You remember where you were on 9/11. Four in ten details are wrongYour memories of how you heard about 9/11 may well be wrong – we’ve been asking the same people what they remember for 25 years

How did you first hear that something had happened on September 11, 2001? A panicked call from your mother, a roommate shaking you awake, anxious talk on the commuter train? Researchers have been asking the same people for 25 years, and their answer is that roughly 40% of those details are wrong.

It is not the event, it is where you were

Psychologists call this a flashbulb memory. Most news is forgotten by the next day, but a handful of events — Kennedy's assassination, for instance — get lodged for life.

In the days after the attacks, researchers asked a few thousand Americans how they had heard, who they were with, where they were, what they had been doing beforehand, how they felt, and how confident they were. Then they went back to the same people after one year, three years, ten, and now a quarter century.

After just one year, about 40% of the details no longer matched what those people had said at the start. One man said he had been on a train when he heard; originally he had said he was at work. Another said she was with her husband; a year later she remembered being with her son.

Once the error settles, it never moves

The strange part is not the mistakes but the reaction: that may be true of other people, but my own memory is correct. The researchers admit they believe the same about themselves.

Worse, the version people settle on after a year stays stable for years afterwards. Wrong, and wrong with conviction.

Why the confidence? The event was so charged that a few key details stick hard, and confidence inflates along with them. And people retell the story, others nod along, and the confidence gets another boost.

Remembering it is claiming an identity

A memory you trust is more likely to define who you are and steer what you do next. The life story people assemble tends to put them in a flattering light.

Flashbulb memories belong to a group; they bind you to one. In a 1970s survey, 75% of Black Americans remembered how they heard about Martin Luther King Jr.'s assassination, against 32% of white Americans. Most Britons remember where they were when Diana died. Most Italians do not.

One study found that Americans with a 9/11 flashbulb memory are seen as more American than those without. Forgetting that memory was judged a bigger loss of identity than forgetting the attack itself.

So the story you told on the anniversary may have details wrong — but it ties you to other people. Getting a few of them wrong may not matter much at all.