During the last few years there has been considerable interest in the role that social networks play in processes of radicalisation, whether we are talking about individual or collective radicalisation, and whether we are talking about ideological or tactical radicalisation, or both. There are a number of factors that account for this interest. First, study after study has pointed to the importance of social networks for processes of socialisation into radical social or political action. Even in the case of lone actor perpetrators of political violence, the idea that such people operate entirely in isolation has over the years been worn down by empirical analyses highlighting how many of these individuals engage with wider networks of similarly-minded activists (Gable and Jackson 2007, Gill and Corner 2015, Pantucci 2011, Sageman 2008, Weimann 2012). Second, there is growing recognition that in the contemporary context non-state political violence itself is often carried out by loosely coordinated networks of actors rather than more formalised groups; and third, the fact that new information and communication technologies have enabled us to trace and analyse these networks in ways that were not previously possible (see Carter, Maher, and Neumann 2014, Chipev et al. 2013, Fisher 2012, Kim et al. 2013, O'Callaghan et al. 2013).
In this presentation I will outline some of the mechanisms through which social networks contribute to processes of radicalisation, as well as giving some sense of the types of networks that appear to be most conducive to such processes.
How social networks contribute to processes of radicalisation
In order to think about how social networks can contribute to processes of radicalisation it is helpful to break the discussion down into two parts relating to:
- Processes of recruitment into activism, and
- Processes of tactical and ideological radicalisation post-recruitment.
Processes of recruitment
The importance of pre-existing social ties is a recurring theme in studies of people’s journeys into radical political activism. Indeed, in several studies it has been observed that recruitment can often precede ideological engagement (Blee 2003, Busher 2015, Ch 2, Fangen 1998, Ranstorp 2010). Such findings are very much in keeping with the wider literature on participation in social movements (McAdam 1986, Nepstad and Smith 1999, Snow, Zurcher, and Ekland-Olson 1980). So what are the mechanisms through which social networks contribute to processes of recruitment into radical political activism?
- Information channels and frame acquisition
Social networks provide an avenue through which prospective participants can come into contact with information about ‘the cause’ and the groups mobilising around this cause. Importantly, the informality and often private nature of these communication channels means that they are not controlled by mainstream media, political elites or the state (Neumann 2013).
- Processes of identification
The forging of collective identities is a crucial element in achieving sustained mobilisation (Casquete 2006, Hunt and Benford 2004, Melucci 1995, Taylor and Whittier 1992). Existing social ties can facilitate such processes (Passy 2003, 23). If my friends are part of a group that identify with a particular issue or collective identity I am also more likely to identify with and feel an affective bond with that issue, or collective identity: ‘We accept a friend’s invitation to a rally because we like her, or because we fear her disapproval if we turn her down, not just because we agree with her’ (Goodwin, Jasper, and Polletta 2001, 8).
This is why networks in which social ties are characterised by strong emotional bonds can provide particularly effective channels for recruitment – informal kinship or close friendship networks are often prominent in accounts of entry into radical political activism (Alonso 2010, Blee 2003, Freilich and Pridemore 2005, Sageman 2004). One of the critical questions for contemporary analysts is how, and the extent to which, the kind of deep emotional bonds that can facilitate radicalisation might be generated through online, non-face-to-face communications.
- Facilitating first contacts
A third mechanism is what Passy (2003) calls a ‘structural-connection function’. As well as enabling information flows and helping to stimulate processes of identification, social networks provide concrete opportunities for participation (McAdam 1986, Snow, Zurcher, and Ekland-Olson 1980). When I was talking with EDL activists, even people with a long history of participation in far right activism or in football hooliganism described how they had felt a certain sense of trepidation about attending their first EDL demonstrations: would they know anybody there? Would they fit in? Would they find anybody to talk to? Would it be what they hoped it would be? Personal ties smoothed these first contacts and put prospective participants at ease (Busher 2015).
Authority figures within the movement can be particularly effective recruiters (Alonso 2010, Passy 2003), perhaps, Passy argues, because such figures are well placed to address the doubts and uncertainties of prospective participants. Social networks that enable prospective participants to come into contact with such figures are likely therefore to be particularly effective at encouraging participation.
- Group decision-making
While some individuals may make a personal decision to become involved in a political movement, decisions to engage in political activism are often at least to some extent collective decisions (Marwell and Oliver 1993). We often find patterns of what Oberschall (1973) calls ‘block recruitment’, wherein whole groups of individuals chose to become involved in a specific movement: a group from a particular church may decide to join the civil rights movement, a group of hooligans from a particular football club may decide collectively to go along to an anti-Muslim street protest and so forth (see also della Porta 1988, 2003, McCauley and Moskalenko 2008, Sageman 2004).
Social networks and post-recruitment processes of radicalisation
Social networks also shape processes of radicalisation post-recruitment. Once again, the literature indicates a number of mechanisms through which this might happen.
- Tactical learning
Perhaps most obviously, social networks often ‘facilitate learning by providing the connections through which network participants share information and experience’ (Kenney et al. 2013, see also Gill and Corner 2015).
- Confirmation bias
Social networks, as Sunstein (2009, 24) argues, ‘can operate as polarization machines because they help to confirm and thus amplify people’s antecedent views.’ Entering into radical political activism alters a person’s social networks. In some cases activists are encouraged by leaders and co-activists to sever ties with people outside the group (Bjørgo 1998, Wasmund 1986), but even where this is not the case radical political activism often becomes the centre of participants’ lives (Blee 2003, Busher 2015, Simi and Futrell 2010). Such selective patterns of interaction make people more likely to be sharing ideas and experiences with like minds (Gill and Corner 2015, Husain 2007), which in turn makes them more likely to become drawn into forms of ‘group-think’ conducive to further ideological or tactical radicalisation (Klatch 2004, 497, NYPD 2007, 43). This is why the social networks that are most conducive to radicalisation are usually those that in effect leave participants cut off from wider social and cultural influences (della Porta 2003, della Porta and Tarrow 1986).
- Shaping conceptions of legitimate action
Activists in all social movement groups develop their tactical tastes and craft their conception of legitimate action through interactions with co-activists and other fellow ideological travellers (Tarrow 1993, Tilly 1986). People associated with radical forms of political action are no different. Again, this is why groups that encourage participants to sever social ties with wider society are particularly prone to tactical radicalisation.
The social ties that people form as they become involved in radical political movements also help to inhibit desistance – they make people less inclined to leave even when they may have doubts about the cause or the tactics being deployed (Bjørgo 2009, 1998, Miller McPherson, Popielarz, and Drobnic 1992). Sometimes this is due to threats of violence if they leave, but is also a function of the strength of the bonds produced through shared experiences of participation in radical political action (Busher 2015, Ch 6, della Porta 2003)
It is clear that by analysing social networks we can strengthen our capacity to understand, and perhaps even to some extent anticipate, patterns of radicalisation. What is also clear is that with new information and communication technologies we are today increasingly well placed to measure and describe these networks.
I would conclude however by drawing attention to three points that require reflection. First, there is a challenge associated with identifying causality when we talk about social networks and what they might or might not do. There is a danger that the argument becomes tautological – i.e. we find ourselves saying that people become part of particular (political) networks because they are already in some way linked into these networks, but we are still left with the problem of how people became embedded in these networks in the first place (Passy and Giugni 2000, 120). In order to cope with this challenge, we must recognise that networks are emergent, just as identities, issue frames and emotions are emergent and should therefore be very cautious about conceiving of them simply as an independent variable.
Second, network effects are extremely patchy. Social contacts with people who hold extreme political views or advocate the use of radical protest tactics do not always lead towards radicalisation, far from it. If we are to account for the patchiness of network effects it is important a) that we find ways of talking about social networks and their effects in ways that do not overlook human agency, and b) that we conceive of social networks as being both structural and cultural phenomena (Emirbayer and Goodwin 1994, Mische 2003, Passy and Giugni 2000) – as well as specifying what ties there are, we also need to say what people do with these ties, what they represent to the people who comprise the network, how these ties are initiated and, ideally, towards what ends.
Finally, and at the risk of stating the obvious, just as social networks may contribute to processes of radicalisation, they may also contribute to processes of deradicalisation or non-radicalisation. It is often the same intense personal ties that characterise and hold radical political groups together that also precipitate their collapse as groups are consumed by bitter squabbles and infighting (Busher 2015, Ch 5, Klatch 2004), and just as we see patterns of ‘block recruitment’ we can also find similar patterns of collective desistance from activism (Sandell 1999). Meanwhile, recent research (Bhui 2015) lends further credence to the idea that people who are anchored into wider society through multiple social networks are less susceptible to being drawn into or developing sympathies for extremist politics. When we study social networks in relation to a particular form of ‘problematic behaviour’, as well as exploring the social networks associated with risk we should also explore those social networks that may build resilience.
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 Gill and Corner (2015, 40) for example note in their recent discussion of the cases of 119 lone actors who have sought to undertake acts of terrorism, ‘while our sample is defined by the fact that they “acted” alone, there is a lot of evidence to suggest that many of these lone actors interact with co-ideologues during their radicalisation and/or attack-planning. Just less than half (47.9 per cent) interacted face-to-face with members of a wider network of political activists, and 35.3 per cent did so virtually’. BACK UP TO TEXT
 Reflecting a broader societal trend towards becoming what some have referred to as a network society (Castells 1996, 2012, Watts 2004), in which social, media and communication networks are transformed into the primary mode of organization at all levels. BACK UP TO TEXT
 NB. Recruitment into activism is not necessarily recruitment into a group; it might be recruitment to a cause or into a more loosely defined network. BACK UP TO TEXT
 Although there has been some debate about the extent to which these networks emerge from the bottom up or are nurtured and exploited from the top down (i.e. by recruiters) (see Jenkins 2007, Sageman 2008, Wiktorowicz 2005). BACK UP TO TEXT
 Studies have highlighted how social networks facilitated recruitment into movements such as the civil rights movement (McAdam 1982, 1986, Morris 1984), environmental movements (Diani and Lodi 1988), the Paris Commune (Gould 1995), the Velvet Revolutions of Eastern Europe (Opp and Gern 1993), the East German civil rights movement (Goodwin and Pfaff 2001), leftist underground movements in Italy and Germany (della Porta 1988, 1995) and so forth. BACK UP TO TEXT
 A similar observation might be made about recruitment into religious cults (Collins 2001, 34, Stark and Bainbridge 1985). BACK UP TO TEXT
 Selective patterns of interaction are also more likely to bring activists into repeated and emotionally charged contact with people articulating views diametrically opposed to their own – for example, the EDL activists I knew often came into contact, usually online, with left-wing and Islamist opponents. These encounters serve to confirm emergent beliefs about the evil that they believe themselves to be fighting against, thereby further hardening their views and in some cases leading towards tactical radicalisation (Busher and Macklin 2014, Macklin and Busher 2015). BACK UP TO TEXT
 Gill and Corner (2015, 41) describe for example how Nidal Malik Hasan, the shooter at Ford Hood, sought out the opinion of Anwar al-Awlaki on whether he would be considered a martyr if he died in the commission of his planned act. BACK UP TO TEXT
 An observation that has also been made about religious cults (Lofland 1966). BACK UP TO TEXT
 Our social ties may both directly and indirectly shape us, the way we think and the way that we behave, be we also do things with social ties – we use them to achieve our own goals. BACK UP TO TEXT
 Nesser (2010), for example adds valuable nuance to his discussion of the jihadist community in Europe through his observations about how while what he calls the ‘entrepreneurs’ and proteges’ tended to actively build networks the ‘receivers’ or ‘drifters’ tended to be carried along by networks. BACK UP TO TEXT