The Memory Illusion: Remembering, Forgetting, and the Science of False Memory

by Julia Shaw

Semantic memory, also called generic memory, refers to the memory of meanings, concepts and facts. Individuals are often better at remembering certain types of semantic information than others.

Semantic memory works alongside episodic memory, or autobiographical memory.

This term refers to our collection of past experiences. It is our personal memory scrapbook; our mind’s diary; our internal Facebook timeline.

Any event, no matter how important, emotional or traumatic it may seem, can be forgotten, misremembered, or even be entirely fictitious.

Our brains piece together information fragments in ways that make sense to us and which can therefore feel like real memories. This is not a conscious decision by the ‘rememberer’, rather something that happens automatically. Two of the main processes during which this occurs are known as confabulation and source confusion.

A concept that often comes up in discussions of short-term memory is that of ‘working memory’. This term generally refers to a larger theoretical construct that has to do with how we flexibly keep information in mind while we do things like problem-solving – short-term memory is generally considered a type of working memory. Conceptual differences between these terms and the way they are used are often incredibly important for researchers, but for the sake of this discussion, I’m going to use them interchangeably.

The research showed that short-term memory is closely related to our ability to use our higher level thinking (frontal lobe) in harmony with our senses and language (parietal lobe), and that this ability improves with age.

What memory researchers mean by ‘long-term’ is often anything that is kept in the memory for longer than 30 seconds (although, once again, researchers argue about this). However, the term also encompasses memories that we have until we die – including our episodic memories of events and our semantic memories of factual information.

Because young children and infants don’t properly understand or discriminate they don’t have any framework for understanding what they should be trying to remember and what they should be forgetting.

The results of this study mean that not only can infants remember things for at least a day, which of course counts as long-term memory, but their brains also process and store information about the emotion that was attached to an experience.

We know that parts of the brain responsible for long-term memory, including part of the frontal lobe and the hippocampus, begin to grow at around eight or nine months,12 so before this it is impossible for infants to have any memories that exceed about 30 seconds.

The basic foundations of long-term autobiographical memory are established within the first few years of life, but the main structures involved in memory (the hippocampus and related cognitive structures) actually continue to mature well into early adulthood.

According to Maja Abitz17 and her team, adults actually have whopping 41 per cent fewer neurons than newborn babies in important parts of the brain that play a role in memory and thinking, such as the mediodorsal nucleus of the thalamus.

Pruning unnecessary synapses is a crucial step in the learning process, as in addition to forming meaningful connections between related concepts in the brain, we need to be able to get rid of inappropriate ones.

Metamemory is an individual’s awareness and knowledge of their own memory. It includes our knowledge of our own memory capacity, as well as an understanding of strategies that can improve our memories. And it also includes our ability to monitor what we can accurately remember, and to analyse our memories to confirm their plausibility.

In addition to seeing, hearing, feeling, tasting and smelling, we are also constantly processing information about gravity, outside temperature, humidity, internal temperature, the location of our limbs in relation to the rest of us, tiredness, how our internal organs are doing, and muscle tension, to name but a few. And as with the other senses, if something is interpreted incorrectly during any of these many simultaneous processes – each of which is imperfect – it has the potential to introduce error into our memories at their inception.

The Yerkes–Dodson theory of performance can help us with this. Developed in 1908 by Robert Yerkes and John Dodson, the theory suggests that performance on any task will improve as arousal increases up to a certain optimum point. However, beyond that point further arousal will actually worsen performance. The suggestion is that at the extremes, at no arousal or incredibly high arousal, a person cannot perform a given task at all.

In other words, as our arousal increases, our memory focus generally narrows. We become better at remembering critical information about the incident that made us aroused, but we often become worse at remembering contextual information.

Sometimes referred to as the fourth dimension – an extension of our 3D physical reality – time is something that could be considered a primarily internal phenomenon. It is characterised by linearity, sequentiality and change; by growth or destruction. Our subjective perception of time is known as chronesthesia,13 and it is studied by researchers from fields as diverse as neurophysiology, psychology and philosophy. And what all of these scientific disciplines have demonstrated is that, perhaps unsurprisingly, memory is vital for our ability to perceive time.

They would say that many individuals, particularly those with time prediction problems, engage in the ‘planning fallacy’,14 which means they overly focus on what they refer to as ‘singular’ information, information that is associated with a single task.

They found that people were generally optimistic in their estimates, tending to discount past failures to complete things on time, and generally underestimating how long tasks actually took to complete. In other words, we seem to believe that our future selves are going to be superheroes at doing things quickly – new you excels at doing things quickly, even if old you was slow. New you is efficient, old you was lazy.

When estimating the efficiency of others we are actually comparatively pessimistic, overestimating how long it will take them to complete tasks, and often predicting that they will run into problems that will delay their completion of the task. Researchers in this area have found that this effect applies across different kinds of task estimation, suggesting that our prospective memory abilities as they relate to other people are equally bad in work or personal contexts

Instead of accurately dating the events, the overwhelming majority of participants engaged in what is referred to as temporal displacement, or ‘telescoping’, which means moving things around in time. We have a tendency to do this. In particular, we often remember things that happened more recently as having happened longer ago than they actually did. Conversely, we often remember things from long ago ‘as if it were yesterday’.

While telescoping is due to a complex interplay of memory biases, one reason we might particularly think that things happened more recently than they actually did (forward telescoping) is because landmark memories are often very accessible. We can recall these important life events easily and with a lot of detail, just like memories of things that happened much more recently. We thus interpret this easy access and high vividness of the memory as indicating that it must have happened fairly recently.

Apparently what remains most are memories from between the ages of 10 and 30. The findings of the study supported what others had shown before them – that before the age of five most people report almost no memories. Then, between five and ten, the number of memories begins to increase, hitting a peak for both genders in the late teens. This period of increased reported memories stays quite high until the early twenties, when it begins to drop and then stabilise for the remaining decades. So we seem to retain the most memories of our teens and twenties.

As the philosopher George Berkeley said, ‘esse est percipi’ – ‘to be is to be perceived’. Only our perception of reality matters. It means that our misperceptions of reality can be placed into our memory systems to be later recalled in spite of never accurately representing more objective reality. While they may generally be close enough to be functionally useful, the truth is that probably every single one of our memories – even the clearest – contains perceptual flaws and inaccuracies, right from the outset.

For any kind of experience to stick around in the form of a memory, it needs to form a physical representation in your brain.

Baudry and his team say that calcium is needed to stimulate the proteins in our brains that allow our synapses to undergo memory-related changes that can last. When a connection between neurons is repeatedly or strongly activated, like an association between memories (‘park’ and ‘trees’, say), calpains are activated at that exact location. The calpains then change the structure of our synapses, leading to a stronger connection between the activated memory cells in the brain. It seems only when calpains come for a visit that we see the transformation from simple experience to lasting memory.

Since the sole purpose of neurons is to make connections and form a brain, isolated neurons immediately begin to search for other neurons to network with. To do this they grow longer dendrites and more synapses.

Prions, short for ‘proteinaceous infectious particles’, can change in shape, folding and reshaping in structurally distinct ways. Another of their notable properties is that they can either exist on their own, or they can form chains. These chains can automatically trigger neighbouring cells to join the chain and therein make a physical connection.

The primary role of prions in memory formation seems to be to stabilise the synapses that constitute long-term memories, thereby adding permanence to the physical changes that have already taken place due to long-term potentiation and the influx of calpains. Calpains are like the architects of the synapse, planning how communications should flow, while prions are the construction workers who make the changes more permanent.

What is more, the rats only forgot the association if the compound was present during the memory recall. If they were given the memory-blocking drug anisomycin in isolation, without being played the tone to make them recall the memory of the shock, nothing happened. This indicates that the drug does not inherently just make any particular kind of memory dissolve. Rather, there seems to be an interaction between an activated memory in the brain and this drug that leads to the memory being erased.

This leads us to one of today’s most en vogue biochemical theories of memory: retrieval-induced forgetting. This theory states that whenever we remember we also forget. So, while it seems intuitively appealing that every time we recall a memory we consolidate it and form a stronger and more accurate memory, this is far from the truth. Instead, every time a memory is recalled it is effectively retrieved, examined, and then recreated from scratch to be stored again. It is the equivalent of keeping a file of index cards, pulling one out to read it, throwing it away, and then copying out a new version on a fresh card for filing once more. And this is thought to happen every time we recall any memory.

memory. So if bad memory interviewing introduces inaccurate information, it can actually lead to a restructuring of the biochemical stamps of memories in the brain with non-medical procedures. This is how retrieval, if interrupted, can actually induce forgetting in a number of ways. It makes every event, every time it is recalled, physiologically vulnerable to distortion and forgetting.

So if bad memory interviewing introduces inaccurate information, it can actually lead to a restructuring of the biochemical stamps of memories in the brain with non-medical procedures. This is how retrieval, if interrupted, can actually induce forgetting in a number of ways. It makes every event, every time it is recalled, physiologically vulnerable to distortion and forgetting.

When you experience something various parts of your brain light up, which is to say that they are activated by a tiny electrical or biochemical charge passing through them. Those same neurons then remain responsible for their particular components of your memory for that same event.

The role of the hippocampus is more one of a mediator. According to neuroscientist Dean Burnett,16 ‘Information is channelled to the hippocampus, the brain region crucial for the formation of new memories and one of the only places in the brain where brand new neurons are regularly generated. The hippocampus links all of the relevant information together and encodes it into a new memory by forming new synapses.

In order to contextualise all of this, it is important to emphasise the fundamental principle of memory – association is everything. It is the association between the individual memory fragments in different parts of the brain that makes what we think of as a whole memory.

According to Aristotle’s On Memory and Reminiscence, there are four laws of association. The first is the law of similarity – the experience or recall of one object will elicit the recall of things similar to that object. Second is the law of contrast – the experience or recall of one object will elicit the recall of opposite things. Third, the law of contiguity – the experience or recall of one object will elicit the recall of things that were originally experienced along with that object. Fourth, the law of frequency – the more frequently two things are experienced together, the more likely it will be that the experience or recall of one will stimulate the recall of the other.

This notion assumes that individuals develop a set of frequently used words and concepts. Each individual concept or word in the brain can be called a node. These nodes can be linked to one another to create complex ideas. Nodes that have similar meanings are thought to have stronger connections.

Associative activation can contribute to false memory formation at two points in time – during encoding and during recall. During encoding, it is possible to present a number of concepts to an individual, without ever mentioning the main concept.

A similar kind of mistake can be made during recall of an event; when trying to remember which concepts were engaged with earlier, an individual may remember that the concepts law and uniform were mentioned, and the sense of familiarity with the concept police officer (again, because it is automatically activated) may encourage the individual to incorporate this into their recall.

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.

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.

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.

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.

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.

In research published in 1963,6 they found that when part of the brain (the parietotemporal cortex) was activated, patients seemed to relive entire scenes from their lives. This effect, however, only happened when the right hemisphere was activated, which was taken to mean that perhaps visual memories were stored primarily on the right side of our brains. These recollections could often be confirmed as real memories, since they mapped onto documented experiences or everyday encounters in these individuals’ lives.

Eidetic images are also different from regular visual memories which can arguably last forever; they fade away involuntarily and can last only a couple of minutes. Apparently the images usually fade away piece by piece rather than as a whole, and the eidetiker has no control over which components remain in place the longest. Eidetic images represent a moment of amazing memory that cannot last. But, while much better than other kinds of visual memories, even they are still prone to manipulations, omissions and false inclusions – the same kinds of distortions as any other kind of memory. According to Searleman, even eidetikers can misremember entire objects and forget pieces of scenes; it seems their exceptional memories for a particular image can still have some flaws.

The rate of incidence is higher among children with developmental disabilities, particularly brain injuries, jumping to 15 per cent. These kinds of findings are what have led some researchers, such as Enrol Giray and colleagues,12 to wonder whether eidetic memory is actually an immature version of memory, one that is used before we are able to think about and encode experiences in a more abstract manner. This could also mean that a child’s eidetic memory is actually a sign of developmental problems, rather than developmental advantages.