So where does that leave us? Both Reicher and Atran believe that future research should focus less on why people decide to perform extreme acts, and more on what draws them to extreme organisations in the first place. Speaking at the UN, Atran argued that young people need a dream. Appeals for moderation will never be attractive to “youth, yearning for adventure, for glory, for significance”, he said.

But Fried is encouraged that neuroscience has bolstered the idea of Syndrome E, and still believes we can benefit from thinking in terms of what is going on inside the brain of a killer. What’s more, group dynamics might help explain why the PFC is at the root of evil. After all, the recently evolved parts of the brain respond to rules precisely because rules are essential for the smooth functioning of groups. The possibility that this useful response may go into overdrive is perhaps the price we pay.

Fried is not a proponent of using drugs to treat Syndrome E. Instead, he thinks we should use our growing neuroscientific knowledge to identify radicalisation early, isolate those affected and help them change. “The signs and symptoms should be made widely known, so that people can spot them,” he says. When it comes to prevention, he thinks education is probably the key. And in that, at least, he agrees with his detractors.