Can episodic memory be a (narrow) cognitive ability? part two: Highly Superior Autobiographical Memory

Can episodic memory be a (narrow) cognitive ability?  Only If it fulfills a number of conditions.  We've discussed one of them in the previous post.  We've seen that episodic memory develops through the lifespan.

Are there individual differences in episodic memory?  Do people in the same age group differ in their episodic memories?   Apparently so.

In this post we'll discuss people with an especially strong and rich episodic memory. 

Episodic memory is memory for life events that we'd experienced in a specific place at a specific time.  Autobiographical memory is composed of episodic memory and semantic knowledge about ourselves and about things that took place in the world during our lifetimes.  Semantic self knowledge is, for example, knowledge about our character and hobbies and about places we've visited, in a way that is not necessarily tied with specific episodic memories (It's possible for me to know I've been to a specific place and to know what it looks like, without recalling the visit itself).

Semantic memory is the fund of knowledge that we've accumulated (facts, ideas, meanings of words and concepts, knowledge about our culture).

In CHC terms the broad ability "Comprehension Knowledge" is the content of our  memory.  The broad ability "Long Term Storage and Retrieval" is the process of storing this content in memory and retrieving it from memory.

In 2000 Prof. McGaugh, a neuropsychologist at California University, received an intriguing email.  The writer was a 34 year old woman who wrote: "…since I was eleven I have had this unbelievable ability to recall my past, but not just recollections… I can take a date, between 1974 and today, and tell you what day it falls on, what I was doing that day and if anything of great importance (i.e.: The Challenger Explosion, Tuesday, January 28, 1986) occurred on that day I can describe that to you as well. I do not look at calendars beforehand and I do not read twenty-four years of my journals either. 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. Some people call me the human calendar while others run out of the room in complete fear but the one reaction I get from everyone who eventually finds out about this “gift” is total amazement. Then they start throwing dates at me to try to stump me… . I haven’t been stumped yet. Most have called it a gift but I call it a burden. I run my entire life through my head every day and it drives me crazy!!!…"

Prof. McGaugh and his staff were very skeptical about the woman's description, but nevertheless they invited her for a meeting.  This meeting led to five years of numerous tests and interviews.  Very early on Prof. McGaugh and his colleagues realized that her memory was different than other cases of good memories reported in literature.  She wasn't good at storing and retrieving long lists of words, for example.  Her memories were very personal.  They were related to things that interested her and to dates from the period of her lifetime.

The researchers validated her autobiographical memory with events she wrote in her personal diaries which she kept since the age of 10 and with events her mother told them.  As for events in the public domain ("The Challenger Explosion") – the researchers could validate the dates, the day of the week on which they happened and details of these events with external data sources.

The researchers were amazed to learn how extraordinary this woman's memory is.  They published her case in a paper in 2006.

A short time after the publication, her story raised a huge interest in the media.  At first she kept her identity secret, but later she decided to come out with her full name – Jill Price. 

Following the publication six more people with this kind of memory were discovered, leading to this 60minutes episode.

Gradually more cases were discovered and this phenomenon was named HSAM – Highly Superior Autobiographical Memory.   By now there are about 50 people in the world known to have HASM, and they seem to have similar characteristics:

a.  Memory organized by dates.  These people can retrieve episodic memories for specific dates in specific years.  They know what day of the week a specific date fell on.   When given a public event that occurred when they were 10 or older, they can say the exact date on which this event happened.  The event does not have to be very salient, but it has to be one that interested them (even a specific episode of a television series).   

b.  When people with HSAM retrieve an episode that took place many years ago, they relive it emotionally as they have when it actually happened.   Joey DeGrandis who has HSAM says:  "For a given date, I could probably tell you something that happened to me on that day, where I was in life, and the emotions attached to that. When I’m recalling these memories I’m really back there, emotionally. I’ll remember how I was feeling at a certain time very vividly...  The memory will trigger images, sentiments, emotions—literally the way someone looked in a certain light or something like that."

C.  Higher than average blending of semantic and episodic memory.  People with HSAM not only have a rich autobiographical memory but also a wide repertoire of information about events that took place in the public domain (all related to the dates they took place on).  Information in the public domain is usually maintained in semantic memory in a decontextualized form.  For instance, I don't remember where I was or what I was doing when I first encountered the term "political correctness".  Obviously there was an event during which I learned about this phrase, but it now exists in my semantic knowledge without the context during which I acquired it.

Only events in the public domain that are very unusual are coded in our memory with their episodic context.  Everybody probably remembers where he was and what he was doing when he learned about 9/11.  It seems to me that the powerful emotional reaction this event raised made the context inseparable from the semantic knowledge about the event.

I guess by what Joey DeGrandis and others have said, that maybe people with HSAM attach powerful emotional reactions to everyday events, which causes their storage in memory with their context.  This makes semantic memory more organized and facilitates retrieval.  People with HSAM have fuzzy boundaries between semantic and episodic memory.

d.  OCD features.  It seems that people with HSAM have OCD-like features.  For instance some of them keep their things in a specific order.  It's unclear whether the superiorly organized autobiographical memory developed as a coping style with anxiety or the OCD tendencies developed as a way to deal with the flood of autobiographical memories, some of them unpleasant.  There could also simply be a correlation between HSAM symptoms and OCD.  There is a resemblance between the brains of people with HSAM and the brains of people with OCD.  Both have enlarged caudate and putamen.

e.  Maintenance.  People with HSAM tend to activate their autobiographical memory when they rest or daydream, in ways that can be conducive to its organization and maintenance.  For example, they recall all dates on which they had dinner at specific restaurant and what happened on each visit.  Or, they recall what happened on a specific day a year ago, two years ago, three years ago and so on.  Or they try to recall as many dates of a specific year as they can.  Some keep a personal diary.  Some researchers see these maintenance habits also as OCD-like features.

f.  Neurological findings.  people with HSAM have morphological changes in nine brain structures as compared to a control group.  Among these areas are, as mentioned above, enlargements of the caudate and the putamen.

g.   Many of the first people with HSAM had difficulty with relationships.  One of the hypotheses about this is that they clearly remember conflicts with their partners, which makes it harder for them to forgive and carry on.

To summarize, we asked whether episodic memory can be a narrow cognitive ability.  In order to be a narrow cognitive ability it has to fulfill a number of criteria.  One of them is interpersonal differences.  In this post we talked about people at one end of the spectrum – people with HSAM – highly superior autobiographical memory.

Parker, E. S., Cahill, L., & McGaugh, J. L. (2006). A case of unusual autobiographical remembering. Neurocase, 12(1), 35-49.‏ http://www.psych.ufl.edu/~fischler/Hm/Parker06_MemorySavant.pdf

LePort, A. K., Mattfeld, A. T., Dickinson-Anson, H., Fallon, J. H., Stark, C. E., Kruggel, F., ... & McGaugh, J. L. (2012). Behavioral and neuroanatomical investigation of highly superior autobiographical memory (HSAM). Neurobiology of learning and memory, 98(1), 78-92. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3764458/

LePort, A. K., Stark, S. M., McGaugh, J. L., & Stark, C. E. (2015).Highly superior autobiographical memory: Quality and quantity of retention over time.Frontiers in psychology, 6.‏ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720782/