Like it was yesterday

October 24th, 2023

Written by: Omer Zeliger

            Think back – do you remember what the weather was like on your seventh birthday? What about what you had for breakfast on the last Saturday of 2017, or what you were wearing on your first day of middle school? It’s normal for memories to fade over time, and for unimportant details to lose clarity. Still, there are some people who excel at remembering small seemingly-insignificant details. Super-recognizers, for example, can glimpse a face and accurately recognize it for years afterwards¹, and competitors in the World Memory Championships memorize the order of entire decks of cards in seconds using mnemonic memory techniques². One group of people, who have a rare condition known as Highly Superior Autobiographical Memory (HSAM), would be able to answer all of these questions with near-perfect accuracy.

            When asked about how she learned to drive, Jill Price told The Guardian “The third time I drove a car was January 10, 1981. Saturday. Teen Auto. That’s where we used to get our driving lessons from.”³ Jill Price is the first of only around 100 people to be diagnosed with HSAM^{3, 4}. People with HSAM have excellent recollection of small details from their day-to-day life, even when those events happened years ago.

            Scientists first recognized HSAM in 2000, when Price contacted neuroscientists about her unusual memory issues^{3, 4}. Price described how she remembered the distant past just as well as she remembered yesterday, and how small triggers such as seeing dates could call up old memories and replay them in her head^{3, 4}. Since then, neuroscientists have worked to uncover where HSAM comes from, how it differs from other forms of exceptional memory, and what it can teach us about memory in day-to-day life.

How does HSAM work?

Unlike the excellent memorization abilities that World Memory Champions boast, HSAM is innate – you’re either born with it or you’re not. No amount of mnemonics or practice will teach it to you^{4, 5}. Also unlike World Memory Champions, who are judged on their ability to quickly memorize long sequences of numbers and words, HSAM only boosts autobiographical memory; that is, memories of a personal narrative, like daily events or things a person did. This doesn’t extend to remembering facts⁶ – much to Price’s frustration at school³. In fact, people with HSAM don’t perform much better than people without HSAM at laboratory memory tests such as memorizing long sequences of words^{5, 7}. Interestingly, people with HSAM seem just as susceptible to creating false memories as people without HSAM. In one study, researchers described footage of a famous event that was never caught on tape. They asked participants if they remembered watching the nonexistent footage, and people who answered ‘yes’ were considered to have created false memories of the footage. People with HSAM were no less likely to mistakenly remember watching the footage⁵.

As of now, we don’t know exactly what causes HSAM. Various studies have found structural differences in brain areas associated with memory⁷ between people with and without HSAM. They’ve also shown that people with HSAM activate more brain areas when remembering autobiographical memories than people without HSAM⁶. Other studies show that in the brains of people with HSAM, the hippocampus – otherwise known as the central memory hub – is more closely connected to a wide range of other brain areas, both in general and when actively remembering^{6, 8} (figure 1, right). Researchers think this could give people with HSAM a boost both in creating new memories and remembering old ones. On top of that, in HSAM the hippocampus is less connected to the brain areas that decide how important something is⁸ (figure 1, left). Scientists speculate that people with HSAM have difficulty separating important memories from unimportant memories, leading them to treat even small details as if they were important, memorable events⁸.

One notable study compared how well people with and without HSAM remember day-to-day events across short and long periods of time⁹. Surprisingly, HSAM and non-HSAM participants remembered the events of one week ago equally well. The difference lay in how fast they forgot. While both HSAM and non-HSAM participants remembered more details from one week ago than from one month ago, HSAM participants remembered significantly more details from a month prior than the non-HSAM participants. The same holds true for even longer delays: non-HSAM participants were hard-pressed to remember even a few details from one year and ten years ago, while HSAM participants were still able to give detailed accounts of their days. According to scientists, this might mean that HSAM doesn’t improve the ability to turn experiences into memories. If it did, they would expect to see HSAM participants remember better even at one-week delays. Instead, they believe that HSAM might make people better at bringing back old memories out of storage, or that it gives them an advantage in reinforcing memories over time to stop them from being forgotten.

Current theories explore how HSAM might cause the latter. Scientists have known for years that replaying memories strengthens them⁹, something that many people with HSAM claim they do nearly-constantly^{3, 4, 10}. If replaying memories really is responsible for HSAM, then people who replay their memories more often should have better memories than those who replay them less. Specifically, scientists noted that passively repeating the same thoughts over and over again is common to both HSAM and OCD, and asked whether this OCD-like symptom could be behind HSAM. To test this idea, researchers had participants fill out an obsessional behavior questionnaire. People with HSAM tended to score as high as people with OCD, higher than people with neither HSAM nor OCD⁹. Furthermore, HSAM participants with higher obsessional behavior scores were more consistent about the details when describing the same memory several weeks apart.

There is anecdotal evidence both for and against this theory. On the one hand, it seems to line up with Rebecca Sharrock’s personal experiences. Sharrock, diagnosed with both HSAM and OCD, told Vice in an interview that her most vivid memories are her oldest ones – the ones she would have had more opportunities to replay¹⁰. On the other hand, Sharrock’s experiences might not be universal. After all, most people with HSAM remember fewer details about their decade-old memories than their week-old ones⁹. On top of that, not everyone with HSAM has OCD¹¹. The truth could be somewhere in between. It is possible that HSAM and OCD share some brain machinery making people with one more likely to have the other as well, or that passive remembering contributes to HSAM in some people but not others.

Living with HSAM

Though it sounds like a dream to possess such a clear memory, people with HSAM have described it as something of a mixed blessing^{3, 4, 10}. Multiple people have told interviewers that they tend to hold onto negative experiences longer than their peers^{4, 10}. In an interview about his experiences, Joey DeGrandis told Time Magazine “…I do tend to dwell on things longer than the average person, and when something painful does happen, like a break-up or the loss of a family member, I don’t forget those feelings.”⁴ The ease with which seemingly innocent things like dates can trigger vivid memories can also cause issues. In an email she shared with The Guardian, Jill Price wrote “Whenever I see a date flash on the television (or anywhere else for that matter), I automatically go back to that day and remember where I was, what I was doing, what day it fell on and on and on and on and on. It is non-stop, uncontrollable and totally exhausting.”³

            That’s not to say it’s all bad, as DeGrandis told Time Magazine. “It can be frustrating, but it’s also really wonderful to have easy access to happy memories. I really try not to take that for granted.”⁴ DeGrandis is happy to participate in memory studies in the hopes that understanding HSAM can help people with all sorts of memory problems.

Future research

            HSAM was only recently discovered, and the research into it is only just starting. We currently don’t know, for example, if HSAM is influenced by genetics, or whether sleep plays a unique role in memory formation in HSAM. Most current studies are observational studies: they ask what traits people with HSAM share with each other, and whether those traits are different from people without HSAM. Unfortunately, these kinds of studies can’t tell us the underlying causes of HSAM. Correlation does not mean causation. If an observational study finds differences in brain structure, it can’t distinguish if the differences cause HSAM, or if HSAM causes the differences, or if an unknown third thing causes both. Finding underlying causes requires experimental studies; for example, disrupting brain activity and seeing how it affects memory in people with and without HSAM.

            Experimental studies are difficult in this case. HSAM is innate – we can’t just tell people to practice different memory mnemonics and see if it gives them HSAM. Still, scientists are making progress. A very recent experiment used noninvasive techniques to temporarily disrupt brain activity of one participant with HSAM to test how it affected their ability to recall specific memories¹². The study is a promising start, and expanding the study to include more participants is a clear next step.

            The difficulty in designing experimental studies is one of several roadblocks to HSAM research. To date, only 100 people have been confirmed to have HSAM⁴, and only a fraction of them will participate in any given study. On top of that, many common laboratory memory tests can’t reliably distinguish between people with and without HSAM^{5, 7}. This complicates designing tests for HSAM. Unlike lab tests, where scientists know for sure whether participants remember correctly, there is no way for scientists to verify whether a small detail someone tells them about their day two months ago is accurate or not. Researchers are forced to rely on other measures besides accuracy; for example, the number of details someone is able to list⁹, which may be a less reliable test of memory.

Despite the obstacles, neuroscientists have been making steady progress in understanding HSAM in the two decades since it was discovered. With time, HSAM could help answer questions about how humans learn and remember. Scientists believe that this research could eventually help treat memory disorders such as dementia or other forms of memory loss^{4, 11}. On a more personal level for many of the participants, continuing this research could teach people with HSAM how to manage its more unpleasant sides. In the meantime, HSAM research has done good in its own right by connecting people with HSAM to each other and validating their experiences^{3, 4, 10}. Jill Price told The Guardian how she felt when she read the first research article written about her experiences¹³: “I cried. I wept while I read it. Someone had finally heard me. Because I’ve spent my whole life screaming at the top of my lungs and nobody has heard anything.”³

References

1. Cimons, M. (2021). They never forget a face. Research delves into how ‘super-recognizers’ can do this. The Washington Post.
2. Goodyear, S. (2023). These Canadian memory champs are building ‘mind palaces’ on the world stage. CBC.
3. Rodriguez McRobbie, L. (2017). Total recall: the people who never forget. The Guardian.
4. MacMillan, A. (2017). The Downside of Having an Almost Perfect Memory. Time.
5. Patihis, L., Frenda, S. J., LePort, A. K., Petersen, N., Nichols, R. M., Stark, C. E., McGaugh, J. L., & Loftus, E. F. (2013). False memories in highly superior autobiographical memory individuals. Proceedings of the National Academy of Sciences of the United States of America, 110(52), 20947–20952.
6. Santangelo, V., Cavallina, C., Colucci, P., Santori, A., Macrì, S., McGaugh, J. L., & Campolongo, P. (2018). Enhanced brain activity associated with memory access in highly superior autobiographical memory. Proceedings of the National Academy of Sciences of the United States of America, 115(30), 7795–7800.
7. LePort, A. K., Mattfeld, A. T., Dickinson-Anson, H., Fallon, J. H., Stark, C. E., Kruggel, F., Cahill, L., & McGaugh, J. L. (2012). Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM). Neurobiology of learning and memory, 98(1), 78–92.
8. Daviddi, S., Pedale, T., Serra, L., Macrì, S., Campolongo, P., & Santangelo, V. (2022). Altered Hippocampal Resting-state Functional Connectivity in Highly Superior Autobiographical Memory. Neuroscience, 480, 1–8.
9. LePort, A. K., Stark, S. M., McGaugh, J. L., & Stark, C. E. (2016). Highly Superior Autobiographical Memory: Quality and Quantity of Retention Over Time. Frontiers in psychology, 6, 2017.
10. Woods, L. (2019). 10 Questions for a Woman Who Remembers Every Moment of Her Life. Vice.
11. Mazzoni, G., Clark, A., De Bartolo, A., Guerrini, C., Nahouli, Z., Duzzi, D., De Marco, M., McGeown, W., & Venneri, A. (2019). Brain activation in highly superior autobiographical memory: The role of the precuneus in the autobiographical memory retrieval network. Cortex; a journal devoted to the study of the nervous system and behavior, 120, 588–602.
12. Talbot, J., Gatti, D., Mitaritonna, D., Marchetti, M., Convertino, G., & Mazzoni, G. (2022). Stimulating a hyper memory: A single case TMS study on an individual with Highly Superior Autobiographical Memory. Brain stimulation, 15(5), 1122–1124.
13. Parker, E. S., Cahill, L., & McGaugh, J. L. (2006). A case of unusual autobiographical remembering. Neurocase, 12(1), 35–49.

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Figure created with BioRender.com