Published online by Cambridge University Press: 26 November 2018
What explains online radicalization and support for ISIS in the West? Over the past few years, thousands of individuals have radicalized by consuming extremist content online, many of whom eventually traveled overseas to join the Islamic State. This study examines whether anti-Muslim hostility might drive pro-ISIS radicalization in Western Europe. Using new geo-referenced data on the online behavior of thousands of Islamic State sympathizers in France, the United Kingdom, Germany, and Belgium, I study whether the intensity of anti-Muslim hostility at the local level is linked to pro-ISIS radicalization on Twitter. The results show that local-level measures of anti-Muslim animosity correlate significantly and substantively with indicators of online radicalization, including posting tweets sympathizing with ISIS, describing life in ISIS-controlled territories, and discussing foreign fighters. High-frequency data surrounding events that stir support for ISIS—terrorist attacks, propaganda releases, and anti-Muslim protests—show the same pattern.
I thank Susanne Baltes, Eli Berman, Abhit Bhandari, Christopher Blattman, Jasper Cooper, Lindsay Dolan, Page Fortna, Grant Gordon, Guy Grossman, Kolby Hanson, Macartan Humphreys, Sarah Khan, Sung Eun Kim, Egor Lazarev, Summer Lindsey, Joshua Mitts, Suresh Naidu, Jacob Shapiro, Kunaal Sharma, Jack Snyder, Camille Strauss-Kahn, Lauren Young, and the Journal’s editor and anonymous reviewers for their helpful feedback. I also benefited from comments from seminar participants at Brown, Chicago, Columbia, Dartmouth, Emory, Michigan, Northwestern, NYU, Stanford, and Vanderbilt. I thank Geffen Huberman for her research assistance. Replication files are available at the American Political Science Review Dataverse: https://doi.org/10.7910/DVN/5QUCW7.