What makes a person want to become a terrorist? Who becomes involved in terrorism, and why? In what ways does participating in violent extremism change someone? And how can people become deradicalized? John Horgan—one of the world’s leading experts on the psychology of terrorism—takes readers on a globe-spanning journey into the terrorist mindset. Drawing on groundbreaking personal interviews as well as decades of research from psychologists and others, he traces the pathways that lead people into violent extremism and explores what happens to them as their involvement deepens. Horgan provides an up-to-date, evidence-based understanding of the patterns, motives, and mentalities of violent extremists from the Islamic State and al-Shabaab to white supremacists and incels. He argues that there is not a straightforward psychological profile of a terrorist, in part because of the great variety of today’s extremists, who are able to attract a more diverse pool of recruits than ever before. But even though there is no one-size-fits-all profile, psychological study can provide crucial insight into why and how people become terrorists. Accessible and nuanced, is an essential book for readers interested in what psychology can explain about extremist behavior.