Quick, where were you when you heard about the 9/11 attacks? Who were you with? If you're like most people, you've got answers at the ready. But as it turns out, there's a decent chance your answers are wrong, reports Time.

That's the upshot of a new study in the Journal of Experimental Psychology, which examines people's remembrances after the attacks. In the days after Sept. 11, 2001, researchers across the country asked more than 2,000 people about their personal experiences with 9/11.

When researchers followed up at later intervals, about 40 percent of the stories—or "flashbulb memories," as they're called in the vernacular—had changed. “Human memory is not like a computer,” says study author William Hirst of the New School for Social Research.

“Human memory is extremely fallible.” One quirk: The stories tended to change fairly early, say in the first year, and then remain constant after that. “You begin to weave a very coherent story,” says Hirst.

“And when you have a structured, coherent story, it’s retained for a very long period of time.” Another 9/11 study suggests that the stress of the day took a toll on the heart health of Americans, even those far removed from the attacks.

Researchers in Utah discovered a spike in heart attacks in the months after 9/11, along with telltale changes in DNA strands called telomeres that are affected by stress, reports the Salt Lake Tribune.

The numbers were up "significantly" when compared to the same period in other years, says a researcher at Intermountain Medical Center Heart Institute Genetics Lab. Adds another, "Even though we weren't participating directly in 9/11, it was a very stressful event for the entire country." (By contrast, optimism might improve heart health.)

This article originally appeared on Newser: Your Memories of 9/11 Might Be Wrong

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