Understanding terrorism and radicalisation: a network approach

New research on networks has put individual well connected agents at the centre of the spread of many social phenomena, including religious ideas. Much can be learnt from the spread of the medieval Cathar heresy by relatively few individuals, the perfecti. The inquisitors sent to suppress them used various unsuccessful strategies, whose failures can be illuminated by modern network theory. Eventually they achieved success by prioritizing the gaining of information about the movements of heretics and isolating their local contacts. England in the 1550s provides an interesting opposite model of how a society can be radicalized through heavy-handed public persecution. Using a network simulation suggests that the martyrdom of key Protestant leaders may have been a sufficient condition for the conversion of England to Protestantism: had Mary's government not burnt anybody, England might well have remained a Catholic country. These cases suggest, first, that it is important for the rest of society that opinion formers within local communities and families are left alone to make their own judgements on extreme Islamist ideologies, unless they can be shown to have strong active links with terrorism. And second, that it is likely to be more effective to isolate key hubs in a terrorist network by neutralising their close contacts, rather than run the risk of creating a cascade effect through direct persecution and martyrdom. Finally, our work is an illustration of a recent important discovery about systems in which social influence is a determinant of behaviour and ideas: deep knowledge about them can be extracted from limited information. Thus we do not need to know the exact details of a past network in order to be able to draw valuable implications for the present day.