It's one of those questions that comes up every now and then: where were you when you heard JFK/Diana died, and where were you on 9/11?
The assumption behind it is that when these big events happen, they stick in our minds. Years later, everyone knows where they were and what was going on in their own lives the moment they heard the news.
But what if that's all wrong?
Shortly after the 9/11 attacks, researchers decided to test how memories of these events hold up over time. They asked 2,100 Americans from all across the country about their own experiences of that day – including where they were when they found out about the attacks, who they were with, and what their reaction was at the time, as well as how confident they were of their own memories.
The study, published by the American Psychological Association, then asked the same participants to answer the same questions 11, 25, and 119 months after the attack.
"The study, therefore, examines retention of flashbulb memories and event memories at a substantially longer retention interval than any previous study using a test–retest methodology, allowing for the study of such memories over the long term," the researchers wrote in the paper.
What they found was that many of the participants changed their story of where they were, or what happened on 9/11 as time went on. What's more, once people had this new narrative of events from that day, that's the story they tended to stick to from there on out. Those first recollections – from just days after 9/11 – were forever distorted, or gone.
"Inconsistent flashbulb memories [of what was happening to the participants at the time] were more likely to be repeated than corrected," the team wrote. "Whereas inaccurate event memories [e.g. What airline or airlines had planes hijacked? How many from each airline? etc] were more likely to be corrected than repeated."
"The accuracy of event memory was mediated by the level of media attention, suggesting that media might not only reinforce accurate [event] memories but also correct inaccuracies."
Essentially, the retelling of the event in the media (through film and documentaries, as well as the news) shaped and corrected event memories, but not personal ones.
"At that point you've told 35 people how you heard about it, and it's been solidified in your memory the way you're telling it, not necessarily how it really happened," flashbulb memory researcher David Rubin explained to the American Psychological Association.
People don't just make errors of omission, Psychologist Jennifer Talarico explained. "They make errors of commission as well, changing a red shirt to a blue one, or saying they were with different people from those they first said they were with."
Memory, as psychology has found for decades, is pretty malleable. In one experiment in 1994, psychologist Elizabeth Loftus famously managed to implant a false memory in around 25 percent of participants that they had been lost in a mall. They were given descriptions of four events from their life, three real ones supplied by relatives, and one false, and asked to write about their memories of the events over a period of five days.
"Chris [one participant] remembered more and more about getting lost. He remembered that the man who rescued him was 'really cool.' He remembered being scared that he would never see his family again. He remembered his mother scolding him," the authors write.
"He remembered the man who rescued him as wearing a blue flannel shirt, kind of old, kind of bald on top.... 'and, he had glasses.' Chris was soon told that one of the memories was false. Could he guess? He selected one of the real memories. When told that the memory of being lost was the false one, he had trouble believing it."
Your own memories of 9/11 and other events from your childhood probably feel similarly firm. So were memories of the participants with changed memories of 9/11.