By CHARLES McGRATH


CAMBRIDGE, Massachusetts - Jessica Stern is a renowned expert on terrorists and terrorism. She has taught about the subject at Harvard University and served on the National Security Council. Her 2003 book, “Terror in the Name of God: Why Religious Militants Kill,” consists largely of interviews with extremists of every stripe: Christian, Jewish, Muslim, anti-abortion militants, even followers of Timothy McVeigh, the Oklahoma City bomber.

“I’ve really been studying perpetrators and violence all my life,” she said.

Ms. Stern has been a victim. In her new book, “Denial: A Memoir of Terror,” she recounts how, in 1973, when she was 15, she and her younger sister were raped at gunpoint in their home in Concord, Massachusetts. The police did not believe the girls’ account and bungled the investigation; their father didn’t think it necessary to cut a trip short and return. The whole community, she writes, seemed to be in denial.

The experience created in Ms. Stern a kind of emotional numbness - a calmness, even a fearlessness, that has proved oddly useful in her current work.

“I am fascinated by the secret motivations of violent men,” she writes in “Denial,” “and I’m good at ferreting them out.”

She found that terrorists would talk openly to her, she said, because she could “go into a state where I almost tried to become that person, and where I felt that if I allowed myself even the tiniest judgmental thought, they could probably sense it.

“I would go into this calm - almost as if I could feel a chemical change in my body,” she added. “That’s probably an aftermath of trauma, but I don’t want to medicalize it too much. I also felt intense curiosity.”

Benjamin Wittes, a senior fellow at the Brookings Institution, a nonprofit public policy organization in Washington, D.C., has been a friend of Ms. Stern’s since the late ‘90s. He was astonished to learn she had been raped. “If you met some completely dysfunctional person who you could see was wearing the scars of such an experience, then you might not be surprised,” he explained. “But that’s not Jessie.”

Not the least of her contributions, he added , was that she was one of the first terrorism scholars to realize that the way to discover what terrorists were thinking was to go and talk to them.

“She was asking the right questions of the right people,” he said, “and if some of that comes from her own experience of being terrorized, then the lessons were very fruitful.”

But a possible downside of not feeling too much is that you also experience less joy, and even become disconnected from your own life. It was recognizing these symptoms in herself, Ms. Stern said, that made her decide, in 2006, when the police reopened her rape case, to revisit the whole experience. She learned her rapist was responsible for at least 44 rapes between 1971 and 1973 and served 18 years in prison before hanging himself.

The book, Ms. Stern said, taught her a lot about the effects of post-traumatic stress syndrome, of which she now considers herself a victim, and refined her thinking about terrorism.

In January, she wrote in an article in Foreign Affairs that the sexual abuse of boys in the Islamic religious schools known as madrasas is not uncommon, and neither is the rape of boys in Afghanistan, especially on Thursday, known as “man-loving day,” because Friday prayers are thought to absolve a sinner of all his guilt.

“I’ve known about this for years,” Ms. Stern said, “but until I wrote this book, I didn’t make the connection. I’m not sure how you study it, but I do think it’s there. Humiliation is definitely a risk factor, and this may be a particular kind of it.”