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10 Influential Memory Theories and Studies in Psychology

Discover the experiments and theories that shaped our understanding of how we develop and recall memories..

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How do our memories store information? Why is it that we can recall a memory at will from decades ago, and what purpose does forgetting information serve?

The human memory has been the subject of investigation among many 20th Century psychologists and remains an active area of study for today’s cognitive scientists. Below we take a look at some of the most influential studies, experiments and theories that continue to guide our understanding of the function of memory.

1 Multi-Store Model

(atkinson & shiffrin, 1968).

An influential theory of memory known as the multi-store model was proposed by Richard Atkinson and Richard Shiffrin in 1968. This model suggested that information exists in one of 3 states of memory: the sensory, short-term and long-term stores . Information passes from one stage to the next the more we rehearse it in our minds, but can fade away if we do not pay enough attention to it. Read More

Information enters the memory from the senses - for instance, the eyes observe a picture, olfactory receptors in the nose might smell coffee or we might hear a piece of music. This stream of information is held in the sensory memory store , and because it consists of a huge amount of data describing our surroundings, we only need to remember a small portion of it. As a result, most sensory information ‘ decays ’ and is forgotten after a short period of time. A sight or sound that we might find interesting captures our attention, and our contemplation of this information - known as rehearsal - leads to the data being promoted to the short-term memory store , where it will be held for a few hours or even days in case we need access to it.

The short-term memory gives us access to information that is salient to our current situation, but is limited in its capacity.

Therefore, we need to further rehearse information in the short-term memory to remember it for longer. This may involve merely recalling and thinking about a past event, or remembering a fact by rote - by thinking or writing about it repeatedly. Rehearsal then further promotes this significant information to the long-term memory store, where Atkinson and Shiffrin believed that it could survive for years, decades or even a lifetime.

Key information regarding people that we have met, important life events and other important facts makes it through the sensory and short-term memory stores to reach the long-term memory .

Learn more about Atkinson and Shiffrin’s Multi-Store Model

2 Levels of Processing

(craik & lockhart, 1972).

Fergus Craik and Robert Lockhart were critical of explanation for memory provided by the multi-store model, so in 1972 they proposed an alternative explanation known as the levels of processing effect . According to this model, memories do not reside in 3 stores; instead, the strength of a memory trace depends upon the quality of processing , or rehearsal , of a stimulus . In other words, the more we think about something, the more long-lasting the memory we have of it ( Craik & Lockhart , 1972). Read More

Craik and Lockhart distinguished between two types of processing that take place when we make an observation : shallow and deep processing. Shallow processing - considering the overall appearance or sound of something - generally leads to a stimuli being forgotten. This explains why we may walk past many people in the street on a morning commute, but not remember a single face by lunch time.

Deep (or semantic) processing , on the other hand, involves elaborative rehearsal - focusing on a stimulus in a more considered way, such as thinking about the meaning of a word or the consequences of an event. For example, merely reading a news story involves shallow processing, but thinking about the repercussions of the story - how it will affect people - requires deep processing, which increases the likelihood of details of the story being memorized.

In 1975, Craik and another psychologist, Endel Tulving , published the findings of an experiment which sought to test the levels of processing effect.

Participants were shown a list of 60 words, which they then answered a question about which required either shallow processing or more elaborative rehearsal. When the original words were placed amongst a longer list of words, participants who had conducted deeper processing of words and their meanings were able to pick them out more efficiently than those who had processed the mere appearance or sound of words ( Craik & Tulving , 1975).

Learn more about Levels of Processing here

3 Working Memory Model

(baddeley & hitch, 1974).

Whilst the Multi-Store Model (see above) provided a compelling insight into how sensory information is filtered and made available for recall according to its importance to us, Alan Baddeley and Graham Hitch viewed the short-term memory (STM) store as being over-simplistic and proposed a working memory model (Baddeley & Hitch, 1974), which replace the STM.

The working memory model proposed 2 components - a visuo-spatial sketchpad (the ‘inner eye’) and an articulatory-phonological loop (the ‘inner ear’), which focus on a different types of sensory information. Both work independently of one another, but are regulated by a central executive , which collects and processes information from the other components similarly to how a computer processor handles data held separately on a hard disk. Read More

According to Baddeley and Hitch, the visuo-spatial sketchpad handles visual data - our observations of our surroundings - and spatial information - our understanding of objects’ size and location in our environment and their position in relation to ourselves. This enables us to interact with objects: to pick up a drink or avoid walking into a door, for example.

The visuo-spatial sketchpad also enables a person to recall and consider visual information stored in the long-term memory. When you try to recall a friend’s face, your ability to visualize their appearance involves the visuo-spatial sketchpad.

The articulatory-phonological loop handles the sounds and voices that we hear. Auditory memory traces are normally forgotten but may be rehearsed using the ‘inner voice’; a process which can strengthen our memory of a particular sound.

Learn more about Baddeley and Hitch’s working memory model here

4 Miller’s Magic Number

(miller, 1956).

Prior to the working memory model, U.S. cognitive psychologist George A. Miller questioned the limits of the short-term memory’s capacity. In a renowned 1956 paper published in the journal Psychological Review , Miller cited the results of previous memory experiments, concluding that people tend only to be able to hold, on average, 7 chunks of information (plus or minus two) in the short-term memory before needing to further process them for longer storage. For instance, most people would be able to remember a 7-digit phone number but would struggle to remember a 10-digit number. This led to Miller describing the number 7 +/- 2 as a “magical” number in our understanding of memory. Read More

But why are we able to remember the whole sentence that a friend has just uttered, when it consists of dozens of individual chunks in the form of letters? With a background in linguistics, having studied speech at the University of Alabama, Miller understood that the brain was able to ‘chunk’ items of information together and that these chunks counted towards the 7-chunk limit of the STM. A long word, for example, consists of many letters, which in turn form numerous phonemes. Instead of only being able to remember a 7-letter word, the mind “recodes” it, chunking the individual items of data together. This process allows us to boost the limits of recollection to a list of 7 separate words.

Miller’s understanding of the limits of human memory applies to both the short-term store in the multi-store model and Baddeley and Hitch’s working memory. Only through sustained effort of rehearsing information are we able to memorize data for longer than a short period of time.

Read more about Miller’s Magic Number here

5 Memory Decay

(peterson and peterson, 1959).

Following Miller’s ‘magic number’ paper regarding the capacity of the short-term memory, Peterson and Peterson set out to measure memories’ longevity - how long will a memory last without being rehearsed before it is forgotten completely?

In an experiment employing a Brown-Peterson task, participants were given a list of trigrams - meaningless lists of 3 letters (e.g. GRT, PXM, RBZ) - to remember. After the trigrams had been shown, participants were asked to count down from a number, and to recall the trigrams at various periods after remembering them. Read More

The use of such trigrams makes it impracticable for participants to assign meaning to the data to help encode them more easily, while the interference task prevented rehearsal, enabling the researchers to measure the duration of short-term memories more accurately.

Whilst almost all participants were initially able to recall the trigrams, after 18 seconds recall accuracy fell to around just 10%. Peterson and Peterson’s study demonstrated the surprising brevity of memories in the short-term store, before decay affects our ability to recall them.

Learn more about memory decay here

6 Flashbulb Memories

(brown & kulik, 1977).

There are particular moments in living history that vast numbers of people seem to hold vivid recollections of. You will likely be able to recall such an event that you hold unusually detailed memories of yourself. When many people learned that JFK, Elvis Presley or Princess Diana died, or they heard of the terrorist attacks taking place in New York City in 2001, a detailed memory seems to have formed of what they were doing at the particular moment that they heard such news.

Psychologists Roger Brown and James Kulik recognized this memory phenomenon as early as 1977, when they published a paper describing flashbulb memories - vivid and highly detailed snapshots created often (but not necessarily) at times of shock or trauma. Read More

We are able to recall minute details of our personal circumstances whilst engaging in otherwise mundane activities when we learnt of such events. Moreover, we do not need to be personally connected to an event for it to affect us, and for it lead to the creation of a flashbulb memory.

Learn more about Flashbulb Memories here

7 Memory and Smell

The link between memory and sense of smell helps many species - not just humans - to survive. The ability to remember and later recognize smells enables animals to detect the nearby presence of members of the same group, potential prey and predators. But how has this evolutionary advantage survived in modern-day humans?

Researchers at the University of North Carolina tested the olfactory effects on memory encoding and retrieval in a 1989 experiment. Male college students were shown a series of slides of pictures of females, whose attractiveness they were asked to rate on a scale. Whilst viewing the slides, the participants were exposed to pleasant odor of aftershave or an unpleasant smell. Their recollection of the faces in the slides was later tested in an environment containing either the same or a different scent. Read More

The results showed that participants were better able to recall memories when the scent at the time of encoding matched that at the time of recall (Cann and Ross, 1989). These findings suggest that a link between our sense of smell and memories remains, even if it provides less of a survival advantage than it did for our more primitive ancestors.

8 Interference

Interference theory postulates that we forget memories due to other memories interfering with our recall. Interference can be either retroactive or proactive: new information can interfere with older memories (retroactive interference), whilst information we already know can affect our ability to memorize new information (proactive interference).

Both types of interference are more likely to occur when two memories are semantically related, as demonstrated in a 1960 experiment in which two groups of participants were given a list of word pairs to remember, so that they could recall the second ‘response’ word when given the first as a stimulus. A second group was also given a list to learn, but afterwards was asked to memorize a second list of word pairs. When both groups were asked to recall the words from the first list, those who had just learnt that list were able to recall more words than the group that had learnt a second list (Underwood & Postman, 1960). This supported the concept of retroactive interference: the second list impacted upon memories of words from the first list. Read More

Interference also works in the opposite direction: existing memories sometimes inhibit our ability to memorize new information. This might occur when you receive a work schedule, for instance. When you are given a new schedule a few months later, you may find yourself adhering to the original times. The schedule that you already knew interferes with your memory of the new schedule.

9 False Memories

Can false memories be implanted in our minds? The idea may sound like the basis of a dystopian science fiction story, but evidence suggests that memories that we already hold can be manipulated long after their encoding. Moreover, we can even be coerced into believing invented accounts of events to be true, creating false memories that we then accept as our own.

Cognitive psychologist Elizabeth Loftus has spent much of her life researching the reliability of our memories; particularly in circumstances when their accuracy has wider consequences, such as the testimonials of eyewitness in criminal trials. Loftus found that the phrasing of questions used to extract accounts of events can lead witnesses to attest to events inaccurately. Read More

In one experiment, Loftus showed a group of participants a video of a car collision, where the vehicle was travelling at a one of a variety of speeds. She then asked them the car’s speed using a sentence whose depiction of the crash was adjusted from mild to severe using different verbs. Loftus found when the question suggested that the crash had been severe, participants disregarded their video observation and vouched that the car had been travelling faster than if the crash had been more of a gentle bump (Loftus and Palmer, 1974). The use of framed questions, as demonstrated by Loftus, can retroactively interfere with existing memories of events.

James Coan (1997) demonstrated that false memories can even be produced of entire events. He produced booklets detailing various childhood events and gave them to family members to read. The booklet given to his brother contained a false account of him being lost in a shopping mall, being found by an older man and then finding his family. When asked to recall the events, Coan’s brother believed the lost in a mall story to have actually occurred, and even embellished the account with his own details (Coan, 1997).

Read more about false memories here

10 The Weapon Effect on Eyewitness Testimonies

(johnson & scott, 1976).

A person’s ability to memorize an event inevitably depends not just on rehearsal but also on the attention paid to it at the time it occurred. In a situation such as an bank robbery, you may have other things on your mind besides memorizing the appearance of the perpetrator. But witness’s ability to produce a testimony can sometimes be affected by whether or not a gun was involved in a crime. This phenomenon is known as the weapon effect - when a witness is involved in a situation in which a weapon is present, they have been found to remember details less accurately than a similar situation without a weapon. Read More

The weapon effect on eyewitness testimonies was the subject of a 1976 experiment in which participants situated in a waiting room watched as a man left a room carrying a pen in one hand. Another group of participants heard an aggressive argument, and then saw a man leave a room carrying a blood-stained knife.

Later, when asked to identify the man in a line-up, participants who saw the man carrying a weapon were less able to identify him than those who had seen the man carrying a pen (Johnson & Scott, 1976). Witnesses’ focus of attention had been distracted by a weapon, impeding their ability to remember other details of the event.

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Theories of Memory, History of

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• David J. Murray 2  

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Introduction

In attempting to formulate a history of theories of memory, it must be noted that the English word “memory” itself has a broadness of application that is not paralleled in other languages. In French, the words la mémoire refer to the ability that the mind–brain system has for retaining representations both of internal events and of external reality; and the words un souvenir refer to an individual retained representation generally identified by its content (referent). For example, if one wanted to translate the question, “Do insects have memory?” into French, one would use la mémoire as an equivalent for the English word “memory.” But if one wanted to translate the question “How strong is your memory of your first day at school?” one would use le souvenir . An analogous classification is found in German, where memory-the-ability is translated as das Gedächtnis and an individually experienced memory representation is translated as eine Erinnerung .

These observations lead to...

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Murray, D.J. (2012). Theories of Memory, History of. In: Rieber, R.W. (eds) Encyclopedia of the History of Psychological Theories. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-0463-8_14

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Synaptic plasticity and memory: an evaluation of the hypothesis

Affiliation.

• 1 Department and Centre for Neuroscience, University of Edinburgh, United Kingdom. [email protected]
• PMID: 10845078
• DOI: 10.1146/annurev.neuro.23.1.649

Changing the strength of connections between neurons is widely assumed to be the mechanism by which memory traces are encoded and stored in the central nervous system. In its most general form, the synaptic plasticity and memory hypothesis states that "activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the information storage underlying the type of memory mediated by the brain area in which that plasticity is observed." We outline a set of criteria by which this hypothesis can be judged and describe a range of experimental strategies used to investigate it. We review both classical and newly discovered properties of synaptic plasticity and stress the importance of the neural architecture and synaptic learning rules of the network in which it is embedded. The greater part of the article focuses on types of memory mediated by the hippocampus, amygdala, and cortex. We conclude that a wealth of data supports the notion that synaptic plasticity is necessary for learning and memory, but that little data currently supports the notion of sufficiency.

Publication types

• Research Support, Non-U.S. Gov't
• Amygdala / physiology
• Evaluation Studies as Topic
• Hippocampus / physiology
• Learning / physiology
• Long-Term Potentiation / physiology
• Memory / physiology*
• Models, Neurological*
• Neural Pathways / physiology
• Neuronal Plasticity / physiology*
• Synapses / physiology*

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9 Lab 9. Recall, Recognition, and Encoding Specificity: I’ve Seen You Before, But I Can’t Remember Where

Lab 9. Recall, Recognition, and Encoding Specificity: I’ve Seen You Before, But I Can’t Remember Where

COGLAB Exercise 28

Introduction

Psychologists who study memory generally recognize three stages in memory:  1) an encoding phase, where the information is first learned and prepared to be remembered; 2) a storage or consolidation phase, in which the information is allowed to “gel” in the brain.  Drugs, alcohol, and head trauma can all disrupt this consolidation phase; and, 3) a retrieval phase, where the stored information is brought back for use.

Much of what we call “forgetting” is really just an encoding failure.  In a recent study, about half of the people in Britain did not know which way the figures on their coins faced.  Did they “forget?”  Not really.  They just never encoded that information to begin with. [1] In this lab we’re interested in looking at retrieval failures.  We all have times (usually during tests) where we know we have the answer to a question, but also know we can’t retrieve it right now.  Sometimes, this is because the retrieval conditions aren’t right, as this lab will demonstrate.

The two primary ways psychologists measure memory accuracy are recall and recognition .  Recall is the act of trying to retrieve information given no cues to help you search.  A type of recall called cued recall is similar, but in a cued recall task you are given some information to use as clues, to aid your recall.  A recognition test involves giving you several alternatives, and asking you to pick the correct answer from among the alternatives.  If I asked you “Which actor played Jack Sparrow in the “Pirates of the Caribbean” series?”, your subsequent memory search would be a recall test.  If I said, he’s also portrayed Edward Scissorhands, Willy Wonka, and the Mad Hatter, I’d be giving you a cued recall test.  If I put the names, George Clooney / Tom Cruise / Johnny Depp / Brad Pitt, in front of you, and had you select the correct choice, this would be a recognition test [2] .

This experiment will allow us to test two different hypotheses concerning memory.  The first is a theory that has been around for a long time–the association hypothesis .  This basically says that memories are formed by making associations between words or concepts, and anything that enhances those associations will improve memory.  The second hypothesis is known as the encoding specificity principle.  As we’ll see later, this looks both at the conditions under which the original memory is first learned, and also the conditions under which that memory is retrieved.

The association hypothesis basically assumes that memory is dependent upon the associative connections between the kinds of units which exist prior to the experiment.  That is, words and concepts that are associated prior to the experiment will still be associated after the experiment.  If you have an association between “chicken” and “egg” before the experiment starts, that association is presumably unaffected by whatever happens during the experiment.

By contrast, the encoding specificity principle says that conditions under which you form your memories are of importance.  If you learn something in one set of conditions, you’ll remember it better if we can reconstruct those conditions during retrieval.  If you learn something while you are in one physiological or emotional state, you’ll better retrieve those items if we can reconstruct those original physiological or emotional states.

To illustrate the two hypotheses, let’s look at two examples.  The words “DOG” and “CAT” are already strongly associated in your memory.  You’ve heard those two words together a number of times.  The association hypothesis says that because you’ve heard those two words together many times, they are already associated in your memory.  Thus, during retrieval, “CAT” would be a good cue to help your retrieve “DOG.” However, say that during the encoding phase, you were thinking about the word “FLEAS” while you were exposed to the word “DOG.”  (We could set you up to think about  “FLEAS” in a number of ways–either by telling you that a dog was scratching, or that a dog was not allowed in the house–or by telling you directly that you should associate “DOG” and “FLEAS” for this trial.)  If that were the case, then the things you were thinking about while you were learning the new association should be better cues.  If I gave you the cue “ITCH” you should do better, despite the fact that the words “DOG” and “ITCH” typically only have a weak association.

The concept of state dependent learning is a good illustration of the encoding specificity principle.  If you learn something in class while you are very depressed, for example, you’ll better retrieve that same information while you are also depressed.  If you drink two pots of coffee while studying for an exam, you’ll do better on the exam if you also had coffee that morning.  The coffee itself won’t help you perform better on the test–but if you DO drink that much coffee while you study, you’ll likely do better if you recreate those conditions during the test.

These two hypotheses allow a strong test of how memory works.  If you’ll look back at the conditions in the experiment, you’ll see that in the encoding stage, we always presented the weak associates.  That means that there was some association of the cue and target words before the experiment began, but only a weak association.  However, during retrieval, sometimes we gave you the strong associates.  That’s where the real difference between the hypotheses emerges.  If the association hypothesis is correct, then you’ll do best when given strong associates during retrieval.  If the encoding specificity principle is correct, though, you’ll do best when we recreate the same conditions under which you learned the items initially.  Therefore, you’ll do best with the weak associates during retrieval, since those are the conditions in which you learned the target items to begin with.

One final prediction of the encoding specificity principle is the comparison of conditions 2 (STRONG CUES) and 3 (NO CUES).  While the association hypothesis assumes that strong associates are always better cues for retrieval, the encoding specificity principle predicts that since those cues were not stored during encoding, they won’t help during retrieval.  A similar experiment was first performed by Tulving and Thompson (Tulving & Thompson, 1973).  Our experiment is more similar to that performed by Watkins and Tulving (1975).

Tulving’s and Thompson’s experiment (1973) involved four phases, shown in Table 9.1.  The first two sets of 24 pairs were really just designed to get you familiar with the situation, and also to induce you into a certain strategy–subjects were supposed to try to remember the pairs by forming associations between the cues and targets.  The first phase, then, was the encoding phase, where subjects learned the third list of cue-target pairs.

After the first phase, the encoding phase, subjects were given certain words and asked to generate associates to those words. They picked those words carefully, though.  They chose words that would be very likely to produce, as associates, words that had been target words in phase I.  For example, subjects were given as a cue-target pair the words HEAD- LIGHT , and were asked to remember the word LIGHT .  During the free association phase, they gave subjects the word DARK.  DARK and LIGHT are very strong associates, so subjects were likely to generate the word LIGHT.

After the generation task, subjects were told that some of the words they had generated had actually been studied in Phase I.  They were told to recognize those words from the list they had generated.

Finally, subjects were given a cued-recall test.  They were given the cue words from Phase I, and asked to generate the appropriate target word.  The steps in this procedure are outlined in Table 9.1 Most people assume that recognition is easier than recall.  This experiment was specifically designed to show you that this is not always the case!

Encoding Specificity (Tulving and Thompson, 1973)

Four Phases

            I.  Encoding

Participants told to learn target word, in presence of cues. Participants also told that they did not need to learn/remember the cue.

CUE                                                     TARGET

head                                                    LIGHT

bath                                                     NEED

pretty                                                   BLUE

II.  Free association

Given words (“cues”), told to generate 4 associated words.  Note that the cues used in Part II are likely to elicit words that had been studied in Part I.

CUE                                                           FREE ASSOCIATES

dark                                         NIGHT      LIGHT      BLACK    ROOM

want                                        NEED       DESIRE    WISH        GET

sky                                          SUN          BLUE        OPEN        CLOUD

III.  Recognition

Participants told that some of the associates generated in Phase II were actually studied in Phase I – asked to identify those words.

dark                                         NIGHT      LIGHT      BLACK      ROOM

sky                                          SUN          BLUE        OPEN        CLOUD

            IV.  Cued recall

Participants given same cue words from Phase I, asked to generate the target words.

bath                                                     ??????

Table 9.1.  Description of Tulving and Thompson’s (1973) procedures.

Background of the Experiment

Tulving (1972) has distinguished between semantic memory and episodic memory [3] .  Both are considered to be long-term memories, but they differ in a number of respects.  Some of the differences between semantic and episodic memory are shown in Table 9.2.

You are certainly familiar with the differences in these kinds of memories.  Episodic memories are your “personal” memories, where you are a vital part of that memory.  You remember your first kiss, the day of your graduation, your first day at Baylor, etc.  All of these memories are organized around temporal events, and the chronological order of those events is very important.

Table 9.2.  Comparison of Semantic and Episodic Memory (from Tulving, 1983)

Semantic memories, by contrast, are memories that are now free from context.  For example, you know that George Washington was the first President of the United States, and that Bill Clinton was President before George W. Bush.  You also know how to compute the average of a set of numbers, as well as the name of the person who came up with the term “semantic memory.”  These are impersonal memories–ones relatively free from the context in which you learned them.  They are not organized in a temporal fashion, but in some kind of conceptual way.  Did you learn the name of Montana or Idaho first?  You probably don’t know, and it also doesn’t matter.  On the other hand, knowing that you went out with person X before you went out with person X’s roommate is important, as the Jerry Springer show readily demonstrates.

For our purposes, one of the most important distinctions between the two kinds of memory is the form of their organization.  As was mentioned before, information in episodic memory is temporally organized.  If two episodic memories are psychologically “close” it’s probably because they occurred close together in time, like your first class at Baylor and your first fraternity or sorority meeting.  Semantic memory, by contrast, is organized in conceptual terms–on the basis of meaning, or appearance, or function.  Lincoln and Kennedy may be “close” in your semantic memory because both were assassinated, or because both were heroic presidents.  SMU and TCU may be close together because they are both (expensive) private colleges in the Dallas-Fort Worth area.  (They are probably “close” for a number of other reasons, too).

The episodic/semantic distinction has been the focus of a great deal of research over the past few decades.  In fact, it may be among the most hotly debated topics in all of memory research.  Regardless of the final outcome of the debate, the episodic/semantic distinction has certainly helped along our understanding of a number of phenomena.  For example, when we talk about somebody suffering from amnesia, or having “lost their memory,” what we really mean is that they have lost their episodic memory.  We would not be too surprised if someone wandered into the hospital and said “I don’t know who I am or where I live.”  By contrast, we would be very surprised if they came into the hospital and said, “I’m John Smith of Pittsburgh, but I’ve forgotten my multiplication tables and state capitols.”  The first case would be an example of someone losing their episodic memories, while the second case would be an example of someone losing their semantic memory.  We see people of the first sort, but have yet to see someone of the second sort.

Mitchell (1989) has used the semantic/episodic memory distinction to explain differential effects on memory in the aging process.  Mitchell’s research shows that memory loss in the elderly is typically restricted to a mild impairment in the formation of new episodic memories.  In fact, Mitchell’s work suggests that if anything, semantic memory actually improves throughout the lifespan!

Episodic memories are quite context-sensitive.  When you learned something in one set of circumstances, you typically remember that information more easily when you recreate those original circumstances.  Have you ever met someone in an unfamiliar place and not recognized them?  Say, you know a person quite well in a classroom situation, but have never seen them out of that context.  Then, one day you run into that person in the airport, or in the mall, and you can’t remember their name.  Or even if you do have a vague sense of knowing them, you can’t remember where you know them from.  This happens quite a bit to professors.  We are used to seeing our students in the classroom, and recognize them quickly and easily if we meet them on campus.  However, if we run into those same individuals in another situation, say in a restaurant, we’ll often forget that person’s name.  The idea of the “absent-minded professor” has some grounding in cognitive theory!

This is explained nicely by the encoding specificity principle .  Remember, this principle says that we not only encode new information, but we also encode the context in which we learned that information.  Retrieval is enhanced if we can recreate those same conditions.  If I met you in class, and learned your name in those circumstances, but then see you in the airport, I have a different set of cues at retrieval than I did at encoding.  My memory for your name will be less accessible.

Virtually all memory theories can account for context effects like these.  However, they differ in exactly how they represent context in memory.  This lab was designed to test two of these theories, called tagging theory and episodic theory .  Episodic theory is a direct extension of encoding specificity developed by Tulving.  Tagging theory was actually a precursor of episodic theory, and presents what was at the time a more conventional approach to the representation of context in memory.  Tagging theory says that the way an item’s context is stored in memory is by attaching some kind of marker–a “tag”–that stores that information.  If you learned the item LIGHT  in the third list, you’ll have a tag that says, “This item was learned in the third list” accompanying that memory.  As you can see, there is no distinction between semantic and episodic memories with tagging theory.

Episodic theory assumes that every new encounter with an item is stored by its own individual memory trace.  You can learn the item LIGHT a number of times, but each time you do, you’ll have stored a new memory trace for that event.  These memory traces can actually be thought of as a subset of pre-existing semantic traces.  You knew the concept LIGHT  before the experiment (it was in your semantic memory), but on this particular trial, this semantic item was learned–you would therefore form a new episodic trace of that event. The cue-target pair DARK- LIGHT might bring to mind things like sunshine, light bulbs, or shades of clothing.  If you study the same word LIGHT  in the context of a cue like HEAVY- LIGHT your representation would be very different.  Now, your episodic trace might have things like “carry” or “weight” with it.

Because of the differences in how items are stored, the two theories make different predictions about retrieval.  According to the encoding specificity principle, you will do best during retrieval if we can recreate the conditions under which you first learned something.  This will be true regardless of whether the test is a recall, recognition, or cued recall test.  Episodic theory makes no distinction between the memory tasks.  Since the retrieval process is thought to involve utilizing information available during a retrieval episode, and that information is the same for both recall and recognition, there should be no differences.

Tagging theory, though, is based on a different assumption.  Tagging theory basically puts forth what is known as a generate-recognize  model of retrieval.  In this theory, recall is a two-stage process:  the person, trying to recall information, must first get that information out of memory (the “generation” task).  After the information is generated, the person must then decide if the information is correct (the “recognize” process).  Notice, though, that a recognition test involves only the “recognition” stage.  For example, on a multiple choice test you do not have to generate the correct answer, you just have to recognize it as being among the possible choices.  On an essay test, you generate your own answer, and then presumably recognize it as the correct one.  (Or perhaps an elaborate guess).  The generate-recognize model of retrieval would make the very strong prediction, then, that you should be able to recognize everything you can recall.  If you can recall something, then both the generation and the recognition processes have succeeded.  If you are only asked to do the second phase, the recognition process–in other words, perform a recognition task–that should be equally successful.  There may also be some times when the generation process fails, but the item can still be recognized.

This experiment tests this prediction.  We made the recognition test very difficult, and the recall test maximally efficient by presenting during retrieval the cues that you learned in the encoding phase.  Tagging theory would predict that the recognition test should show better performance–all you are asked to do is the editing task.  Presumably, there may be some items you cannot generate, but if you can generate it, you should be able to recognize it.

Episodic theory, though, makes very different predictions.  Because of the context-sensitivity of the process, you may find that the recognition test is more difficult than the recall test.  After all, the recognition test provides you with a different set of retrieval cues, cues that were not present during encoding.  The cued-recall test, though, presents to you the same cues at retrieval that you had during encoding.

At this time, complete the experiment Encoding Specificity in COGLAB.  Instructions can be found in Lab 28 of the COGLAB Website.

Questions for Lab 9

• What are the independent variables? What are the dependent variables?
• Analyze the graph of your results, both individual and class – Do they agree with the predictions of tagging theory or encoding specificity theory?
• Do cues always help memory study and recall? Explain your answer.
• Using the findings surrounding encoding specificity, what suggestions about studying would you give someone who wanted to improve his/her performance on tests?
• Students sometimes claim to study differently for different types of exams. That is, if they know they will be given a multiple choice test (a recognition test) they say they study differently than if the test is going to be an essay exam (a recall test). Do you think there is any truth to this?  Why or why not?  Do you think it is possible that the results of this experiment are due to different types of study for the different kinds of tests?  Why or why not?  Is this consistent with encoding

specificity?

• To get a driver’s license, one usually must pass a written exam as well as an in-car driving test. From what you know about encoding specificity, why is the in-car test so important?
• Morris, Bransford, and Franks (Morris, Bransford, & Franks, 1977), in a study designed to test the Levels of Processing (LOP) hypothesis, found some intriguing and counter-intuitive results. Like we discussed in class, Morris et al. had subjects perform either a semantic encoding task or a rhyming encoding task.  After this encoding phase, one half the subjects were given a standard recognition test.  The other half of the subjects were given a rhyme recognition test; instead of recognizing the previously learned items from a list of distracters, these subjects had to recognize all the items that rhymed with the original items.  If, for example, the word TOY was one of the target words studied in Phase I, the subject was to pick out a word like BOY in the rhyme recognition test, since BOY rhymes with TOY.  As you would guess, the standard recognition test produced results consistent with the LOP predictions:  subjects who processed words at the semantic level demonstrated better performance.  However, in the rhyme recognition test, the results were exactly opposite–those who had done the rhyme encoding task did better on the rhyme recognition test.

Given what you know about the LOP hypothesis, and the encoding specificity principle, provide an account of these results.  What implications do these results have for the LOP hypothesis?  What does this say about “depth” of encoding?

Data Sheet for Lab 9

Encoding Specificity

Report Mean Percent Recalled:

Lure: __________

Graphs for Lab 9

Recall, Recognition, and Encoding Specificity

Individual Data

Turn this graph in along with your lab

[1] Don’t feel too smug, you American, you.  We don’t do much better.  Nickerson and Adams (1976) had Americans draw the penny, and we fared almost as bad.  Give it a try–draw the front of a penny without looking.

[2] If you don’t know the answer, please don’t ask me;  I feel old enough as it is..

[3] In his later work, Tulving distinguished a third kind of memory–procedural memory.  Procedural memory (also sometimes referred to as implicit memory, by those wishing to be “theoretically neutral”) is your memory for events that don’t necessarily require conscious recollection, like memories for how to ride a bike.  In fact, one of the ways to impair those kinds of memories is to make them subject to conscious recollection.  Next time your are playing golf or tennis with a friend, ask them if they breathe on their upswing (or as they are tossing the ball to serve).  Chances are they won’t know, and by making them attend to it, you can make their performance suffer.If you remember our brief discussion of H. M. in Lab 1, you might remember that I told you he had been unable to form any new long-term memories since his surgery in the early 1950s.  This is technically not true.  He is able to form new procedural memories.  That is, he can learn things, but has no realization that he has learned them.  We’ll discuss this in more detail in Lab 10.

Laboratory in Cognition Student Manual Copyright © by Charles Weaver, III. All Rights Reserved.

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• How Memory Works

Memory is the ongoing process of information retention over time. Because it makes up the very framework through which we make sense of and take action within the present, its importance goes without saying. But how exactly does it work? And how can teachers apply a better understanding of its inner workings to their own teaching? In light of current research in cognitive science, the very, very short answer to these questions is that memory operates according to a "dual-process," where more unconscious, more routine thought processes (known as "System 1") interact with more conscious, more problem-based thought processes (known as "System 2"). At each of these two levels, in turn, there are the processes through which we "get information in" (encoding), how we hold on to it (storage), and and how we "get it back out" (retrieval or recall). With a basic understanding of how these elements of memory work together, teachers can maximize student learning by knowing how much new information to introduce, when to introduce it, and how to sequence assignments that will both reinforce the retention of facts (System 1) and build toward critical, creative thinking (System 2).

Dual-Process Theory

Think back to a time when you learned a new skill, such as driving a car, riding a bicycle, or reading. When you first learned this skill, performing it was an active process in which you analyzed and were acutely aware of every movement you made. Part of this analytical process also meant that you thought carefully about why you were doing what you were doing, to understand how these individual steps fit together as a comprehensive whole. However, as your ability improved, performing the skill stopped being a cognitively-demanding process, instead becoming more intuitive. As you continue to master the skill, you can perform other, at times more intellectually-demanding, tasks simultaneously. Due to your knowledge of this skill or process being unconscious, you could, for example, solve an unrelated complex problem or make an analytical decision while completing it.

In its simplest form, the scenario above is an example of what psychologists call dual-process theory. The term “dual-process” refers to the idea that some behaviors and cognitive processes (such as decision-making) are the products of two distinct cognitive processes, often called System 1 and System 2 (Kaufmann, 2011:443-445). While System 1 is characterized by automatic, unconscious thought, System 2 is characterized by effortful, analytical, intentional thought (Osman, 2004:989).

Dual-Process Theories and Learning

How do System 1 and System 2 thinking relate to teaching and learning? In an educational context, System 1 is associated with memorization and recall of information, while System 2 describes more analytical or critical thinking. Memory and recall, as a part of System 1 cognition, are focused on in the rest of these notes.

As mentioned above, System 1 is characterized by its fast, unconscious recall of previously-memorized information. Classroom activities that would draw heavily on System 1 include memorized multiplication tables, as well as multiple-choice exam questions that only need exact regurgitation from a source such as a textbook. These kinds of tasks do not require students to actively analyze what is being asked of them beyond reiterating memorized material. System 2 thinking becomes necessary when students are presented with activities and assignments that require them to provide a novel solution to a problem, engage in critical thinking, or apply a concept outside of the domain in which it was originally presented.  

It may be tempting to think of learning beyond the primary school level as being all about System 2, all the time. However, it’s important to keep in mind that successful System 2 thinking depends on a lot of System 1 thinking to operate. In other words, critical thinking requires a lot of memorized knowledge and intuitive, automatic judgments to be performed quickly and accurately.

How does Memory Work?

In its simplest form, memory refers to the continued process of information retention over time. It is an integral part of human cognition, since it allows individuals to recall and draw upon past events to frame their understanding of and behavior within the present. Memory also gives individuals a framework through which to make sense of the present and future. As such, memory plays a crucial role in teaching and learning. There are three main processes that characterize how memory works. These processes are encoding, storage, and retrieval (or recall).

• Encoding . Encoding refers to the process through which information is learned. That is, how information is taken in, understood, and altered to better support storage (which you will look at in Section 3.1.2). Information is usually encoded through one (or more) of four methods: (1) Visual encoding (how something looks); (2) acoustic encoding (how something sounds); (3) semantic encoding (what something means); and (4) tactile encoding (how something feels). While information typically enters the memory system through one of these modes, the form in which this information is stored may differ from its original, encoded form (Brown, Roediger, & McDaniel, 2014).

• Retrieval . As indicated above, retrieval is the process through which individuals access stored information. Due to their differences, information stored in STM and LTM are retrieved differently. While STM is retrieved in the order in which it is stored (for example, a sequential list of numbers), LTM is retrieved through association (for example, remembering where you parked your car by returning to the entrance through which you accessed a shopping mall) (Roediger & McDermott, 1995).

Improving Recall

Retrieval is subject to error, because it can reflect a reconstruction of memory. This reconstruction becomes necessary when stored information is lost over time due to decayed retention. In 1885, Hermann Ebbinghaus conducted an experiment in which he tested how well individuals remembered a list of nonsense syllables over increasingly longer periods of time. Using the results of his experiment, he created what is now known as the “Ebbinghaus Forgetting Curve” (Schaefer, 2015).

Through his research, Ebbinghaus concluded that the rate at which your memory (of recently learned information) decays depends both on the time that has elapsed following your learning experience as well as how strong your memory is. Some degree of memory decay is inevitable, so, as an educator, how do you reduce the scope of this memory loss? The following sections answer this question by looking at how to improve recall within a learning environment, through various teaching and learning techniques.

As a teacher, it is important to be aware of techniques that you can use to promote better retention and recall among your students. Three such techniques are the testing effect, spacing, and interleaving.

• The testing effect . In most traditional educational settings, tests are normally considered to be a method of periodic but infrequent assessment that can help a teacher understand how well their students have learned the material at hand. However, modern research in psychology suggests that frequent, small tests are also one of the best ways to learn in the first place. The testing effect refers to the process of actively and frequently testing memory retention when learning new information. By encouraging students to regularly recall information they have recently learned, you are helping them to retain that information in long-term memory, which they can draw upon at a later stage of the learning experience (Brown, Roediger, & McDaniel, 2014). As secondary benefits, frequent testing allows both the teacher and the student to keep track of what a student has learned about a topic, and what they need to revise for retention purposes. Frequent testing can occur at any point in the learning process. For example, at the end of a lecture or seminar, you could give your students a brief, low-stakes quiz or free-response question asking them to remember what they learned that day, or the day before. This kind of quiz will not just tell you what your students are retaining, but will help them remember more than they would have otherwise.
• Spacing.  According to the spacing effect, when a student repeatedly learns and recalls information over a prolonged time span, they are more likely to retain that information. This is compared to learning (and attempting to retain) information in a short time span (for example, studying the day before an exam). As a teacher, you can foster this approach to studying in your students by structuring your learning experiences in the same way. For example, instead of introducing a new topic and its related concepts to students in one go, you can cover the topic in segments over multiple lessons (Brown, Roediger, & McDaniel, 2014).
• Interleaving.  The interleaving technique is another teaching and learning approach that was introduced as an alternative to a technique known as “blocking”. Blocking refers to when a student practices one skill or one topic at a time. Interleaving, on the other hand, is when students practice multiple related skills in the same session. This technique has proven to be more successful than the traditional blocking technique in various fields (Brown, Roediger, & McDaniel, 2014).

As useful as it is to know which techniques you can use, as a teacher, to improve student recall of information, it is also crucial for students to be aware of techniques they can use to improve their own recall. This section looks at four of these techniques: state-dependent memory, schemas, chunking, and deliberate practice.

• State-dependent memory . State-dependent memory refers to the idea that being in the same state in which you first learned information enables you to better remember said information. In this instance, “state” refers to an individual’s surroundings, as well as their mental and physical state at the time of learning (Weissenborn & Duka, 2000). 
• Schemas.  Schemas refer to the mental frameworks an individual creates to help them understand and organize new information. Schemas act as a cognitive “shortcut” in that they allow individuals to interpret new information quicker than when not using schemas. However, schemas may also prevent individuals from learning pertinent information that falls outside the scope of the schema that has been created. It is because of this that students should be encouraged to alter or reanalyze their schemas, when necessary, when they learn important information that may not confirm or align with their existing beliefs and conceptions of a topic.
• Chunking.  Chunking is the process of grouping pieces of information together to better facilitate retention. Instead of recalling each piece individually, individuals recall the entire group, and then can retrieve each item from that group more easily (Gobet et al., 2001).
• Deliberate practice.  The final technique that students can use to improve recall is deliberate practice. Simply put, deliberate practice refers to the act of deliberately and actively practicing a skill with the intention of improving understanding of and performance in said skill. By encouraging students to practice a skill continually and deliberately (for example, writing a well-structured essay), you will ensure better retention of that skill (Brown et al., 2014).

For more information...

Brown, P.C., Roediger, H.L. & McDaniel, M.A. 2014.  Make it stick: The science of successful learning . Cambridge, MA: Harvard University Press.

Gobet, F., Lane, P.C., Croker, S., Cheng, P.C., Jones, G., Oliver, I. & Pine, J.M. 2001. Chunking mechanisms in human learning.  Trends in Cognitive Sciences . 5(6):236-243.

Kaufman, S.B. 2011. Intelligence and the cognitive unconscious. In  The Cambridge handbook of intelligence . R.J. Sternberg & S.B. Kaufman, Eds. New York, NY: Cambridge University Press.

Osman, M. 2004. An evaluation of dual-process theories of reasoning. Psychonomic Bulletin & Review . 11(6):988-1010.

Roediger, H.L. & McDermott, K.B. 1995. Creating false memories: Remembering words not presented in lists.  Journal of Experimental Psychology: Learning, Memory, and Cognition . 21(4):803.

Schaefer, P. 2015. Why Google has forever changed the forgetting curve at work.

Weissenborn, R. & Duka, T. 2000. State-dependent effects of alcohol on explicit memory: The role of semantic associations.  Psychopharmacology . 149(1):98-106.

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Multi-Store Memory Model: Atkinson and Shiffrin

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

What is the Multi-Store Model?

• The multi-store model is an explanation of memory proposed by Atkinson and Shiffrin which assumes there are three unitary (separate) memory stores, and that information is transferred between these stores in a linear sequence.
• The three main stores are the sensory memory, short-term memory (STM) and long-term memory (LTM).
• Each of the memory stores differs in the way information is processed (encoding), how much information can be stored (capacity), and for how long (duration).
• Information passes from store to store in a linear way, and has been described as an information processing model (like a computer) with an input, process and output.
• Information is detected by the sense organs and enters the sensory memory , which stores a fleeting impression of sensory stimuli. If attended to this information enters the STM and if the information is given meaning (elaborative rehearsal) it is passed on to the LTM

The multi-store model of memory (also known as the modal model) was proposed by Richard Atkinson and Richard Shiffrin (1968) and is a structural model. They proposed that memory consisted of three stores: a sensory register, short-term memory (STM) and long-term memory (LTM).

The Memory Stores

Each store is a unitary structure and has its own characteristics in terms of encoding, capacity and duration.

Encoding is the way information is changed so that it can be stored in the memory. There are three main ways in which information can be encoded (changed):

1. visual (picture),

2. acoustic (sound),

3. semantic (meaning).

Capacity concerns how much information can be stored.

Duration refers to the period of time information can last in the memory stores.

Sensory Memory

• Duration: ¼ to ½ second

• Capacity: all sensory experience (v. larger capacity)

• Encoding: sense specific (e.g. different stores for each sense)

The sensory stores are constantly receiving information but most of this receives no attention and remains in the sensory register for a very brief period.

In the sensory memory store , information arrives from the 5 senses such as sight (visual information), sounds and touch. The sensory memory store has a large capacity but a very brief duration, it can encode information from any of the senses and most of the information is lost through decay.

Attention is the first step in remembering something, if a person’s attention is focused on one of the sensory stores then the data is transferred to STM.

Short Term Memory

• Duration: 0-18 seconds

• Capacity: 7 +/- 2 items

• Encoding: mainly auditory

The short-term memory store has a duration of up to 30 seconds, has a capacity of 7+/-2 chunks and mainly encodes information acoustically. Information is lost through displacement or decay.

Maintenance rehearsal is the process of verbally or mentally repeating information, which allows the duration of short-term memory to be extended beyond 30 seconds. An example of maintenance rehearsal would be remembering a phone number only long enough to make the phone call.

This type of rehearsal usually involves repeating information without thinking about its meaning or connecting it to other information.

Continual rehearsal “regenerates” or “renews” the information in the memory trace, thus making it a stronger memory when transferred to the Long Term store.

If maintenance rehearsal (repetition) does not occur, then information is forgotten, and lost from short term memory through the processes of displacement or decay.

Long Term Memory

• Duration: Unlimited

• Capacity: Unlimited

• Encoding: Mainly Semantic (but can be visual and auditory)

Long-term memory store has unlimited capacity and duration and encodes information semantically. Information can be recalled from LTM back into the STM when it is needed.

If the information is given meaning (elaborative rehearsal) it is passed on to the LTM.

Elaborative rehearsal involves the process of linking new information in a meaningful way with information already stored in long-term memory. For example,

you could learn the lines in a play by relating the dialogue and behavior of your character to similar personal experiences you remember.

Elaborative rehearsal is more effective than maintenance rehearsal for remembering new information as it helps to ensure that information is encoded well. It is a deeper level of information-processing.

Key Studies

Glanzer and Cunitz showed that when participants are presented with a list of words, they tend to remember the first few and last few words and are more likely to forget those in the middle of the list, i.e. the serial position effect.

This supports the existence of separate LTM and STM stores because they observed a primacy and recency effect.

Words early on in the list were put into long term memory (primacy effect) because the person has time to rehearse the word, and words from the end went into short term memory (recency effect).

Other compelling evidence to support this distinction between STM and LTM is the case of KF (Shallice & Warrington, 1977) who had been in a motorcycle crash where he had sustained brain damage.

His LTM seemed to be unaffected but he was only able to recall the last bit of information he had heard in his STM.

Critical Evaluation

One strength of the multistore model is that is gives us a good understanding of the structure and process of the STM. This is good because this allows researchers to expand on this model.

This means researchers can do experiments to improve on this model and make it more valid and they can prove what the stores actually do. Therefore, the model is influential as it has generated a lot of research into memory.

Many memory studies provide evidence to support the distinction between STM and LTM (in terms of encoding, duration and capacity). The model can account for primacy & recency effects .

The case of HM also supports the MSM as he was unable to encode new long-term memories after surgery during which his hippocampus was removed but his STM was unaffected.

He has remembered little of personal (death of mother and father) or public events (Watergate, Vietnam War) that have occurred over the last 45 years. However his short-term memory remains intact.This supports the view that the LTM and the STM are two separate stores.

The model is oversimplified, in particular when it suggests that both short-term and long-term memory each operate in a single, uniform fashion.  We now know is this not the case.

It has now become apparent that both short-term and long-term memory are more complicated that previously thought.  For example, the Working Model of Memory proposed by Baddeley and Hitch (1974) showed that short term memory is more than just one simple unitary store and comprises different components (e.g. central executive, Visuospatial etc.).

In the case of long-term memory, it is unlikely that different kinds of knowledge, such as remembering how to play a computer game, the rules of subtraction and remembering what we did yesterday are all stored within a single, long-term memory store.

Indeed different types of long-term memory have been identified, namely episodic (memories of events), procedural (knowledge of how to do things) and semantic (general knowledge).

Rehearsal is considered a too simple explanation to account for the transfer of information from STM to LTM. For instance, the model ignores factors such as motivation, effect and strategy (e.g. mnemonics) which underpin learning.

Also, rehearsal is not essential to transfer information into LTM. For example, why are we able to recall information which we did not rehearse (e.g. swimming) yet unable to recall information which we have rehearsed (e.g. reading your notes while revising).

Therefore, the role of rehearsal as a means of transferring from STM to LTM is much less important than Atkinson and Shiffrin (1968) claimed in their model.

The models main emphasis was on structure and tends to neglect the process elements of memory (e.g. it only focuses on attention and maintenance rehearsal). For example, elaboration rehearsal leads to recall of information than just maintenance rehearsal.

Elaboration rehearsal involves a more meaningful analysis (e.g. images, thinking, associations etc.) of information and leads to better recall. For example, giving words a meaning or linking them with previous knowledge. These limitations are dealt with by the levels of processing model (Craik, & Lockhart, 1972).

Note: although rehearsal was initially described by Atkinson and Shiffrin as maintenance rehearsal (repetition of information), Shiffrin later suggested that rehearsal could be elaborative (Raaijmakers, & Shiffrin, 2003).

The multi store model has been criticized for being a passive/one way/linear model.

Atkinson, R. C., & Shiffrin, R. M. (1968). Chapter: Human memory: A proposed system and its control processes. In Spence, K. W., & Spence, J. T. The psychology of learning and motivation (Volume 2). New York: Academic Press. pp. 89–195.

Baddeley, A .D., & Hitch, G. (1974). Working memory. In G.H. Bower (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 8, pp. 47–89). New York: Academic Press.

Craik, F. I. M., & Lockhart, R. S. (1972). Levels of processing: A framework for memory research. Journal of Verbal Learning and Verbal behavior, 11, 671-684.

Raaijmakers, J.G.W. & Shiffrin, R.M. (2003). Models versus descriptions: Real differences and langiage differences . behavioral and Brain Sciences , 26, 753.

Shallice, T., & Warrington, E. K. (1977). Auditory-verbal short-term memory impairment and conduction aphasia. Brain and Language, 4(4) , 479-491.

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Reid on Memory and Personal Identity

Thomas Reid held a direct realist theory of memory. Like his direct realism about perception, Reid developed his account as an alternative to the model of the mind that he called ‘the theory of ideas.’ On such a theory, mental operations such as perception and memory have mental states—ideas or impressions—as their direct objects. These mental states are understood as representations that encode information about their causes. The mind is directed towards and reads off from these representations, information about extra-mental items. By contrast, Reid holds that the direct objects of memory and perception are extra-mental. In the case of perception, the mind is directed to present material objects and properties; in the case of memory, the mind is directed towards past events to which the person was agent or witness. In other words, according to Reid, when we remember, we do not recall previous experiences. In memory, the mind is directed neither towards an idea experienced previously nor towards an idea of a previous experience. Rather, we recall events , experienced previously.

Reid is interested in the notion of memory not only for its own sake but also because of its conceptual connection to the notion of personal identity. Reid criticizes Locke’s theory of personal identity for inferring a metaphysical hypothesis now called the Memory Theory from the conceptual connection between memory and personal identity. On this theory, personal identity consists in memory; sameness of memory is metaphysically necessary and sufficient for sameness of persons. According to Reid, memory is neither necessary nor sufficient for personal identity, metaphysically speaking. Indeed, Reid holds that it is impossible to account for personal identity in any terms other than itself. Personal identity is simple and unanalyzable. Though memory is not the metaphysical ground of personal identity, according to Reid, it provides first-personal evidence of personal identity. I know that I was present at my graduation because I remember being there. Memories do not make one the same person over time. Rather, memories allow one to know one’s own past, immediately and directly.

1. Criticizing the Storehouse Model of Memory

2. a direct realist theory of memory, 3. objecting to locke on personal identity, 4. personal identity as simple and unanalyzable, primary works, secondary works, other internet resources, related entries.

Reid traces the target of his criticisms back to the Ancients, whom he depicts as holding that the mind is a sensorium—a repository of past ideas and impressions ( Essays , 280). [ 1 ] On this theory, perception, memory and imagination are causal processes beginning with purely physiological events: impressions on the brain. These physiological states are taken to have mental correlates—sensations or ideas of sense or sense impressions—which are the objects of perception, memory and imagination. These ideas or impressions are representations in the sense that they preserve, or re-present information from their physiological correlates. According to Reid, this view recognizes no distinction between imagination and memory. Each consists in having a picture-like impression that remains after the object that impressed upon the senses is gone. The only difference between the two is in the fidelity of the imagistic impression to its cause. Memory consists in the preservation of images imprinted in the mind from previous experiences, while imagination consists in constructing images that lack a duplicate in experience.

Reid offers two criticisms of the ancient theory, as he understands it. First, the theory falls afoul of one of Reid’s own methodological strictures, namely, that a theory must adhere to Newton’s regulae philosophandi , or rules of philosophizing ( Inquiry , 12). The first rule is to posit no merely theoretical causes and in Reid’s view the second rule forbids positing causes insufficient to explain the phenomenon in question. According to Reid, there is no observational evidence of the existence of impressions on the brain—they are merely theoretical entities ( Essays , 281). Furthermore, even if we granted the otherwise theoretical existence of impressions, such entities would not be sufficient to explain memory. We might establish a correlation between impressions and memories, but it would remain at best just that: a correlation, not a causal explanation. Having learned Hume’s lessons about causation, Reid denies any necessary connections between impressions and memories sufficient to regard the former as a cause of the latter. Reid also considers whether resemblance could ground such a causal explanation, but, having learned Berkeley’s lessons about resemblance, he denies that any mental states can resemble material states such as impressions on the brain. Reid’s second criticism is that even if we were to grant that impressions remain after the objects that impressed upon the senses are gone, this would entail that we should continue to perceive objects rather than remember them, since on the ancient theory, impressions are the immediate causes and objects of perception ( Essays , 282).

Though Reid identifies his target as having ancient origins, his primary concern is with what he regards as its modern equivalent. This modern theory was introduced by Locke and, according to Reid, extended to its inevitable idealist and skeptical conclusions by Berkeley and Hume. Reid excerpts passages from Locke’s Essay Concerning Human Understanding to illustrate the misleading metaphors Locke inherits from the ancient theory—metaphors of the mind as a storehouse and of ideas and impressions as pictures.

The other way of Retention is the Power to revive again in our Minds those Ideas , which after imprinting have disappeared, or have been as it were laid aside out of sight…This is Memory , which is as it were the Store-house of our Ideas …But our Ideas being nothing but actual Perceptions in the Mind, which cease to be any thing, when there is no perception of them, this laying up of our Ideas in the Repository of the Memory, signifies no more but this, that the Mind has a Power, in many cases, to revive Perceptions, which it once had, with this additional Perception annexed to them, that it has had them before. And in this Sense it is, that our Ideas are said to be in our Memories, when indeed, they are actually no where, but only there is an ability in the Mind, when it will, to revive them again; and as it were paint them anew on it self, though some with more, some with less difficulty; some more lively, and others more obscurely (Locke, Essay , Book II.x.1–2).

As this passage illustrates, Locke himself acknowledges that the notion that the mind is a kind of repository or storehouse is metaphorical. According to Locke’s own theory, ideas and impressions cannot be stored. Locke is committed to the thesis that ideas are momentary and non-continuous and to the thesis that identity over time requires continuous existence. These two theses jointly entail that numerically identical ideas cannot be stored over time. Nevertheless, Reid criticizes Locke for being unable to extricate himself from metaphor when Locke claims that in memory, “the mind, as it were, paints ideas anew on it self.” On what model does the mind paint the idea anew? In order to use a previous idea as its model, the mind must remember it. But then the ability to paint ideas anew upon itself presupposes rather than explains memory.

Locke offers a non-metaphorical account of memory when he claims that memory consists of two perceptions: a present perception and a belief about that present perception, namely that one has enjoyed the perception before. Because Locke is committed to the thesis that numerically identical ideas cannot be stored over time, the belief must be the belief that one has previously enjoyed a perception qualitatively similar to the present perception, rather than numerically identical with it. Reid criticizes this account as circular, once more. A first-personal belief that one’s present perception is qualitatively similar to a perception one had in the past requires remembering having had that previous perception and recalling its quality and character. As before, Locke’s account presupposes rather than explains the phenomenon of memory ( Essays , 285).

Reid criticizes Hume’s account of memory for duplicating Locke’s mistakes. He quotes from Hume’s Treatise of Human Nature :

We find by experience, that when any impression has been present with the mind, it again makes its appearance there as an idea; and this it may do after two different ways: Either when in its new appearance it retains a considerable degree of its first vivacity, and is somewhat intermediate betwixt an impression and an idea; or when it entirely loses that vivacity, and is a perfect idea. The faculty by which we repeat our impressions in the first manner, is call’d the MEMORY, and the other the IMAGINATION (Hume, Treatise , 1.1.3.1).

Like Locke, Hume holds that ideas have no continued existence. And so, Reid argues, Hume cannot claim that a numerically identical idea can reappear. In addition, Hume’s account faces the same circularity objection as Locke’s. Hume accounts for memory by appealing to an idea that is qualitatively similar to, but less forceful and vivacious than a previous idea. But the ability to judge qualitative similarity and degrees of force and vivacity between present ideas and past impressions presupposes memory.

Reid provides additional criticisms of Hume’s account of memory. First, Reid interprets Hume’s account of memory as committing him to the position that we have the power to repeat ideas (though notice that Hume does not commit to this in the quoted passage). Reid argues that this position is inconsistent with Hume’s claim that impressions are the efficient causes of ideas. Reid’s second criticism is more insightful; he argues that differences in degrees of force and vivacity are insufficient to sustain the distinctions between perception, memory and imagination. Reid interprets Hume as holding that these three faculties do not differ in kind, but rather in the degree of force and vivacity of the ideas that are their objects. Ideas with the greatest degree of force and vivacity are perceptions, those with a lesser degree are memories, and those with the least degree of force and vivacity are imaginings. Reid criticizes this taxonomy on phenomenological grounds. Some perceptions are less forceful and lively than some memories, as when lost in reminiscence, and some memories are less forceful and lively than imaginings, as when lost in reverie. Furthermore, increasing the degree of force and vivacity does not transform a memory or an imagining into a perception. Reid compares striking one’s head against the wall to lightly touching it to the wall. The latter has much less force and vivacity than the former, yet lightly touching one’s head to the wall is neither a memory nor an imagining ( Essays , 289).

Reid grants that perceptions, memories and imaginings often differ in degree of force and vivacity, but, he argues, this difference is insufficient to account for the special quality of presentness represented in perceptions, the special quality of pastness represented in memories, and the special quality of atemporality represented in imaginings ( Inquiry , 197). While memories may be faint, or weak, these features are not necessary to these states being memories, and so cannot be used to individuate them. In addition, a present idea—whatever its degree of force and vivacity—cannot ground judgments about events in the past because present ideas represent events as present.

For according to that theory, the immediate object of memory, as well as every other operation of the understanding, is an idea present to the mind. And, from the present existence of this idea of memory I am led to infer, by reasoning, that six months ago or six years ago, there did exist an object similar to this one…But what is there in the idea that can lead me to this conclusion? What mark does it bear of the date of its archetype? ( Essays , 476)

Present ideas contain no information, qualitatively or representationally, that could serve as the basis of judgments about past events. As a result, no reflection on present ideas and their quality or character is sufficient for a representation of events in the past, as past.

Contemporary philosophers and cognitive scientists recognize that memory is a diverse phenomenon and they draw some useful distinctions among varieties of memory. [ 2 ] For example, Endel Tulving distinguishes between episodic memory, semantic memory and procedural memory. Remembering how to ride a bike is an example of procedural memory. Remembering that Napoleon was defeated at Waterloo is an example of a semantic memory. Remembering one’s tenth birthday party is an example of an episodic memory.

The distinction most relevant to the issues Reid, Locke and Hume raise for memory and personal identity is between semantic and episodic memory. Henri Bergson and Bertrand Russell developed a similar distinction, and Russell’s distinction between factual and personal memory accords with that between semantic and episodic memory. Semantic memories are properly reported using a factive complement—a that-clause—after the verbs ‘remember’ or ‘recall’, as in ‘Jane remembers that Napoleon was defeated at Waterloo’. In particular, a semantic memory cannot be reported using the form ‘ S remembers/recalls [ x ] f -ing’, as in ‘Jane recalls her tenth birthday party,’ or ‘John remembers falling off his bike.’ Only episodic memories may be properly reported using this form. No one today can properly report ‘I remember Napoleon being defeated at Waterloo,’ though many may properly report ‘I remember that Napoleon was defeated at Waterloo.’ On the other hand, an episodic memory can be reported using the same form by which semantic memories are reported because episodic memories may ground semantic memories under certain circumstances. It is legitimate to state both ‘I recall my tenth birthday party,’ in reporting an episodic memory of that event and to state ‘I remember that I had a tenth birthday party’, in reporting a semantic memory, whose justification would appeal to the previous episodic memory.

Episodic memories are further distinguished from semantic memories by the Previous Awareness Condition on episodic memory. The Previous Awareness Condition has been developed and examined by Sydney Shoemaker (1970), among others. Put simply, one has an episodic memory of an event only if one was agent or witness to the event remembered. The Previous Awareness Condition is a necessary but insufficient condition on episodic memory. If one has an experience as of being lost in a store as a child, but one was not in fact lost in a store as a child, such an experience is not an episodic memory. On the other hand, each of us has been agent or witness to many events of which we have no episodic memory. For example, one may not remember one’s third birthday party and so lack an episodic memory of an event to which one was surely witness.

Reid is most interested in episodic memory. Though Reid does not use the contemporary terminology, his theory draws upon both the distinction between episodic and semantic memory and the Previous Awareness Condition on episodic memory. As he puts the matter:

Things remembered must be things formerly perceived or known. I remember the transit of Venus over the sun in the year 1769. I must therefore have perceived it at the time it happened, otherwise I could not now remember it. Our first acquaintance with any object of thought cannot be by remembrance. Memory can only produce a continuance or renewal of a former acquaintance with the things remembered ( Essays , 255).

Though Reid uses the term ‘acquaintance,’ the things retained through memory are things previously perceived or experienced. The term ‘acquaintance’ has acquired a technical sense that it did not have in Reid’s day, so it is better to see Reid as holding that memory preserves contact with events previously apprehended through perception and thereby known by acquaintance. Acquaintance presupposes apprehension, and prior episodes of apprehension are necessary for retained acquaintance.

According to Reid, episodic memory is not a current apprehension of a past event, nor is it a current apprehension of a past experience. These theoretical options were ruled out by Reid’s criticism of Locke and Hume. Rather, according to Reid, memory is an act that preserves a past apprehension. Reid characterizes memory as exhibiting what we now call the Previous Awareness Condition. He holds that reports of episodic memory are true only if the person reporting satisfies the condition, and that experiences that otherwise appear to be episodic memories, but which fail the condition, are not episodic memories ( Essays , 264).

Reid does not count what we term ‘semantic memories’ as memories in the proper sense. He discounts them not because they fail to meet the Previous Awareness Condition, but because he holds that semantic memories are better classified as beliefs or knowledge rather than memories. For example, he would hold that a person today who reports remembering that Napoleon was defeated at Waterloo expresses a belief or knowledge rather than a memory. He holds this because he requires a distinction between two sorts of beliefs that would otherwise be obscured by the fact that each sort can be expressed in the form of a semantic memory report. The distinction is between beliefs that play a role in preserving past apprehension (and which are constituents of episodic memory), and those that do not play a role in preserving past apprehension (and which are not, strictly speaking, memories). For example, Jane believes that she dined with a friend last night. Jane has an episodic memory of this event, and according to Reid, her belief ‘that I dined with a friend last night,’ plays a role in preserving Jane’s past apprehension of dining with her friend. On the other hand, Jane’s belief that she had a third birthday party does not play a role in preserving her past apprehension of her third birthday party; she has no episodic memory of her third birthday party. The difference between these two sorts of belief is obscured by the fact that each may be expressed by using the factive compliment: ‘Jane remembers that she dined with a friend last night,’ and ‘Jane remembers that she had a third birthday party.’

According to Reid, a memory consists in a conception of a past event and a belief about that past event, that it happened to the person who is represented in that memory as agent or witness ( Essays , 228, 232, 254, 257). This conception-belief structure mirrors Reid’s accounts of perception and consciousness, each of which also consist in a conception and belief. Folescu (2018a) examines whether memorial conception differs from or is the same as the kind of conception ingredient in perception, consciousness, and other intentional mental states. The belief that is a constituent of memory, on Reid’s view, is a belief of some past event, that it happened. In particular, it is a belief that it happened to me, where the pronoun is indexed to the person who is represented in the memory as agent or witness to the event ( Essays , 255, 262). The belief is about or of the event because the other constituent of memory—the conception—supplies the event, which is the object of the belief. On Reid’s view, the objects of memory are the events presented in past apprehensions. Memory preserves past apprehensions by relating us to the events originally presented in perception—memory preserves past apprehension through conception and belief. In particular, the objects of memory are not the past apprehensions themselves but that which is presented in the past apprehensions, namely, the original event ( Inquiry , 28). Folescu (2018b) examines a tension in Reid’s accounts of memory and perception. According to Reid, we remember events that were apprehended in the past by perception. But Reid insists that perception is confined to the present. Because perception is confined to the present, we cannot perceive events, which have a duration. How, then, can we remember what we cannot have perceived?

Reid holds that memory is not a current apprehension of an event already presented in a past apprehension. In other words, we do not remember events by re-apprehending them. Rather, the past apprehension is itself preserved by the act of remembering the event apprehended. Memory is an act of preservation through conception and belief. Such preservation does not itself constitute an additional apprehension over and above the apprehension preserved. Indeed, according to Reid, it is impossible to currently apprehend any events in the past; apprehension is confined to perceiving present objects or being conscious of present mental operations ( Essays , 23, 253). Reid does not deny that memory is itself a current mental state, nor does he deny that memory presupposes a past apprehension. He denies only that memory is a current apprehension, and that the object of a memory is a past apprehension ( Essays , 253). Memory preserves past apprehension by conceiving of an event previously apprehended and believing, of this event, that it happened to me.

Reid holds that memory, like perception, is immediate. Neither the conception nor the belief that are the ingredients of memory are formed on the basis of reasoning or testimony. Memory is an original faculty of our constitution governed by what Reid calls “the first principles of contingent truths.” In the case of memory, the governing principle is that “those things did really happen which I distinctly remember” ( Essays , 474). On Reid’s view, a normally functioning human does not and need not infer to a past event in episodic memory. In order to infer to a past event, one must have some prior, non-inferential relation to the event if it is to be a memory rather than a belief or knowledge. But then this prior, non-inferential relation would be an episodic memory. In addition, if episodic memory involved an inference to the effect that the event happened to me, the inference would be otiose because, as Reid claims, such a belief is already an immediate, non-inferential component of episodic memory. In principle, one could infer from the conception and belief that are ingredients in memory to a further belief that the event happened. But if such a belief plays a role in preserving past apprehension then it is superfluous—such a belief, subject to the Previous Awareness Condition, is already embedded in episodic memory. If the belief does not play a role in preserving past apprehension then it is a semantic memory, which, according to Reid, is among the species of belief or knowledge rather memory.

The distinction between beliefs that are ingredients in episodic memories and beliefs that are based on, but not ingredients in, episodic memories allows Reid to account for cases in which a memorial experience continues to represent an event as having happened, even when the person who seems to remember the event has what she regards as an overriding reason to believe that the event did not occur. The belief that is an ingredient in the experience represents the event as having happened to the person who seems to remember it. Further, the belief will continue to represent the event as having happened to the person, even under conditions in which she forms a separate belief, not embedded in the memorial experience, to the effect that it did not happen to her.

The distinction also allows Reid to satisfy a constraint on any adequate theory of memory; namely, that it explain why memory represents events as having the special quality of being in the past. If belief were not an ingredient in episodic memory, then though we might believe that the events we remember are in the past, memory could not represent events as past. If belief were not an ingredient in memory, then memory alone would relate us to an event previously apprehended. But the apprehension preserved is an apprehension of an event that was, at that time, represented in that apprehension as present. The pastness of the event apprehended is not part of the content of the past apprehension. But because a belief that the event happened to me is embedded in the memory itself, memory represents not merely past events, but past events as having occurred. In other words, the belief that is partly constitutive of episodic memory is tensed.

One might wonder whether Reid’s account of memory is subject to the same criticisms he levels against Locke and Hume. Does Reid appeal to the storehouse metaphor when he claims that memory is preserved past apprehension? Reid criticizes Locke and Hume for begging the question. Yet by holding that memory is in part constituted by a belief, does Reid not also assume the very phenomenon to be explained? Reid can avoid the criticisms to which the theory of ideas is vulnerable by insisting that memory is not a current apprehension, but rather a preserved past apprehension. His theory of memory is a direct realist theory because, according to Reid, memory is not directed towards any present perceptions, ideas, or impressions—stored or otherwise. Neither is memory directed towards any past perceptions, ideas, or impressions—stored or otherwise. Memory is directed towards the events presented in past apprehensions. Because apprehensions, perceptions, ideas, and impressions are never the objects of memory, they do not need to be stored for use by memory. Likewise, the belief that is an ingredient in memory is not about any present or past apprehensions. If it were, Reid’s theory would be subject to the same circularity objection he presses against Locke and Hume.

On Reid’s theory of memory, an apprehension establishes a direct relation to an event, which relation is preserved in memory by the acts of conceiving the event and believing of the event conceived that it happened to the person who remembers. It is a direct realist theory of memory because it departs from the model on which memory is a current apprehension of a past event or a current apprehension of a past apprehension. On the direct realist view, memory preserves past apprehension of an event through conception and belief. Reid’s theory captures how memory, like perception, represents the world, rather than our experiences of the world.

Reid, Locke and others are interested in the notion of episodic memory not only for its own sake, but also because of its conceptual connection to the notion of personal identity. If Joe remembers, episodically, winning the World Series, then Joe must have existed at the time of his winning the World Series. This is why the Previous Awareness Condition characterizes episodic but not semantic memory. Unlike Joe’s memory that Napoleon was defeated at Waterloo, his memory of winning the World Series logically entails Joe’s existence at the time of the event remembered. In other words, episodic memory is logically sufficient for personal identity: if S remembers at time t n (episodically) an event at time t 1 , then S existed at time t 1 . In addition, memory reports are often taken to be prima facie evidence for statements about the past history of the person reporting.

Reid’s main criticism of Locke’s theory of personal identity is that Locke moves from these truisms concerning the conceptual and evidential relations among the notions of memory and personal identity to a hypothesis concerning the metaphysical relations among them ( Essays , 277). In this, Reid follows Butler’s influential dissertation “Of Personal Identity,” appended to The Analogy of Religion in 1736.

Reid interprets Locke as holding what is now called the Memory Theory of personal identity ( Essays , 277). On this theory, personal identity consists in memory; sameness of episodic memory is metaphysically necessary and sufficient for sameness of persons. In other words, on the Memory Theory, what makes a person identical with herself over time is her remembering or being able to remember the events to which she was witness or agent. If she cannot episodically remember an event, then she is not identical with any of the persons who was witness or agent to the event. In such a case, she would bear the same relation to that event as any other person for whom a memory of the event could rise at best to the level of a semantic memory. If she can episodically remember an event, then her recollection or ability to recall that event makes her identical with the person represented in that memory as agent or witness to the event.

But there is a secondary, more subtle line of disagreement between Reid and Locke. Much of Locke’s chapter Identity and Diversity is dedicated to establishing that the self is not a substance, material or immaterial. By contrast, Reid holds that the self is a simple, unanalyzable immaterial substance with active powers. Reid argues that Locke cannot sustain both the thesis that the self is not a substance and the thesis that self remains identical over time. While Reid’s criticisms of the Memory Theory are more well known, his criticism of Locke’s insistence that the self is not a substance reveals two very different accounts of the metaphysics of identity. While Locke argues that the identity conditions for different kinds of things differ, so that the conditions under which a mass of matter, and an animal, and a person are not the same, Reid holds that identity is confined solely to substances that have a continued, uninterrupted existence and which do not have parts. In other words, according to Reid, strictly speaking the only real identity is personal identity ( Essays , 266–267). “The identity…we ascribe to bodies, whether natural or artificial, is not perfect identity; it is rather something which, for the conveniency of speech, we call identity” ( Essays , 266).

Reid begins his interpretation and criticism of Locke’s theory by noting that Locke defines the term ‘person’ as meaning “a thinking intelligent Being, that has reason and reflection…” (Locke Essay , Book II.xxvii.9). Reid is friendly to this characterization of the self. But, Reid notes, Locke appears to equivocate between the notion of a person as a ‘thinking Being,’ and the notion of a person as that which is preserved through consciousness and memory. Reid paraphrases a passage from Locke’s Essay Concerning Human Understanding :

Mr LOCKE tells us however, “that personal identity, that is, the sameness of a rational being, consists in consciousness alone, as, as far as this consciousness can be extended backwards to any past action or thought, so far reaches the identity of that person. So that whatever hath the consciousness of present and past actions, is the same person to whom they belong” ( Essays 275–276).

The passage in Locke differs from Reid’s paraphrase:

… personal Identity, i.e. the sameness of a rational Being: And as far as this consciousness can be extended backwards to any past Action or Thought, so far reaches the Identity of that Person ; it is the same self now it was then; and ‘tis by the same self with this present one that now reflects on it, that that Action was done (Locke, Essay , Book II.xxvii.9).

Reid’s first criticism rests on his interpreting Locke’s definition as committing him to the position that a person is a subject of thought, which Reid regards as implying that a person is a thinking substance. At the same time, Locke appears to be committed to an analysis of personal identity in terms of memory, or, as Locke would put it, consciousness of the past. Reid notes that Locke is aware of some of the consequences of the Memory Theory: if sameness of consciousness or memory is necessary and sufficient for sameness of person, then it is possible for there to be sameness of person without sameness of thinking Being. In other words, it is logically and metaphysically possible for a person to be “transferred from one intelligent being to another,” or for “two or twenty intelligent beings to be the same person” ( Essays , 276). Locke’s response to these worries, as well as worries about periods of interrupted consciousness, as in sleep, highlights Reid’s criticism: “…[I]n all these cases…doubts are raised whether we are the same thinking thing; i.e. the same substance or no. Which however reasonable, or unreasonable, concerns not personal Identity at all. The Question being what makes the same Person , and not whether it be the same Identical Substance…” (Locke, Essay , Book II.xxvii.10). Reid’s criticism is not that cases of transfer or fission are incoherent, though he thinks they are. Rather, his criticism is that the possibility of sameness of person without sameness of thinking Being that the Memory Theory allows is inconsistent with Locke’s characterization of a person as a ‘thinking Being’. Given that Reid thinks that this initial characterization is correct, he regards this as a reductio of the Memory Theory.

Reid’s second criticism is his most famous and is often referred to as the case of the Brave Officer:

Suppose a brave officer to have been flogged when a boy at school, for robbing an orchard, to have taken a standard from the enemy in his first campaign, and to have been made a general in advanced life: Suppose also, which must be admitted to be possible, that when he took the standard, he was conscious of his having been flogged at school, and that when made a general he was conscious of his taking the standard, but had absolutely lost the consciousness of his flogging.

These things being supposed, it follows, from Mr LOCKE’s doctrine, that he who was flogged at school is the same person who took the standard, and that he who took the standard is the same person who was made a general. When it follows, if there be any truth in logic, that the general is the same person with him who was flogged at school. But the general’s consciousness does not reach so far back as his flogging, therefore, according to Mr LOCKE’s doctrine, he is not the person who was flogged. Therefore the general is, and at the same time is not the same person as him who was flogged at school ( Essays , 276).

According to the Memory Theory, personal identity consists in memory; that is, sameness of memory is metaphysically necessary and sufficient for sameness of person. On this account, given that sameness of memory is sufficient for sameness of person, if a person at time t n remembers (episodically) an event that occurred at time t 1 then the person at time t n is identical with the person who was witness or agent to the event at time t 1 . If the brave officer who has just taken the flag of the enemy remembers being beaten at school, then the brave officer is identical with the boy who was beaten. So too, if the general remembers taking the enemy’s flag, then the general is identical with the brave officer. If the general is identical with the brave officer, and the brave officer is identical with the boy, then by the transitivity of identity, the general is identical with the boy.

However, on this account, given that sameness of memory is a necessary condition for sameness of person, if a person at time t n does not remember (episodically) an event that occurred at time t 1 , then the person at time t n cannot be identical with any person who was witness or agent to the event at time t 1 . If the general cannot remember being beaten at school, he cannot be identical with the boy who was beaten. Thus, the Memory Theory is committed to mutually incompatible theses: that the General is identical with the boy and that he is not.

Reid’s third criticism is terminological: he argues that Locke confounds consciousness with memory—elsewhere Reid also argues that Locke confounds consciousness with reflection ( Essays , 58). Consciousness and memory are distinct phenomena, according to Reid. The former is directed towards present mental acts and operations, while the latter is directed towards past events to which one was agent or witness. If consciousness could extend to past events, then memory would be redundant ( Essays , 277).

According to Reid, memory is neither necessary nor sufficient for personal identity, metaphysically speaking, despite the conceptual and evidential relations memory bears to personal identity. It is not a necessary condition because each us has been agent or witness to many events that we do not now remember. “I may have other good evidence of things which befell me, and which I do not remember: I know who bare me, and suckled me, but I do not remember these events” ( Essays , 264). It is not a sufficient condition, for, as Butler showed, while having an episodic memory of an event entails that one existed at the time of the event remembered, it is not the recollection or the ability to recall that makes one identical with the person who was witness or agent to the event. “It may here be observed…that it is not my remembering any action of mine that makes be to be the person who did it. This remembrance makes me know assuredly that I did it; but I might have done it, though I did not remember it” ( Essays , 265). Reid’s fourth criticism is that while memory is tied to personal identity conceptually and evidentially, such ties do not entail a metaphysical connection that would license analyzing the latter in terms of the former ( Essays , 277).

Reid’s final criticism is that the Memory Theory is committed to the absurdity that identity consists in something that has no continued existence ( Essays , 278). Reid and Locke agree that memory, consciousness, thought, and other mental operations have no continued existence. They are fleeting and non-continuous. But they also agree that identity, and in particular personal identity, requires a continued existence over time. As Locke puts it, “one thing cannot have two beginnings of Existence, nor two things one beginning” (Locke, Essay , Book II.xxvii.1). But these commitments are jointly inconsistent with the thesis that personal identity consists in memory.

A theory of personal identity is intended to account for how a person remains identical over time. When analyzed in terms of items that are fleeting and non-continuous—ideas, memories, thoughts—identity is reduced to diversity; that is, it is eliminated. By contrast, if one locates personal identity in that which thinks and remembers, and which has a continued, uninterrupted existence, one purchases personal identity at the cost of admitting that the self is a substance. Reid captures Locke on the horns of a dilemma: either the self is a substance, in which case it remains identical over time, or the self is not a substance, in which case there is no personal identity. Reid holds that this dilemma applies with equal force against any reductionist account of personal identity that employs the theory of ideas, for example Hume’s bundle theory of the self ( Essays , 473–474).

Those familiar with the contemporary literature on personal identity, with its emphasis on the necessary and sufficient conditions under which a person remains identical over time, may wonder: if Reid holds that memory is not the criterion of identity, and if Reid’s substance dualism rules out bodily identity as a criterion of personal identity, in what does personal identity consist? Reid’s answer is that identity cannot be accounted for in any terms other than itself. This is neither quietism nor epistemic humility on Reid’s part. Rather, Reid argues that the nature of personal identity—its simplicity and indivisibility—rules out any reductive account that appeals to notions other than identity in explaining how a person persists over time.

Reid holds that numerical identity is, strictly speaking, indefinable, but it can be contrasted with other relations, such as diversity, similarity and dissimilarity ( Essays , 263). It requires a continued existence over time—a duration—and requires that there be no two beginnings of existence. Because mental states are fleeting and non-continuous they cannot remain identical over time. A mental state may be indistinguishable from a previous mental state, but because mental states do not have a continued existence, no mental state at one time can be numerically identical with another at a different time. As a result, persons cannot be identified with their thoughts, actions or feelings ( Essays , 264). However, according to Reid, thoughts, actions, feelings and all other mental operations are had or performed by a subject that has a continued existence and that bears the same relation to all them. The subject is an immaterial substance that thinks, acts and feels. According to Reid, this substantial self has no parts—it is indivisible—which contributes to its resistance to reductive explanation. Reid appeals to Leibniz’s notion of a monad to describe the indivisibility of this immaterial, substantial self ( Essays , 264).

Though memory is not the metaphysical ground of personal identity, it provides first-personal evidence of it. Reid notes that the evidence we use to make judgments about our own pasts is different from the evidence we use to make judgments about other people and their pasts ( Essays 266). Memory justifies first-personal reports about one’s own witnessed past, while judgments of qualitative similarity justify third-personal statements about the identities of other persons. I know that I was present at my wedding because I remember being there. I know that the man I live with was at my wedding because he looks like the man I married.

First-personal, memorial reports about one’s own past are either true or false: if the memorial experience is a genuine episodic memory, then it is impossible for it to testify falsely concerning one’s presence at the event remembered. This aspect of episodic memory reports is often expressed by saying that they are immune to error through misidentification. If the memorial experience testifies falsely concerning one’s presence at the event remembered, then it cannot be an episodic memory. For example, if I have an experience as of having been lost in a shopping mall as a child, but I was never lost, I cannot be said to remember having been lost, strictly speaking. The upshot is that first-personal memorial reports, if they are episodic memory reports, provide certainty concerning one’s presence at the event remembered. Because third-personal judgments about the pasts of other persons are based on judgments of qualitative similarity rather than episodic memory, they are never certain; they are only ever more or less well justified ( Essays 264–265).

It is important to notice that while Reid uses the term ‘evidence,’ when describing the role that memory plays in first-personal knowledge of one’s own past, memory is not used by persons to justify judgments or beliefs about their own pasts. In other words, people do not remember events and then conclude from having remembered them, that it was they who were witness to the events. Rather, memory itself represents one’s presence at the event remembered. According to Reid, a memory consists in a conception of an event and a belief, about the event conceived, that it happened to me, where the pronoun is indexed to the person who is represented in the memory as agent or witness. In other words, memory consists in part in a judgment that represents one’s presence at the event. Any further judgment, justified by memory, to the effect that I was the person who was there would be superfluous—memory already testifies to my having been there. This is why Reid calls the evidence of memory immediate : first-personal statements about one’s own past are memory statements, not statements made on the basis of memory.

Reid’s picture is one on which each of us is immediately and justifiably aware of our own past because each of us remembers having been there. This is the moral of the story concerning the logical relationship between the concept of memory and the concept of personal identity. Memories do not make me the same person as the person represented in my memories. Rather, memories allow me to know my own past, immediately and directly.

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• Van Woudenberg, R., 2004, “Reid on Memory and the Identity of Persons,” in The Cambridge Companion to Thomas Reid , T. Cuneo and R. Van Woudenberg (eds.), Cambridge: Cambridge University Press, pp. 204 –221.
• –––, 1999, “Thomas Reid on Memory,” Journal of the History of Philosophy , 37: 117–133.
• Ward, A., 2000, “Reid on Personal Identity: Some Comparisons with Locke and Kant,” Reid Studies , 3: 55–64.
• Yaffe, G., 2010, “Beyond the Brave Officer: Reid on the Unity of Mind, the Moral Sense, and Locke’s Theory of Personal Identity,” in Reid on Ethics , S. Roeser (ed.), Basingstoke: Palgrave Macmillan.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• Works of Thomas Reid , at Early Modern Philosophy Texts
• The papers of Thomas Reid , held by Aberdeen University Library

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8.2 Parts of the Brain Involved in Memory

Learning objectives.

By the end of this section, you will be able to:

• Explain the brain functions involved in memory
• Recognize the roles of the hippocampus, amygdala, and cerebellum

   Are memories stored in just one part of the brain, or are they stored in many different parts of the brain? Karl Lashley began exploring this problem, about 100 years ago, by making lesions in the brains of animals such as rats and monkeys. He was searching for evidence of the engram: the group of neurons that serve as the “physical representation of memory” (Josselyn, 2010). First, Lashley (1950) trained rats to find their way through a maze. Then, he used the tools available at the time—in this case a soldering iron—to create lesions in the rats’ brains, specifically in the cerebral cortex. He did this because he was trying to erase the engram, or the original memory trace that the rats had of the maze.

Lashley did not find evidence of the engram, and the rats were still able to find their way through the maze, regardless of the size or location of the lesion. Based on his creation of lesions and the animals’ reaction, he formulated the  equipotentiality hypothesis: if part of one area of the brain involved in memory is damaged, another part of the same area can take over that memory function (Lashley, 1950). Although Lashley’s early work did not confirm the existence of the engram, modern psychologists are making progress locating it.

Many scientists believe that the entire brain is involved with memory. However, since Lashley’s research, other scientists have been able to look more closely at the brain and memory. They have argued that memory is located in specific parts of the brain, and specific neurons can be recognized for their involvement in forming memories. The main parts of the brain involved with memory are the amygdala, the hippocampus, the cerebellum, and the prefrontal cortex.

Figure 8.07.  The amygdala is involved in fear and fear memories. The hippocampus is associated with declarative and episodic memory as well as recognition memory. The cerebellum plays a role in processing procedural memories, such as how to play the piano. The prefrontal cortex appears to be involved in remembering semantic tasks.

Long term memory represents the final stage in the information-processing model where informative knowledge is stored permanently (the idea of memory permanences will be discussed in a later section). Memories we have conscious storage and access to are known as explicit memory (also known as declarative memory) and are encoded by the hippocampus, the entorhinal cortex, and the perihinal cortex which are important structures in the limbic system . The limbic system represents a set of brain structures located on both sides of the thalamus, immediately beneath the cerebral cortex, and is important for a variety of functions including emotion, motivation, long-term memory, and olfaction.

Within the category of explicit memories, e pisodic memories represent times, places, associated emotions and other contextual information that make up autobiographical events. These types of memories are sequences of experiences and past memories that allows the individual to figuratively travel back in time to relive or recall the event that took place at a particular time and place. Episodic memories have been demonstrated to rely heavily on neural structures that were activated during a procedure when the event was being experienced. Gottfried and colleagues (2004) used fMRI scanners to observe brain activity when participants were trying to remember images they had first viewed in the presence of a specific scent. When recalling the images participants had viewed with the accompanying smell, areas of the primary olfactory cortex (the prirform cortex) were more active compared to no scent pairing conditions (Gottfried, Smith, Rugg & Doland, 2004), suggesting memories are retrieved by reactivating the sensors areas that were active while experiencing the original event. This indicates sensory input is extremely important for episodic memories which we use to try to recreate the experience of what had occurred.

Semantic memory  represents a second of the three main types of explicit memory and refers to general world knowledge we possess and have collected throughout our lives. These facts about the world, ideas, meanings and concepts are mixed with our experiences from episodic memory and are emphasized by cultural differences. Within the field of cognitive neuroscience there are many views regarding the locations in the brain where semantic memories are stored. One view suggests that semantic memories are stored by the same neural structures that assist in creating episodic memories. Areas such as the medial temporal lobes, the hippocampus and fornix which encode the information and build connections with areas of the cortex where they can be accessed at a later time. Other research has suggested that the hippocampus and neighboring structures of the limbic system are more crucial to the storage and retrieval of semantic memories than areas related to motor activities or sensory processing used during the time of encoding (Vargha-Khadem et al., 1997). Still other groups have suggested semantic memories are retrieved from areas of the frontal cortex and stored in areas of the temporal lobe (Hartley et al., 2014, Binder et al., 2009) . Overall, evidence suggests that many areas of the brain are related to the storage and retrieval of explicit memory as opposed to singular structures.

The final main group of memory under the category of explicit memory is known as  Autobiographical memory . This memory system is made up of both episodic, and semantic aspects of memory and is a collection of memories specifically related to the self. This could be how you look, your height, specific meaningful points in your life, or the general idea of your concept of self. The specific locations where this type of memory are stored and accessed are especially controversial due to the close relationship between autobiographical information and conscious experience. Conway and Pleydell-Pearce (2000) suggested a model describing autobiographical memories as transitory mental compositions stored within a self-memory system containing an autobiographical knowledge base and current goals of the working self. According to this approach, within the self memory system, control processes exist that modulate the ability to associate information to the self knowledge base by continually editing cues used to activate autobiographical memory. Therefore the concepts of self and memories related to self can be influenced by the context of self perceptions at the time of memory encoding. Modern neuroimaging research suggests that autobiographical memory is distributed throughout many complex neural networks including the recruitment neuron groups in the medial and ventrolateral prefrontal cortex, as well as the medial and lateral temporal cortex, the temporal-parietal junction, posterior cingulate cortex, and the cerebellum (Svoboda, E., McKinnon, M. C., Levine, B., 2006).

In contrast to the memory systems covered above related to explicit encoding and retrieval memory processes,  implicit memory  as discussed in the previous section refers to memories that are acquired and recalled unconsciously. Modern research has suggested that the cerebellum, the basal ganglia (a group of subcortical structures associated with voluntary motor control, procedural learning, and emotion as well as many other behaviors), the motor cortex, and various areas of the cerebral cortex (Dharani, 2014) are related to the storage and retrieval of implicit memory.

THE AMYGDALA

   The  amygdala  is an extremely important structure for the creation and recall of both explicit and implicit memory. The main job of the amygdala is to regulate emotions, such as fear and aggression. The amygdala plays a part in how memories are stored as information storage is influenced by emotions and stress. Jocelyn (2010) paired a neutral tone with a foot shock to a group of rats to evaluate the rats fear related to the conditioning with the tone. This produced a fear memory in the rats. After being conditioned, each time the rats heard the tone, they would freeze (a defense response in rats), indicating a memory for the impending shock. Then the researchers induced cell death in neurons in the lateral amygdala, which is the specific area of the brain responsible for fear memories in rats. They found the fear memory became extinct (the fear memory faded). Because of its role in processing emotional information, the amygdala is also involved in memory consolidation: the process of transferring new learning into long-term memory. The amygdala seems to facilitate encoding memories at a deeper level when the event is emotionally arousing. For instance, in terms of the Craik and Lockhart’s (1972) depth of processing model, recent research has demonstrated memories encoded of images that elicit an emotional reaction tend to be remembered more accurately and easier compared to neutral images (Xu et al., 2014). Additionally, fMRI research has demonstrated stronger coupled activation of the amygdala and hippocampus while encoding predicts stronger and more accurate recall memory ability (Phelps, 2004). Greater activation of the amygdala predicting higher probabilities of accurate recall provides evidence illustrating how association with an emotional response can create a deeper level of processing during encoding, resulting in a stronger memory trace for later recall.

THE HIPPOCAMPUS

   The hippocampal formation is made up of a group of substructures including the hippocampus, the dentate gyrus, and the subiculum all of which are located in the interior of the temporal lobe organized in a similar shape to a letter C. Together these structures represent the main areas of the brain associated with the formation of long term memories.

Clark, Zola and Squire (2000) experimented with rats to learn how the  hippocampus  functions in memory processing. They created lesions in the hippocampi of the rats, and found that the rats demonstrated memory impairment on various tasks, such as object recognition and maze running. They concluded that the hippocampus is involved in creating memories, specifically normal recognition memory as well as spatial memory (when the memory tasks are like recall tests). The hippocampus also projects information to cortical regions that give memories meaning and connect them to other bits of information. In addition, it also plays a main role in memory consolidation: the process of transferring new learning into long-term memory.

Injury to this area interferes with the ability to form new memories but does not significantly impair their ability to retrieve memories already stored as long term memories (Hudspeth et al., 2013). One famous patient, known for years only as H. M., had both his left and right temporal lobes (hippocampi) removed in an attempt to help control the seizures he had been suffering from for years (Corkin, Amaral, González, Johnson, & Hyman, 1997). As a result, his declarative (explicit) memory was significantly affected, and he could not form new semantic knowledge. He lost the ability to form new memories, yet he could still remember information and events that had occurred prior to the surgery. His story provides strong evidence in humans that the hippocampus is mainly related to memory consolidation.

THE CEREBELLUM AND PREFRONTAL CORTEX

   The cerebellum plays a large role in implicit memories (procedural memory, motor learning, and classical conditioning). For example, an individual with damage to their hippocampus will still demonstrate a conditioning response to blink when they are given a series of puffs of air to their eyes. However, when researchers damaged the cerebellums of rabbits, they discovered that the rabbits were not able to learn the conditioned eye-blink response (Steinmetz, 1999; Green & Woodruff-Pak, 2000). This experiment demonstrates the important role the cerebellum plays in the formation of implicit memories and conditioned responses.

Recent estimates of counts of neurons in various brain regions suggests there are about 21 to 26 billion neurons in the human cerebral cortex (Pelvig et al., 2008), and 101 billion neurons in the cerebellum (Andersen, Korbo & Pakkenberg, 1992), yet the cerebellum makes up roughly only 10% of the brain (Siegelbaum et al., 2013). The cerebellum is composed of a variety of different regions that receive projections from different parts of the brain and spinal cord, and project mainly to motor related brain systems in the frontal and parietal lobes.

In addition to contributions to implicit memory, conditioned responses, fine motor movements, posture and coordination, the cerebellum also maintains internal representations of the external world, which allow you to navigate through your living room to find your keys in complete darkness, and professional baseball players to coordinate their movement so they can catch outfield fly balls.

Other researchers have used brain imaging measuring metabolic processes, including positron emission tomography (PET) scans, to learn how people process and retain information. From these studies, the prefrontal cortex appears to be active during a variety of memory related tasks. In one study, participants had to complete two different tasks: either looking for the letter  a  in words (considered a perceptual task) or categorizing a noun as either living or non-living (considered a semantic task) (Kapur et al., 1994). Participants were then asked which words they had previously seen, and reported much better recall for the semantic task compared to the perceptual task. According to PET scans, there was much more activation in the left inferior prefrontal cortex in the semantic task. In another study, encoding was associated with left frontal activity, while retrieval of information was associated with the right frontal region (Craik et al., 1999).

Another widely held view of prefrontal cortex function is that it encodes task relevant information in working memory (Baddeley, 2003). Many studies have shown greater amounts of prefrontal cortex activity during delay periods in working memory tasks demonstrating prefrontal rehearsal processes leading to the transition of information from short term working memory to long term memory (Wilson et al., 1993; Levy & Goldman-Rakic, 2000). More recent work evaluating greater prefrontal activity during working memory task delays suggest the activity of the prefrontal cortex during these delay periods may not be neural signatures of long term memory encoding, but may actually be top-down signals that influence encoding in posterior sensory and association areas where the actual working memory representations are maintained (Lara & Wallis, 2015).

NEUROTRANSMITTERS

   There also appear to be specific neurotransmitters involved with the process of memory, such as epinephrine, dopamine, serotonin, glutamate, and acetylcholine (Myhrer, 2003). There continues to be discussion and debate among researchers as to the specific roles each  neurotransmitter  plays (Blockland, 1996). Although there is much debate defining conclusive causal relationships between specific neurotransmitters and specific behaviors by way of experimental design, researchers are able to use two general methods to make inferences about these relationships.

The first method is known as an interventional strategy pharmacological tools or lesions/stimulation are used on specific neurotransmitters and their receptors. The second method is known as a correlational method, where different naturally occurring conditions (neurological diseases, aging) that affect different neurotransmitter systems are compared in humans or animal models. Using these methods, several neurotransmitter groups and pathways have been consistently found to be important for a variety of memory processes (Chapoutier, 1989; Decker and McGaugh, 1991). Repeated activity by neurons leads to greater releases of neurotransmitters in the synapses and stronger neural connections between neuron groups creating memory consolidation.

It is also believed that strong emotions trigger the formation of strong memories, and weaker emotional experiences form weaker memories; this is called  arousal theory  (Christianson, 1992). For example, strong emotional experiences can trigger the release of neurotransmitters, as well as hormones, which strengthen memory; therefore, our memory for an emotional event is usually better than our memory for a non-emotional event. When humans and animals are stressed, the brain secretes more of the neurotransmitter glutamate , which helps to remember the stressful event (Szapiro et al, 2003). This provides the functional basis of a phenomenon commonly referred to  as flashbulb memory.

Early research into functional properties of glutamate used a compound known as proline to study responses in the avian (bird) retina. Cherkin, Eckardt and Gerbrandt (1976), found the administration of proline would reduce learning and memory in birds, suggesting that because proline acts as a glutamate antagonist (reducing the release of glutamate in the synapse), glutamate must be involved in some process related to learning and memory. Further studies used other glutamate antagonists to demonstrate that overall, reducing the amount of glutamate in the synapse reduces the ability to learn and form memories. In response to this early research, further studies have summarized a critical process related to learning and memory known as long term potentiation. This process relies on the stimulation of glutamate pathways in the brain (Malenka and Nicoll, 1999). Additionally, human conditions related to major disruption of learning and memory have consistently tended to be related to significant absences of glutamate neurotransmitters and receptors. Squire (1986) found reduced numbers of glutamate receptors in the hippocampus of amnesic patients, and Hyman and colleagues (1987) documented that extreme reductions in glutaminergic neurons in the entorhinal cortex and hippocampus represent a distinct feature of Alzheimer’s disease.

GABA (γ-Aminobutyric Acid)

Until the discovery of benzodiazepines, GABA had been relatively ignored in terms of its affects on learning and memory processes. Benzodiazepines were eventually found to drive activity of GABA at one of its various types of receptors (GABA A ), as well as produce dramatic learning impairments (Lister, 1985). McGaugh (1989) used local administration of GABA producing compounds (agonists) or inhibiting compounds (antagonists) demonstrating they could selectively produce learning and memory impairments or enhancements depending on whether they used the GABA agonist (learning and memory impairments) or GABA antagonists (learning and memory enhancements). This body of research suggests GABA’s inhibitory nature. Specifically, a reduction of GABA in the synapse or great inhibition of the release of GABA can increase rates of firing between cells leading to greater long term potentiation and thus learning and memory consolidation.

Acetylcholine

Studies using pharmachological methods to reduce the amount of acetylcholine in the synapse (by way of compounds that inhibit acetylcholine, or compounds that completely block acetylcholine receptors) within human learning tasks and animal models have found cognitive impairment related to learning and memory (Deutsch, 1983, Coyle et al., 1983). Chapoutier (1989) additionally found that memory impairment in individuals with Parkinson’s disease is correlated with acetylcholine functioning in the frontal cortex. Winson (1990) has provided evidence that acetylcholine function can modulate rhythmic electrical brain activity (specifically in the theta and gamma frequencies) that are important for producing optimal firing rates leading to long term potentiation.

Catecholamines and Serotonin

Catecholamine systems such as epinephrine, norepinephrine and dopamine have been documented to be recruited during spatial learning and memory recall, and blockage of acetylcholine release has been demonstrated to reduce catecholamine system function (Brandeis, Brandys & Yehuda, 1989). Hatfield and McGaugh (1999) also demonstrated using a water maze task depletion of noradrenaline affected consolidation processes making the memory trace less stable (worse later recall) and more susceptible to interference. Other chemical compounds that act as neurotransmitters to bind with receptor sites have been demonstrated to play a role in memory consolidation and recall (D’Hooge & De Deyn, 2001) suggesting many different systems work together and in opposition to modulate our ability to encode and consolidate long term memories.

EMOTIONS AND FALSE MEMORIES

   A  flashbulb memory  is a highly detailed, exceptionally vivid episodic memory of the circumstances surrounding a piece of surprising, consequential, or emotionally arousing news was heard. However, even flashbulb memories can have decreased accuracy with the passage of time, even with very important events. For example, on at least three occasions, when asked how he heard about the terrorist attacks of 9/11, President George W. Bush responded inaccurately. In January 2002, less than 4 months after the attacks, the then sitting President Bush was asked how he heard about the attacks. He responded:

I was sitting there, and my Chief of Staff—well, first of all, when we walked into the classroom, I had seen this plane fly into the first building. There was a TV set on. And you know, I thought it was pilot error and I was amazed that anybody could make such a terrible mistake. (Greenberg, 2004, p. 2)

Contrary to what President Bush recalled, no one saw the first plane hit, except people on the ground near the twin towers. The first plane was not videotaped because it was a normal Tuesday morning in New York City, until the first plane hit.

Some people attributed Bush’s wrong recall of the event to conspiracy theories. However, there is a much more benign explanation: human memory, even flashbulb memories, can be frail. In fact, memory can be so frail that we can convince a person an event happened to them, even when it did not. In a study, participants were given a list of 15 sleep-related words, but the word “sleep” was not on the list. Participants recalled hearing the word “sleep” even though they did not actually hear it (Roediger & McDermott, 2000). The researchers who discovered this named the theory after themselves and a fellow researcher, calling it the Deese-Roediger-McDermott paradigm .

   Beginning with Karl Lashley, researchers and psychologists have been searching for the engram, which is the physical trace of memory. Lashley did not find the engram, but he did suggest that memories are distributed throughout the entire brain rather than stored in one specific area. Now we know that three brain areas do play significant roles in the processing and storage of different types of memories: cerebellum, hippocampus, and amygdala. The cerebellum’s job is to process procedural memories; the hippocampus is where new memories are encoded; the amygdala helps determine what memories to store, and it plays a part in determining where the memories are stored based on whether we have a strong or weak emotional response to the event. Strong emotional experiences can trigger the release of neurotransmitters, as well as hormones, which strengthen memory, so that memory for an emotional event is usually stronger than memory for a non-emotional event. This is shown by what is known as the flashbulb memory phenomenon: our ability to remember significant life events. However, our memory for life events (autobiographical memory) is not always accurate.

References:

Openstax Psychology text by Kathryn Dumper, William Jenkins, Arlene Lacombe, Marilyn Lovett and Marion Perlmutter licensed under CC BY v4.0. https://openstax.org/details/books/psychology

Review Questions:

1. ________ is another name for short-term memory.

a. sensory memory

b. episodic memory

c. working memory

d. implicit memory

2. The storage capacity of long-term memory is ________.

a. one or two bits of information

b. seven bits, plus or minus two

d. essentially limitless

3. The three functions of memory are ________.

a. automatic processing, effortful processing, and storage

b. encoding, processing, and storage

c. automatic processing, effortful processing, and retrieval

d. encoding, storage, and retrieval

4. This physical trace of memory is known as the ________.

b. Lashley effect

c. Deese-Roediger-McDermott Paradigm

d. flashbulb memory effect

5. An exceptionally clear recollection of an important event is a (an) ________.

b. arousal theory

c. flashbulb memory

d. equipotentiality hypothesis

Critical Thinking Questions:

1. What might happen to your memory system if you sustained damage to your hippocampus?

Personal Application Questions:

1. Describe a flashbulb memory of a significant event in your life.

arousal theory

equipotentiality hypothesis

flashbulb memory

Answers to Exercises

1. Because your hippocampus seems to be more of a processing area for your explicit memories, injury to this area could leave you unable to process new declarative (explicit) memories; however, even with this loss, you would be able to create implicit memories (procedural memory, motor learning and classical conditioning).

arousal theory:  strong emotions trigger the formation of strong memories and weaker emotional experiences form weaker memories

engram:  physical trace of memory

equipotentiality hypothesis:  some parts of the brain can take over for damaged parts in forming and storing memories

flashbulb memory:  exceptionally clear recollection of an important event

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8.2 Parts of the Brain Involved with Memory

Learning objectives.

By the end of this section, you will be able to:

• Explain the brain functions involved in memory
• Recognize the roles of the hippocampus, amygdala, and cerebellum

Are memories stored in just one part of the brain, or are they stored in many different parts of the brain? Karl Lashley began exploring this problem, about 100 years ago, by making lesions in the brains of animals such as rats and monkeys. He was searching for evidence of the engram : the group of neurons that serve as the “physical representation of memory” (Josselyn, 2010). First, Lashley (1950) trained rats to find their way through a maze. Then, he used the tools available at the time—in this case a soldering iron—to create lesions in the rats’ brains, specifically in the cerebral cortex. He did this because he was trying to erase the engram, or the original memory trace that the rats had of the maze.

Lashley did not find evidence of the engram, and the rats were still able to find their way through the maze, regardless of the size or location of the lesion. Based on his creation of lesions and the animals’ reaction, he formulated the equipotentiality hypothesis : if part of one area of the brain involved in memory is damaged, another part of the same area can take over that memory function (Lashley, 1950). Although Lashley’s early work did not confirm the existence of the engram, modern psychologists are making progress locating it. For example, Eric Kandel has spent decades studying the synapse and its role in controlling the flow of information through neural circuits needed to store memories (Mayford, Siegelbaum, & Kandel, 2012).

Many scientists believe that the entire brain is involved with memory. However, since Lashley’s research, other scientists have been able to look more closely at the brain and memory. They have argued that memory is located in specific parts of the brain, and specific neurons can be recognized for their involvement in forming memories. The main parts of the brain involved with memory are the amygdala, the hippocampus, the cerebellum, and the prefrontal cortex ( Figure 8.8 ).

The Amygdala

First, let’s look at the role of the amygdala in memory formation. The main job of the amygdala is to regulate emotions, such as fear and aggression ( Figure 8.8 ). The amygdala plays a part in how memories are stored because storage is influenced by stress hormones. For example, one researcher experimented with rats and the fear response (Josselyn, 2010). Using Pavlovian conditioning, a neutral tone was paired with a foot shock to the rats. This produced a fear memory in the rats. After being conditioned, each time they heard the tone, they would freeze (a defense response in rats), indicating a memory for the impending shock. Then the researchers induced cell death in neurons in the lateral amygdala, which is the specific area of the brain responsible for fear memories. They found the fear memory faded (became extinct). Because of its role in processing emotional information, the amygdala is also involved in memory consolidation: the process of transferring new learning into long-term memory. The amygdala seems to facilitate encoding memories at a deeper level when the event is emotionally arousing.

Link to Learning

In this TED Talk called “A Mouse. A Laser Beam. A Manipulated Memory,” Steve Ramirez and Xu Liu from MIT talk about using laser beams to manipulate fear memory in rats. Find out why their work caused a media frenzy once it was published in Science .

The Hippocampus

Another group of researchers also experimented with rats to learn how the hippocampus functions in memory processing ( Figure 8.8 ). They created lesions in the hippocampi of the rats, and found that the rats demonstrated memory impairment on various tasks, such as object recognition and maze running. They concluded that the hippocampus is involved in memory, specifically normal recognition memory as well as spatial memory (when the memory tasks are like recall tests) (Clark, Zola, & Squire, 2000). Another job of the hippocampus is to project information to cortical regions that give memories meaning and connect them with other memories. It also plays a part in memory consolidation: the process of transferring new learning into long-term memory.

Injury to this area leaves us unable to process new declarative memories. One famous patient, known for years only as H. M., had both his left and right temporal lobes (hippocampi) removed in an attempt to help control the seizures he had been suffering from for years (Corkin, Amaral, González, Johnson, & Hyman, 1997). As a result, his declarative memory was significantly affected, and he could not form new semantic knowledge. He lost the ability to form new memories, yet he could still remember information and events that had occurred prior to the surgery.

The Cerebellum and Prefrontal Cortex

Although the hippocampus seems to be more of a processing area for explicit memories, you could still lose it and be able to create implicit memories (procedural memory, motor learning, and classical conditioning), thanks to your cerebellum ( Figure 8.8 ). For example, one classical conditioning experiment is to accustom subjects to blink when they are given a puff of air to the eyes. When researchers damaged the cerebellums of rabbits, they discovered that the rabbits were not able to learn the conditioned eye-blink response (Steinmetz, 1999; Green & Woodruff-Pak, 2000).

Other researchers have used brain scans, including positron emission tomography (PET) scans, to learn how people process and retain information. From these studies, it seems the prefrontal cortex is involved. In one study, participants had to complete two different tasks: either looking for the letter a in words (considered a perceptual task) or categorizing a noun as either living or non-living (considered a semantic task) (Kapur et al., 1994). Participants were then asked which words they had previously seen. Recall was much better for the semantic task than for the perceptual task. According to PET scans, there was much more activation in the left inferior prefrontal cortex in the semantic task. In another study, encoding was associated with left frontal activity, while retrieval of information was associated with the right frontal region (Craik et al., 1999).

Neurotransmitters

There also appear to be specific neurotransmitters involved with the process of memory, such as epinephrine, dopamine, serotonin, glutamate, and acetylcholine (Myhrer, 2003). There continues to be discussion and debate among researchers as to which neurotransmitter plays which specific role (Blockland, 1996). Although we don’t yet know which role each neurotransmitter plays in memory, we do know that communication among neurons via neurotransmitters is critical for developing new memories. Repeated activity by neurons leads to increased neurotransmitters in the synapses and more efficient and more synaptic connections. This is how memory consolidation occurs.

It is also believed that strong emotions trigger the formation of strong memories, and weaker emotional experiences form weaker memories; this is called arousal theory (Christianson, 1992). For example, strong emotional experiences can trigger the release of neurotransmitters, as well as hormones, which strengthen memory; therefore, our memory for an emotional event is usually better than our memory for a non-emotional event. When humans and animals are stressed, the brain secretes more of the neurotransmitter glutamate, which helps them remember the stressful event (McGaugh, 2003). This is clearly evidenced by what is known as the flashbulb memory phenomenon.

A flashbulb memory is an exceptionally clear recollection of an important event ( Figure 8.9 ). Many people who have lived through historic and momentous events can recall exactly where they were and how they heard about them. For example, a Pew Research Center (2011) survey found that for those Americans who were age 8 or older at the time of 9/11 terrorist attacks, 97% can recall the moment they learned of this event, even a decade after it happened. Many widely discussed examples of flashbulb memories pertain to national or global events, but according to their initial definition by researchers Brown and Kulik (1977) as well as additional work by more recent researchers, such a widely shared event is not required (Hirst & Phelps, 2016). Family members might always remember how they heard about an important event in their lives, or people in a school may recall nearly everything about the way they experienced a major event in that setting. And although most studies (and many conversations) involve negative memories, positive events can also elicit flashbulb memories.

Inaccurate and False Memories

Even flashbulb memories for important events can have decreased accuracy with the passage of time. For example, on at least three occasions, when asked how he heard about the terrorist attacks of 9/11, President George W. Bush responded inaccurately. In January 2002, less than 4 months after the attacks, the then sitting President Bush was asked how he heard about the attacks. He responded:

I was sitting there, and my Chief of Staff—well, first of all, when we walked into the classroom, I had seen this plane fly into the first building. There was a TV set on. And you know, I thought it was pilot error and I was amazed that anybody could make such a terrible mistake. (Greenberg, 2004, p. 2)

Contrary to what President Bush stated, no one saw the first plane hit, except people on the ground near the twin towers. No one watching live TV would have watched the first plane hit the twin towers. Until the first plane hit, it was a normal Tuesday morning.

Memory is not like a video recording. Human memory, even flashbulb memories, can be frail. Different parts of them, such as the time, visual elements, and smells, are stored in different places. When something is remembered, these components have to be put back together for the complete memory, which is known as memory reconstruction. Each component creates a chance for an error to occur. False memory is remembering something that did not happen. Research participants have recalled hearing a word, even though they never heard the word (Roediger & McDermott, 2000).

Do you remember where you were when you heard about a historic or perhaps a tragic event? Who were you with and what were you doing? What did you talk about? Can you contact those people you were with? Do they have the same memories as you or do they have different memories?

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Access for free at https://openstax.org/books/psychology-2e/pages/1-introduction

• Authors: Rose M. Spielman, William J. Jenkins, Marilyn D. Lovett
• Publisher/website: OpenStax
• Book title: Psychology 2e
• Publication date: Apr 22, 2020
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September 29, 2015

Morals, Not Memories, Define Who We Are

A new study has implications for patients with Alzheimer’s and other disorders

By Bobby Azarian

Although Alzheimer’s and other neurodegenerative diseases may powerfully impact the mental functioning of individuals, sufferers can find some solace in the fact that substantial memory deficits—when unaccompanied by changes in moral characteristics—seem to have no effect on how others perceive “who you are.”

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Have you ever wondered just what it is that makes you, you? If all your memories were to fade away, would your identity dissolve along with them? Would friends and family no longer perceive you to be the same person as before? For the 5.3 million Americans experiencing memory loss due to Alzheimer’s disease, these frightening questions are more than just theoretical.

Fortunately, science appears to suggest that being robbed of one’s memory does not equate with being robbed of one’s identity. A new study has found that “who one is” is largely defined by one’s moral behavior, and not by one’s memory capacity or other cognitive abilities. Thus, although Alzheimer’s and other neurodegenerative diseases may powerfully impact the mental functioning of individuals, sufferers can find some solace in the fact that substantial memory deficits—when unaccompanied by changes in moral characteristics—seem to have no effect on how others perceive “who you are.”

Determining the factors that define one’s identity is an old philosophical problem that first received serious consideration in the 17th century by the early British empiricist, John Locke. According to Locke’s “ memory theory ”, a person’s identity only reaches as far as their memory extends into the past. In other words, who one  is  critically depends upon what one remembers. Thus, as a person’s memory begins to disappear, so does his identity.

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This notion of identity as memory has received experimental support from psychology research. A 2004 study  followed Alzheimer’s patients and found that those exhibiting impairments in autobiographical memory—one’s knowledge of their own past experiences and events—on standard psychological tests showed changes in the strength and quality of identity. The strength of identity was measured by the number of unique statements given by the patient in response to the question, “Who am I?” while the quality of identity was measured by the abstractness of their answers, i.e., their lack of specific details. These findings seem to imply that autobiographical memories create a continuous first-person narrative that helps form a sense of self.

However, other scientists remain unconvinced of Locke’s premise, as some theorize that more central to identity is moral capacity—a variable that these previous studies did not adequately control for. Evidence for this idea comes from social cognition research that has found that impression formation is largely dependent on the moral dimension . In other words, how we see people—whether they are positive or negative, to be approached or avoided—is mostly determined by our assessment of their moral character, and not their intellect, knowledge, or other personality traits. The concept that morals are essential to identity is aptly known as the essential-moral-self hypothesis.

Researchers from the University of Arizona and Yale decided to investigate this hypothesis directly in a real-world clinical population. Their study was designed to test what types of cognitive damage cause people to no longer appear to be themselves to others. A crucial element of the design was testing for changes in identity from the perspective of a third person observer, rather than the individual himself. In addition to sidestepping many of the reliability problems intrinsic to first-person accounts, focusing on perceived identity allowed the investigators to assess the effects of memory and moral changes on the patient’s relationship with others. This is an extremely important facet because when someone appears to be “not the same person,” the social bonds between patients and loved ones or caregivers quickly deteriorate. These bonds are critical to one’s well-being and health, as they are the source of the connectedness one feels to the people in their lives and the outside world.

The investigators recruited 248 volunteers with family members who suffered from one of three types of neurodegenerative diseases. Patients had either Alzheimer’s disease, frontotemporal dementia, or amyotrophic lateral sclerosis (ALS), each of which are characterized by relatively distinct cognitive and behavioral changes. While ALS primarily affects motor but not mental function, both Alzheimer’s and frontotemporal dementia affect cognition. However, where Alzheimer’s strongly affects things like memory and IQ, those with frontotemporal dementia tend to undergo changes in moral traits—i.e., things like honesty, compassion, decency, and integrity.

The participants, most of who were married to or romantically involved with the patients, were instructed to indicate how much the patient had changed in 30 trait categories since the disease began; 15 were related to morality and the other 15 to personality. To evaluate the degree of change in the perceived identity, participants were asked to give information regarding any differences in their relationship with the patient that had occurred over the course of the disease’s progression. For example, they were asked questions like, “Does the patient ever seem like a stranger to you?” and “Do you feel like you still know who the patient is?”

Analysis of the data revealed that participants perceived the greatest disruptions in patients’ identity when they observed changes in moral traits. Other cognitive deficits—like those seen with amnesia—had no measurable effect on the perception of identity. Consequently, those with frontotemporal dementia showed the greatest changes in perceived identity, since it specifically affects the frontal lobe functions underlying moral reasoning and behavior. 

Interestingly, those with ALS showed no significant change in perceived identity despite the greatly distorted physical appearance that results from the widespread deterioration of motor function. Although there was minor change in identity perception in those with Alzheimer’s, this was associated with changes in moral traits and not memory loss.

These findings have important implications for patients with neurodegenerative diseases. Efforts aimed at helping sufferers to understand themselves in terms of their moral traits—characteristics like altruism, mercy, and generosity—can restore their sense of identity and control as memory fades or cognition declines. Simply knowing that others continue to perceive them as the same person, even when they feel that their own identity is changing, can allow them to securely protect their sense of self. Additionally, the results highlight the need for future neurological interventions and clinical therapies that specifically focus on maintaining those cognitive faculties involved in moral function in the face of disease.

This new research is also an important intellectual contribution to the discussion surrounding the ancient question of what makes someone who they are.  It appears that it is not our intelligence or our knowledge of the past that defines us, but instead our moral behavior. Essentially, identity is not what we know, but what we stand for.

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To understand cognition — and its dysfunction — neuroscientists must learn its rhythms

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It could be very informative to observe the pixels on your phone under a microscope, but not if your goal is to understand what a whole video on the screen shows. Cognition is much the same kind of emergent property in the brain .  It can only be understood by observing how millions of cells act in coordination, argues a trio of MIT neuroscientists. In a new article ,  they lay out a framework for understanding how thought arises from the coordination of neural activity driven by oscillating electric fields — also known as brain “waves” or “rhythms.”

Historically dismissed solely as byproducts of neural activity, brain rhythms are actually critical for organizing it, write Picower Professor Earl Miller and research scientists Scott Brincat and Jefferson Roy in  Current Opinion in Behavioral Science . And while neuroscientists have gained tremendous knowledge from studying how individual brain cells connect and how and when they emit “spikes” to send impulses through specific circuits, there is also a need to appreciate and apply new concepts at the brain rhythm scale, which can span individual, or even multiple, brain regions.

“Spiking and anatomy are important, but there is more going on in the brain above and beyond that,” says senior author Miller, a faculty member in The Picower Institute for Learning and Memory and the Department of Brain and Cognitive Sciences at MIT. “There’s a whole lot of functionality taking place at a higher level, especially cognition.”

The stakes of studying the brain at that scale, the authors write, might not only include understanding healthy higher-level function but also how those functions become disrupted in disease.

“Many neurological and psychiatric disorders, such as schizophrenia, epilepsy, and Parkinson’s, involve disruption of emergent properties like neural synchrony,” they write. “We anticipate that understanding how to interpret and interface with these emergent properties will be critical for developing effective treatments as well as understanding cognition.”

The emergence of thoughts

The bridge between the scale of individual neurons and the broader-scale coordination of many cells is founded on electric fields, the researchers write. Via a phenomenon called “ephaptic coupling,” the electrical field generated by the activity of a neuron can influence the voltage of neighboring neurons, creating an alignment among them. In this way, electric fields both reflect neural activity and also influence it. In a  paper in 2022 , Miller and colleagues showed via experiments and computational modeling that the information encoded in the electric fields generated by ensembles of neurons can be read out more reliably than the information encoded by the spikes of individual cells. In 2023 Miller’s lab provided evidence that rhythmic electrical fields may  coordinate memories  between regions.

At this larger scale, in which rhythmic electric fields carry information between brain regions, Miller’s lab has published numerous studies showing that lower-frequency rhythms in the so-called “beta” band originate in deeper layers of the brain’s cortex and  appear to regulate  the power of faster-frequency “gamma” rhythms in more superficial layers. By recording neural activity in the brains of animals engaged in working memory games, the lab has shown that beta rhythms carry “top-down” signals to control when and where gamma rhythms can encode sensory information, such as the images that the animals need to remember in the game.

Some of the lab’s latest evidence suggests that beta rhythms apply this control of cognitive processes to physical patches of the cortex, essentially acting like stencils that pattern where and when gamma can encode sensory information into memory, or retrieve it. According to this theory, which Miller calls “ Spatial Computing ,” beta can thereby establish the general rules of a task (for instance, the back-and-forth turns required to open a combination lock), even as the specific information content may change (for instance, new numbers when the combination changes). More generally, this structure also enables neurons to flexibly encode more than one kind of information at a time, the authors write, a widely observed neural property called “mixed selectivity.” For instance, a neuron encoding a number of the lock combination can also be assigned, based on which beta-stenciled patch it is in, the particular step of the unlocking process that the number matters for.

In the new study, Miller, Brincat, and Roy suggest another advantage consistent with cognitive control being based on an interplay of large-scale coordinated rhythmic activity: “subspace coding.” This idea postulates that brain rhythms organize the otherwise massive number of possible outcomes that could result from, say, 1,000 neurons engaging in independent spiking activity. Instead of all the many combinatorial possibilities, many fewer “subspaces” of activity actually arise, because neurons are coordinated, rather than independent. It is as if the spiking of neurons is like a flock of birds coordinating their movements. Different phases and frequencies of brain rhythms provide this coordination, aligned to amplify each other, or offset to prevent interference. For instance, if a piece of sensory information needs to be remembered, neural activity representing it can be protected from interference when new sensory information is perceived.

“Thus the organization of neural responses into subspaces can both segregate and integrate information,” the authors write.

The power of brain rhythms to coordinate and organize information processing in the brain is what enables functional cognition to emerge at that scale, the authors write. Understanding cognition in the brain, therefore, requires studying rhythms.

“Studying individual neural components in isolation — individual neurons and synapses — has made enormous contributions to our understanding of the brain and remains important,” the authors conclude. “However, it’s becoming increasingly clear that, to fully capture the brain’s complexity, those components must be analyzed in concert to identify, study, and relate their emergent properties.”

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Unlocking consciousness: A new frontier in neuroscientific fusion

I n a recent paper published in the International Journal of Psychiatry Research , Dr. Gerard Marx from MX Biotech and Prof. Chaim Gilon from the Hebrew University of Jerusalem present an innovative integration of two notable neuroscience theories—the Global Neuronal Network (GNW) hypothesis and the Tripartite Mechanism of Memory.

Titled "'Consciousness' as a Fusion of the Global Neuronal Network (GNW) Hypothesis and the Tripartite Mechanism of Memory," the study provides fresh perspectives on the complex phenomena of consciousness and memory.

The research tackles a significant challenge in the study of consciousness that has long been considered insurmountable. Dr. Marx and Prof. Gilon propose that memory plays a pivotal role in shaping consciousness, contrasting the idea that computer-based Information Theory provides a sufficient framework for understanding neural memory.

They contend that the emotional content stored within the neural network diverges from standard computer data, laying the foundation for neural memory and adding depth and significance to conscious experience.

The researchers suggest integrating the Global Neuronal Workspace (GNW) theory with the Tripartite Mechanism of Memory to better understand how the brain creates experiential memories. In their model, they posit that the complex electro-chemical activities of individual neurons are unified by the structural units of the brain, creating a unified network that facilitates consciousness through emotional memory.

Key findings of the study include the proposed concept of a "brain cloud" that highlights the interconnected flow of information throughout the brain's anatomical regions, facilitated by the Global Neuronal Workspace (GNW).

A tripartite mechanism for neural memory has also been identified, wherein neurons utilize trace metal cations and neurotransmitters to encode emotive states within the extracellular matrix.

The study also underscores the evolutionary importance of bacterial chemical signaling processes in the development of neural memory and consciousness in complex organisms.

Through a biochemical lens, the research elucidates how life transitions to consciousness via memory evolution. By mapping the progress of neural-net signaling from bacterial chemical communication to primate consciousness, the study provides a comprehensive framework for exploring the intricate interplay among memory, consciousness, and evolution.

"Our research on the tripartite mechanism of memory delves into the collaborative roles of neurons, the neural extracellular matrix, trace metals, and neurotransmitters in memory formation, storage, and retrieval.

"We discovered that certain metals binding within the matrix can alter its structure, forming complexes that serve as the fundamental units of memory. These metal complexes have the ability to interact with neurotransmitters, resulting in the formation of emotional memory units. These memory units collectively create a framework for storing information in the brain.

"This proposed mechanism sheds light on how disturbances in metal levels could potentially impact memory functions. Furthermore, we speculate that disorders such as Alzheimer's and autism may be linked to dysregulation of metal handling by the body.

"Understanding these intricate relationships provides insight into the processes of memory formation and retrieval, aiding in comprehension of conditions ranging from short-term memory loss to more severe memory impairments," state the researchers.

Gerard Marx comes from a background of blood coagulation and biotechnology. Chaim Gilon is a Emeritus Professor Active specializing in the development and synthesis of peptide based drugs.

More information: "Consciousness" as a Fusion of the Global Neuronal Network (GNW) Hypothesis and the Tripartite Mechanism of Memory. www.scivisionpub.com/abstract-display.php?id=3266

Provided by Hebrew University of Jerusalem