Health and Medicine
PUBLISHED
Remembering what you had for dinner last night, or why you entered the room you just walked into, can be a tricky task, so imagine what it would be like to recall any given day in your past at the drop of a hat.
People with highly superior autobiographical memory (HSAM) don’t have to imagine; they possess the incredible ability to access memories from their own lives with ease, even decades later.
A rare ability
HSAM, or hyperthymesia, is extremely rare. Studies have documented only around 100 people with the ability. The first official record was a subject known as AJ in 2006, although there are descriptions of individuals who seem to possess the same traits going back to the 1870s.
“Internal or external cues, including dates from one’s life span […] can elicit HSAM individuals to access specific memories from nearly every day of their past,” a 2024 systematic review explains.
“The skill also involves a remarkable ability to locate memories temporally; participants can accurately and confidently report exact time-related details (e.g., day of the week) of events of their own life and public events of which they have a personal recall.”
The recall, it goes on to say, is “accurate” and “extensively detailed”.
However, this isn't the same as “photographic memory” – a concept that cognitive neuroscientist Professor Jon Simons previously told IFLScience is “not supported by scientific evidence”. HSAM “doesn’t involve perfect recall of visual details like images or texts”, the way the movies might have you believe.
That, Simons explained, is probably closer to eidetic memory – which is real but again exceptionally rare, and is most often found in children.
Memory itself is still shrouded in many unanswered scientific questions, and our understanding of why this small group of people possess such a hyperactive memory of personal events is similarly limited.
A new person identified
In a new study, scientists attempted to address some of these questions by documenting the case of a 16-year-old boy, KCL. He had contacted one of the authors himself seeking testing, as he believed his autobiographical memory was unusually good.
First, they confirmed that KCL met the criteria for HSAM. On two different tests, KCL’s performance was well above average compared with a control group, with some elements of his memory recall classified by the authors as “extreme”.
One of these tests was the Random Dates Quiz, where the maximum possible score was 30 points. KCL achieved 25, compared to an age-matched control participant who scored just 7.
This test involved the participants remembering the day of the week, any public events, and any personal memories from 10 randomly selected dates.
Do you know what you were doing on, say, September 28, 1999? Or even March 4, 2026? You might be able to work out the day of the week if you’re a math whizz, but do you remember it? Yeah, us neither. But the authors noted that KCL generally wasn’t guessing and could actually remember these things with confidence.
A world-first experiment
Once it was established that KCL truly does have HSAM, the authors wanted to learn more about how it works, using an experimental approach that, to their knowledge, has not been used before.
When the case of AJ was first reported in 2006, it was noted that her recall was “automatic, involuntary, and persistent”, the study authors explain. That was distinct from others who had shown incredible memory abilities, but who were using strategies like mnemonics.
Interestingly, though, HSAM is not thought to be associated with exceptional cognitive ability more generally, or above-average recall of other types of memory.
It’s also thought that individuals with HSAM are susceptible to false memories and memory distortion in the same way the rest of us are – their recollections may be very detailed, but they’re not necessarily perfectly accurate.
The scientists particularly wanted to investigate KCL’s involuntary memory recall to learn more about this process.
While performing a computerized task, KCL was periodically asked about the thoughts that had crossed his mind. The data showed that KCL was spontaneously remembering events from his own lifetime much more frequently than average.
“Our results provide the first laboratory-based evidence that HSAM may be associated with an increased frequency of involuntary autobiographical memories,” the authors write.
The results also corroborated what had been previously observed: that KCL’s exceptional cognitive traits were specific to his autobiographical memory, and that his cognitive performance more generally was within the typical range.
“Overall, the present study advances current understanding of HSAM by demonstrating that its uniqueness may lie not only in what is remembered, but in how autobiographical memories are accessed,” the authors write, “highlighting accessibility and retrieval dynamics as key mechanisms underlying exceptional autobiographical memory.”
The study is published in the journal Cortex.
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