material and emotional rewards.
Material incentives are monetary rewards, and mostly appear in the literature focusing on
jihadist radicalisation in Africa.75 Material incentives (especially in association with criminal
activities) are also mentioned in the context of far-right extremism in Canada and Russia.76
The only case in which material incentives are cited in the European context concerns illegal
immigrants in the Netherlands.77 Emotional incentives concern the fulfilment of the desire for
adventure and excitement, and they are found in research on jihadism in the Western
countries,78 and Russia,79 and extremist groups in Colombia.80 Emotional triggers are also
found in research that analysed extremists’ propaganda, specifically audio-visual material,81
and leaders’ speeches.82 Another emotional pull factor is the excitement for violence,
especially in far-right contexts.83
We found no significant differences in the number of articles that mentioned pull
factors to explain the two dependent variables. Pull factors are mentioned in about three-
quarters (75.8%) of the articles on cognitive radicalisation, and about four-fifths (79.1%) of
the articles on behavioural radicalisation. We also found no significant differences when we
looked at the proportions of articles mentioning pull factors to explain individual versus
The personal factors of radicalisation
The personal factors of radicalisation appear in about two-fifths (39.2%) of the
articles (N=58). The first and most important category of personal factors concerns the
individual’s mental health, which appears in the cases of lone wolf terrorism in terms of
psychological disorder,84 mental illness,85 and disturbance.86 In the cases of cognitive and
behavioural radicalisation in Western countries (not necessarily lone wolf), key psychological
issues are described in terms of depression,87 low self-esteem,88 personal alienation, isolation,
friendless, loneliness and misfit.89 Those psychological states are often associated with a
personal crisis,90 a cognitive opening,91 and the consequent search for meaning,92 that is then
fulfilled with extremist worldviews.
Another category of personal factors concerns the personality traits and cognitive
structure of the individuals who engage in violent extremism, who have been found to have
narcissistic personality,93 low tolerance of ambiguity,94 high personal uncertainty,95 black-
and-white type of thinking,96 and impulsiveness.97
Certain demographic characteristics have also been found to be prevalent among
violent extremists: extremists tend to be young,98 male,99 and in the case of far-right
extremism also white,100 and are generally born in the country where they live.101 Moreover,
previous experiences such as criminal behaviour leading to having a criminal record,
substance abuse, military experience and knowledge of weapons is associated with violent
extremism, especially for far-right and lone wolf offenders.102
Personal factors are more often used to explain cognitive radicalisation than
behavioural radicalisation in association with push and pull factors. Personal factors also
appear as the sole factor of radicalisation to explain behavioural radicalisation when there are
strong psychological disorders. The differences in proportions are statistically significant, X2
(1, N=148) = 7.24, p = 0.3 (Table II).
Table II. Personal factors by dependent variables (frequencies and column percentages).
No personal factors
Personal factors in combination
Personal factors only
X2 (1, N=148) = 7.24, p = 0.3
Personal factors appear in about a half (53.0%, N=53) of the articles that focus on
individual radicalisation, but only in about one-tenth (10.2%, N=5) of the articles that explain
group radicalisation, X2 (1, N = 148) = 24.68, p < .01. This is not surprising because personal
factors capture subjective elements that pertain to the individual sphere. Personal factors are
also more frequently cited in articles that focused on lone wolf attacks, with the difference
approaching statistical significance X2 (1, N = 148) = 4.55, p < .10.
We noticed that articles focusing on North America, Australia and Europe,
investigated cognitive radicalisation more than articles focusing on the rest of the world, X2
(1, N = 148) = 6.86, p < .05 (Table III).
Table III. Dependent variables by geographical focus (frequencies and column percentages).
Australia and EU
X2 (1, N = 148) = 6.86, p = 0.01
Overall, push factors are mentioned as factors of radicalisation across different
geographical areas. The indicators of disadvantage (including inequality, exclusion, poverty,
unemployment, access to education, and in general sources of injustice, marginalisation,
grievance and victimisation) appear in very similar proportion across geographical areas.
Even though the differences are not statistically significant (p > .1), state repression, threat,
and Western foreign policies are less cited in studies focusing on North America, Australia
and Europe, compared to other geographical areas (Table IV).
Table IV. Push factors of radicalisation by geographical focus (frequencies and column
percentages). Please note that categories are not mutually exclusive.
Australia and EU
Push factors (overall)*
Western foreign policies
*X2 (1, N = 148) = 0.76, p = .38
Pull factors are also consistently mentioned as factors of radicalisation across
different geographical areas. Even though the difference only approaches statistical
significance (p =.06), material pulls (i.e. economic incentives) are less cited in studies
focused on North America, Australia and Europe, compared to other geographical areas
(Table V). All other pull factors proportionally appear across different contexts.
Table V. Pull factors of radicalisation by geographical focus (frequencies and column
percentages). Please note that categories are not mutually exclusive.
Australia and EU
Pull factors (overall)*
*X2 (1, N = 148) = 0.01, p = .97
As Table VI shows, personal factors appear more frequently in studies that focus on
North America, Australia and Europe, compared to the rest of the world, X2 (1, N = 148) =
5.52, p < .05. Specifically, the factors that appears proportionally more in studies focusing on
North America, Australia and Europe are mental health issues, X2 (1, N = 148) = 9.15, p <
.01. Military experience is not mentioned as a personal factor of radicalisation in countries
other than in North America, Australia and Europe.
Table VI. Personal factors of radicalisation by geographical focus (frequencies and column
percentages). Please note that categories are not mutually exclusive
Australia and EU
Personal factors (overall)*
*X2 (1, N = 148) = 5.52, p < .05
An important issue that needs to be addressed is whether or not the factors predicting
radicalisation into violent extremism are the same across different ideologies. What we
found is that there are no significant differences in the proportions of push factors across
studies that looked at different ideologies. The only factor where differences approach
statistical significance is that of state repression, which is more present in articles about
jihadist radicalisation, X2 (2, N = 117) = 54.93, p < .1 (articles focused on multiple ideologies
were excluded from this calculation). Outrage at Western foreign policies is, in the literature
reviewed, exclusively a factor of jihadist radicalisation. This aside, there are no statistically
significant differences in the proportions of pull factors across studies that looked at different
ideologies. No significant differences appear also for personal factors in general.
Military experience exclusively appears as a predictor of far-right extremism, even
though anecdotally we know that in some instances jihadist-inspired attacks have been
conducted by individuals with military background (such as Nidal Hasan’s fort Hood
shooting). At the same time, being male appears as a predictor of far-right extremism more
than in other ideologies, X2 (2, N = 117) = 12.39, p < .1.
Is the use of a specific method or sample consistently associated with a research focus
on a certain factor of radicalisation? We found articles using data from existing datasets (e.g.
opinion polls or the GTD) being more likely to identify push factors as causes of
radicalisation, X2 (1, N = 148) = 3.62, p = .06). Also, qualitative studies mention pull factors
as drivers of radicalisation significantly more than quantitative and mixed-methods studies,
X2 (1, N = 148) = 8.03, p < .01. Personal factors appear less frequently in studies that used
text analysis X2 (1, N = 148) = 7.08, p < .01), and in articles using qualitative methodologies
X2 (1, N = 148) = 16.30, p < .01.
Finally, and very importantly, we found that the articles that exclusively used
qualitative methodologies gave a more narrowly defined explanation of radicalisation as a
product of either single types of factors (e.g. only pull) or as a combination of two factors
(e.g. push and pull) X2 (2, N = 148) = 6.05, p < .05. Conversely, articles that used quantitative
or mixed methodologies more often proposed an explanation of radicalisation that included a
combination of push, pull and personal factors.
This article presents a systematic scoping review of the literature about radicalisation into
violent extremism. The findings show that there has been an increase of empirical research
over time, which is an extremely positive trend. However, studies in the field - as reflected in
the 2001-2015, empirically based, English-language journal articles studied – are
predominantly focused on jihadist radicalisation in North America, Europe and Australia -
and largely use exclusively qualitative methodologies.
The empirical research disproportionately focuses on pull factors, which appear in
78.4% of the articles, while push factors (appearing in 57.4% of the articles) and personal
factors (appear in 39.2% of the articles) are comparatively under-researched. This finding
appears to contradict, at least in part, that of Sedgwick, who stated that “the concept of
radicalisation emphasizes the individual and, to some extent, the ideology and the group, and
significantly de-emphasized the wider circumstances.”103
We acknowledge that our coding decisions have influenced the low rate at which
personal factors appear in the literature. As a robustness check, we recoded all micro-level
studies (i.e., the studies focussing on a small sample of less than 50 individuals), and we
placed factors like unemployment and poverty in the “personal” category instead of the
“push” category. After the re-coding, push factors were cited as drivers of radicalisation in
49.3% (N=73) instead of 57.4% (N=85) of the articles, and personal factors were cited as
drivers of radicalisation in 47.3% (N=70) instead of 39.2% (N=58) of the articles. We re-run
all the analysis and we found no change in the results of the Chi-square tests that we report in
this article. After the re-coding, however, the number of articles focussing of personal and
push factors becomes almost identical.
This review shows that there is a dominant focus in the scholarly literature on pull
factors, and a lesser focus on personal factors. Some could interpret the lower appearance of
personal factors in the literature as a sign that they are less relevant to explain radicalisation.
We believe, however, together with King and Taylor,104 that this more likely reflects a lack of
research on personal factors, especially outside North America, Australia and Europe. As
King and Taylor noted: “current theorising emphasizes situational factors as the primary –
and in some cases the exclusive – drivers of radicalisation”, but it fails to understand the role
of individual characteristics in determining “how people respond to situations.”105 The
comparatively lower appearance of personal factors in the literature might also reflect a
problem to access reliable biographical data in the field, even though recent databases have
proposed to fill this void (see for example the PIRUS database published by START).
Personal factors are more often cited to explain cognitive radicalisation, but they also appear
as a unique cause of behavioural radicalisation in relation to lone wolf behaviour. This
confirms McCauley and Moskalenko’s observation that “lone attackers are likely to have
weapons experience, depression or other mental disorder.”106
Overall, we found that push and pull factors of radicalisation are evenly mentioned in
the scholarly literature across case-studies drawn from different geographical regions. For
example, the indicators of disadvantage (including inequality, exclusion, poverty,
unemployment, access to education, and in general sources of injustice, marginalisation,
grievance and victimisation) are mentioned as factors of radicalisation in empirical research
from all over the world, including Western and non-Western countries. Similarly, group
processes and propaganda pulls appear as relevant factors of radicalisation across all
geographical regions. Moreover, we found that push, pull and personal factors are present in
similar proportions across studies that focus on different ideological groups. Clearly, some
factors such as a sense of outrage generated by perceptions of Western foreign policies being
adversarial to Muslims are exclusively present among jihadist groups.
Nevertheless, there were no other statistically significant differences emerging from
our review. This suggests that radicalisation, in its fundamental mechanisms, so far as recent
scholarly literature in English is a guide, is a cross-ideological and global process that entails
similar fundamental categories of factors: 1- a political grievance, 2- a reward or appeal of
violent extremism and 3- a personal vulnerability or predisposition. We believe that various
combinations of push, pull and personal factors largely capture the dimensions that allow us
to understand the “richness and diversity of situations that breed terrorism.”107 Although the
radicalisation process entails similar categories of factors, we acknowledge that there may be
important geographical or other differences in the frequency of the factors within the larger
aggregate categories of push, pull and personal factors. In other words, the causes of
radicalisation may differ in different contexts, even though the categories of factors are
At the same time, however, when we zoom into each category of radicalisation
factors, we start to see important variations. For example, poverty is only cited as a
radicalisation factor in articles that focus on African countries. Also, even though the
difference is not statistically significant, state repression, threat, and Western foreign policies
are less cited in studies focused on North America, Australia and Europe, compared to other
geographical areas. Material incentives are more frequently cited in developing countries
(although not absent in Europe, such as among extremely disadvantaged groups like illegal
immigrants), and certain personal characteristics like being a male and having a military
background are more often associated with right-wing extremism in Western settings.
Finally, we found that qualitative methods tend to over-represent pull factors as a
cause of radicalisation, and also tend to fail in detecting the interactions between personal,
push and pull factors. This suggests that the imperative to construct an explanatory narrative
inherent in qualitative methods results in an overly simplistic reading of the dynamics
involves. It also suggests that there has not been a dramatic change since Silke’s 2001 review
of the methods used in the field, when he wrote that “the methods used by terrorism
researchers are essentially exploratory.”108 Rigorous hypothesis-testing continues to be rare:
for example, only 12.8% (N = 19) of the studies considered in this review uses a control
group, and only one single study used a control group of non-violent extremists to identify
the distinct characteristics and risk factors of violent extremism.109 In future, rigorous
research designs that include the use of control groups of non-violent extremists will be
necessary to distinguish between cognitive and behavioural radicalisation, and to identify the
specific and unique factors that lead an individual from support to action. Given the growth
of empirical research in the past years (see Figure 1), however, and the relatively small quota
of more systematic research, we agree with the viewpoint presented by Freilich et al., that
“there is reason to be optimistic about the future of terrorism studies.”110
Limitations and future research directions
The main limitation of this review concerns the flexibility of the operationalisation of
the concepts contained in the articles that we reviewed. In most of the qualitative research the
dependent and the independent variables were not explicitly defined, let alone operationalised
in standardised terms. As a consequence, the coding process involved a degree of
subjectivity. Nevertheless, we addressed this issue by transparently reporting the methods and
by reaching satisfactory inter-coder reliability. However, we also acknowledge that the
coding system could have been conducted differently, which might have led to slightly
different results. Findings from different cultural contexts might have been forced into the a-
priori categories of push, pull and personal factors, because the coders had the implicit
assumption that those categories would be meaningful across such diverse cases.
For practical reasons we did not collect information about the factors that the
empirical studies found to be uncorrelated with radicalisation. We made this choice because
most of the existing empirical research does not use hypothesis-testing designs, and it is
therefore impossible to rigorously determine when an article had empirical evidence about a
factor having a “null” effect on the dependent variable. Therefore, we decided to exclusively
focus on the “positive” effects. We acknowledge that this choice has potentially silenced
disagreement within the field. For example, Campana and Lapointe (2012) found that
variables such as economic development, economic inequalities and socio-economic
conditions had positive, negative and null tests in the literature, which means that there is no
agreement about their impact on the number of terrorist attacks.111 However, the
methodological variability and lack of rigour in the field does not allow to properly conduct
this type of test for the literature that we considered in this review. We also acknowledge that
by only searching for the terms “radicali*ation” and “extremis” we might have missed
important works that prefer to use the term terrorism and not mention the terms radicalisation
or extremism. Including the search term “terrorism” would have retrieved too many non-
relevant articles and would have exponentially increased the number of articles to be
manually screened by the coders’ team, making the size of the review impracticable.
Finally, the lack of rigorous methods in the field also leaves unanswered the questions
about the causal relations between the factors that we assumed to be dependent and
independent variables. This issue has been highlighted also in recent reviews in the field of
suicide terrorism.112 For example, there is no definitive answer to the question whether the
adoption of an extreme ideology precedes engagement in violence or it follows it. Moreover,
certain push factors (such as poverty) and personal factors (such as demographic
characteristics and personality traits) certainly precede radicalisation because of their nature,
but others (such as the development of a mental disorder) might, at least in some cases, also
follow or develop alongside radicalisation, being, in part, caused by it. In this article we
accept the causal direction that the authors of the research articles that we considered suggest,
but we acknowledge that it might be problematic. We believe that this is one of the most
important future challenges for the entire field of terrorism studies.
We believe that our categorisation of the literature allows to identify the main
characteristics of the field. Moreover, our system of categorisation highlights the basic
structure of the process of radicalisation as a mechanism that entails a real or perceived
political grievance, a perceived reward or appeal of violent extremism and a personal
vulnerability. Our review is limited to articles published through 2015. We envisage that the
wave of the ISIS-inspired attacks around the world in 2016 and 2017, and in 2018 continuing
beyond the collapse physical caliphate in Syria and Iraq, would have inspired more studies on
personal factors of radicalisation, especially focused on lone wolves and jihadist
radicalisation. Moreover, we expect that new datasets (such as the PIRUS database developed
by START) would trigger more quantitative empirical research in the field, continuing the
increase in empirical studies that we captured in this review.
We propose that future research should aim to understand the interaction between
push, pull and personal factors for both cognitive and behavioural radicalisation, and the
specific conditions that develop the emergence of different types of those factors in certain
contexts. A number of very important questions remain to be addressed. For example: do all
push, personal factors have the same effect on the radicalisation process? What is the specific
combination of personal, push and pull factors that triggers radicalisation in a specific
context? Are there any differences in the push, pull and personal factors that predict cognitive
and behavioural radicalisation? What factors are more important to identify the move to
action? We believe that these represent some of the most important questions that disciplined
and theoretically informed empirical research should focus on, to move the field of terrorism
1For example, Magnus Ranstorp, “Introduction: Mapping Terrorism Research—Challenges and
Priorities,” in Magnus Ranstorp (ed.), Mapping Terrorism Research: State of the Art, Gaps and
Future Direction (London-New York: Routledge, 2007): 1-28.
2 For example, Michele Grossman et al., “Stocktake Research Project. A Systematic Literature and
Selected Program Review on Social Cohesion, Community Resilience and Violent Extremism 2011-
2015”, (Victoria University and Australian Multicultural Foundation, Melbourne, 2016).
3See for example, Michael Horowitz, “The Rise and Spread of Suicide Bombing,” Annual Review of
Political Science 18 (May 2015): 69-84; Ignacio Sanchez-Cuenca and Luis de la Calle, “Domestic
Terrorism: The Hidden Side of Political Violence,” Annual Review of Political Science 12 (June
2009): 31-49’ Randy Borum, “Radicalization into Violent Extremism I: A Review of Social Science
Theories”, Journal of Strategic Security, 4:4 (Winter 2011):7-36. Jeff Victoroff, “The Mind of the
Terrorism. A Review and Critique of Psychological approaches” Journal of Conflict Resolution, 49:1
(February 2005), 3-42
4 Aurelie Campana and Luc Lapointe, “The Structural “Root” Causes of Non-Suicide Terrorism: A
Systematic Scoping Review,” Terrorism and Political Violence 24, no. 1 (2012): 79- 104.
5Karen Jacques and Paul Taylor, “Female Terrorism: A Review,” Terrorism and Political Violence
21, no. 3 (2009): 499-515.
6Mark Sedgwick, “The Concept of Radicalization as a Source of Confusion,” Terrorism and Political
Violence 22, no. 4 (2010): 479-494.
7Andrew Hoskins and Ben O’Loughlin, “Media and the myth of radicalization,” Media, War and
Conflict 2, no. 2 (2009):107-110.
8Richard English, “The future study of terrorism,” European Journal of International Security 1, no.2
9 Sedgwick, (see note 6 above), 479-494; Peter Neumann, “The trouble with radicalization,”
International Affairs 89, no.4 (2013): 873-893.
10 Robert Pape, “Introduction: What is New About Research on Terrorism," Security Studies 18, no. 4
(2009): 643-650. Robert Pape “The strategic logic of suicide terrorism”, American Political Science
Review, 97, no. 3 (2003): 343-361
11 For example see, Marc Sageman, “The Stagnation in Terrorism Research,” Terrorism and Political
Violence 26, no. 4 (2014): 565-580.
12 Marcel Dijkers, “What is a scoping review?,” KT Update 4, no.1 (2015): 1-5.
13 Neumann, (see note 9 above), 873-893.
14 For example see, Campana and Lapointe, (see note 4 above), 79- 104.
15 Scott Atran et al., “Challenges in researching terrorism from the field,” Science 355, no. 6323
16 Scott Kleinmann, “Radicalization of Homegrown Sunni Militants in the United States: Comparing
Converts and Non-Converts,” Studies in Conflict & Terrorism 35, no. 4 (2012): 278-297.
17 Lauren Duncan, “The Psychology of Collective Action,” in The Oxford Handbook of Personality
and Social Psychology, eds. Kay Deaux and Mark Snyder (Oxford: Oxford University Press, 2012):
18 See for example, Mark Elchardus and Jessy Siongers, “Ethnocentrism, taste and symbolic
boundaries,” Poetics 35, no.4-5 (2007): 215-238.
19 See for example, Steven Chermak and Jeffrey Gruenewald, “Laying a Foundation for the
Criminological Examination of Right-Wing, Left-Wing, and Al Qaeda-Inspired Extremism in the
United States,” Terrorism and Political Violence 27, no. 1 (2014): 133-159.
20 See for example, Arie Kruglanski et al., “The Psychology of Radicalization and Deradicalization:
How Significance Quest Impacts Violent Extremism,” Political Psychology 35, no. 1 (2014): 69–93.
21 See for example, Jeffry Halverson and Amy Way, “The Curious Case of Colleen LaRose: Social
Margins, New Media, and Online Radicalization,” Media, War and Conflict 5, no. 2 (2012): 139-153.
22 See for example, Johannes Due Enstad, ““Glory to Breivik!”: The Russian Far Right and the 2011
Norway Attacks,” Terrorism and Political Violence 29, no. 5 (2015): 773-792. DOI:
23 For example see, Daniela Pisoiu, “Subcultural Theory Applied to Jihadi and Right-Wing
Radicalization in Germany,” Terrorism and Political Violence 27, no. 1 (2015): 9-28.
24 Lindsay Scorgie-Porter, “Militant Islamists or borderland dissidents? An exploration into the Allied
Democratic Forces' recruitment practices and constitution,” The Journal of Modern African Studies
53, no. 1 (2015): 1-25.
25 Alessandro Orsini, “Interview with a Terrorist by Vocation: A Day Among the Diehard Terrorists,
Part II,” Studies in Conflict & Terrorism 36 no. 8 (2013): 672-684.
26 Scorgie-Porter (see note 24 above), 1-25.
27 Anneli Botha, “Political Socialization and Terrorist Radicalization Among Individuals Who Joined
al-Shabaab in Kenya,” Studies in Conflict & Terrorism 37, no. 11 (2014): 895-919.
28 Tahir Abbas and Assma Siddique, “Perceptions of the processes of radicalisation and de-
radicalisation among British South Asian Muslims in a post-industrial city,” Journal for the Study of
Race, Nation and Culture 18, no. 1 (2012): 119-134.
29 Gaetano Joe Ilardi, “Interviews with Canadian Radicals,” Studies in Conflict & Terrorism 36, no. 9
30 Stefan Malthaner, “Contextualizing Radicalization: The Emergence of the "Sauerland-Group" from
Radical Networks and the Salafist Movement,” Studies in Conflict & Terrorism 37, no. 8 (2014): 638-
31 Willem De Koster and Dick Houtman, “Stormfront is like a second home to me,” Information,
Communication & Society 11, no. 8 (2008): 1155-1176.
32 Franklin Charles Graham IV, “Abductions, kidnappings and killings in the Sahel and Sahara,”
Review of African Political Economy 38, no.130 (2011): 587-604.
33 Clark McCauley, “Testing Theories of Radicalization in Polls of U.S. Muslims,” Analyses of Social
Issues and Public Policy 12, no. 1 (2012): 296-311.
34 Guy Fricano, “Horizontal and vertical honour in the statements of Osama Bin Laden,” Critical
Studies on Terrorism 5, no. 2 (2012): 197-217.
35 Jonathan Githens-Mazer, “The Blowback of Repression and the Dynamics of North African
Radicalization,” International Affairs 85, no. 5 (2009): 1015-1029.
36 Kirill Zhirkov, Maykel Verkuyten, and Jeroen Weesie, “Perceptions of world politics and support
for terrorism among Muslims: Evidence from Muslim countries and Western Europe,” Conflict
Management and Peace Science 31, no. 5 (2014): 481-501.
37 Denis Davydov, “The causes of youth extremism and ways to prevent it in the educational
environment” Russian Education & Society 57, no. 3 (2015): 146-162.
38 Bertjan Doosje, Annemarie Loseman, and Kees van den Bos, “Determinants of Radicalization of
Islamic Youth in the Netherlands: Personal Uncertainty, Perceived Injustice, and Perceived Group
Threat,” Journal of Social Issues 69, no. 3 (2013): 586-604.
39 Arie Perliger and Ami Pedahzur, “Counter Cultures, Group Dynamics and Religious Terrorism,”
Political Studies 64, no. 2 (2014): 297-314.
40 Irfan Ahmad, “Theorizing Islamism and democracy: Jamaat-e-Islami in India,” Citizenship Studies
16, no. 7 (2012): 887-903.
41 Genevive Boucher Boudreau, “Radicalization of the Settlers' Youth: Hebron as a Hub for Jewish
Extremism,” Global Media Journal 7, no. 1 (2014): 69-85.
42 Katerina Dalacoura, “ Islamist terrorism and the Middle East democratic deficit: Political exclusion,
repression and the causes of extremism,” Democratization 13, no. 3 (2006): 508-525; Abdulmalik
Mohammad Abdullah Eissa, “Islamist political movements in Yemen,” Contemporary Arab
Affairs 6, no. 1 (2013): 41-70; Githens-Mazer, (see note 35 above), 1015-1029; Ulrich Kropiunigg,
“Framing Radicalization and Deradicalization: A Case Study from Saudi Arabia,” Journal of
Individual Psychology 69, no. 2 (2013): 97-117.
43 Gordon Hahn, “The Rise of Islamist Extremism in Kabardino-Balkariya,” Demokratizatsiya: The
Journal of Post-Soviet Democratization 13, no. 4 (2005): 543- 594; Domitilla Sagramoso, “The
Radicalisation of Islamic Salafi Jamaats in the North Caucasus: Moving Closer to the Global Jihadist
Movement?,” Europe-Asia Studies 64, no. 3 (2012): 561-595.
44 Frans Wijsen, “‘There are Radical Muslims and Normal Muslims’: An Analysis of the Discourse on
Islamic Extremism,” Religion, 43, no. 1 (2013): 70-88.
45 René Karpantschof, “Violence that matters! Radicalization and Deradicalization of Leftist, Urban
Movements – Denmark 1981–2011,” Behavioral Sciences of Terrorism and Political Aggression 7,
no. 1 (2015): 35-52.
46 Farhad Khosrokhavar, “Radicalization in Prison: The French Case,” Politics, Religion & Ideology
14, no. 2 (2013): 284-306.
47 Graham Macklin and Joel Busher, “The Missing Spirals of Violence: Four Waves of Movement-
Countermovement Contest in Post-War Britain,” Behavioral Sciences of Terrorism and Political
Aggression 7, no. 1 (2015): 53-68.
48 John Amble and Alexander Meleagrou-Hitchens, “Jihadist Radicalization in East Africa: Two Case
Studies,” Studies in Conflict & Terrorism 37, no. 6 (2014): 523-540; Kwesi Aning and Mustapha
Abdallah, “Islamic Radicalisation and Violence in Ghana,” Conflict, Security & Development 13, no.
2 (2013): 149-167; Eissa, (see note 42 above), 41-70; Graham IV, (see note 32 above), 587-604; Kate
Meagher, “Leaving No One Behind?: Informal Economies, Economic Inclusion and Islamic
Extremism in Nigeria,” Journal of International Development 27, no. 6 (2015), 835-855.
49 Davydov, (see note 37 above), 146-162.
50 Iro Aghedo and Oarhe Osumah, “The Boko Haram Uprising: how should Nigeria respond?,” Third
World Quarterly 33, no. 5 (2012), 853-869; Tiffiany Howard, “Failed States and the Spread of
Terrorism in Sub-Saharan Africa,” Studies in Conflict & Terrorism 33, no. 11 (2010), 960-988;
Meagher, (see note 48 above), 835-855.
51 See, Gabriel Acevedo and Ali Chaudhary, “Religion, Cultural Clash, and Muslim American
Attitudes About Politically Motivated Violence,” Journal for the Scientific Study of Religion 54, no. 2
(2015): 242-260; Aghedo and Osumah, (see note 50 above), 853-869; Kamaldeep Bhui, Nasir Warfa,
and Edgar Jones, “Is Violent Radicalisation Associated with Poverty, Migration, Poor Self-Reported
Health and Common Mental Disorders?,” PLOS ONE 9, no. 3, (2014): DOI:
http://dx.doi.org/10.1371/journal.pone.0090718; Marc Coester, “Commentary: Right-Wing
Extremism and Bias Crime in Germany,” Journal of Ethnicity in Criminal Justice 8, no. 1 (2010): 46-
69; Davydov, (see note 37 above), 146-162; John Mueller and Mark Stewart, “Terrorism,
counterterrorism, and the Internet: The American cases,” Dynamics of Asymmetric Conflict 8, no. 2
(2015): 176-190; Perliger and Pedahzur, (see note 39 above), 297-314.
52 For example see, Aghedo and Osumah, (see note 50 above), 853-869.
53 See for example, Perliger and Pedahzur, (see note 39 above), 297-314.
54 Aghedo and Osumah, (see note 50 above), 853-869; Tarek Al Baghal, “Estimating Support for
Extremism and Its Correlates: The Case of Pakistan,” Research & Methods 23, no. 1 (2014): 35-56;
Bhui, Warfa, and Jones, (see note 51 above); Joel Capellan, “Lone Wolf Terrorist or Deranged
Shooter? A Study of Ideological Active Shooter Events in the United States, 1970–2014,” Studies in
Conflict & Terrorism 38, no. 6 (2015): 395-413; Coester, (see note 51 above), 46-69; Davydov, (see
note 37 above), 146-162; Howard, (see note 50 above), 960-988; McCauley, (see note 33 above), 296-
311; Irina Molodikova and Victoria Galyapina, “Islamic education among Chechens and Ingush:
Pupils', teachers' and experts' opinions,” Religion, State and Society 39, no. 2-3 (2011): 263-279;
Magdalena Wojcieszak, ““Carrying online participation offline” - Mobilization by radical online
groups and politically dissimilar offline ties,” Journal of Communication 59, no. 3 (2009): 564-586;
Zhirkov, Verkuyten, and Weesie, (see note 36 above), 481-501.
55 For example see, Zhirkov, (See note 36 above), 481-501.
56 See for example, Perliger and Pedahzur, (See note 39 above), 297-314.
57 Haroro Ingram, “The strategic logic of Islamic State information operations,” Australian Journal of
International Affairs 69, no. 6 (2015), 729-752; Dany Badran, “Hybrid genres and the cognitive
positioning of audiences in the political discourse of Hizbollah,” Critical Discourse Studies 7, no. 3
(2010): 191-201; Jamie Bartlet and Carl Miller, “The Edge of Violence: Towards Telling the
Difference Between Violent and Non-Violent Radicalization,” Terrorism and Political Violence 24,
no. 1 (2012): 1-21.
58 Mark Hamm, “Prison Islam in the age of sacred terror,” The British Journal of Criminology 49, no.
5 (2009): 667-685; Macklin and Busher, (see note 47 above), 53-68; Perliger and Pedahzur, (see note
39 above), 297-314; Jessica Stern, “X: A Case Study of a Swedish Neo-Nazi and His Reintegration
into Swedish Society,” Behavioral Sciences and the Law 32, no. 3 (2014): 440-453; Davydov, (see
note 37 above), 146-162.
59 Johnny Ryan, “The Four P-Words of Militant Islamist Radicalization and Recruitment: Persecution,
Precedent, Piety, and Perseverance,” Studies in Conflict & Terrorism 30, no. 11 (2007): 985-1011;
Githens-Mazer, (see note 35 above), 1015-1029.
60 Naumana Amjad and Alex Wood, “Identifying and changing the normative beliefs about aggression
which lead young Muslim adults to join extremist anti-Semitic groups in Pakistan,” Aggressive
Behavior 35, no. 6 (2009): 514- 519; David Hofmann, “Quantifying and qualifying charisma: A
theoretical framework for measuring the presence of charismatic authority in terrorist groups,” Studies
in Conflict & Terrorism 38, no. 9 (2015): 710-733; Jitpiromsri Srisompob and Sobhonvasu Panyasak,
“Unpacking Thailand's southern conflict: The poverty of structural explanations,” Critical Asian
Studies 38, no. 1 (2006): 95-117; Domenico Tosini, “A Sociological Understanding of Suicide
Attacks,” Theory, Culture and Society 26, no. 4 (2009): 67-96.
61 Al Baghal, (see note 54 above), 35-56.
62 See for example, Tosini, (see note 61 above), 67-96.
63 Anthony Lemieux and Victor Asal, “Grievance, social dominance orientation, and authoritarianism
in the choice and justification of terror versus protest,” Dynamics of Asymmetric Conflict 3, no. 3
(2010): 194-207; Lieven Pauwels and Maarten De Waele, “Youth involvement in politically
motivated violence: Why do social integration, perceived legitimacy, and perceived discrimination
matter?” International Journal of Conflict and Violence 8, no. 1 (2014): 134-153; Hans Peter Kunh,
“Adolescent voting for right-wing extremist parties and readiness to use violence in political action:
Parent and peer contexts,” Journal of Adolescence 27, no. 5 (2004): 561-581.
64 Acevedo and Chaudhary, (see note 51 above), 242-260; Zhirkov, Verkuyten, and Weesie, (see note
36 above), 481-501.
65 Bartlet and Miller, (see note 57 above), 1-21; Ian Gargan et al., “Terrorists meeting their victims: a
case study of psychologists' experiences of former terrorists meeting survivors,” Journal of
Aggression, Conflict and Peace Research 4, no. 4 (2012): 216 – 225; Ilardi, (see note 29 above), 713-
738; Lorenzo Vidino, “The Buccinasco Pentiti: A Unique Case Study of Radicalization,” Terrorism
and Political Violence 23, no. 3 (2011): 398-418.
66 Thomas Hegghammer, “Terrorist recruitment and radicalization in Saudi Arabia,” Middle East
Policy 13, no. 4 (2006): 39-60; Boudreau, (see note 41 above), 69-85.
67 Botha, (see note 27 above), 895-919; David Canter, Sudhadshu Sarangi, and Donna Youngs,
“Terrorists' personal constructs and their roles: A comparison of the three Islamic terrorists,” Legal
and Criminological Psychology 19, no. 1 (2014): 160-178; Paul Joosse, Sandra Bucerius, and Sara
Thompson, “Narratives and Counternarratives: Somali-Canadians on Recruitment as Foreign Fighters
to Al-Shabab,” British Journal of Criminology 55, no. 4 (2015): 811-832; Malthaner, (see note 30
above), 638-653; Perry and Scrivens, (see note 57 above), 819-841; Anne Aly and Jason-Leigh
Striegher, “Examining the Role of Religion in Radicalization to Violent Islamist Extremism,” Studies
in Conflict & Terrorism 35, no. 12 (2012): 849-862.
68 Julie Chernov Hwang, “Terrorism in Perspective: An Assessment of ‘Jihad Project’ Trends in
Indonesia,” Honolulu: East-West Center 104, (September 2012):
and Pedahzur, (see note 39 above), 297-314; William Rosenau et al., “Why They Join, Why They
Fight, and Why They Leave: Learning from Colombia's Database of Demobilized Militants,”
Terrorism and Political Violence 26, no. 2 (2014): 277-285.
69 Jeff Gruenewald, “A Comparative Examination of Homicides Perpetrated by Far-Right
Extremists,” Homicide Studies 15, no. 2 (2011): 177-203.
70 See for example, Louise Porter and Mark Kebbell, “Radicalization in Australia: Examining
Australia’s Convicted Terrorists,” Psychiatry, Psychology and Law 18, no. 2 (2011): 212-231; Marco
Nilsson, “Foreign Fighters and the Radicalization of Local Jihad: Interview Evidence from Swedish
Jihadists,” Studies in Conflict & Terrorism 38, no. 5 (2015): 343-358; Botha, (see note 27 above),
71 Charlie Edwards and Luke Gribbon, “Pathways to Violent Extremism in the Digital Era,” The RUSI
Journal 158, no. 5 (2013), 40-47; Magdalena Wojcieszak, “'Don't talk to me': Effects of ideologically
homogeneous online groups and politically dissimilar offline ties on extremism,” New Media &
Society 12, no. 4 (2010): 637-655.
72 Hegghammer, (see note 67 above), 39-60; Ilardi, (see note 29 above), 713-738; Kleinmann, (see
note 16 above), 278-297.; Lindsay Scorgie-Porter, (see note 24 above), 1-25.
73 Alberto Testa and Gary Armstrong, “Words and actions: Italian ultras and neo-fascism,” Social
Identities 14, no. 4 (2008): 473-490; Hofmann, (see note 61 above), 710-733.
74 Abbas and Siddique, (see note 28 above), 119-134; Aghedo and Osumah, (see note 50 above), 853-
869; Amble and Meleagrou-Hitchens, (see note 48 above), 523-540; Botha, (see note 27 above), 895-
919; Hwang, (see note 69 above); Molodikova and Galyapina, (see note 54 above), 263-279; Porter
and Kebbell, (see note 71 above) 212-231; Sagramoso, (see note 43 above), 561-595; Vidino, (see
note 66 above), 398-418.
75 Amble and Meleagrou-Hitchens, (see note 48 above), 523-540; Botha, (see note 27 above), 895-
919; Graham IV, (see note 32 above), 587-604.
76 Perry and Scrivens, (see note 57 above), 819-841; Davydov, (see note 37 above), 146-162;
77 Jasper De Bie, Christianne de Poot, and Joanne van der Leun, “Jihadi networks and the involvement
of vulnerable immigrants: reconsidering the ideological and pragmatic value,” Global Crime 15, no.
3-4 (2014): 275-298;
78 Elena Mastors and Rhea Siers, “Omar al-Hammami: A Case Study in Radicalization,” Behavioral
Sciences & the Law 32, no. 3 (2014): 377-388; Bartlet and Miller, (see note 57 above), 1-21; Joosse,
Bucerius, and Thompson, (see note 68 above), 811-832.
79 Zaid Abdulagatov, “The Influence of the Religious Factor on the Extremist Behavior of Dagestani
Youth,” Russian Education & Society 55, no. 2 (2013): 67-81; Davydov, (see note 37 above), 146-
80 Rosenau et al., (see note 69 above), 277-285.
81 Kurt Braddock, “The utility of narratives for promoting radicalization: The case of the animal
liberation front,” Dynamics of Asymmetric Conflict 8, no. 1 (2014): 38-59.
82 David Matsumoto, Mark Frank, and Hyisung Hwang, “The Role of Intergroup Emotions in Political
Violence,” Current Directions in Psychological Science 24, no. 5 (2015): 369-373.
83 Stern, (see note 59 above), 440-453; Testa and Armstrong, (see note 74 above), 473-490.
84 Clark McCauley and Sophia Moskalenko, “Toward a Profile of Lone Wolf Terrorists: What Moves
an Individual From Radical Opinion to Radical Action,” Terrorism and Political Violence 26, no. 1
(2014): 69-85; Mark Palermo, “Developmental Disorders and Political Extremism: A Case Study of
Asperger Syndrome and the Neo-Nazi Subculture,” Journal of Forensic Psychology Practice 13, no.
4 (2013): 341-354.
85 Jeff Gruenewald, Steven Chermak, and Joshua Freilich, “Overview of: "Distinguishing 'Loner'
Attacks from Other Domestic Extremist Violence: A Comparison of Far-Right Homicide Incident and
Offender Characteristics," Criminology & Public Policy 12, no. 1 (2013): 63-64.
86 Ramon Spaaij, “The Enigma of Lone Wolf Terrorism: An Assessment,” Studies in Conflict and
Terrorism 33, no. 9 (2010): 854-870.
87 Kamaldeep Bhui, Brian Everitt, and Edgar Jones, “Might depression, psychosocial adversity, and
limited social assets explain vulnerability to and resistance against violent radicalisation?” PLOS ONE
9, no. 9 (2014): DOI: http://dx.doi.org/10.1371/journal.pone.0105918.
88 Kleinmann, (see note 16 above), 278-297; Kunh, (see note 64 above), 561-581.
89 Perliger and Pedahzur, (see note 39 above), 297-314; Manuel Torres Soriano, “Between the Pen and
the Sword: The Global Islamic Media Front in the West,” Terrorism and Political Violence 24, no. 5
(2012): 769-786; Palermo, (see note 85 above), 341-354; Mueller and Stewart, (see note 51 above),
176-190; Vidino, (see note 66 above), 398-418; Porter and Kebbell, (see note 71 above) 212-231.
90 Kleinmann, (see note 16 above), 278-297; Mueller and Stewart, (see note 51 above), 176-190;
Porter and Kebbell, (see note 71 above), 212-231.
91 Ilardi, (see note 29 above), 713-738; Mirra Noor Milla, Faturochman, and Djamaludin Ancok, “The
impact of leader–follower interactions on the radicalization of terrorists: A case study of the Bali
bombers,” Asian Journal of Social Psychology 16, no. 2 (2013): 92–100; Vidino, (see note 66 above),
92 Kleinmann, (see note 16 above), 278-297; Mastors and Siers, (see note 79 above), 377-388; Daniela
Pisoiu and Felix Lang, “The Porous Borders of Extremism: Autonomous Nationalists at the Crossroad
with the Extreme Left,” Behavioral Sciences of Terrorism and Political Aggression 7, no. 1 (2015):
69-83; Torres Soriano, (see note 90 above), 769-786; De Bie, de Poot, and van der Leun, (see note 78
above), 275-298; Gargan et al., (see note 66 above), 216 – 225.
93 Allard Feddes, Liesbeth Mann, and Bertjan Doosje, “Increasing self-esteem and empathy to prevent
violent radicalization: a longitudinal quantitative evaluation of a resilience training focused on
adolescents with a dual identity,” Journal of Applied Social Psychology 45, no. 7 (2015): 400–411.
94 Kleinmann, (see note 16 above), 278-297.
95 Doosje, Loseman, and van den Bos, (see note 38 above), 586-604; Michael Hogg and Janice
Adelman, “Uncertainty–Identity Theory: Extreme Groups, Radical Behavior, and Authoritarian
Leadership,” Journal of Social Issues 69, no. 3 (2013): 436–454.
96 Canter, Sarangi, and Youngs, (see note 68 above) 160-178; James Pennebaker, “Using computer
analyses to identify language style and aggressive intent: The secret life of function words,” Dynamics
of Asymmetric Conflict 4, no. 2 (2011): 92-102.
97 Pauwels and De Waele, (see note 64 above), 134-153.
98 Acevedo and Chaudhary, (see note 51 above), 242-260; Bhui, Warfa, and Jones, (see note 51
above); Gruenewald, Chermak, and Freilich, (see note 86 above); Eissa, (see note 42 above), 41-70;
Zhirkov, Verkuyten, and Weesie, (see note 36 above), 481-501; Al Baghal, (see note 54 above), 35-
99 Coester, (see note 51 above), 46-69; Gruenewald, (see note 70 above), 177-203; Gruenewald,
Chermak, and Freilich, (see note 86 above): 63-64; Kunh, (see note 64 above), 561-581.
100 Gruenewald, (see note 70 above), 177-203.
101 Coester, (see note 51 above), 46-69; Bhui, Warfa, and Jones, (see note 51 above).
102 Coester, (see note 51 above), 46-69; Capellan, (see note 54 above), 395-413; Gruenewald,
Chermak, and Freilich, (see note 86 above), 63-64; McCauley and Moskalenko, (see note 85 above),
103 Sedgwick, (see note 6 above), 480-481.
104 Michael King and Donald M. Taylor, “The Radicalization of Homegrown Jihadists: A Review of
Theoretical Models and Social Psychological Evidence,” Terrorism and Political Violence 23, no. 4
105 Ibid., 614.
106 McCauley and Moskalenko, (see note 85 above), 83.
107 Atran et al., (see note 15 above), 353.
108 Andrew Silke, “The Devil You Know: Continuing Problems with Research on Terrorism,
Terrorism and Political Violence 13, no. 4 (2001): 13, DOI: 10.1080/09546550109609697.
109 Bartlet and Miller, (see note 57 above), 1-21.
110 Joshua Freilich, Steven Chermak, and Jeff Gruenwald, “The Future of Terrorism Research: A
Review Essay,” International Journal of Comparative and Applied Criminal Justice 39, no. 4 (2015):
111 Campana and Lapointe, (see note 4 above), 79-104.
112 See, Horowitz, (see note 3 above), 69-84.