Whitehouse's emphasis on the role of “relational ties” in the justification of extreme acts of self-sacrifice holds great promise for illuminating this perplexing phenomenon. We believe that his model, which focuses on groups of interacting individuals who perceive one another as fictive kin, could be extended in a way that can help us make sense of self-radicalised individuals who are not active in cliques relevant to their fused identity. Previous research suggests that individuals can incorporate concepts of other people, concepts of “God,” and even concepts related to their social identity into their self-image (Aron et al. Reference Aron, Aron, Tudor and Nelson1991; Hodges et al. Reference Hodges, Sharp, Gibson and Tipsord2013; Mashek et al. Reference Mashek, Aron and Boncimino2003; Sharp et al. Reference Sharp, Rentfrow and Gibson2015; Smith & Henry Reference Smith and Henry1996).

As a complement to Whitehouse's use of relational ties, we suggest the idea of “conceptual ties,” which are ties between beliefs that define one's social group and one's own personal identity. Conceptual ties can be formed without local interaction between individuals affiliated with an extremist group. Reflection on emotionally arousing experiences can lead some individuals to incorporate beliefs from a group's social schema into their own self-image. We hypothesize that the formation of such conceptual ties can help explain self-radicalisation in cases where there is no clear evidence of direct interaction of the sort that typically facilitates fusion. Examples include the 2013 Boston Bombing by the Tsarnaev brothers and the 2015 San Bernardino attack by Rizwan Farook and Tashfeen Malik. Although these were not suicide bombings, the perpetrators were ready to become martyrs and die for their religion (Baker & Santora Reference Baker and Santora2015; Chappell Reference Chappell2013).

Data collected by the START project (National Consortium for the Study of Terrorism and Responses to Terrorism 2018), which profiles individuals radicalised in the United States, lend support to both Whitehouse's and our own proposal. Previous analyses of the START project's data set indicate that two of the key factors that drive radicalisation are “community crisis” and “cognitive frame alignment.” The former refers to “collective feelings of intense trouble, difficulty, or danger that often produce instability within a community” (Jensen et al. Reference Jensen, Atwell Seate and James2018, p. 7). This strengthens Whitehouse's claims about group threat as an important moderating variable. Cognitive frame alignment refers to “the learning processes an individual undergoes in forming radical beliefs” (p. 14). The discovery of this radicalisation-promoting factor lends some support to our claim that the internalisation of group beliefs at a distance through conceptual ties could play a role in motivating extreme self-sacrifice.

Our own analysis of the START data also provides warrant for our hypothesis about conceptual ties. Of the radicalised individuals in that data set, 58.5% were not known to be part of a clique, and 64.59% of those individuals who were known to be part of a clique were radicalised prior to membership in the clique. Radicalisation clearly coincides with clique membership for 33.97% of individuals, who were known to be part of a clique. This suggests that local fusion may be relevant in one third of the sample. Furthermore, there is a statistically significant association between the maximum extent of radicalisation manifested in behaviour and clique-mediated individual radicalisation (χ[30] = 75.90, p < .01), suggesting that more extreme behaviours are not performed by those individuals who were radicalised as part of a clique. The data also reveal that individuals’ beliefs radicalise gradually more often (27.7%) than suddenly after a key moment (12.2%). Individual behaviours also radicalise gradually (26.4%) more often than suddenly (17.5%). This highlights the role of reflection as a key component in the radicalisation process and suggests that there are instances when one might “prefer to die for an extended fusion target over a local one” (sect. 6, para. 7).

We argue that relational ties – either actual or perceived – might not be the only means by which individuals become fused to a group and commit extreme violent acts on its behalf. As noted above, many radicalised extremists in the U.S. context are not part of cliques. These data trends suggest that, in some cases, extreme pro-group behaviour and self-sacrifice can result from the gradual internalisation of a group's beliefs into an individual's personal self-schema, which creates conceptual ties (which may act as “sacred values” [Atran et al. Reference Atran, Axelrod and Davis2007]). We suggest that this results in extended fusion by means of “conceptual ties.” Naturally, the data here are suggestive at best; more empirical research is needed to provide additional warrant for our amendment to Whitehouse's theory.