memory essay psychology

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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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Psychology Discussion

Essay on memory: (meaning and types).

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Read this Comprehensive Essay on Memory: Meaning, Nature and Types of Memory !

Meaning and Nature :

Memory is one of the important cognitive processes. Memory involves remembering and forgetting.

These are like two faces of a coin. Though these two are opposed to each other by nature, they play an important role in the life of an individual.

Remembering the pleasant experiences makes living happy, and on the other hand remembering unpleasant experiences makes living unhappy and miserable. So here forgetting helps individual to forget unwanted and unpleasant experiences and memories and keeps him happy.

In this way, remembering the pleasant and forgetting the- unpleasant both are essential for normal living. In the case of learners, remembering is very important, because without memory there would be no learning.

If learning has to progress, remembering of what is already learnt is indispensable, otherwise every time the learner has to start from the beginning.

The memory is defined as ‘the power to store experiences and to bring them into the field of consciousness sometime after the experience has occurred’. Our mind has the power of conserving experiences and mentally receiving them whenever such an activity helps the onward progress of the life cycle.

The conserved experience has a unity, an organisation of its own and it colours our present experience.

However, as stated above we have a notion that memory is a single process, but an analysis of it reveals involvement of three different activities- learning, retention and remembering.

This is the first stage of memory. Learning may be by any of the methods like imitation, verbal, motor, conceptual, trial and error, insight, etc. Hence, whatever may be the type of learning; we must pay our attention to retain what is learnt. A good learning is necessary for better retention.

Retention is the process of retaining in mind what is learnt or experienced in the past. The learnt material must be retained in order to make progress in our learning. Psychologists are of the opinion that the learnt material will be retained in the brain in the form of neural traces called ‘memory traces’, or ‘engrams’, or ‘neurograms’.

When good learning takes place –clear engrams are formed, so that they remain for long time and can be remembered by activation of these traces whenever necessary.

Remembering:

It is the process of bringing back the stored or retained information to the conscious level. This may be understood by activities such as recalling, recognising, relearning and reconstruction.

Recalling is the process of reproducing the past experiences that are not present. For example, recalling answers in the examination hall.

Recognising:

It is to recognise a person seen earlier, or the original items seen earlier, from among the items of the same class or category which they are mixed-up.

Relearning:

Relearning is also known as saving method. Because we measure retention in terms of saving in the number of repetition or the time required to relearn the assignment. The difference between the amount of time or trials required for original learning and the one required for relearning indicates the amount of retention.

Reconstruction:

Reconstruction is otherwise called rearrangement. Here the material to learn will be presented in a particular order and then the items will be jumbled up or shuffled thoroughly and presented to the individual to rearrange them in the original order in which it was presented.

Types of Memory :

There are five kinds of memory. These are classified on the basis of rates of decay of the information.

a. Sensory memory:

In this kind of memory, the information received by the sense organs will remain there for a very short period like few seconds. For example, the image on the screen of a TV may appear to be in our eyes for a fraction of time even when it is switched off, or the voice of a person will be tingling in our ears even after the voice is ceased.

b. Short-term memory (STM):

According to many studies, in STM the memory remains in our conscious and pre-conscious level for less than 30 seconds. Later on this will be transferred to long-term memory.

c. Long-term memory (LTM):

LTM has the unlimited capacity to store information which may remain for days, months, years or lifetime.

d. Eidetic memory:

It is otherwise called photographic memory in which the individual can remember a scene or an event in a photographic detail.

e. Episodic memory:

This is otherwise called semantic memory which is connected with episodes of events. The events are stored in the form of episodes and recalled fully in the manner of a sequence.

Related Articles:

• 11 Factors that Influence Memory Process in Humans
• 7 Main Factors that Influence Retention Power | Memory | Psychology
• Essay on Forgetting: Causes and Theories
• Memory Types: 3 Main Types of Memory | Remembering | Psychology

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8.1 Memories as Types and Stages

Learning objectives.

• Compare and contrast explicit and implicit memory, identifying the features that define each.
• Explain the function and duration of eidetic and echoic memories.
• Summarize the capacities of short-term memory and explain how working memory is used to process information in it.

As you can see in Table 8.1 “Memory Conceptualized in Terms of Types, Stages, and Processes” , psychologists conceptualize memory in terms of types , in terms of stages , and in terms of processes . In this section we will consider the two types of memory, explicit memory and implicit memory , and then the three major memory stages: sensory , short-term , and long-term (Atkinson & Shiffrin, 1968). Then, in the next section, we will consider the nature of long-term memory, with a particular emphasis on the cognitive techniques we can use to improve our memories. Our discussion will focus on the three processes that are central to long-term memory: encoding , storage , and retrieval .

Table 8.1 Memory Conceptualized in Terms of Types, Stages, and Processes

Explicit Memory

When we assess memory by asking a person to consciously remember things, we are measuring explicit memory . Explicit memory refers to knowledge or experiences that can be consciously remembered . As you can see in Figure 8.2 “Types of Memory” , there are two types of explicit memory: episodic and semantic . Episodic memory refers to the firsthand experiences that we have had (e.g., recollections of our high school graduation day or of the fantastic dinner we had in New York last year). Semantic memory refers to our knowledge of facts and concepts about the world (e.g., that the absolute value of −90 is greater than the absolute value of 9 and that one definition of the word “affect” is “the experience of feeling or emotion”).

Figure 8.2 Types of Memory

Explicit memory is assessed using measures in which the individual being tested must consciously attempt to remember the information. A recall memory test is a measure of explicit memory that involves bringing from memory information that has previously been remembered . We rely on our recall memory when we take an essay test, because the test requires us to generate previously remembered information. A multiple-choice test is an example of a recognition memory test , a measure of explicit memory that involves determining whether information has been seen or learned before .

Your own experiences taking tests will probably lead you to agree with the scientific research finding that recall is more difficult than recognition. Recall, such as required on essay tests, involves two steps: first generating an answer and then determining whether it seems to be the correct one. Recognition, as on multiple-choice test, only involves determining which item from a list seems most correct (Haist, Shimamura, & Squire, 1992). Although they involve different processes, recall and recognition memory measures tend to be correlated. Students who do better on a multiple-choice exam will also, by and large, do better on an essay exam (Bridgeman & Morgan, 1996).

A third way of measuring memory is known as relearning (Nelson, 1985). Measures of relearning (or savings) assess how much more quickly information is processed or learned when it is studied again after it has already been learned but then forgotten . If you have taken some French courses in the past, for instance, you might have forgotten most of the vocabulary you learned. But if you were to work on your French again, you’d learn the vocabulary much faster the second time around. Relearning can be a more sensitive measure of memory than either recall or recognition because it allows assessing memory in terms of “how much” or “how fast” rather than simply “correct” versus “incorrect” responses. Relearning also allows us to measure memory for procedures like driving a car or playing a piano piece, as well as memory for facts and figures.

Implicit Memory

While explicit memory consists of the things that we can consciously report that we know, implicit memory refers to knowledge that we cannot consciously access. However, implicit memory is nevertheless exceedingly important to us because it has a direct effect on our behavior. Implicit memory refers to the influence of experience on behavior, even if the individual is not aware of those influences . As you can see in Figure 8.2 “Types of Memory” , there are three general types of implicit memory: procedural memory, classical conditioning effects, and priming.

Procedural memory refers to our often unexplainable knowledge of how to do things . When we walk from one place to another, speak to another person in English, dial a cell phone, or play a video game, we are using procedural memory. Procedural memory allows us to perform complex tasks, even though we may not be able to explain to others how we do them. There is no way to tell someone how to ride a bicycle; a person has to learn by doing it. The idea of implicit memory helps explain how infants are able to learn. The ability to crawl, walk, and talk are procedures, and these skills are easily and efficiently developed while we are children despite the fact that as adults we have no conscious memory of having learned them.

A second type of implicit memory is classical conditioning effects, in which we learn, often without effort or awareness, to associate neutral stimuli (such as a sound or a light) with another stimulus (such as food), which creates a naturally occurring response, such as enjoyment or salivation. The memory for the association is demonstrated when the conditioned stimulus (the sound) begins to create the same response as the unconditioned stimulus (the food) did before the learning.

The final type of implicit memory is known as priming , or changes in behavior as a result of experiences that have happened frequently or recently . Priming refers both to the activation of knowledge (e.g., we can prime the concept of “kindness” by presenting people with words related to kindness) and to the influence of that activation on behavior (people who are primed with the concept of kindness may act more kindly).

One measure of the influence of priming on implicit memory is the word fragment test , in which a person is asked to fill in missing letters to make words. You can try this yourself: First, try to complete the following word fragments, but work on each one for only three or four seconds. Do any words pop into mind quickly?

_ i b _ a _ y

_ h _ s _ _ i _ n

_ h _ i s _

Now read the following sentence carefully:

Then try again to make words out of the word fragments.

I think you might find that it is easier to complete fragments 1 and 3 as “library” and “book,” respectively, after you read the sentence than it was before you read it. However, reading the sentence didn’t really help you to complete fragments 2 and 4 as “physician” and “chaise.” This difference in implicit memory probably occurred because as you read the sentence, the concept of “library” (and perhaps “book”) was primed, even though they were never mentioned explicitly. Once a concept is primed it influences our behaviors, for instance, on word fragment tests.

Our everyday behaviors are influenced by priming in a wide variety of situations. Seeing an advertisement for cigarettes may make us start smoking, seeing the flag of our home country may arouse our patriotism, and seeing a student from a rival school may arouse our competitive spirit. And these influences on our behaviors may occur without our being aware of them.

Research Focus: Priming Outside Awareness Influences Behavior

One of the most important characteristics of implicit memories is that they are frequently formed and used automatically , without much effort or awareness on our part. In one demonstration of the automaticity and influence of priming effects, John Bargh and his colleagues (Bargh, Chen, & Burrows, 1996) conducted a study in which they showed college students lists of five scrambled words, each of which they were to make into a sentence. Furthermore, for half of the research participants, the words were related to stereotypes of the elderly. These participants saw words such as the following:

The other half of the research participants also made sentences, but from words that had nothing to do with elderly stereotypes. The purpose of this task was to prime stereotypes of elderly people in memory for some of the participants but not for others.

The experimenters then assessed whether the priming of elderly stereotypes would have any effect on the students’ behavior—and indeed it did. When the research participant had gathered all of his or her belongings, thinking that the experiment was over, the experimenter thanked him or her for participating and gave directions to the closest elevator. Then, without the participants knowing it, the experimenters recorded the amount of time that the participant spent walking from the doorway of the experimental room toward the elevator. As you can see in Figure 8.3 “Results From Bargh, Chen, and Burrows, 1996” , participants who had made sentences using words related to elderly stereotypes took on the behaviors of the elderly—they walked significantly more slowly as they left the experimental room.

Figure 8.3 Results From Bargh, Chen, and Burrows, 1996

Bargh, Chen, and Burrows (1996) found that priming words associated with the elderly made people walk more slowly.

Adapted from Bargh, J. A., Chen, M., & Burrows, L. (1996). Automaticity of social behavior: Direct effects of trait construct and stereotype activation on action. Journal of Personality & Social Psychology, 71 , 230–244.

To determine if these priming effects occurred out of the awareness of the participants, Bargh and his colleagues asked still another group of students to complete the priming task and then to indicate whether they thought the words they had used to make the sentences had any relationship to each other, or could possibly have influenced their behavior in any way. These students had no awareness of the possibility that the words might have been related to the elderly or could have influenced their behavior.

Stages of Memory: Sensory, Short-Term, and Long-Term Memory

Another way of understanding memory is to think about it in terms of stages that describe the length of time that information remains available to us. According to this approach (see Figure 8.4 “Memory Duration” ), information begins in sensory memory , moves to short-term memory , and eventually moves to long-term memory . But not all information makes it through all three stages; most of it is forgotten. Whether the information moves from shorter-duration memory into longer-duration memory or whether it is lost from memory entirely depends on how the information is attended to and processed.

Figure 8.4 Memory Duration

Memory can characterized in terms of stages—the length of time that information remains available to us.

Adapted from Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. In K. Spence (Ed.), The psychology of learning and motivation (Vol. 2). Oxford, England: Academic Press.

Sensory Memory

Sensory memory refers to the brief storage of sensory information . Sensory memory is a memory buffer that lasts only very briefly and then, unless it is attended to and passed on for more processing, is forgotten. The purpose of sensory memory is to give the brain some time to process the incoming sensations, and to allow us to see the world as an unbroken stream of events rather than as individual pieces.

Visual sensory memory is known as iconic memory . Iconic memory was first studied by the psychologist George Sperling (1960). In his research, Sperling showed participants a display of letters in rows, similar to that shown in Figure 8.5 “Measuring Iconic Memory” . However, the display lasted only about 50 milliseconds (1/20 of a second). Then, Sperling gave his participants a recall test in which they were asked to name all the letters that they could remember. On average, the participants could remember only about one-quarter of the letters that they had seen.

Figure 8.5 Measuring Iconic Memory

Sperling (1960) showed his participants displays such as this one for only 1/20th of a second. He found that when he cued the participants to report one of the three rows of letters, they could do it, even if the cue was given shortly after the display had been removed. The research demonstrated the existence of iconic memory.

Adapted from Sperling, G. (1960). The information available in brief visual presentation. Psychological Monographs, 74 (11), 1–29.

Sperling reasoned that the participants had seen all the letters but could remember them only very briefly, making it impossible for them to report them all. To test this idea, in his next experiment he first showed the same letters, but then after the display had been removed , he signaled to the participants to report the letters from either the first, second, or third row. In this condition, the participants now reported almost all the letters in that row. This finding confirmed Sperling’s hunch: Participants had access to all of the letters in their iconic memories, and if the task was short enough, they were able to report on the part of the display he asked them to. The “short enough” is the length of iconic memory, which turns out to be about 250 milliseconds (¼ of a second).

Auditory sensory memory is known as echoic memory . In contrast to iconic memories, which decay very rapidly, echoic memories can last as long as 4 seconds (Cowan, Lichty, & Grove, 1990). This is convenient as it allows you—among other things—to remember the words that you said at the beginning of a long sentence when you get to the end of it, and to take notes on your psychology professor’s most recent statement even after he or she has finished saying it.

In some people iconic memory seems to last longer, a phenomenon known as eidetic imagery (or “photographic memory”) in which people can report details of an image over long periods of time. These people, who often suffer from psychological disorders such as autism, claim that they can “see” an image long after it has been presented, and can often report accurately on that image. There is also some evidence for eidetic memories in hearing; some people report that their echoic memories persist for unusually long periods of time. The composer Wolfgang Amadeus Mozart may have possessed eidetic memory for music, because even when he was very young and had not yet had a great deal of musical training, he could listen to long compositions and then play them back almost perfectly (Solomon, 1995).

Short-Term Memory

Most of the information that gets into sensory memory is forgotten, but information that we turn our attention to, with the goal of remembering it, may pass into short-term memory . Short-term memory (STM) is the place where small amounts of information can be temporarily kept for more than a few seconds but usually for less than one minute (Baddeley, Vallar, & Shallice, 1990). Information in short-term memory is not stored permanently but rather becomes available for us to process, and the processes that we use to make sense of, modify, interpret, and store information in STM are known as working memory .

Although it is called “memory,” working memory is not a store of memory like STM but rather a set of memory procedures or operations. Imagine, for instance, that you are asked to participate in a task such as this one, which is a measure of working memory (Unsworth & Engle, 2007). Each of the following questions appears individually on a computer screen and then disappears after you answer the question:

Is 10 × 2 − 5 = 15? (Answer YES OR NO) Then remember “S”

Is 12 ÷ 6 − 2 = 1? (Answer YES OR NO) Then remember “R”

Is 10 × 2 = 5? (Answer YES OR NO) Then remember “P”

Is 8 ÷ 2 − 1 = 1? (Answer YES OR NO) Then remember “T”

Is 6 × 2 − 1 = 8? (Answer YES OR NO) Then remember “U”

Is 2 × 3 − 3 = 0? (Answer YES OR NO) Then remember “Q”

To successfully accomplish the task, you have to answer each of the math problems correctly and at the same time remember the letter that follows the task. Then, after the six questions, you must list the letters that appeared in each of the trials in the correct order (in this case S, R, P, T, U, Q).

To accomplish this difficult task you need to use a variety of skills. You clearly need to use STM, as you must keep the letters in storage until you are asked to list them. But you also need a way to make the best use of your available attention and processing. For instance, you might decide to use a strategy of “repeat the letters twice, then quickly solve the next problem, and then repeat the letters twice again including the new one.” Keeping this strategy (or others like it) going is the role of working memory’s central executive —the part of working memory that directs attention and processing. The central executive will make use of whatever strategies seem to be best for the given task. For instance, the central executive will direct the rehearsal process, and at the same time direct the visual cortex to form an image of the list of letters in memory. You can see that although STM is involved, the processes that we use to operate on the material in memory are also critical.

Short-term memory is limited in both the length and the amount of information it can hold. Peterson and Peterson (1959) found that when people were asked to remember a list of three-letter strings and then were immediately asked to perform a distracting task (counting backward by threes), the material was quickly forgotten (see Figure 8.6 “STM Decay” ), such that by 18 seconds it was virtually gone.

Figure 8.6 STM Decay

Peterson and Peterson (1959) found that information that was not rehearsed decayed quickly from memory.

Adapted from Peterson, L., & Peterson, M. J. (1959). Short-term retention of individual verbal items. Journal of Experimental Psychology, 58 (3), 193–198.

One way to prevent the decay of information from short-term memory is to use working memory to rehearse it. Maintenance rehearsal is the process of repeating information mentally or out loud with the goal of keeping it in memory . We engage in maintenance rehearsal to keep a something that we want to remember (e.g., a person’s name, e-mail address, or phone number) in mind long enough to write it down, use it, or potentially transfer it to long-term memory.

If we continue to rehearse information it will stay in STM until we stop rehearsing it, but there is also a capacity limit to STM. Try reading each of the following rows of numbers, one row at a time, at a rate of about one number each second. Then when you have finished each row, close your eyes and write down as many of the numbers as you can remember.

If you are like the average person, you will have found that on this test of working memory, known as a digit span test , you did pretty well up to about the fourth line, and then you started having trouble. I bet you missed some of the numbers in the last three rows, and did pretty poorly on the last one.

The digit span of most adults is between five and nine digits, with an average of about seven. The cognitive psychologist George Miller (1956) referred to “seven plus or minus two” pieces of information as the “magic number” in short-term memory. But if we can only hold a maximum of about nine digits in short-term memory, then how can we remember larger amounts of information than this? For instance, how can we ever remember a 10-digit phone number long enough to dial it?

One way we are able to expand our ability to remember things in STM is by using a memory technique called chunking . Chunking is the process of organizing information into smaller groupings (chunks), thereby increasing the number of items that can be held in STM . For instance, try to remember this string of 12 letters:

You probably won’t do that well because the number of letters is more than the magic number of seven.

Now try again with this one:

Would it help you if I pointed out that the material in this string could be chunked into four sets of three letters each? I think it would, because then rather than remembering 12 letters, you would only have to remember the names of four television stations. In this case, chunking changes the number of items you have to remember from 12 to only four.

Experts rely on chunking to help them process complex information. Herbert Simon and William Chase (1973) showed chess masters and chess novices various positions of pieces on a chessboard for a few seconds each. The experts did a lot better than the novices in remembering the positions because they were able to see the “big picture.” They didn’t have to remember the position of each of the pieces individually, but chunked the pieces into several larger layouts. But when the researchers showed both groups random chess positions—positions that would be very unlikely to occur in real games—both groups did equally poorly, because in this situation the experts lost their ability to organize the layouts (see Figure 8.7 “Possible and Impossible Chess Positions” ). The same occurs for basketball. Basketball players recall actual basketball positions much better than do nonplayers, but only when the positions make sense in terms of what is happening on the court, or what is likely to happen in the near future, and thus can be chunked into bigger units (Didierjean & Marmèche, 2005).

Figure 8.7 Possible and Impossible Chess Positions

Experience matters: Experienced chess players are able to recall the positions of the game on the right much better than are those who are chess novices. But the experts do no better than the novices in remembering the positions on the left, which cannot occur in a real game.

If information makes it past short term-memory it may enter long-term memory (LTM) , memory storage that can hold information for days, months, and years . The capacity of long-term memory is large, and there is no known limit to what we can remember (Wang, Liu, & Wang, 2003). Although we may forget at least some information after we learn it, other things will stay with us forever. In the next section we will discuss the principles of long-term memory.

Key Takeaways

• Memory refers to the ability to store and retrieve information over time.
• For some things our memory is very good, but our active cognitive processing of information assures that memory is never an exact replica of what we have experienced.
• Explicit memory refers to experiences that can be intentionally and consciously remembered, and it is measured using recall, recognition, and relearning. Explicit memory includes episodic and semantic memories.
• Measures of relearning (also known as savings) assess how much more quickly information is learned when it is studied again after it has already been learned but then forgotten.
• Implicit memory refers to the influence of experience on behavior, even if the individual is not aware of those influences. The three types of implicit memory are procedural memory, classical conditioning, and priming.
• Information processing begins in sensory memory, moves to short-term memory, and eventually moves to long-term memory.
• Maintenance rehearsal and chunking are used to keep information in short-term memory.
• The capacity of long-term memory is large, and there is no known limit to what we can remember.

Exercises and Critical Thinking

• List some situations in which sensory memory is useful for you. What do you think your experience of the stimuli would be like if you had no sensory memory?
• Describe a situation in which you need to use working memory to perform a task or solve a problem. How do your working memory skills help you?

Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. In K. Spence (Ed.), The psychology of learning and motivation (Vol. 2). Oxford, England: Academic Press.

Baddeley, A. D., Vallar, G., & Shallice, T. (1990). The development of the concept of working memory: Implications and contributions of neuropsychology. In G. Vallar & T. Shallice (Eds.), Neuropsychological impairments of short-term memory (pp. 54–73). New York, NY: Cambridge University Press.

Bargh, J. A., Chen, M., & Burrows, L. (1996). Automaticity of social behavior: Direct effects of trait construct and stereotype activation on action. Journal of Personality & Social Psychology, 71 , 230–244.

Bridgeman, B., & Morgan, R. (1996). Success in college for students with discrepancies between performance on multiple-choice and essay tests. Journal of Educational Psychology, 88 (2), 333–340.

Cowan, N., Lichty, W., & Grove, T. R. (1990). Properties of memory for unattended spoken syllables. Journal of Experimental Psychology: Learning, Memory, and Cognition, 16 (2), 258–268.

Didierjean, A., & Marmèche, E. (2005). Anticipatory representation of visual basketball scenes by novice and expert players. Visual Cognition, 12 (2), 265–283.

Haist, F., Shimamura, A. P., & Squire, L. R. (1992). On the relationship between recall and recognition memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 18 (4), 691–702.

Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63 (2), 81–97.

Nelson, T. O. (1985). Ebbinghaus’s contribution to the measurement of retention: Savings during relearning. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11 (3), 472–478.

Peterson, L., & Peterson, M. J. (1959). Short-term retention of individual verbal items. Journal of Experimental Psychology, 58 (3), 193–198.

Simon, H. A., & Chase, W. G. (1973). Skill in chess. American Scientist, 61 (4), 394–403.

Solomon, M. (1995). Mozart: A life . New York, NY: Harper Perennial.

Sperling, G. (1960). The information available in brief visual presentation. Psychological Monographs, 74 (11), 1–29.

Unsworth, N., & Engle, R. W. (2007). On the division of short-term and working memory: An examination of simple and complex span and their relation to higher order abilities. Psychological Bulletin, 133 (6), 1038–1066.

Wang, Y., Liu, D., & Wang, Y. (2003). Discovering the capacity of human memory. Brain & Mind, 4 (2), 189–198.

Introduction to Psychology Copyright © 2015 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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• Introduction

The significance of forgetting

• Executive attention
• Patterns of acquisition in working memory
• Mnemonic systems
• Physiological aspects of long-term memory
• Autobiographical memory
• Eyewitness memory
• Interference
• Challenges to interference theory

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• Table Of Contents

memory , the encoding, storage, and retrieval in the human mind of past experiences.

That experiences influence subsequent behavior is evidence of an obvious but nevertheless remarkable activity called remembering. Memory is both a result of and an influence on perception , attention , and learning . The basic pattern of remembering consists of attention to an event followed by the representation of that event in the brain . Repeated attention, or practice , results in a cumulative effect on memory and enables activities such as a skillful performance on a musical instrument , the recitation of a poem, and reading and understanding words on a page.

Learning could not occur without the function of memory. So-called intelligent behavior demands memory, remembering being prerequisite to reasoning . The ability to solve any problem or even to recognize that a problem exists depends on memory. Routine action, such as the decision to cross a street, is based on remembering numerous earlier experiences. The act of remembering an experience and bringing it to consciousness at a later time requires an association, which is formed from the experience, and a “retrieval cue,” which elicits the memory of the experience.

Practice (or review) tends to build and maintain memory for a task or for any learned material. During a period without practice, what has been learned tends to be forgotten . Although the adaptive value of forgetting may not be obvious, dramatic instances of sudden forgetting (as in amnesia ) can be seen to be adaptive. In this sense, the ability to forget can be interpreted as having been naturally selected in animals . Indeed, when one’s memory of an emotionally painful experience leads to severe anxiety , forgetting may produce relief. Nevertheless, an evolutionary interpretation might make it difficult to understand how the commonly gradual process of forgetting was selected for.

In speculating about the evolution of memory, it is helpful to consider what would happen if memories failed to fade. Forgetting clearly aids orientation in time; since old memories weaken and new ones tend to be vivid, clues are provided for inferring duration. Without forgetting, adaptive ability would suffer; for example, learned behavior that might have been correct a decade ago may no longer be appropriate or safe. Indeed, cases are recorded of people who (by ordinary standards) forget so little that their everyday activities are full of confusion. Thus, forgetting seems to serve the survival not only of the individual but of the entire human species.

Additional speculation posits a memory-storage system of limited capacity that provides adaptive flexibility specifically through forgetting. According to this view, continual adjustments are made between learning or memory storage (input) and forgetting (output). There is evidence in fact that the rate at which individuals forget is directly related to how much they have learned. Such data offer gross support for models of memory that assume an input-output balance.

Whatever its origins, forgetting has attracted considerable investigative attention. Much of this research has been aimed at discovering those factors that change the rate of forgetting. Efforts are made to study how information may be stored, or encoded in the human brain. Remembered experiences may be said to consist of encoded collections of interacting information, and interaction seems to be a prime factor in forgetting.

Memory researchers have generally supposed that anything that influences the behavior of an organism endowed with a central nervous system leaves—somewhere in that system—a “trace” or group of traces. So long as these traces endure, they can, in theory, be restimulated, causing the event or experience that established them to be remembered.

Time-dependent aspects of memory

Research by the American psychologist and philosopher William James (1842–1910) led him to distinguish two types of memory: primary, for handling immediate concerns, and secondary, for managing a storehouse of information accumulated over time. Memory researchers have since used the term short-term memory to refer to the primary or short-lived memory functions identified by James. Long-term memory refers to the relatively permanent information that is stored in and retrieved from the brain.

Psychology Memory Revision Notes

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

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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.

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On This Page:

What do the examiners look for?

• Accurate and detailed knowledge
• Clear, coherent, and focused answers
• Effective use of terminology (use the “technical terms”)

In application questions, examiners look for “effective application to the scenario,” which means that you need to describe the theory and explain the scenario using the theory making the links between the two very clear. If there is more than one individual in the scenario you must mention all of the characters to get to the top band.

Difference between AS and A level answers

The descriptions follow the same criteria; however, you have to use the issues and debates effectively in your answers. “Effectively” means that it needs to be clearly linked and explained in the context of the answer.

Read the model answers to get a clearer idea of what is needed.

The Multi-Store Model

The multistore model of memory was proposed by Atkinson and Shiffrin and is a structural model. They proposed that memory consisted of three stores: sensory register, short-term memory (STM), and long-term memory (LTM). Information passes from store to store in a linear way. Both STM and LTM are unitary stores.

Sensory memory is the information you get from your sense, your eyes, and ears. When attention is paid to something in the environment, it is then converted to short-term memory.

Information from short-term memory is transferred to long-term memory only if that information is rehearsed (i.e., repeated).

Maintenance rehearsal is repetition that keeps information in STM, but eventually, such repetition will create an LTM.

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

Each store 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 memory. There are three main ways in which information can be encoded (changed): 1. visual (picture), 2. acoustic (sound), and 3. semantic (meaning).
• Capacity concerns how much information can be stored.
• Duration refers to the period of time information can last in-memory stores.

Sensory register

• Duration: ¼ to ½ second
• Capacity: all sensory experience (v. larger capacity)
• Encoding: sense specific (e.g., different stores for each sense)

Short Term Memory

• Duration: 0-18 seconds
• Capacity: 7 +/- 2 items
• Encoding: mainly acoustic

Long Term Memory

• Duration: Unlimited
• Capacity: Unlimited
• Encoding: Mainly semantic (but can be visual and acoustic)

AO2 Scenario Question

The multi-store model of memory has been criticized in many ways. The following example illustrates a possible criticism.

Some students read through their revision notes lots of times before an examination but still, find it difficult to remember the information. However, the same students can remember the information in a celebrity magazine, even though they read it only once.

Explain why this can be used as a criticism of the multi-store model of memory.

“The MSM states that depth of memory trace in LTM is simply a result of the amount of rehearsal that takes place.

The MSM can be criticized for failing to account for how different types of material can result in different depth memory traces even though they’ve both been rehearsed for a similar amount of time.

For example, people may recall information they are interested in (e.g., information in celebrity magazines) more than the material they are not interested in (e.g., revision notes) despite the fact that they have both been rehearsed for a similar amount of time.

Therefore, the MSM’s view of long-term memory can be criticized for failing to take into account that material we may pay more attention to or is more meaningful/interesting to us may cause a deeper memory trace which is recalled more easily.”

One strength of the multistore model is that it 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.

The model is supported by studies of amnesiacs: For example the patient H.M. case study. HM is still alive but has marked problems in long-term memory after brain surgery.

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.

It has now become apparent that both short-term and long-term memory is more complicated than 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.).

The model suggests rehearsal helps to transfer information into LTM, but this is not essential. 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.

Research Study for both STM & LTM

Research studies can either be knowledge or evaluation:

• If you refer to the procedures and findings of a study, this shows knowledge and understanding (AO1).
• If you comment on what the studies show and what it supports and challenges the theory in question, this shows evaluation (AO3).

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, 1970), 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.

Types of Long-Term Memory

One of the earliest and most influential distinctions of long-term memory was proposed by Tulving (1972).  He proposed a distinction between episodic, semantic, and procedural memory.

Procedural Memory

Procedural memory is a part of the implicit long-term memory responsible for knowing how to do things, i.e., a memory of motor skills. A part of long-term memory is responsible for knowing how to do things, i.e., the memory of motor skills.  It does not involve conscious (i.e., it’s unconscious-automatic) thought and is not declarative.

For example, procedural memory would involve knowledge of how to ride a bicycle.

Semantic Memory

Episodic memory.

Episodic memory is a part of the long-term memory responsible for storing information about events (i.e., episodes) that we have experienced in our lives.

It involves conscious thought and is declarative.  An example would be a memory of our 1st day at school.

Cohen and Squire (1980) drew a distinction between declarative knowledge and procedural knowledge .  Procedural knowledge involves “knowing how” to do things. It included skills such as “knowing how” to play the piano, ride a bike, tie your shoes, and other motor skills.

It does not involve conscious thought (i.e., it’s unconscious-automatic).  For example, we brush our teeth with little or no awareness of the skills involved.

Whereas declarative knowledge involves “knowing that”; for example, London is the capital of England, zebras are animals, your mum’s birthday, etc.  Recalling information from declarative memory involves some degree of conscious effort – information is consciously brought to mind and “declared.”

The knowledge that we hold in semantic and episodic memories focuses on “knowing that” something is the case (i.e., declarative).  For example, we might have a semantic memory for knowing that Paris is the capital of France, and we might have an episodic memory for knowing that we caught the bus to college today.

Evidence for the distinction between declarative and procedural memory has come from research on patients with amnesia . Typically, amnesic patients have great difficulty in retaining episodic and semantic information following the onset of amnesia.

Their memory for events and knowledge acquired before the onset of the condition tends to remain intact, but they can’t store new episodic or semantic memories. In other words, it appears that their ability to retain declarative information is impaired.

However, their procedural memory appears to be largely unaffected. They can recall skills they have already learned (e.g., riding a bike) and acquire new skills (e.g., learning to drive).

Working Memory Model

The working memory model (Baddeley and Hitch, 1974) replaced the idea of a unitary STM. It suggests a system involving active processing and short-term storage of information.

Key features include the central executive, the phonological loop, and the visuospatial sketchpad.

The central executive has a supervisory function and acts as a filter, determining which information is attended to.

It can process information in all sensory forms, direct information to other slave systems, and collects responses. It has limited capacity and deals with only one piece of information at a time.

One of the slave systems is the phonological loop which is a temporary storage system for holding auditory information in a speech-based form.

It has two parts: (1) the phonological store (inner ear), which stores words you hear; and (2) the articulatory process (inner voice), which allows maintenance rehearsal (repeating sounds or words to keep them in working memory while they are needed). The phonological loop plays a key role in the development of reading.

The second slave system is the Visuospatial sketchpad (VSS). The VSS is a temporary memory system for holding visual and spatial information. It has two parts: (1) the visual cache (which stores visual data about form and color) and (2) the inner scribe (which records the arrangement of objects in the visual field and rehearses and transfers information in the visual cache to the central executive).

The third slave system is the episodic buffer which acts as a “backup” (temporary) store for information that communicates with both long-term memory and the slave system components of working memory. One of its important functions is to recall material from LTM and integrate it into STM when working memory requires it.

Bryan has been driving for five years. Whilst driving, Bryan can hold conversations or listen to music with little difficulty.

Bob has had four driving lessons. Driving requires so much of Bob’s concentration that, during lessons, he often misses what his driving instructor is telling him. With reference to features of the working memory model, explain the different experiences of Bryan and Bob. (4 marks)

A tricky question – the answer lies in Bryan being able to divide the different components of his STM because he is experienced at driving and doesn’t need to devote all his attention to the task of driving (controlled by the visuospatial sketchpad).

“Because Bryan has been driving for five years it is an ‘automated’ task for him; it makes fewer attentional demands on his central executive, so he is free to perform other tasks (such as talking or listening to music) and thus is able to divide resources between his visuospatial sketch pad (driving) and phonological loop (talking and listening to music).

As Bob is inexperienced at driving, this is not the case for him – his central executive requires all of his attentional capacity for driving and thus cannot divide resources effectively between components of working memory.”

Working memory is supported by dual-task studies. It is easier to do two tasks at the same time if they use different processing systems (verbal and visual) than if they use the same slave system.

For example, participants would find it hard to do two visual tasks at the same time because they would be competing for the same limited resources of the visuospatial sketchpad. However, a visual task and a verbal task would use different components and so could be performed with minimum errors.

The KF Case Study supports the Working Memory Model. KF suffered brain damage from a motorcycle accident that damaged his short-term memory. KF’s impairment was mainly for verbal information – his memory for visual information was largely unaffected.

This shows that there are separate STM components for visual information (VSS) and verbal information (phonological loop). However, evidence from brain-damaged patients may not be reliable because it concerns unique cases with patients who have had traumatic experiences.

One limitation is the fact that little is known about how the central executive works. It is an important part of the model, but its exact role is unclear.

Another limitation is that the model does not explain the link between working memory and LTM.

Research Study for WM

• If you refer to the procedures and findings of a study, this shows knowledge and understanding.
• If you comment on what the studies show and what it supports and challenges the theory in question, this shows evaluation.

Baddeley and Hitch conducted an experiment in which participants were asked to perform two tasks at the same time (dual task technique). A digit span task required them to repeat a list of numbers, and a verbal reasoning task which required them to answer true or false to various questions (e.g., B is followed by A?).

Results : As the number of digits increased in the digit span tasks, participants took longer to answer the reasoning questions, but not much longer – only fractions of a second. And they didn’t make any more errors in the verbal reasoning tasks as the number of digits increased.

Conclusion : The verbal reasoning task made use of the central executive, and the digit span task made use of the phonological loop.

Explanations for Forgetting

Interference.

Interference is an explanation for forgetting from long-term memory – two sets of information become confused.

• Proactive interference (pro=forward) is where old learning prevents the recall of more recent information. When what we already know interferes with what we are currently learning – where old memories disrupt new memories.
• Retroactive interference (retro=backward) is where new learning prevents the recall of previously learned information. In other words, later learning interferes with earlier learning – where new memories disrupt old memories.

Proactive and retroactive Interference is thought to be more likely to occur where the memories are similar, for example: confusing old and new telephone numbers. Chandler (1989) stated that students who study similar subjects at the same time often experience interference. French and Spanish are similar types of material which makes interference more likely.

Semantic memory is more resistant to interference than other types of memory.

Postman (1960) provides evidence to support the interference theory of forgetting. A lab experiment was used, and participants were split into two groups. Both groups had to remember a list of paired words – e.g., cat – tree, jelly – moss, book – tractor.

The experimental group also had to learn another list of words where the second paired word is different – e.g., cat – glass, jelly- time, book – revolver. The control group was not given the second list.

All participants were asked to recall the words on the first list. The recall of the control group was more accurate than that of the experimental group. This suggests that learning items in the second list interfered with participants’ ability to recall the list. This is an example of retroactive interference.

Although proactive and retroactive interference is reliable and robust effects, there are a number of problems with interference theory as an explanation for forgetting.

First, interference theory tells us little about the cognitive processes involved in forgetting. Secondly, the majority of research into the role of interference in forgetting has been carried out in a laboratory using lists of words, a situation that is likely to occur fairly infrequently in everyday life (i.e., low ecological validity). As a result, it may not be possible to generalize from the findings.

Baddeley states that the tasks given to subjects are too close to each other and, in real life; these kinds of events are more spaced out. Nevertheless, recent research has attempted to address this by investigating “real-life” events and has provided support for interference theory. However, there is no doubt that interference plays a role in forgetting, but how much forgetting can be attributed to interference remains unclear.

Retrieval failure

Retrieval failure is where information is available in long-term memory but cannot be recalled because of the absence of appropriate cues.

When we store a new memory, we also store information about the situation and these are known as retrieval cues. When we come into the same situation again, these retrieval cues can trigger the memory of the situation.

Types of cues that have been studied by psychologists include context, state, and organization.

• Context – external cues in the environment, e.g., smell, place, etc. Evidence indicates that retrieval is more likely when the context at encoding matches the context at retrieval.
• State – bodily cues inside of us, e.g., physical, emotional, mood, drunk, etc. The basic idea behind state-dependent retrieval is that memory will be best when a person’s physical or psychological state is similar to encoding and retrieval.

For example, if someone tells you a joke on Saturday night after a few drinks, you”ll be more likely to remember it when you”re in a similar state – at a later date after a few more drinks. Stone cold sober on Monday morning, you”ll be more likely to forget the joke.

• Organization – Recall is improved if the organization gives a structure that provides triggers, e.g., categories.

According to retrieval-failure theory, forgetting occurs when information is available in LTM but is not accessible. Accessibility depends in large part on retrieval cues.

Forgetting is greatest when context and state are very different at encoding and retrieval. In this situation, retrieval cues are absent, and the likely result is cue-dependent forgetting.

Evaluation (AO3)

People tend to remember material better when there is a match between their mood at learning and at retrieval. The effects are stronger when the participants are in a positive mood than when they are in a negative mood. They are also greater when people try to remember events having personal relevance.

A number of experiments have indicated the importance of context-based (i.e., external) cues for retrieval. An interesting experiment conducted by Baddeley indicates the importance of context setting for retrieval.

Baddeley (1975) asked deep-sea divers to memorize a list of words. One group did this on the beach, and the other group underwater. When they were asked to remember the words, half of the beach learners remained on the beach, and the rest had to recall underwater.

Half of the underwater group remained there, and the others had to recall on the beach. The results show that those who had recalled in the same environment (i.e., context) and who had learned recalled 40% more words than those recalling in a different environment. This suggests that the retrieval of information is improved if it occurs in the context in which it was learned.

A study by Goodwin investigated the effect of alcohol on state-dependent (internal) retrieval. They found that when people encoded information when drunk, they were more likely to recall it in the same state.

For example, when they hid money and alcohol when drunk, they were unlikely to find them when sober. However, when they were drunk again, they often discovered the hiding place. Other studies found similar state-dependent effects when participants were given drugs such as marijuana.

The ecological validity of these experiments can be questioned, but their findings are supported by evidence from outside the laboratory. For example, many people say they can’t remember much about their childhood or their school days. But returning to the house in which they spent their childhood or attending a school reunion often provides retrieval cues that trigger a flood of memories.

Eyewitness Testimony

Misleading information.

Loftus and Palmer investigated how misleading information could distort eyewitness testimony accounts.

Procedure : Forty-five American students formed an opportunity sample. This was a laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design ).

Participants were shown slides of a car accident involving a number of cars and asked to describe what had happened as if they were eyewitnesses. They were then asked specific questions, including the question, “About how fast were the cars going when they (hit/smashed/collided/bumped/contacted ) each other?”

Findings : The estimated speed was affected by the verb used. The verb implied information about the speed, which systematically affected the participants’ memory of the accident.

Participants who were asked the “smashed” question thought the cars were going faster than those who were asked the “hit” question. The participants in the “smashed” condition reported the highest speeds, followed by “collided,” “bumped,” “hit,” and “contacted” in descending order.

The research lacks mundane realism, as the video clip does not have the same emotional impact as witnessing a real-life accident, and so the research lacks ecological validity.

A further problem with the study was the use of students as participants. Students are not representative of the general population in a number of ways. Importantly they may be less experienced drivers and, therefore, less confident in their ability to estimate speeds. This may have influenced them to be more swayed by the verb in the question.

A strength of the study is it’s easy to replicate (i.e., copy). This is because the method was a laboratory experiment that followed a standardized procedure.

The Yerkes-Dodson effect states that when anxiety is at low and high levels, EWT is less accurate than if anxiety is at a medium level. Recall improves as anxiety increases up to an optimal point and then declines.

When we are in a state of anxiety, we tend to focus on whatever is making us feel anxious or fearful, and we exclude other information about the situation. If a weapon is used to threaten a victim, their attention is likely to focus on it. Consequently, their recall of other information is likely to be poor.

Clifford and Scott (1978) found that people who saw a film of a violent attack remembered fewer of the 40 items of information about the event than a control group who saw a less stressful version. As witnessing a real crime is probably more stressful than taking part in an experiment, memory accuracy may well be even more affected in real life.

However, a study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory. Twenty-one witnesses observed a shooting incident in Canada outside a gun shop in which one person was killed and a 2nd seriously wounded. The incident took place on a major thoroughfare in the mid-afternoon.

All of the witnesses were interviewed by the investigating police, and 13 witnesses (aged 15-32 yrs) agreed to a research interview 4-5 months after the event. The witnesses were also asked to rate how stressed they had felt at the time of the incident using a 7-point scale. The eyewitness accounts provided in both the police and research interviews were analyzed and compared.

The results of the study showed the witnesses were highly accurate in their accounts, and there was little change in the amount or accuracy of recall after five months. The study also showed that stress levels did not have an effect on memory, contrary to lab findings.

All participants showed high levels of accuracy, indicating that stress had little effect on accuracy. However, very high anxiety was linked to better accuracy. Participants who reported the highest levels of stress were most accurate (about 88% accurate compared to 75% for the less-stressed group).

One strength of this study is that it had high ecological validity compared with lab studies which tend to control variables and use student populations as research participants.

One weakness of this study was that there was an extraneous variable. The witnesses who experienced the highest levels of stress were actually closer to the event (the shooting), and this may have helped with the accuracy of their memory recall.

Reduced accuracy of information may be due to surprise rather than anxiety – Pickel found that identification was least accurate in high surprise conditions rather than high threat conditions – The weapon focus effect may be related to surprise rather than anxiety; therefore, research may lack internal validity.

Real-world application: We can apply the Yerkes-Dodson effect to predict that stressful incidents will lead to witnesses having relatively inaccurate memories as their anxiety levels would be above the optimum – We can avoid an over-reliance on eyewitness testimony that may have been impacted by anxiety.

The Cognitive Interview

The cognitive interview is a police technique for interviewing witnesses to a crime which encourages them to recreate the original context in order to increase the accessibility of stored information.

The cognitive interview involves a number of techniques:

Context Reinstatement

Trying to mentally recreate an image of the situation, including details of the environment, such as the weather conditions, and the individual’s emotional state, including their feelings at the time of the incident. This makes memories accessible and provides emotional and contextual cues.

Recall from a Changed Perspective

Recall in reverse order, report everything.

The interviewer encourages the witness to report all details about the event, even though these details may seem unimportant. Memories are interconnected so that recollection of one item may then cue a whole lot of other memories.

The Enhanced Cognitive Interview

The main additional features are:-

• Encourage the witness to relax and speak slowly.
• Offer comments to help clarify witness statements.
• Adapt questions to suit the understanding of individual witnesses.

One limitation is the cognitive interview is that it’s time-consuming to conduct and takes much longer than a standard police interview. It is also time-consuming to train police officers to use this method. This means that it is unlikely that the “proper” version of the cognitive interview is used.

Another limitation is that some elements of the cognitive interview may be more valuable than others. For example, research has shown that using a combination of “report everything” and “context reinstatement” produced better recall than any of the conditions individually.

A final criticism is that police personnel have to be trained, and this can be expensive and time-consuming.

Geiselman (1985) set out to investigate the effectiveness of the cognitive interview. Participants viewed a film of a violent crime and, after 48 hours, were interviewed by a policeman using one of three methods: the cognitive interview, a standard interview used by the Los Angeles Police, or an interview using hypnosis.

The number of facts accurately recalled and the number of errors made was recorded. The average number of correctly recalled facts for the cognitive interview was 41.2. For hypnosis, it was 38.0, and for the standard interview, it was 29.4.

A-Level Psychology Revision Notes

A-Level Psychology Attachment

Social Influence Revision Notes

Psychopathology Revision Notes

Psychology Approaches Revision for A-level

Research Methods: Definition, Types, & Examples

Issues and Debates in Psychology (A-Level Revision)

is the ability to understand and then internalize information into the memory stores based on the processes of learning, encoding, retention and then retrieval and reactivation of a memory when stimulated. Research has implied that for every fact or memory, a new neuron is formed in the brain.

Introduction

One of the most important mental processes that characterizes the human experience is Memory, which is being researched by neuroscientists and psychologists. By enabling us to store and retrieve information, it maintains our identities and facilitates learning. From simple sensory processing to higher cognitive abilities like language and thought, it is a fundamental mechanism involved in a wide range of cognitive abilities.

Memory is referred to as the process of encoding, storing, and retrieving information in psychology. We can form relationships, adjust to new circumstances, learn from experience, and make sense of the world around us thanks to this intricate system. Everything we remember is included in memory, and it affects almost everything we do.

Background and Context

Historical perspective.

The study of memory as a science has a long history. But Hermann Ebbinghaus didn't start his groundbreaking research into memory using scientific methods until the late 19th century . Ebbinghaus created the first numerical method of measuring memory, which he dubbed the "forgetting curve."

Since then, numerous models of memory have been proposed, including the influential stage model of memory by Atkinson and Shiffrin in the 1960s, which proposed three stages of memory processing: sensory memory, short-term memory, and long-term memory.

Current State of Research

Research into memory has grown tremendously since the early work of Ebbinghaus and Atkinson and Shiffrin . Current research spans numerous areas, including understanding how memories are encoded and stored in the brain, how they are recalled, and how they can be influenced and distorted.

Recent developments include the growing understanding of the role of sleep in memory consolidation, the elucidation of the mechanisms behind "flashbulb memories" (vivid memories of significant events), and the exploration of how traumatic memories contribute to conditions like post-traumatic stress disorder (PTSD).

Numerous facets of our lives depend on memory. It enables us to retrieve information that is stored in the brain, recall previously learned skills, or recall a priceless memory. Individual can use memory to make future plans based on past experiences.

We wouldn't have an identity, a sense of continuity, or the capacity to learn without memory. Understanding this complex cognitive function is crucial because many mental health conditions, including PTSD, Alzheimer's disease , and dementia, involve serious memory problems.

Key Concepts and Terminologies

• Encoding : The process by which we transform what we perceive, think, or feel into an enduring memory.
• Storage : The process of maintaining information in memory over time.
• Retrieval : The process of bringing to mind information that has been previously encoded and stored.
• Working Memory : This is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior.
• Long-Term Memory : This is the continuous storage of information. Unlike short-term memory, the storage capacity of long-term memory is seemingly unlimited. It can hold information for a little while or as long as decades.

Practical Applications and Implications

Numerous practical applications of memory research have been made, ranging from developing better study methods to treating memory-related disorders. Following are some advice drawn from psychological research:

• Use active recall : Research has shown that actively recalling information, rather than just rereading it, significantly improves memory retention.
• Distribute your study : Spacing out learning over time, a technique known as distributed practice , can enhance long-term memory.
• Take care of your mental health : Mental health problems, such as stress and depression, can adversely affect memory. Seeking help for these issues can protect your memory function.
• Lead a healthy lifestyle : Regular physical exercise, a balanced diet, and adequate sleep can all contribute to improved memory and brain health.

Frequently Asked Questions

What is memory and why is it important.

Encoding, storing, and retrieving information are all processes carried out in memory. It is crucial for education, preparation, and identity formation.

How do psychologists conduct research and gather data about memory?

Psychologists use a variety of methods to study memory, including laboratory experiments, brain imaging techniques, neuropsychological studies of patients with memory disorders , and longitudinal studies of healthy individuals.

What are the different branches of memory research?

Memory research is divided into several subfields, such as cognitive psychology, which focuses on memory functions, neuropsychology , which examines the neural bases of memory, and clinical psychology , which examines memory disorders and their management.

How do memory principles apply to daily life?

Learning and studying skills can be improved, memory in old age can be improved, memory disorders can be understood and managed, and the legal system can be informed about the accuracy of eyewitness memory .

Ebbinghaus, H. (1913). Memory: A Contribution to Experimental Psychology . Teachers College, Columbia University.

Atkinson, R.C., & Shiffrin, R.M. (1968). Human memory: A proposed system and its control processes . The psychology of learning and motivation, 2, 89-195.

Baddeley, A. D. (1992). Working memory. Science, 255(5044), 556-559. DOI: 10.1126/science.1736359

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Can You Trust Your Memories?

4 practices to safeguard your shape-shifting memories..

Updated July 30, 2024 | Reviewed by Michelle Quirk

• Our memories aren't snapshots of the past but rather reconstructions shaped by our life experiences.
• The media and our emotions, social circle, and imagination reshape our memories.
• We can safeguard our memories with four simple practices.

For as long as I can remember, I’ve told a story about how Joe Biden first captured my attention in 1972 when I eagerly rushed home from school to watch the Watergate hearings—my first youthful foray into the rough and tumble world of politics . I can vividly recall Mo Dean, with her blond updo, sitting behind her husband as he was grilled by Joe Biden. My story continued that, years later, I remember I was sewing curtains as I listened to Senator Biden interrogate Clarence Thomas during his Supreme Court hearing.

It's possible I even shared my sweet memory with then-presidential candidate Biden when I met with him a few years ago. If I did, it should be noted he was gracious and didn't tell me he didn't become a U.S. Senator until 1973.

It was only recently an astute friend pointed out my historical error. I was stunned. That memory is, well, so real.

“Memory is a treacherous thing,” wrote author Haruki Murakami, something I recently learned.

How malleable are our memories?

An avalanche of research reveals that our memories aren’t static imprints of past events but rather reconstructions of our experiences. What we remember is continually reshaped by new information and a variety of factors that influence what we recall and how we recall it. Here are a few:

• Media and external events can seep into and reconstruct our memory bank. News reports, social media , and even casual conversations influence our recollections and blur the line between our experience and secondhand information. For example, after 911, the constant exposure to footage of the second plane hitting the World Trade Center led many to form detailed memories of having seen it live, even if they didn’t. This phenomenon, known as flashbulb memories, shows how repetitive media can distort our memories.
• Imagination can be a culprit that distorts our memories. Our minds tend to fill in gaps with assumed or imagined details, blending into past events what we wish or imagine could have happened. For instance, if you imagine yourself as magnanimous in a past conflict, you might start believing you behaved magnanimously, even though perhaps you did not. Were you really as kind as you remember?
• Emotions profoundly impact how we remember the past. Emotionally charged events are more vividly recalled because stress hormones enhance memory formation, and negative emotions tend to overpower and supplant positive ones. This distorts our memories, making deeply emotional aspects of an event stand out while more positive aspects fade away. For instance, a family vacation may be remembered mostly for a meltdown with teenagers rather than for the relaxing moments at the beach.
• Social influences also transform our memories. When engaging with friends and colleagues, we often craft shared narratives to bond or fit in. This can result in the memories of others overriding our own. For example, if a friend mistakenly recalls that you both attended a book fair together years ago, you might start to believe you were there and adopt her memories as your own, even if you actually weren't there.

This shape-shifting nature of memories is akin to the classic game of telephone. A whispered story morphs and mutates with each retelling, as players add their own selective hearing, interpretations, and biases. Ultimately, the final story little resembles the original. Similarly, when you repeatedly mull over an old memory, it can become difficult to distinguish the original details from newly introduced ones.

You can safeguard your memories with four simple practices:

• Acknowledge the chameleon-like nature of memory. Accepting that your memories are wily shape-shifters makes it easier to handle disagreements over past events. This will foster more open and less contentious discussions with others about a long-held and disputed memory.
• Document your life. Journaling, videos, and photographs all help pinpoint and confirm specific details. Documentation also serves as a practical tool for preserving personal history.
• Keep a timeline. We think we will always remember the details of our life experiences, both large and small, but in reality, we won’t. A timeline is a practical reference that you can return to when memories become fuzzy.
• Relive memories with others. Sharing old stories with family and friends who were present will clarify details. As a bonus, research shows that reliving happy memories boosts one’s happiness .

Reflecting on my faux memory of Joe Biden and the Watergate hearings, it's now clear I conflated two distinct memories of separate hearings. This confluence of experiences embellished my recollection that, if nothing else, made for a great story! This is a stark reminder of Joan Didion's wise observation: "Memory is not a container, but a living organism, and it changes with time."

De Brigard, F. (2022). Memory, imagination, and mental time travel. Annual Review of Psychology, 73 , 319–343.

Hirst, W., Manier, D., & Cohn, M. (2009). The influence of social interactions on memory: A review. Memory & Cognition, 37 (2), 278–295.

Phelps, E. A., LaBar, K. S., & Spencer, D. D. (2004). Memory for emotional words as a function of emotional intensity. Learning & Memory, 11 (1), 43–54.

Conway, M. A., & Pleydell-Pearce, C. W. (2000). The construction of autobiographical memories in the self-memory system. Psychological Review, 107 (2), 261–288.

Loftus, E. F., & Pickrell, J. E. (1995). The formation of false memories. Psychological Science, 7 (4), 251–254.

Bohn, A., & McGaugh, J. L. (2023). The impact of personal timelines on memory retrieval and accuracy. Journal of Experimental Psychology: General, 152 (2), 284–298.

Cohen-Lavian, S., & Coman, A. (2021). Repetitive public messaging impacts social memory. Journal of Experimental Psychology: General , 150(3), 470–482.

Gina Vild , the co-author of Two Most Important Days, How to Find Your Purpose, and Live a Happier Healthier Life, is a former Associate Dean and Chief Communications Officer at Harvard Medical School.

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The neurobiological foundation of memory retrieval

Paul w. frankland.

1 Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.

2 Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.

3 Department of Psychology, University of Toronto, Toronto, Ontario, Canada.

4 Department of Physiology, University of Toronto, Toronto, Ontario, Canada.

5 Child & Brain Development Program, Canadian Institute for Advanced Research, Toronto, Ontario, Canada.

Sheena A. Josselyn

6 Brain, Mind & Consciousness Program, Canadian Institute for Advanced Research, Toronto, Ontario, Canada.

Stefan Köhler

7 Department of Psychology, University of Western Ontario, London, Ontario, Canada.

8 The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.

Memory retrieval involves the interaction between external sensory or internally generated cues and stored memory traces (or engrams) in a process termed ‘ecphory’. While ecphory has been examined in human cognitive neuroscience research, its neurobiological foundation is less understood. To the extent that ecphory involves ‘reawakening’ of engrams, leveraging recently developed technologies that can identify and manipulate engrams in rodents provides a fertile avenue for examining retrieval at the level of neuronal ensembles. Here we evaluate emerging neuroscientific research of this type, using cognitive theory as a guiding principle to organize and interpret initial findings. Our Review highlights the critical interaction between engrams and retrieval cues (environmental or artificial) for memory accessibility and retrieval success. These findings also highlight the intimate relationship between the mechanisms important in forming engrams and those important in their recovery, as captured in the cognitive notion of ‘encoding specificity’. Finally, we identify several questions that currently remain unanswered.

In 1966, Tulving and Pearlstone 1 reported a highly influential finding that profoundly altered the direction of subsequent research on memory in ways that few papers do. Up until this point, almost all experimental research on human memory was concerned with learning or forgetting. The prevalent perspective at the time considered failure in memory performance as the outcome of two possible scenarios. Failure might indicate either that information had not been learned or that it had been learned but subsequently forgotten. However, Tulving and Pearlstone’s work suggested a third possibility. Memory failure could also reflect a problem in retrieval. Specifically, they demonstrated that the same memory could be retrieved successfully with some retrieval cues, but not others ( Fig. 1 ).

Subjects were presented with a series of words. These words were drawn from multiple categories (for example, types of birds, flowers, etc.). In the test phase, subjects were asked to recall as many words as they could from the list (free recall) or from the specific categories (cued recall). The cued recall group performed considerably better than the free recall group across categories, indicating that retrieval cues present at the time of recall determine engram accessibility and subsequent success at remembering.

From this work, Tulving developed an important conceptual distinction between availability versus accessibility of information in memory. According to this view 2 , 3 , some forms of memory failure reflect a lack of availability of pertinent information (i.e., permanent loss), whereas other forms of memory failure reflect temporary problems in accessibility. Phenomenologically, this relates to the common ‘tip of the tongue’ experience, in which one might struggle to recall a familiar name or place while having the strong impression that the information is present. Indeed, often this information subsequently comes to mind. Cues available at retrieval represent perhaps the most critical factor that determines memory accessibility and corresponding success at remembering.

In making this distinction between memory availability versus accessibility, Tulving also recognized 3 earlier work by Richard Semon, a German scientist working at the turn of the twentieth century. Semon 4 first emphasized the role of retrieval cues in remembering and introduced specific terminology to capture this process. Ecphory describes the memory retrieval process, and Semon argued that ecphory reflects the unique interplay between cues and stored memory traces at retrieval. He also coined the term engram’ to refer to such memory traces as biological entities; this may be considered his better-known contribution to the field 5 . Although engrams had not yet been identified empirically, the concept of ecphory became central to the cognitive psychology of memory retrieval 6 .

In the last decade, enormous progress has been made in identifying and manipulating engrams in rodents 7 – 10 . In large part, this progress may be attributed to the development of tools that allow researchers to map engrams to specific neuronal ensembles and manipulate these ensembles using genetically encoded actuators 10 – 15 ( Box 1 ). To date, these approaches have provided evidence for the existence of engrams at the cellular level 7 – 9 , but they may also shed light on the biological basis of memory retrieval 16 , 17 (or, more precisely, ecphory). To the extent that ecphory involves reawakening specific engrams, the ability to identify and manipulate engrams is a prerequisite for gaining mechanistic insights into the retrieval process at the level of neuronal ensembles. Therefore, the recent progress in understanding engrams puts us in position to ask meaningful questions about the neurobiological basis of retrieval. Here we evaluate contemporary neuroscientific research on retrieval at the level of neuronal ensembles using the conceptual framework introduced by Semon and later elaborated by Tulving in his empirical and theoretical work. Although this research also has potentially interesting translational implications, they will not be covered here (but see ref. 18 ).

Approaches for tagging and manipulating engrams in rodents

The allocation strategy takes advantage of the finding that, within a given brain region, eligible excitatory neurons compete for allocation to an engram. This strategy biases which neurons are allocated to an engram by artificially manipulating excitability before a training event. For example, before a training event, a small, random subpopulation of excitatory neurons (purple) is infected with a viral vector expressing a transgene that increases neuronal excitability, such as ChR2 ( Box Fig. a ) 21 , 27 or CREB 20 , 22 , 23 , 108 , 109 . Infected neurons with relatively greater excitability at the time of training are biased for allocation to a resulting engram (red outline). Once allocated, these neurons become both necessary (indispensable) and sufficient (inducing) components of the engram supporting a memory.

In the tagging strategy, neurons that happen to be sufficiently active (that would normally express an activity-dependent immediate early gene) at the time of training are tagged with an actuator (such as an excitatory or inhibitory opsin or chemogenetic construct). To tag active neurons, activity-dependent immediate early gene (IEG) promoters (c-Fos, Arc or others, including synthetic promoters such as E-SARE (enhanced synaptic activity-responsive element) 110 ) are paired with an inducer that ‘opens the tagging window’. Two general types of inducers are used:

• Tetracycline transactivator (tTA)-inducible tagging system. The initial studies 13 , 26 using this approach took advantage of two transgenic mouse lines (but viral vectors can also be used 14 ). In the first transgenic line, tTA (tetracycline-controlled transactivator) is expressed downstream of an IEG promoter. In active cells, neural activity results in tTA expression. However, this process is blocked in the presence of doxycycline (DOX). In second transgenic mouse line, the transgene of interest (depicted as ChR2 in Box Fig. b ) is expressed downstream of a tetracycline response element (TRE). TRE is activated by tTA. Therefore, the absence of DOX opens the tagging window, allowing the transgene of interest to be expressed in active cells.
• Cre recombinase-inducible tagging system. In this system, two transgene cassettes are generally used. In the first, a tamoxifen (TAM)-dependent Cre recombinase (CreER T2 ) is expressed under control of an IEG promoter while in the second, a loxP-flanked STOP signal is placed between a constitutive promoter and the transgene of interest ( Box Fig. c ). In the absence of TAM, the transgene is not expressed. However, in the presence of TAM, Cre recombinase translocates to the nucleus, cleaves the loxP sites, and removes the STOP signal, allowing expression of the transgene. TAM administration opens the tagging window allowing the transgene of interest to be expressed in active cells 12 , 111 .

Manipulating retrieval

Ecphory emphasizes that retrieval reflects interactions between cues, either external sensory or internally generated, and the engram. In other words, memory retrieval can be understood as cue-induced behavioral expression of the engram. It may occur in situations where we intentionally strive to recover a memory in relation to a specific cue (for example, trying to remember where we initially encountered a person we just again met). In other situations, cues may spontaneously trigger memory retrieval (for example, seeing a picture of Paris and remembering a recent visit there).

Contemporary engram studies have examined ecphory in three ways. The first type of experiment asked whether it is possible to prevent ecphory in the presence of external sensory retrieval cues ( Fig. 2a ). For instance, Tanaka and colleagues 19 used a tetracycline-based system (TetTag) to label a contextual fear memory engram in mice, such that CA1 neuronal ensembles that were active during conditioning expressed an inhibitory opsin (ArchT). When subsequently placed back in the training context, mice typically freeze, indicating they recognized that this was the place where the footshock was previously administered. Critically, optogenetic inhibition of the ArchT-tagged neuronal ensemble during this test session reduced conditioned freezing levels (indicating impairment in memory retrieval). Of particular relevance, from the perspective of ecphory, is that the freezing behavior was context-specific (i.e., cue-specific). When a non-overlapping neuronal ensemble tagged in a different context (context B) was silenced during contextual fear testing in context A, mice froze, indicating that this intervention did not interfere with retrieval of the context A fear memory. Similar disruption of cue-induced retrieval by silencing corresponding engrams was observed across a variety of experimental conditions. These include silencing other brain regions (for example, the amygdala 20 – 22 and insular cortex 23 ), in tasks other than fear conditioning (for example, cocaine-cue memory 24 ), as well as using alternate genetic ensemble tagging systems (for example, cre-inducible systems 11 , 12 , 25 ).

a , In this experiment 19 , neuronal ensembles in the CA1 region of the hippocampus were tagged with the inhibitory opsin, ArchT, during contextual fear conditioning (left). When placed back into the training context (i.e., the retrieval cue), mice froze (middle). However, optogenetic inhibition of the tagged ensemble during this test reduced freezing levels (right), indicating that engram silencing can prevent ecphory even in the presence of natural retrieval cues. b , In this experiment 26 , neuronal ensembles in the DG region of the hippocampus were tagged with the excitatory opsin, ChR2, during contextual fear conditioning (left). When placed into a distinct context, mice did not freeze (middle). However, optogenetic activation of the tagged ensemble during this test induced freezing (right), indicating that engram activation, in the absence of natural retrieval cues, can induce ecphory.

The second type of experiment asked the converse question: is it possible to induce memory expression in the absence of sensory retrieval cues via direct stimulation of a tagged engram ( Fig. 2b )? For instance, Liu and colleagues 26 used a similar TetTag approach to express an excitatory opsin (ChR2) in neuronal ensembles that were active during contextual fear conditioning. Following conditioning, placing mice in a context distinct from the training context resulted in little freezing behavior. However, direct photostimulation of the ChR2-tagged neuronal ensemble in the dentate gyrus (DG) induced freezing. Subsequent studies generalized these findings across experimental conditions 11 , 25 and in other brain regions (including the lateral amygdala (LA) 27 – 30 , basolateral amygdala (BLA) 31 and retrosplenial cortex 32 ). Together, these types of experiments indicate it is possible to bypass the requirement for natural retrieval cues in ecphory and to induce memory expression via direct stimulation of the putative engram. One interpretation is that stimulation reflects a reinstatement of an otherwise natural cue.

The first two types of studies used experience-dependent tagging approaches to label neurons that were endogenously active at the time of an event, and then used artificial means (for example, photostimulation) to either block or elicit ecphory. This begs the question of whether the opposite is possible: to create an engram by artificial means and then probe ecphory using natural cues. This question has been addressed in the third type of study considered here ( Fig. 3 ). In this study 33 , photostimulation of a specific olfactory glomerulus (M72) was paired with photostimulation of specific projections that mediate aversion (from the lateral habenula to the ventral tegmental area (VTA)) to create an artificial engram. When mice were subsequently presented with a real M72-activating odorant (acetophenone), they exhibited conditioned avoidance, even though they had not encountered this odor previously. If, instead, M72 activation was paired with photostimulation of reward-mediating projections (laterodorsal tegmental nucleus → VTA), mice subsequently approached, rather than avoided, the M72 odorant, acetophenone. Retrieval of these artificially generated memories and real odor memories (in which acetophenone was actually paired with shock) engaged similar neural circuits, and suppressing neuronal activity in the BLA prevented expression of both artificial and real memories. Three aspects of this work illustrate nicely the tight interplay between engrams and retrieval cues, as initially suggested by Semon. First, artificial engram expression was demonstrated via presentation of a natural external sensory retrieval cue. Second, memory expression reflected the predicted content of the stored information (i.e., mice either approached or avoided acetophenone, depending on which VTA inputs, rewarding or aversive, were stimulated during the training phase). Third, behavioral responding was restricted to the trained cue and did not occur in the presence of unrelated cues.

a , In these experiments 33 , mice formed either a real (top) or an artificial (bottom) odor aversion memory. For the real odor memory, an odor (acetophenone; green) was paired with shock during training. When mice were subsequently presented with the conditioned odor (acetophenone) or a distinct odor (carvone; orange), mice exhibited conditioned aversion to acetophenone. For the artificial odor memory, photostimulation of a specific olfactory glomerulus (M72) was paired with photostimulation of lateral habenula inputs into the VTA. When mice were subsequently tested, they avoided the M72 odorant acetophenone (green), preferring to spend time on the carvone (non-M72 odorant; orange) side of the apparatus. b , In these experiments 33 , mice formed either a real (top) or an artificial (bottom) odor attraction memory. For the real odor memory, an odor (acetophenone; green) was paired with food during training. When mice were subsequently presented with the conditioned odor (acetophenone) or a distinct odor (carvone; orange), mice exhibited conditioned attraction to acetophenone. For the artificial odor memory, photostimulation of the M72 olfactory glomerulus was paired with photostimulation of laterodorsal tegmental nucleus inputs into the VTA. When mice were subsequently tested, they approached (rather than avoided) the M72 odorant acetophenone (green), even though they had never had never encountered this odor previously.

Accessibility of engrams

The studies reviewed so far indicate that it is possible to both disrupt and to mimic ecphory by directly manipulating the activity of neuronal ensembles that were active during encoding. However, they do not address Tulving’s distinction between engram accessibility versus availability. Another category of studies speaks to this distinction, aiming to recover apparently ‘lost’ memories via direct optogenetic stimulation of the tagged engram. By doing so, these studies shed light on the biological mechanisms that distinguish whether a memory can be accessed in principle or not (i.e., when it is unavailable).

In one experiment, Ryan and colleagues 30 tagged neuronal ensembles in either the DG or CA1 region of the hippocampus that were activated during contextual fear conditioning. Immediately following training, mice were treated with the protein synthesis inhibitor anisomycin and were tested 1 day later by returning mice to the training context. As expected, protein synthesis inhibition impaired consolidation and prevented subsequent memory expression. Despite this apparent amnesia in the presence of natural retrieval cues, however, optogenetic reactivation of the tagged neuronal ensemble enabled memory recovery 30 .

Similar recovery from amnesia has been observed across a range of conditions. For instance, following post-training protein synthesis inhibition, artificial engram reactivation in the DG or LA allows for recovery of place aversion or tone fear memories, respectively 30 , 34 . Moreover, memory recovery is not limited to amnestic states produced by protein synthesis inhibition during the consolidation period. Protein synthesis inhibition following natural memory retrieval blocks reconsolidation 35 , 36 , and this lost memory can be recovered via artificial engram reactivation 30 . Memory recovery has also been observed from other amnestic states, including in mouse models for studying Alzheimer’s disease 37 , 38 , infantile amnesia that naturally occurs in early development 39 , and following natural forgetting of social memories 40 .

These results suggest that the underlying engram corresponding to the presumably forgotten event is not completely erased or, using Tulving’s terminology, unavailable. Rather, these engrams exist in otherwise inaccessible states, in which natural retrieval cues (such as exposure to the training context) typically are not sufficient to induce successful ecphory and resulting memory expression. Engrams in this state have been termed ‘silent’ 37 . This is distinct from the notion of latent engrams introduced by Semon, which are both available and accessible through natural cues in principle, only not being accessed in the moment. By contrast, the silent engram is an in-between state: it is available, but nonetheless inaccessible by any natural means. Recent work shows that during engram formation, there is a specific increase in synapses between ‘engram cells’ 30 , 41 , 42 . Maintaining these enhanced synaptic connections may be key to their later accessibility, as evidence suggests that weakening synaptic connections among the neurons of the critical ensembles and, additionally, between these ensembles and downstream regions, is associated with engram silencing 30 , 34 , 37 . Direct photostimulation of the silent engram may temporarily reinstate these weakened connections, leading to memory recovery.

While photostimulation of silent engrams induces memory expression, memory recovery is only transient: freezing behavior is typically only observed during photostimulation 30 , 34 , 37 – 40 . The absence of memory expression in the light-off epochs suggests that the engram remained inaccessible by natural cues. Might interventions that permanently reinstate connectivity shift an engram from a silent state back into a latent state, where it is available and accessible through natural cues? A number of strategies have been used to address this question. For instance, spine density is reduced on DG and CA1 neurons in mouse models for Alzheimer’s disease. High-frequency photostimulation of perforant path afferents (i.e., ‘opto-LTP’) restores spine density on these engram cells, as well as their connectivity to downstream targets (for example, in CA3 and BLA). Critically, in these experiments, presentation of natural cues (i.e., the training context) was now sufficient to induce memory expression in tests performed several days later, suggesting that the opto-LTP intervention had successfully transformed the engram from a silent to latent state 37 . Similarly, overexpression of a dominant active form of PAK1 in experience-tagged CA1 neurons restores spine density and allows memories lost through protein synthesis inhibition to be recovered by natural cues 34 . In related work, Nabavi and colleagues 43 demonstrated that it was possible to modulate engram accessibility by manipulating the strength of synaptic inputs to the LA using opto-LTP (long-term potentiation) and opto-LTD (long-term depression) protocols.

The general picture emerging from this work is that engrams can differ in their degree of accessibility ( Fig. 4 ) and that changes in accessibility reflect underlying changes in synaptic organization. Silent engrams are unique in that they can only be accessed by artificial means. The silent state may be transitional and mark the boundary between lack of engram accessibility and availability.

Engrams exist in a dormant state (where natural retrieval cues induce engram activation and successful retrieval), a silent state (where only direct optogenetic engram activation induces successful retrieval) and an unavailable state (where all information has been lost, and the memory is inaccessible regardless of the nature of access attempts). Transitions from dormant → silent→ unavailable likely reflect forgetting mechanisms (for example, weakening and loss of synaptic connectivity among engram cells or the addition of new connectivity as a consequence of neurogenesis). LTD, long-term depression.

Above we discussed the fact that some seemingly lost memories may simply be inaccessible by natural cues. Are some memories entirely unavailable? This is a difficult, if not impossible, question to answer. To the extent that any testing involves exploration with a finite number of cues, it is always a possibility that successful memory recovery could be achieved with cues that were not tested 44 . Similarly, failure to recover memories with optogenetic stimulation of tagged ensembles might simply reflect failure to test all stimulation protocols. Methods allowing for unambiguous labeling of specific engrams might one day offer researchers the unique opportunity to determine whether an engram has completely disappeared and is truly unavailable. While there are indeed techniques that allow permanent labeling of different components of engrams (for example, at the neuronal ensemble level 45 or synapse level 41 ), it is not clear at what point one could conclude that the absence of a marker indicates that the engram is completely gone. There might always be other markers that could point to remnants of the engram.

That being said, a large body of research shows that forgetting curves have canonical forms that ultimately approach zero (performance level) across whichever behavioral assessments are employed. Recent studies have identified a variety of active forgetting mechanisms at the neurobiological level, including dopamine-initiated signaling cascades, receptor trafficking and hippocampal neurogenesis, all of which could lead to erosion of the engram 46 – 48 . While this line of research is still in its infancy, this class of mechanisms may be of the kind that leads to silencing, ultimately rendering the engram unavailable over the course of forgetting, regardless of the nature of access attempts.

Retrieval as neuronal reinstatement

Recognition of the important distinction between accessibility and availability in cognitive psychology, which began with Tulving and Pearlstone’s findings 1 , led to critical insights on the relationship between encoding and retrieval. To understand what constitutes an effective retrieval cue, it is necessary to consider how the engram was initially formed. Specifically, Tulving and Thomson 49 hypothesized that an engram is shaped by environmental features and internal cognitive or affective states during encoding. In turn, they argued, retrieval cues can only be successful to the extent that they overlap with these environmental features and internal states: that is, the greater the match between encoding and retrieval states, the higher the probability of retrieval success, a principle they termed ‘encoding specificity’. At the behavioral level, evidence in human and nonhuman species suggests that reinstatement of encoding context at the time of retrieval boosts recovery of information acquired in this context 50 – 52 . In fear conditioning, such context specificity provides the organism with adaptive flexibility, ensuring that expression of conditioned fear is usually limited to the training context (or very similar contexts) 53 , 54 .

In contemporary functional neuroimaging and recording studies in humans, the encoding specificity principle has been linked to neuronal reinstatement. Research asking to what extent neural activity patterns at encoding and retrieval overlap provides evidence for spatial and temporal forms of reinstatement that supports this principle 55 – 62 . Moreover, such studies reveal that the extent of this overlap impacts success and phenomenological attributes of retrieval. For instance, in visual cortex, increasing activation overlap predicts memory vividness during retrieval 63 . Interestingly, retrieval success may depend on concurrent hippocampal engagement, not only during encoding 64 but also during retrieval 65 , 66 , with the latter perhaps reflecting a pivotal role of the hippocampus in pattern completion. The importance of neuronal reinstatement for context-specific retrieval has been demonstrated in work showing that its behavioral benefits are most pronounced when encoding and retrieval context match 67 .

The encoding specificity principle can also be evaluated in rodent studies in which cue-induced reactivation of neuronal ensembles active at encoding is examined at the cellular level. Initial work took advantage of a method that images the subcellular location of mRNA for the immediate early gene Arc , catFISH (cellular compartment analysis of temporal activity by fluorescent in situ hybridization), as a way to identify active neurons at two distinct time points. In this experiment 68 , rats were exposed consecutively to either identical (‘AA’ condition) or different (‘AB’ condition) environments, and neuronal ensembles activated by each exposure were assessed. In hippocampal CA1, higher levels of overlap in the AA, compared to the AB, condition suggested that retrieval re-engaged the neuronal ensemble active during initial encoding. While this study did not examine a behavioral readout of memory, subsequent studies linked behavioral expression of memory at retrieval to reactivation of the ensemble active at encoding using ensemble tagging approaches 12 – 14 , 25 , 69 – 72 . For instance, Reijmers and colleagues 13 trained mice in a tone fear conditioning paradigm. Subsequent replacement in the training context reactivated neurons in the basal amygdala at above chance rates. Crucially, the rate of reactivation predicted memory strength, supporting the idea that greater similarity between encoding and retrieval states is associated with greater probability of retrieval success 73 .

In agreement with results examining context specificity in human neuroimaging 67 , studies in rodents reveal that neuronal ensembles activated at retrieval show context specificity related to behavior 25 , 74 . In one study 74 , a tone was paired with footshock in context A during training. Rats were subsequently given extinction training in context B, and then the tone conditioned stimulus (CS) was presented both in the extinction context (context B) and a third, distinct context (context C). Consistent with the idea that extinction is context-specific, rats froze in context C but not in context B (the extinction context) in these tests. At the neuronal level, presentation of the same tone CSs activated distinct populations of neurons in the B and C contexts. Moreover, activation of these different neuronal populations was critical for context-specific expression of extinction 25 .

Given that natural retrieval cues reactivate neural ensembles active at encoding and that the rate of reactivation relates to the strength of memory expression, we can ask whether the same holds for artificially induced memory retrieval. Recent studies 30 , 34 have addressed this question. In these studies, during contextual fear conditioning, cells active in the CA3 and BLA were tagged. Posttraining, mice were administered a protein synthesis inhibitor to silence these engrams. As expected of a silent engram, no freezing was observed when the mice were placed back in the training context. However, optogenetic reactivation of the tagged DG cells produced freezing, and reactivation efficiency (i.e., the extent to which photostimulation induced reactivation of tagged encoding cells) predicted the strength of the artificially retrieved memory (i.e., freezing levels).

While many studies show that artificial reactivation of engrams induces memory expression, typically this expression is weaker than that evoked by natural cues. This finding is in agreement with the encoding specificity principle because it is unlikely that optogenetic stimulation fully recapitulates the state of the organism and the corresponding patterns of neural activity that occurred during encoding. While the local spatial features of activity patterns are preserved by optogenetic stimulation, temporal features are not faithfully reproduced. The development of holographic photostimulation approaches (that preserve both spatial and temporal patterning) may overcome this limitation of current optogenetic techniques 75 – 77 . In the future, closed-loop optogenetic systems could allow the recording and subsequent holographic reproduction of an endogenous ecphoric event 78 , 79 .

Although artificial engram manipulations are typically focal in nature, their effects may be more widespread. Experiences are encoded in hippocampal-cortical networks, and according to many contemporary accounts, the hippocampus plays a pivotal role both in the formation of memory as well as its recovery. At retrieval, the hippocampus is thought to reinstate patterns of activity in the cortex that were present at encoding 80 – 83 . Tanaka and colleagues 19 tested this idea by tagging CA1 neuronal ensembles that were active during contextual fear conditioning. Silencing these tagged hippocampal cells during retrieval impaired memory expression and, critically, reduced reactivation of tagged cortical ensembles.

Conversely, activation, rather than inhibition, of tagged hippocampal neurons reinstates patterns of cortical activity present at encoding. For instance, Guskjolen and colleagues 39 trained infant mice in contextual fear conditioning, tagging active ‘encoding’ ensembles with ChR2. When these mice were tested at later time points, they exhibited pronounced forgetting, a phenomenon resembling infantile amnesia in humans 84 . However, photostimulation of ChR2-tagged neurons in the DG induced memory recovery and reactivation of CA3, CA1 and cortical neurons that were tagged during training.

These types of findings support the idea that some engrams are distributed, spanning neuronal ensembles across subcortical and cortical brain regions 85 . Within this distributed network, each region may carry unique information about the encoded episode (for example, sensory, affective, spatial information), and the route by which network activation is triggered likely impacts phenomenological aspects of memory retrieval. The finding that activation of the hippocampus is essential for reinstating patterns of activity in the cortex that occurred during encoding (as also suggested by human neuroimaging studies 65 , 66 ) additionally supports the view that the hippocampus is a critical hub within these distributed networks. However, it is unlikely that this region is the only hub with a critical role in reinstatement of neuronal states during retrieval 32 , 86 . Moreover, which regions serve as hubs likely changes over time, reflecting ongoing processes that modify the engram after initial memory formation, including consolidation and transformation 87 , 88 .

Equivalency

Artificially reactivating a naturally formed engram induces memory expression. But is ecphory induced by artificial means equivalent to natural ecphory? Next, we highlight four aspects of equivalency between artificially and naturally induced memories.

First, a naturally retrieved memory can serve as a CS for new learning 89 . A study by Ramirez and colleagues 71 tested whether an artificially retrieved memory can similarly support new learning. In this experiment, neuronal ensembles activated by placing a mouse in a neutral context (context A) were tagged with ChR2. One day later, mice were foot-shocked in a second context (context B) while the tagged neuronal ensemble in the DG (corresponding to context A) was simultaneously reactivated. In subsequent testing, mice froze in context A (but not in a dissimilar context, C), even though context A had never been paired with footshock. A study by Ohkawa and colleagues 90 went further. They used similar approaches to separately tag hippocampal and amygdala ensembles corresponding to context exposure (CS) and shock exposure (unconditioned stimulus, US), respectively. To create an artificial association between these ensembles corresponding to otherwise discontiguous events, the tagged CS and US ensembles were synchronously reactivated in the mouse’s home cage. Remarkably, when later placed in the original context, mice now froze even though they had never received a shock in this context.

Second, naturally retrieved memories extinguish. Repeated CS presentations in the absence of US lead to reduced conditioned responding. Khalaf and colleagues 70 asked whether artificially retrieved fear memories similarly extinguish. To do this, they tagged hippocampal ensembles that were activated when mice were placed in a training context that had previously been paired with footshock. Repeated exposure to this training context led to a reduction in freezing behavior (i.e., extinction). However, reactivating the tagged hippocampal ensembles during extinction training accelerated extinction. Conversely, silencing this same population during extinction training slowed extinction. Recently, a related study tagged dorsal hippocampal ensembles during contextual fear conditioning. They then found that repeated, artificially induced retrieval, even in the absence of exposure to the training context, induced extinction of the contextual fear memory 91 .

Third, naturally retrieved memories reconsolidate. Retrieval destabilizes engrams, and protein synthesis is necessary for their restabilization (a process termed reconsolidation). Kim and colleagues 28 asked whether a reconsolidation-like process occurs following artificially induced memory retrieval. In their experiment, CREB-overexpressing neurons in the LA were allocated to a tone fear memory during training. Artificially reactivating this allocated ensemble induced memory expression. However, pharmacological blockade of protein synthesis following artificial induction of ecphory impaired reconsolidation: when subsequently presented with the tone (i.e., the natural cue), mice treated with the protein synthesis inhibitor showed memory disruption. These results indicate that either artificial or natural retrieval destabilizes engrams, leading to the requirement for protein synthesis for their subsequent restabilization.

Fourth, naturally retrieved memories are subject to interference. If similar events are encountered either before or following the event in question, recovery of this target event can be compromised. That is, the ‘wrong’ (i.e., non-target) event or a merged event that combines the target and a similar lures could be recovered 92 . A similar phenomenon was observed following artificially induced retrieval in mice. Garner and colleagues 93 tagged neuronal ensembles activated by exposure to a neutral context (context A) with the excitatory designer receptor exclusively activated by designer drug (DREADD) hM3Di. Mice were subsequently trained in a second context (context B) and tested 24 h later in the same context (context B). Chemogenetic activation of the context A ensemble while testing in context B reduced freezing levels, suggesting that reactivating the ‘wrong’ event interfered with natural cue-induced retrieval of the context A memory.

Retrieval over time: future challenges

This Review highlights the considerable progress made in gaining mechanistic insight into the process of memory retrieval at the biological level. This progress has been enabled by the development of new technologies that allow engrams to be visualized and manipulated in rodents at the level of neuronal ensembles. Combining this increased understanding of engrams with the cognitive theory developed by Endel Tulving 2 permitted us to interpret contemporary research findings with respect to two major themes. First, when viewed in total, neurobiological findings support the cognitive theory that engram accessibility and memory retrieval success critically depend on interactions between engrams and retrieval cues (environmental or artificial). Second, the data also support the close ties between forming of engrams and their recovery, as captured by the notion of encoding specificity. However, the neurobiological study of retrieval is still in its infancy, and many important questions remain unanswered. We emphasize some of the most pressing issues in this remaining section.

Broadly speaking there is a dearth of knowledge as to how processes operating on engrams after their formation influence mechanisms of retrieval. Post-formation changes to the engram can be considered at two levels 87 . First, an engram for an individual episode or event changes over time. Second, multiple engrams (of distinct events or for the same re-encoded event) may interact. We assume that both types of change, which are likely not independent and are often considered together under the broad umbrella of systems consolidation, affect mechanisms of retrieval.

Psychological research suggests that forgetting is not indiscriminate and typically preserves gist over detail in the retention of events (for example, ref. 94 ). It has been argued that this property is adaptive, with gist being particularly important when using memory to guide future behavior and make related predictions 95 . Currently, it is unclear how these dynamics and resulting changes in engram organization affect the neural mechanisms of retrieval. A shift toward more gist-like representation likely occurs hand-in-hand with large-scale shifts in network engagement during retrieval. For example, it has been proposed that retrieval of a gist-based representation (lacking episodic detail) may increasingly engage cortical regions over time, and, furthermore, hippocampal integrity may not be required for its retrieval 96 . At the level of neuronal ensembles, this shift toward more gist-like representation may involve partial silencing of hippocampal engrams. One recent study in mice 97 labeled cells active during contextual fear conditioning in DG and medial prefrontal cortex (mPFC). When placed back in the context 1 day after training, only the DG engram was reactivated (whereas the mPFC engram was not). However, when tested 12 days after training, the mPFC engram, but not the DG engram, was engaged. Nonetheless, optogenetic stimulation of the DG engram (at the remote time point) or the mPFC engram (at the recent time point), respectively, induced artificial memory expression in an alternate context 97 . These changes can be understood as region-specific shifts in engram accessibility (rather than availability) 98 , which may go hand-in-hand with changes in the specificity of the memory expressed in behavior.

Beyond the fate of individual engrams, interactions between engrams may also influence subsequent memory retrieval. Indeed, there is a rich cognitive neuroscience literature focusing on the extraction of regularities across multiple experiences 99 and the resulting changes in network engagement during retrieval. Data addressing this question at the level of neuronal ensembles, however, are only beginning to emerge. An initial study by Rashid and colleagues 21 revealed that the engrams underlying two events experienced within a short period of time (<6 h) engage overlapping engrams and serve to link the two events, such that recall of one event produces recall of the other. In contrast, engrams supporting the same two events experienced with a longer intervening time (24 h) engage non-overlapping neural ensembles, and these events are remembered separately. Moreover, recalling an older event in the hours before experiencing a new event also links the two memories. Although these findings were initially reported for auditory fear memories and neural ensembles in the LA, other groups reported similar findings in the hippocampus supporting two context memories 100 and a conditioned fear and conditioned taste aversion memory in the LA 101 . These findings provide evidence supporting the notion that once formed, engrams do not persist in isolation. However, as of yet the findings do not offer any insight that directly speaks to consequences for mechanisms engaged during retrieval.

One outcome of the extraction of regularities across multiple experiences is the development of schemas 102 . Schemas have received much attention in psychological research on retrieval, but have only recently been studied using neurobiological methods, albeit with promising initial results 103 , 104 . How schemas are organized at the level of neuronal ensembles, however, remains uncharted territory. It has been argued that the availability of a schema qualitatively changes the retrieval process; rather than directly accessing an engram, retrieval involves the reconstruction of a specific episode based on schema knowledge derived from multiple experiences 105 . It is difficult to determine, in particular for remote memories, the extent to which neuronal activity during retrieval reflects such reconstruction vs true engram reactivation 106 , 107 .

Here we have reviewed the current state of knowledge on the mechanisms of memory retrieval at the level of neuronal ensembles. Although recent progress in developing techniques for identifying and manipulating engrams at the level of neuronal ensembles has increased our understanding of engrams in the rodent brain, our understanding of the neurobiological underpinnings of retrieval remains rudimentary Guided by cognitive theories of ecphory, here we integrated and interpreted the findings of several studies taking advantage of the ability to tag and manipulate engrams. We hope this will spur further neuroscientific research into mechanisms underlying retrieval.

Acknowledgements

We thank A.Ramsaran and A.Park for drawing the figures, and we thank T. Ryan for comments on an earlier draft of this manuscript. This work was supported by Canadian Institutes of Health Research grants to P.W.F. (FDN-143227) and S.A.J. (FDN-388455) and a Natural Sciences and Engineering Research Council Discovery grant to S.K. (RGPIN-5770).

Competing interests

The authors declare no competing interests.

Peer review information Nature Neuroscience thanks Stephen Maren and Steve Ramirez for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Memory Topic Essays for AQA A-Level Psychology

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A set of 10 exemplar Topic Essays for the AQA A-Level Psychology Memory topic.

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This set of 10 essays demonstrates how to write a top mark band response to a range of questions for the Memory topic, covering the entire specification.

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Understanding Developmental Psychology

Physical, Cognitive, Emotional, and Social Development Through the Lifespan

• What is Developmental Psychology

When to See a Developmental Psychologist

Frequently asked questions.

Change is inevitable. As humans, we constantly grow throughout our lifespans, from conception to death (or 'womb to tomb'). The field of developmental psychology explores the physical, cognitive, emotional, and social changes that happen as people age.

Psychologists strive to understand and explain how and why people change throughout life. While many of these changes are normal and expected, they can still pose challenges that people sometimes need extra assistance to manage.

The principles of normative development with specific milestones help professionals spot potential problems and provide early intervention for better outcomes. Developmental psychologists can work with people of all ages to address roadblocks and support growth. However, some choose to specialize in a specific age group, such as childhood, adulthood, or old age.

Lifespan Development: How We Grow and Change Over the Years

Developmental psychology is the branch of psychology that focuses on how people grow and change over the course of a lifetime.

Those who specialize in this field are not just concerned with the physical changes that occur as people grow; they also look at the cognitive, emotional, and social development that occurs throughout life.

Some of the many issues developmental psychologists assist with include:

• Cognitive development during childhood and throughout life
• Developmental challenges and learning disabilities
• Emotional development
• Language acquisition
• Moral reasoning
• Motor skill development
• Personality development
• Self-awareness and self-concept
• Social and cultural influences on child development

These professionals spend a great deal of time investigating and observing how these processes occur under normal circumstances. Still, they are also interested in learning about things that can disrupt developmental processes.

By better understanding how and why people change and grow, developmental psychologists help people live up to their full potential. Understanding the course of normal human development and recognizing potential problems early on can prevent difficulties with depression, low self-esteem, frustration, and poor achievement in school or work.

Developmental Psychology Theories

Developmental psychologists often consider a wide array of theories to consider different aspects of human development. A few examples are listed below:

• Cognitive development. A psychologist assessing intellectual growth in a child might consider Jean Piaget's theory of cognitive development , which outlines the key stages children go through as they grow and learn.
• Attachment . A psychologist working with a child might also want to consider how the child's relationships with caregivers influence their behaviors, so they might turn to John Bowlby's theory of attachment .
• Personality . Sigmund Freud's psychosexual theory of personality development is another influential theory that explains the importance of childhood experiences on personality development and how maladaptive coping styles and defense mechanisms emerge.
• Social and emotional growth. Psychologists are also interested in looking at how social relationships influence children's and adults' development. Erik Erikson's theory of psychosocial development and Lev Vygotsky's theory of sociocultural development are two popular theoretical frameworks that address the social influences on the developmental process.

Each approach tends to stress different aspects of development, such as mental, parental, social, or environmental influences on children's growth and progress .

Developmental Psychology Stages

As you might imagine, developmental psychologists often break down development according to various phases of life. Each of these periods of development represents a time when different milestones are typically achieved.

People may face particular challenges at each point, and developmental psychologists can often help people who might be struggling with problems to get back on track.

Prenatal Development

Developmental psychologists are interested in the prenatal period , seeking to understand how the earliest influences on development can impact later growth during childhood. They may examine how primary reflexes emerge before birth, how fetuses respond to stimuli in the womb, and the sensations and perceptions that fetuses are capable of detecting prior to birth.

Developmental psychologists may also look at potential problems such as Down syndrome, maternal drug use, and inherited diseases that might have an impact on the course of future development.

Early Childhood Development

The period from infancy through early childhood is a time of remarkable growth and change. Developmental psychologists examine the physical , cognitive , and socio-emotional growth during this critical development period.

In addition to providing interventions for potential developmental problems at this point, psychologists are also focused on helping kids achieve their full potential. Parents and healthcare experts are often on the lookout to ensure that kids are growing properly, receiving adequate nutrition, and achieving cognitive milestones appropriate for their age.

Middle Childhood Development

This period of development is marked by both physical maturation and the increased importance of social influences as children make their way through elementary school.

Kids begin to make their mark on the world as they build their unique sense of self , form friendships , grasp principles of logic , and gain competency through schoolwork and personal interests. Parents may seek the assistance of a developmental psychologist to help kids deal with potential problems that might arise at this age, including academic, social, emotional, and mental health issues.

Adolescent Development

The teenage years are often the subject of considerable interest as children experience the psychological turmoil and transition that often accompanies this period of development. Psychologists such as Erik Erikson were especially interested in looking at how navigating this period leads to identity formation .

At this age, kids often test limits and explore new identities as they question who they are and who they want to be. Developmental psychologists can help support teens as they deal with some of the challenging issues unique to the adolescent period, including puberty, emotional turmoil, and social pressure.

Early Adult Development

This period of life is often marked by forming and maintaining relationships. Critical milestones during early adulthood may include forming bonds, intimacy, close friendships, and starting a family and career.

Those who can build and sustain such relationships tend to experience connectedness and social support, while those who struggle with such relationships may feel alienated and lonely .

People facing such issues might seek the assistance of a developmental psychologist to build healthier relationships and combat emotional difficulties.

Middle Adult Development

This stage of life tends to center on developing a sense of purpose and contributing to society. Erikson described this as the conflict between generativity and stagnation .

Those who engage in the world, contribute things that will outlast them, and leave a mark on the next generation emerge with a sense of purpose. Activities such as careers, families, group memberships, and community involvement are all things that can contribute to this feeling of generativity.

Older Adult Development

The senior years are often viewed as a period of poor health, yet many older adults can remain active and busy well into their 80s and 90s. Increased health concerns mark this period of development, and some individuals may experience mental declines related to dementia.

Theorist Erik Erikson also viewed the elder years as a time of reflecting back on life . Those who can look back and see a life well-lived emerge with a sense of wisdom and readiness to face the end of their lives, while those who look back with regret may be left with feelings of bitterness and despair.

Developmental psychologists may work with elderly patients to help them cope with issues related to the aging process.

While development tends to follow a fairly predictable pattern, there are times when things might go off course. Parents often focus on what are known as developmental milestones, which represent abilities that most children tend to display by a certain point in development. These typically focus on each of four main areas:

• Physical milestones
• Cognitive milestones, including language development
• Emotional milestones
• Social milestones

For example, walking is one physical milestone most children achieve between 9 and 15 months. If a child is not walking or attempting to walk by 16 to 18 months, parents might consider consulting with their family physician to determine if a developmental issue might be present.

While all children develop at different rates, when a child fails to meet certain milestones by a certain age, there may be cause for concern.

By being aware of these milestones, parents can seek assistance, and healthcare professionals can offer interventions to help kids overcome developmental delays.

These professionals often evaluate children to determine if a developmental delay might be present, or they might work with elderly patients who are facing health concerns associated with old age, such as cognitive declines, physical struggles, emotional difficulties, or degenerative brain disorders.

Developmental psychologists can support individuals at all stages of life who may be facing developmental issues or problems related to aging.

Diagnosing Developmental Issues

To determine if a developmental problem is present, a psychologist or other highly trained professional may administer a developmental screening or evaluation.

For children, such an evaluation typically involves interviews with parents and other caregivers to learn about behaviors they may have observed, a review of a child's medical history, and standardized testing to measure functioning in terms of physical and motor development, cognitive skills, language development and communication skills, and social/emotional skills.

If a problem is found, the patient may be referred to a specialist, such as a speech-language pathologist, physical therapist, or occupational therapist.

Coping With a Developmental Diagnosis

Receiving a diagnosis of a developmental issue can often feel both confusing and frightening, particularly when you, your own child, or an elderly parent is affected. Once you or your loved one has received a diagnosis of a developmental issue, spend some time learning as much as you can about the diagnosis and available treatments.

Prepare a list of questions and concerns you may have and discuss these issues with your doctor, developmental psychologist, and other healthcare professionals who may be part of the treatment team. By taking an active role in the process, you will feel better informed and equipped to tackle the next steps in the treatment process.

The four major developmental psychology issues are focused on physical, cognitive, emotional, and social development.

The Eight major stages of development are:

• Prenatal development
• Infant development
• Early childhood development
• Middle childhood development
• Adolescent development
• Early adult development
• Middle adult development
• Older adult development

The principles of developmental psychology outlined by Paul Baltes suggest that development is (1) lifelong, (2) multidimensional, (3) multidirectional, (4) involves gains and losses, (5) plastic (malleable and adaptive), and (6) multidisciplinary. 

Four developmental issues that psychologists explore are focused on the relative contributions of:

• Nature vs. nurture : Is development primarily influenced by genetics or environmental factors?
• Early vs. later experience : Do early childhood events matter more than events that happen later in life?
• Continuity vs discontinuity : Is developmental change a gradual process, or do changes happen suddenly and follow a specific course?
• Abnormal behavior vs. individual differences : What represents abnormal development, and what can be considered individual variations in development?

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Vygotsky LS.  Play and its role in the mental development of the child .  International Research in Early Childhood Education . 2016;7(2):3-25.

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Keenan T, Evans S. An Introduction to Child Development . 2nd ed. SAGE; 2009.

Whitebread D, Grau V, Kumpulainen K, McClelland MM, Perry NE, Pino-Pasternak D.  The Sage Handbook of Developmental Psychology and Early Childhood Education . SAGE Publications Ltd; 2019. doi:10.4135/9781526470393

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."