‘She’s afflicted by these memories… they flood her’

Not many people can remember their first birthday, but Rebecca Sharrock has no trouble recalling hers in vivid detail. Her present was a Minnie Mouse toy, coloured bright red and white with pink bows on it. She didn't like its smile.

'It had a distinctive comical face,' she says. 'I couldn't verbalise it at that age but the toy terrified me. Its face and all the bright colours scared me, so I'd push it away and cry whenever it was shown to me. Whenever it was in my cot I'd just throw it out.'

That day after breakfast, Sharrock recalls her mum putting her in an itchy satin dress before her birthday celebrations, which were held in her family garden in Queensland, Australia. She clearly remembers her homemade birthday cake and also, unfortunately, putting her finger in the candle.

Her birthday isn't the only very early memory Sharrock recalls. In fact she can remember what was happening on every date since 1 January 2004, when she got her first calendar. What was she doing on 23 May 2006? 'It was a few weeks since the Tanzanian miners had been rescued. They had gone over to America and gone on Good Morning America and talked to Diane Sawyer, and it was Todd Russell and Brant Webb; they were the ones rescued. But they were actually rescued from the mine on the 9th of May, which was two weeks before. All our media was focused on them at that time, on the 23rd.'

It was a Tuesday, which was Sharrock's least favourite day at school. 'I had art, which I liked doing, but I didn't like my teacher that much and the classes were an hour and half long. I had Art, History and English that day. Whenever I went to bed on a Monday night, I'd dread waking up the next day.'

It wasn't until she was 21 – on 23 January 2011 – that Sharrock realised she had a rare condition. Her parents were watching a TV programme that had a group of six people who had been identified by the University of California, Irvine (UCI) as people with highly superior autobiographical memory (HSAM). Reporters were talking about the participants' recollections and commenting on how amazing it was, which initially confused Sharrock. She saw that kind of recall as 'normal'.

Sharrock's parents then sent UCI an email and a fortnight later, they got a reply from the university, saying they were willing to test Sharrock to see if she had the right kind of memory for their study. She did.

Discovering HSAM

People with HSAM are able to instantly able to recall an unusually large amount of their past, often from a very early age. It is a condition that has only been diagnosed with 60 people in world, but some psychologists believe it is more common than we might think.

The first identified case of HSAM was Jill Price. In 2000 she emailed Dr James McGaugh at UCI saying she had a problem with her memory. She had been remembering every day of her life since she was 14, on Monday 24 August 1981, when she began keeping diaries (Parker et al., 2006).

Although McGaugh is mainly retired now, Dr Michael Yassa, Director of the Center for the Neurobiology of Learning and Memory at UCI, is following in his footsteps and researching HSAM. Yassa and Dr Craig Stark have been working with groups studying identical twins with HSAM, as well as adult participants. Yassa believes that the condition is not as rare as the numbers imply. 'I think frequency and the prevalence is much higher than we can appreciate by just looking at those numbers. There's a major selection bias as you can imagine – the people that are reaching out are people that have found out that this may be something special.'

Yassa says it is likely there are many people with HSAM that see it as everyday cognition and because of this haven't come forward. 'If we had access to people's biographic memories in very, very large cohort studies with thousands of people, I could probably give you a much better estimate as to how frequent it is,' he says.

Professor Michael Anderson, senior scientist and programme leader at the Neuroscience faculty at Cambridge University, whose work specialises in memory control, says: 'It's only something that's came on our radar since Jim McGaugh's paper and the emergence of Jill Price… as a consequence, we don't have any real sense of what the actual frequency is. The number 60 is the number of people who have been successfully identified and that have come out of woodwork on their own.'

Nature or nurture?

There are two main schools of thought regarding the cause of HSAM. Psychologists like McGaugh, Stark and Yassa believe individuals with the condition have different neural makeup to people with normal memory. Yassa deems HSAM 'a big caveat' for the understanding of memory and anticipates new chapters in textbooks being written on it.

But there are other psychologists who believe that people with HSAM weren't born with biological differences. Instead, they believe it is derivative of other behaviours, such as having an obsessive compulsion to remember dates. A representative of this school of thought is Swedish psychologist K. Anders Ericsson.

Ericsson, who focuses on the psychology of expertise, conducted famous studies on memory in the 1980s, one in which he trained a man (named SF) with an average memory to report back as high as 80 digits in a row presented one digit at a time (Chase & Ericsson, 1982). Such studies suggest that people with HSAM have learnt techniques to recite vast quantities of information from when they were young by habit, rather than being born with biological differences that then lead to superior memory.

Although Michael Anderson leans to the McGaugh side, he believes that HSAM hasn't been studied in enough detail to fully ascertain which point of view is correct. 'People with HSAM tend to rehearse their memories a lot. Jill Price kept a meticulous collection of diaries, recording everything that happened to her every day of her life. You think that if you write things down, you're going to think about it in detail and remember it better. Maybe she's not extraordinary; maybe she just developed ways of remembering these things, like the examples in Ericsson's studies."

However, Anderson says there are many behavioural indications that suggest that the answer is more complicated than that. 'What happens with Jill is that she's afflicted by these memories. She walks around in her daily life and whenever she looks at a tree, she gets ten memories about a tree. She's not surfing through her organisational network trying to remember things that she's intentionally memorised. They flood her, and she seems to do this with very little effort.'

Professor Lawrence Patihis, at the University of South Mississippi, is another person more convinced by McGaugh's theory. Patihis's research has looked into the relationship between HSAM and other individual differences, including emotion and sleep quantity. 'What I think you need to develop HSAM is a healthy brain with perhaps good genetics for memory structures, an obsession or passion with remembering autobiographical events, a motivation to link dates to events and recall previous dates on a frequent basis,' he says. 'You also need a good imagination and to be easily absorbed into current and past events, and years and years of practice and repetition.'

Patihis believes that people who train to remember vast quantities of information will not be able to sustain it long-term without three stable personality traits: being mildly obsessive of life events and dates, being highly imaginative and being highly absorptive. 'For others, if you keep up practising HSAM for a few weeks here and there, you will not develop memories connected to every date for a period of 20 or 30 years. It takes stable personality tendencies to keep it going daily for decades.'

Although it's an area of interest, Yassa doubts you can teach HSAM to individuals with normal memory. 'You probably can get people to be much more mindful and able to remember details of everyday life, but the individuals we've tested are truly off the charts. I really struggle to see that if we train someone for a year or two, how we would be able to get someone to [remember to] that extent.'

Despite having exceptional memory for life events, people with HSAM don't have perfect memories. Sharrock calls her photographic memory 'terrible', often performing poorly in some of the photographic memory tests at UCI. Although compared with her long-term memory it is not as strong, Sharrock's short-term memory is still quite high: in a memory test for which controls typically get around 50 per cent, she scored 90 per cent.

Some studies suggest people with HSAM are able to forget short-term memories (LePort et al., 2016) and create false memories (Patihis et al., 2013). 'People with HSAM forget over a 24-hour period just as much as you or I would,' says Yassa. 'The difference is that after 24 hours have passed, they are likely to continue to remember for a good long time, whereas you or I just precipitously decline.'

Neural basis and comorbidities

Sharrock's favourite aspect of her condition is that it gives her the chance to contribute to research. By studying people with HSAM and SDAM (severely deficient autobiographical memory, the opposite of HSAM), neuroscientists may be able to find cures for memory loss in diseases like Alzheimer's or Parkinson's.

Most of a person's memories are storied in the hippocampus region of the brain. In Alzheimer's, damage to the hippocampus affects a person's short-term memory and their sense of direction (Hyman et al., 1984). Yassa says his team has found a slight enlargement in certain brain regions of people with HSAM compared with controls, including the medial temporal lobes (associated episodic memory) and caudate nucleus (associated with habit formation).

However, Yassa says that people with HSAM do not seem to be struggling in a clinical or psychiatric sense, although 'the overwhelming majority to this point' have expressed symptoms of obsessions and compulsions (LePort et al., 2012). 'It's possibly associated with the HSAM phenomenon itself; it's possible that the HSAM is part of an obsessive compulsive syndrome, but certainly you don't see everyone with obsessive-compulsive disorder having HSAM – that would be oversimplifying it, I think. Although HSAM isn't a clinical condition, I believe OCD may be a comorbidity – it tends to happen with it and quite often, but may have a distinguishable neural basis.'

Anderson agrees, believing that people with HSAM process their memories in different ways to the average person. 'What we know is that they tend to reflect on their memories a lot more; they're much more obsessive about rethinking about and reviewing their memories.'

No one in else in Sharrock's family has been identified with HSAM, but her mother and her sister have really strong memory for past conversations. Sharrock's mother often brings up conversations she had with her friends over 20 years ago. Sharrock also has relatives on both sides of the family with autism. Yassa adds that more HSAM participants are coming to the UCI labs with autism than there was initially, suggesting there could be a link between the two conditions. 'I think that could be another comorbidity but the association between either OCD or autism and HSAM still needs to be clarified quite a bit.'

A blessing or a burden?

The majority of Yassa's participants think that having HSAM is a blessing that helps with everyday social interaction. According to Yassa, many of them are successful in people-based jobs such as media and communications.

The condition helps Sharrock memorise scripts for public talks, so she has a backup if she gets tongue-tied. HSAM also helps her write and memorise books she reads. Sharrock is a big fan of Harry Potter, having read the books several times and memorised them word for word.

Now nearly 28 and having been aware of her condition for seven years, Sharrock has been writing her own book, called My Life Is a Puzzle, which is written like an autobiography. It has been in the works for six months, and Sharrock is now writing up the 17th year of her life. 'Every year of life I've had a lot of memories. And since a lot of people are really interested in how I thought as a newborn child, I've added to that chapter,' she says.

As she writes, Sharrock experiences the emotions she felt at the time, meaning she finds it difficult to write about the negative memories, which she often finds hard to suppress. 'I call them intrusive memories – when I get a memory of a bad experience and it just intrudes on what's supposed to be happy. Whenever I relive a bad experience, these same emotions come back and I re-experience. My conscious reasoning is like an adult, but my emotions are however old I was at the time of that memory. So, if I was depressed when I was a young child, I'd relive it with it with the same emotion as I did back then. It makes me confused and anxious because my mind is still like an adult's.'

Often the intrusive memories stop Sharrock sleeping. 'Whenever I'm in the dark in silence, all of a sudden, all of these memories involuntarily come through in flashes and it keeps me awake. I have to go to sleep by being stimulated. I've got to have at least a bit of light on and noise such as the radio or television to distract my mind from those memories.'

Sharrock often finds it difficult to make plans in the future, but has got better at it by learning specific techniques that work for her. 'It's really hard for me, because I'm more connected to my past than my future. Whenever I plan ahead, I have to base my future on my past.'

Future research

Yassa is working on several projects, including a distinct population of HSAM adults that have been tracked at UCI since 2006. The university is also working with children with HSAM and their parents. 'We're trying to identify the extent we can emulate their highly superior autobiographical memory in the laboratory, as opposed to just relying on their own testimonies from their past histories. We're also trying to understand the neural basis, certainly expanding our sample size and looking at the developmental trajectories in children.'
Yassa hopes that in the next couple of years, he'll be able to get large-scale funding to do an HSAM study on not just hundreds, but thousands of individuals. This way he can avoid selection bias by actually contacting the HSAM participants himself, allowing him and his colleagues to do a massive screening of people.

He's also looking to create an animal model of the ability in order to closely examine differences in neurotransmitters between HSAM individuals and controls. 'Understanding the fundamental biology of these individuals will allow us to have informed translational approaches to a lot of clinical disorders, including autism, OCD, dementing illnesses and other diseases that have to do with memory loss,' says Yassa.

If there is a neurochemical process or a protein expression that is found to be rampant in HSAM individuals, it can give the UCI targets to manipulate with therapeutics to help treat conditions such a dementia.

Yassa adds: 'The implications are really limitless, but the emphasis for us is to be able to understand the fundamental biology of those individuals. That will really be the first key step before we can start applying it to disease.'

Box: HSAM in fiction

Although highly superior autobiographical memory (HSAM) is a relatively little-known condition, there have been a number of instances where it has appeared in fiction, whether that's in books, films or television shows.

One notable example is in the US TV series House, in an episode called 'You Must Remember This', which tells the story of a waitress with HSAM. The waitress is able to remember a woman who had come to her café before and recall precise details about her, including what colour her hair was and what dish she ordered when she previously came in. HSAM also heavily features in the aptly titled Unforgettable, a TV series about a detective who is able to remember in a way someone with HSAM can. Despite its title suggesting otherwise, Unforgettable does concede that HSAM memory isn't flawless – it poses problems for the lead character Carrie Wells when she is not able to remember what happened on the day her sister was murdered.

There's also an example of HSAM in film. In the 2014 movie The Dark Place the story's protagonist, Keegan Dark, often sees memories as screens in the air. The flashbacks are often distressing and intense. Despite its original content, the film wasn't well received, scoring a measly 4.6 out of 10 on online movie database IMDb.

A short story written over 70 years before The Dark Place portrays someone with HSAM-like characteristics. In 1942, Argentine writer Jorge Luis Borges wrote 'Funes the Memorious', a short story about Ireneo Funes, a boy who was able to remember anything. Although some of Funes' symptoms weren't typical of HSAM, such as always able to tell the correct time without looking at a clock, many of them were. Borges says Funes was able to know 'by heart the forms of southern clouds at dawn on the 30 April 1882' and could compare them in his memory 'with the mottled streaks on a book in Spanish binding he had only seen once and with the outlines of the foam raised by an oar in Rio Negro the night before the Quebracho uprising'. However, the author sees Funes' remarkable memory as something that limits him from thinking, as 'to think is to forget differences, generalise, make abstractions'. Borges says that in Funes' world, 'there were only details, almost immediate in their presence'. Unlike many people with HSAM, the tale says that Funes was not born with an incredible memory: instead he acquired it after falling off his horse and receiving a serious head injury. Although highly superior autobiographical memory (HSAM) is a relatively little-known condition, there have been a number of instances where it has appeared in fiction, whether that's in books, films or television shows.

- Jack Dutton is a freelance writer
[email protected]

- For more on Rebecca Sharrock, see our Research Digest 'super week' from 2013.

References

Chase, W.G. & Ericsson, K.A. (1982). Skill and working memory. In G.H. Bower (Ed.) The psychology of learning and motivation (pp.1–58). New York: Academic Press.

Hyman, B.T., Van Hoesen, G.W., Damasio, A.R. & Barnes, C.L. (1984). Alzheimer's disease: Cell-specific pathology isolates the hippocampal formation. Science, 225(4667), 1168–1170.

LePort, A.K., Mattfeld, A.T., Dickinson-Anson, H. et al. (2012). Behavioral and neuroanatomical investigation of highly superior autobiographical memory (HSAM). Neurobiology of Learning and Memory, 98(1), 78–92.

LePort, A.K.R., Stark, S.M., McGaugh, J.L. & Stark, C.E. (2016). Highly superior autobiographical memory: Quality and quantity of retention over time. Frontiers in Psychology. doi:10.3389/fpsyg.2015.02017

Parker, E.S., Cahill, L. & McGaugh, J.L. (2006). A case of unusual autobiographical remembering. Neurocase, 12(1), 35–49.

Patihis, L., Frenda, S.J., LePort, A.K.R. et al. (2013). False memories in highly superior autobiographical memory individuals. Proceedings of the National Academy of Sciences, 110(52), 20947–20952.