Jessica Stern Reflects on the Legacy of 9/11, Terrorism, and the Lessons Still Unlearned
Twenty-five years after the attacks of September 11, 2001, Research Professor Jessica Stern and one of the world’s leading experts on terrorism and perpetrator psychology, reflected on the lasting impact of 9/11 in a recent episode of Harvard University’s Colloquy podcast. Speaking with host Paul Massari, Stern discussed how the attacks transformed American society, shaped counterterrorism policy, and influenced her own career studying violent extremism. Recalling the day of the attacks, Stern remembered immediately recognizing that the event would mark a turning point for the United States,
“We have lived through the safest and happiest years of our lives as a nation, and things are going to go downhill.”
Drawing on decades of research and interviews with terrorist leaders and recruits around the world, Stern challenged common assumptions about what motivates people to embrace extremist violence. Early in her career, she accepted the prevailing belief that terrorists were primarily ideological fanatics.
However, after conducting fieldwork with members of organizations ranging from Hamas and Hezbollah to Pakistani jihadist groups, she reached a different conclusion. “The terrorists themselves taught me that I was wrong,” Stern explained.
Many individuals are drawn into extremist movements through a combination of personal trauma, social relationships, economic incentives, and a search for belonging, with ideology being only one factor among many. Her experiences interviewing militant leaders also challenged romanticized notions of extremism, revealing how, in some contexts, involvement in terrorism can function as a career or pathway to status rather than a purely ideological mission.
Stern also discussed how the nature of terrorism has evolved since 9/11. While international terrorist networks remain a concern, she noted that the U.S. has significantly strengthened its defenses against large-scale attacks.
We’ve made it very hard for a terrorist organization to repeat 9/11. In fact, all the terrorist attacks since 9/11 that have occurred in the United States have been carried out by US citizens or legal US residents, except one. Just one was carried out by a foreign terrorist. We’ve made a lot of progress.
Today, Stern sees growing threats from domestic extremists and what the FBI describes as “nihilistic violent extremism,” a form of violence motivated less by political goals than by destruction itself. Research she has conducted on radicalized youth suggests that mental distress, social isolation, and personal grievances often play a greater role than ideology in contemporary cases of violent radicalization.
Looking to the future, Stern emphasized the importance of prevention and thoughtful policymaking. Drawing parallels between public health approaches and violence prevention, she highlighted programs that identify at-risk individuals early and provide mentorship, counseling, and other interventions before violence occurs.
At the same time, Stern argued that one of the most important lessons of 9/11 remains insufficiently learned: the need for leaders to resist “action bias” in moments of crisis. Reflecting on the wars, policies, and national decisions that followed the attacks, she urged policymakers to carefully weigh the long-term consequences of their responses. For Stern, understanding both the trauma of terrorism and the complexity of those who perpetrate it remains essential to preventing future violence while responding wisely to emerging threats.
The full interview can be read and watched here.
Jessica Stern is a research professor at Boston University’s Pardee School of Global Studies and a globally leading expert on perpetrator psychology. A 2024-2025 Harry Frank Guggenheim Distinguished Scholar, Stern has taught courses on counterterrorism for over 25 years – at Boston University, Harvard, and CIA University. She has also been named a John Simon Guggenheim Fellow. She is the author of five books on perpetrators of violence and is currently at work on a book on prevention.