One Person’s Astounding Memory Could Help Build Better Brain Tests

Unprompted Flashbacks May Explain Teen’s Rare Memory of Past Days

Hand this 16-year-old girl a date from the past few years, and she can recount the day of the week, the weather, and what she wore. Researchers tested her on eight dates, plus holidays and family trips, and every answer that could be checked held up.

She has highly superior autobiographical memory, or HSAM, a rare ability to recall nearly all of one’s personal past in vivid, accurate detail. Experts think as few as 100 people worldwide may have it. She also reports that old memories pop into her mind uninvited far more often than they did for the 200 people in an earlier survey, by a margin statisticians call unusually large.

Standard memory tests have never explained HSAM, and her scores on them were unremarkable, matching earlier research. A case study in the journal Neurocase now proposes an answer: memories that keep resurfacing on their own may get reinforced each time, until they stick. The researchers say the case could also help improve memory tests for patients.

Teen With Highly Superior Autobiographical Memory Recalled Every Date Tested

Her parents noticed that her memory was unusually strong, and a colleague at Johns Hopkins University referred the family to Emory University in Atlanta. She had no significant medical or psychiatric history. Her mother said she could remember every day from about age 12 onward. If her mother asked how many times she had been to a certain restaurant, the teen could recall each visit. She described her memories as mostly visual, like scenes she can look back on from her own point of view or from outside.

During a June 2024 interview, researchers gave her eight dates, some planned and some chosen on the spot, followed by four holidays and two family trips. “Give me a date and I will tell you everything that happened on that day,” she told them.

For November 5, 2021, she said it was a Friday, her school was closed for the Atlanta Braves’ World Series parade, the sky was overcast, and the sunset was beautiful. She also described her outfit, a taco lunch, and the movie she watched at a sleepover that night. A news article, weather records, and a dated sunset photo posted online confirmed the details that could be checked, including the parade and the weather.

Questionnaire Answers Put Her Unprompted Memories Far Above Average

Her main test was a questionnaire that tracks how often memories surface without being sought, with answers ranging from never to once an hour or more. These results rest on her own reports, since researchers did not monitor her thoughts as they happened or count the episodes themselves.

On the questions about the past, she rated her unprompted memories as popping up somewhere between daily and hourly. The 200 people in a 2015 study that set the benchmark averaged closer to weekly.

Two other traits the researchers examined looked ordinary. Her déjà vu, the feeling of reliving a moment that is actually new, occurred a few times a year, similar to a typical college student. A mental imagery questionnaire put her almost exactly at the average for people with typical imagery, so unusually vivid mental pictures appear not to explain her memory.

Highly Superior Autobiographical Memory May Be Built by Involuntary Replays

Anne M. Cleary of Colorado State University, who led the study, put the proposal in plain terms. “It seems as if people with HSAM are reliving these past experiences more frequently and that strengthens the memories overall, making memories more stable over time for them,” Cleary said in a university release. Asked whether she uses strategies to remember, the teen said she can, “But usually it just sort of happens, just naturally.”

Such a process could also explain why lab tests, which mostly measure deliberate recall, miss what sets people with HSAM apart. It is a bit like measuring rainfall by checking the sky for one minute.

Cause and effect remain unproven. Her case shows HSAM and frequent unprompted memories appearing together in one teenager, not that replays create HSAM. A preprint, a study not yet reviewed by outside experts, reported a 16-year-old boy with HSAM who also showed more frequent involuntary memories on two different measures.

Study Could Point to Better Memory Tests for Surgery Patients

As an example, Cleary pointed to people who have brain surgery to treat epilepsy, a seizure disorder, when medication has not worked. Those patients take memory tests before and after treatment. Some come out with no memory deficit at all, while others pass standard tests but their families still report something lacking.

“We may not have the right assessments in place to fully capture what is going on or to make useful comparisons that would help us learn more about healthy brain functions related to memory,” she said. Studying someone so young may also open new research into Alzheimer’s disease, which affects memory later in life.

Many standard memory tests ask patients to try. This case argues for tests that also catch the memories arriving unasked, the kind that may be missing when families sense something is off after surgery.

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Disclaimer: This article is based on a single case study and is intended for general informational purposes only. It is not medical advice. Readers with concerns about their own or a family member’s memory should speak with a qualified health professional.

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