The Memory Illusion

by Dr Julia Shaw

  Engram spots Kevin. Who the hell invited Kevin? One of his colleagues admits that he let news of the party slip, and then felt it necessary to invite him. Nobody likes Kevin. Kevin seems to take it upon himself to ruin every party. Kevin is an unwanted memory fragment. Perhaps today Kevin is the memory of a news article you read on a recent park stabbing. Or perhaps Kevin is the emotional memory of something really embarrassing that you did in a park years ago. You do not really want to think about such horrible associations, but because they are activated automatically, there is very little you can do to stop yourself. Kevin isn’t just unwanted, he is also very hard to shake off.

  Luckily for Engram, just as he is fuming about Kevin’s unwanted appearance, a friend arrives at Engram’s party with whom he has not connected in an incredibly long time. Engram is excited to reconnect. They find that they still have many things in common, and their bond strengthens. This friend is the memory fragment that is activated through strange or atypical connections in content. Perhaps on just one occasion when you are thinking about the park you are reminded of a trip to Brazil that you took years ago. You are reminded of the lush parks in Brazil, and by increasingly thinking about this experience, you may strengthen the association you have between your local park and your Brazil trip. Engram has so much fun with this friend that he decides he should come to all future parties – you have successfully connected your Brazil memory with your park memory, so every time you think about the park in the future you are also likely to think of Brazil.

  Two people from an adjacent table start talking to one of Engram’s friends and they end up joining the group’s conversation. One of them is incredibly boring. He has nothing exciting, unusual or memorable to contribute, and no one really pays attention to him. He eventually leaves, and it is likely Engram will completely forget he ever interacted with him. This is a situation when there is potential for a new association to be formed, but because of a lack of characteristics that are important for memory formation, the memory is not integrated in the existing network of memories in the brain. This is a situation where no memory is formed.

  In contrast, everyone gets along swimmingly with the other new arrival. She has a lot in common with Engram and a number of other existing group members – she is so interesting and exciting that a few people even add her on Facebook. Here, a new experience has been stored as a new memory, and associations with relevant existing memories formed, which is stored in the brain and linked with existing structures. Perhaps you meet an attractive stranger in the park. The memory of that meeting becomes a new addition to the memories you recall when you think about the park.

  The party is in full swing and some of Engram’s friends are clearly looking for love. The attractive new addition is getting a lot of unwanted attention, and Engram also catches two of his friends getting it on in the spare room. Like people, memory fragments actively look for other memory fragments to make new connections. They are a bit promiscuous – they are willing to hook up with pretty much any other memory fragment if the situation is right. And, thank goodness for that, as it is these automatic attachments of engrams to one another that enable interesting ideas to form. Through our brains experimentally combining memories and ideas in novel ways, we get new associations – it is this that forms the foundations for our ability to be creative and artistic, to birth new ideas and solve complex problems. However, this same tendency can also lead to memory illusions when engrams become connected in ways that are inaccurate.

  All right, party’s over. Beat it, Kevin.

  Fuzzy traces

  One theory that attempts to explain more precisely why we can develop inaccurate memories builds on the theory of associative activation. It is called fuzzy trace theory. I have long thought this to be the cutest name for a theory, and I like to think that the mini-marathon of YouTube cat videos which I tend to use to introduce it in lectures gives my students a great way to remember it. It’s an elegant theory that can be used to explain a lot of memory phenomena. It posits that remembering involves two things: gist and verbatim memory traces. Put simply, a gist trace is a memory of the meaning of an experience, and a verbatim trace is a memory of specific details. Most memories contain both gist and verbatim components. It might be helpful to think about a conversation between two people. Individuals are likely to remember both what a conversation was generally about – the gist – and exact words or sentences that were said – verbatim.

  Memory scientists Charles Brainerd and Valerie Reyna at the University of Arizona20 believe this theory can explain a diverse set of false memory phenomena and can be summarised as a number of major principles. Of these, I think four are sufficient to understand the fundamental mechanisms which enable memory illusions.

  Principle 1: Parallel Processing and Storage. The first principle is that there is a parallel processing of inputs – individuals store ‘verbatim’ and ‘gist’ memory traces at the same time, and store them as independent pieces in the brain. So when looking at a scene we process what it looks like (verbatim) and what meaning or interpretation we assign it (gist) at the same time, and these two sets of information are stored separately.

  Principle 2: Separate Recall. The second principle is that these gist and verbatim traces are also recalled separately. This means that one type of memory trace from an experience can be stronger than another. It also means that one, both, or neither type of memory trace might be accessible in response to a given situation. This helps explain why sometimes we may be able to remember someone’s name (verbatim trace) but cannot remember what they are like (gist trace), and other times we may remember what a person is like but cannot remember their name. In the worst-case we remember neither; in the best-case scenario we remember both. The important point is that the recall of verbatim and gist memory can happen independently of one another, with gist memory being generally more stable over time than verbatim memory.

  Principle 3: Error-proneness. The independent recall of the two types of memory traces opens individuals up to a host of potential memory errors. The inherently imprecise nature of gist memory fragments allows for feelings of familiarity derived from them about a given event to cause the fabrication of verbatim details. For example, an individual might recollect a gist trace that they had a conversation with their friend over coffee (gist), and this could lead to their erroneously placing the conversation at a specific local coffee shop (verbatim). This is a normal process in which an individual tries to make sense of their gist memories in a manner that fits with their personal history. Alternatively, an individual might have a strong verbatim memory of talking to their friend in a specific coffee shop, remembering the exact seats they took, and what they were wearing, but forgetting the gist of why they were there. Building on the strong verbatim trace, the individual may extrapolate and generate a false memory about why they were there.

  While these illusions can happen spontaneously in everyday life, researchers are also able to generate them by intentionally misleading an individual’s connections between gist and verbatim memory fragments. This is something that will be explored in detail in further chapters, as many false memory experiments use this technique.

  Principle 4: Vividness. The fourth principle is that both verbatim and gist processing cause vivid remembering. When verbatim traces are recalled, individuals often seem to re-experience the items and specific contexts. Gist trace retrieval, on the other hand, is sometimes considered a more generic remembering, and is associated with experienced familiarity and the perception that something occurred but cannot be explicitly recalled.

  As already mentioned, when gist traces are particularly strong, they can encourage what are referred to as phantom recollective experiences, which take the familiarity of the gist as a good cue for verbatim interpretations. An individual could feel a sense of familiarity when asked whether a friend partook in an event which they might plausibly have attended – I feel like he was there – and from this might generate an erroneous ve
rbatim memory of actually seeing the friend at the event – he was there. In other words, the realism of gist and verbatim memory traces can be sustained when these traces are recalled separately from each other and recombined with others in such a way as to create a false memory.

  These four principles give fuzzy trace theory a broad explanatory framework that can encompass many of the mechanisms proposed by researchers to help explain when, how and why false memories are generated. To summarise, fuzzy trace theory proposes that memory illusions are possible because each of our experiences is stored as multiple fragments, and these fragments can be recombined in ways that never actually happened. Clearly, our brains are biological and chemical marvels which have some built-in mechanisms on a physiological level that can lead to the generation of complex, physiologically-based, memory illusions. These potential routes for error are largely incidental as a result of the benefits of an associative memory system, for without these associations we would be unable to have the creative, adaptive minds we cherish.

  4. MEMORY WIZARDS

  HSAMs, braincams,

  and islands of genius

  Why no one has infallible memory

  HOW MUCH INFORMATION can the human mind store? This is a question that everyone asks themselves at least once in their lives. Perhaps while Googling frantically for ways to help remember the information we suddenly need to squeeze into our heads for an exam, a job interview, or something similarly daunting. Maybe there are tricks that can help me? Maybe these memory athletes know a secret that I don’t? Or is it just genetics? Oh, I hope it’s not just genetics.

  Leaving aside worries about our own memories for a moment, we know there are individuals who can perform amazing feats of memory. They are sometimes called memory wizards: people who can verifiably recall important information at will – minutes, days or years later – in astonishing detail.

  As described in their 2006 paper ‘A case of unusual autobiographical remembering’,1 James McGaugh and his colleagues at the University of California researched this amazing phenomenon and were contacted via email by a woman they now refer to as AJ:

  Dear Dr. McGaugh,

  As I sit here trying to figure out where to begin explaining why I am writing you and your colleague I just hope somehow you can help me. I am thirty-four years old and since I was eleven I have had this unbelievable ability to recall my past, but not just recollections. My first memories are of being a toddler in the crib (circa 1967) however 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!

  McGaugh and his team agreed to meet with AJ, although they were sceptical about what they would find. It’s not unusual for people to claim to have superior memory, but when tested most of them fall far short of their claims. However, AJ agreed to be tested and probed with a wide variety of memory performance tests and she seemed to be different from all the other cases. The researchers give verbatim examples of her amazing abilities in their paper:

  April 3, 1980? ‘I see it. Spring break. Passover, I went to that week. I was on Spring Break. I see the week. I was in 9th grade. The week before I was on Spring Break. I was into General Hospital.’

  July 1, 1986? ‘I see it all, that day, that month, that summer. Tuesday. Went with (friend’s name) to (restaurant name).’

  October 3, 1987? ‘That was a Saturday. Hung out at the apartment all weekend, wearing a sling – hurt my elbow.’

  Luckily for the researchers, AJ had kept a journal from the ages of 10 to 34, which they could use to verify many of her memories. The team believed AJ’s ability was unique, and found it so astonishing that they thought it should have its own term: hyperthymesia (constructed from the Greek words thymesis, which means remembering, and hyper, meaning more than normal). Based on AJ’s case, they asserted that hyperthymesics could be defined by two features. The first is that they spend a considerable amount of time thinking about their personal past; the second that they have an extraordinary capacity to recall specific events from that personal past.

  This is different from superior memory, which is an enhanced ability to acquire and recall new non-autobiographical information. While AJ has an exceptional memory for her own life events she does not have the same incredible ability to recall information unrelated to her life, whereas superior memory individuals generally excel at this, being extremely good at retaining numbers and facts. The current view of superior rememberers is that their skills are the result of the application of memory strategies acquired through practice, and not innate abilities.2 On the other hand AJ, whose memory abilities were exclusively autobiographical, claimed to be unable to consciously apply strategies to help her learn and retain other kinds of information. This was evidenced by her lack of success in school and bouts of unemployment – indeed she had few of the features one might tend to associate with such an amazing mind. Her memory for numbers and facts was nowhere near as good as her memory for her own life. So what can we learn from such cases about the limits of human memory? Is their perfect memory actually as flawless as it seems? And is such a ‘superpower’ actually desirable?

  HSAMs

  In the last few years hyperthymesics have largely come to be referred to as HSAMs; highly superior autobiographical memory individuals. The whole subject has only really gathered any scientific momentum since AJ came forward in 2005. According to research published in 2013 by Lawrence Patihis and his team at the University of California,3 ‘Highly superior autobiographical memory (HSAM; also known as hyperthymesia) individuals can remember the day of the week a date fell on and details of what happened that day from every day of their life since mid-childhood. For details that can be verified, HSAM individuals are correct 97 per cent of the time.’

  After the research into AJ’s case was published, more than 200 people claiming to have similar abilities contacted McGaugh and his team. There was a new sense of excitement in the scientific community – maybe this kind of ability was more prevalent than had previously been believed; maybe they just hadn’t been looking in the right places. This influx of new claimants had the potential to create a whole new world of groundbreaking memory research. But, just as in many previous instances, case after case turned out to not meet the criteria of true hyperthymesia. The people who contacted them had good memories, but they were not exceptional like AJ.

  Then, just as the researchers were about to give up hope, something magical happened. A second memory unicorn appeared: Brad Williams.

  And, then another, Rick Baron.

  Followed by Bob Petrella.

  And in 2010 the group was even joined by a celebrity, the actress Marilu Henner.

  According to reports,4 at least 56 HSAMs have been identified around the world to date. It remains a small and exclusive club, but it’s a great deal more useful and significant that having just one, solitary, case. Of course, the question on everyone’s mind once they had found a whole herd of these amazing HSAMs, was, ‘How does it work?’

  While it is far too early to have a strong and well-supported scientific explanation for the phenomenon, there are a number of hypotheses.

 
Braincams

  Perhaps memory is like a video recorder, keeping track of everything we do, and HSAMs are just better at using the playback feature than the rest of us. A landmark publication from 1952 simply entitled Memory Mechanisms5, written by the now infamous American neurosurgeon Wilder Penfield, suggests there may be some evidence to support this idea. One of Penfield’s main research interests was treating patients with epilepsy by cutting through parts of their brain. While he had the brain exposed during surgery he also took the opportunity to poke around a bit. He would use electrical probes to stimulate different brain regions and ask his still-conscious patients to report what they experienced. Through this process he was able to identify the parts of the brain responsible for various senses and those responsible for the movement of various body parts. These sensory and motor cortices were mapped out so well by his technique that we actually still use his map today – it is referred to as the cortical homunculus.

  What he found was that when he was stimulating certain parts of the brain, particularly the temporal lobes, his patients reported complex hallucinatory experiences (the temporal lobe is a large part of the brain which sits essentially behind your ears on both sides of your head). When electricity passed along the right and left hemispheres of the temporal lobe, patients reported hearing the voices of loved ones, or spontaneously hearing songs play. This region seemed to directly stimulate their auditory memories.