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Ch 7: Memory

Memory (Encoding, Storage, Retrieval)

We may be top-notch learners, but if we don’t have a way to store what we’ve learned, what good is the knowledge we’ve gained?

Take a few minutes to imagine what your day might be like if you could not remember anything you had learned. You would have to figure out how to get dressed. What clothing should you wear, and how do buttons and zippers work? You would need someone to teach you how to brush your teeth and tie your shoes. Who would you ask for help with these tasks, since you wouldn’t recognize the faces of these people in your house? Wait . . . is this even your house? Uh oh, your stomach begins to rumble and you feel hungry. You’d like something to eat, but you don’t know where the food is kept or even how to prepare it. Oh dear, this is getting confusing. Maybe it would be best just go back to bed. A bed . . . what is a bed?

We have an amazing capacity for memory, but how, exactly, do we process and store information? Are there different kinds of memory, and if so, what characterizes the different types? How, exactly, do we retrieve our memories? And why do we forget? This chapter will explore these questions as we learn about memory.

“ Memory ” is a single term that reflects a number of different abilities: holding information briefly while working with it (working memory), remembering episodes of one’s life (episodic memory), and our general knowledge of facts of the world (semantic memory), among other types. Remembering episodes involves three processes: encoding information (learning it, by perceiving it and relating it to past knowledge), storing it (maintaining it over time), and then retrieving it (accessing the information when needed). Failures can occur at any stage, leading to forgetting or to having false memories. The key to improving one’s memory is to improve processes of encoding and to use techniques that guarantee effective retrieval. Good encoding techniques include relating new information to what one already knows, forming mental images, and creating associations among information that needs to be remembered. The key to good retrieval is developing effective cues that will lead the rememberer back to the encoded information.

Learning Objectives

In this chapter, you will

• Define and note differences between the following forms of memory: working memory, episodic memory, semantic memory, collective memory.
• Describe the three stages in the process of learning and remembering.
• Describe strategies that can be used to enhance the original learning or encoding of information.
• Describe strategies that can improve the process of retrieval.
• Explain the brain functions involved in memory; recognize the roles of the hippocampus, amygdala, and cerebellum in memory

Our memory has three basic functions: encoding, storing, and retrieving information. Encoding is the act of getting information into our memory system through automatic or effortful processing. Storage is retention of the information, and retrieval is the act of getting information out of storage and into conscious awareness through recall, recognition, and relearning. There are various models that aim to explain how we utilize our memory. In this section, you’ll learn about some of these models as well as the importance of recall, recognition, and relearning.

To get a good overview of all of these concepts and to pique your interest, you may choose to begin this module by watching John Gabrieli’s lecture on memory. Listen for some key vocabulary terms you’ll learn about soon, particularly:

• the three-stage model of memory
• short-term memory
• serial position effect
• Ebbinghaus forgetting curve
• proactive interference
• retroactive interference
• flashbulb memories
• false memories

You can view the transcript for “Lec 10 | MIT 9.00SC Introduction to Psychology, Spring 2011” here (opens in new window) .

How Memory Functions

• Explain the three types of encoding
• Describe the three stages of memory storage
• Describe and distinguish between procedural and declarative memory and semantic and episodic memory
• Explain retrieval cues and define recall, recognition, and relearning

Varieties of Memory

For most of us, remembering digits relies on short-term memory , or working memory —the ability to hold information in our minds for a brief time and work with it (e.g., multiplying 24 x 17 without using paper would rely on working memory). Another type of memory is episodic memory —the ability to remember the episodes of our lives. If you were given the task of recalling everything you did 2 days ago, that would be a test of episodic memory; you would be required to mentally travel through the day in your mind and note the main events. Semantic memory is our storehouse of more-or-less permanent knowledge, such as the meanings of words in a language (e.g., the meaning of “parasol”) and the huge collection of facts about the world (e.g., there are 196 countries in the world, and 206 bones in your body). Both of these types of memory are considered long-term memory.  Collective memory refers to the kind of memory that people in a group share (whether family, community, schoolmates, or citizens of a state or a country). For example, residents of small towns often strongly identify with those towns, remembering the local customs and historical events in a unique way. That is, the community’s collective memory passes stories and recollections between neighbors and to future generations, forming a memory system unto itself.

Psychologists continue to debate the classification of types of memory, as well as which types rely on others (Tulving, 2007), but for this module we will focus on episodic memory. Episodic memory is usually what people think of when they hear the word “memory.” For example, when people say that an older relative is “losing her memory” due to Alzheimer’s disease, the type of memory-loss they are referring to is the inability to recall events, or episodic memory. (Semantic memory is actually preserved in early-stage Alzheimer’s disease.) Although remembering specific events that have happened over the course of one’s entire life (e.g., your experiences in sixth grade) can be referred to as autobiographical memory , we will focus primarily on the episodic memories of more recent events.

Three Stages of the Learning/Memory Process

Psychologists distinguish between three necessary stages in the learning and memory process: encoding , storage , and retrieval (Melton, 1963). Encoding is defined as the initial learning of information; storage refers to maintaining information over time; retrieval is the ability to access information when you need it. If you meet someone for the first time at a party, you need to encode her name (Lyn Goff) while you associate her name with her face. Then you need to maintain the information over time. If you see her a week later, you need to recognize her face and have it serve as a cue to retrieve her name. Any successful act of remembering requires that all three stages be intact. However, two types of errors can also occur. Forgetting is one type: you see the person you met at the party and you cannot recall her name. The other error is misremembering (false recall or false recognition): you see someone who looks like Lyn Goff and call the person by that name (false recognition of the face). Or, you might see the real Lyn Goff, recognize her face, but then call her by the name of another woman you met at the party (misrecall of her name).

Whenever forgetting or misremembering occurs, we can ask, at which stage in the learning/memory process was there a failure?—though it is often difficult to answer this question with precision. One reason for this inaccuracy is that the three stages are not as discrete as our description implies. Rather, all three stages depend on one another. How we encode information determines how it will be stored and what cues will be effective when we try to retrieve it. And too, the act of retrieval itself also changes the way information is subsequently remembered, usually aiding later recall of the retrieved information. The central point for now is that the three stages—encoding, storage, and retrieval—affect one another, and are inextricably bound together.

Memory is an information processing system; therefore, we often compare it to a computer. Memory is the set of processes used to encode, store, and retrieve information over different periods of time.

Encoding refers to the initial experience of perceiving and learning information. Psychologists often study recall by having participants study a list of pictures or words. Encoding in these situations is fairly straightforward. However, “real life” encoding is much more challenging. When you walk across campus, for example, you encounter countless sights and sounds—friends passing by, people playing Frisbee, music in the air. The physical and mental environments are much too rich for you to encode all the happenings around you or the internal thoughts you have in response to them. So, an important first principle of encoding is that it is selective: we attend to some events in our environment and we ignore others. A second point about encoding is that it is prolific; we are always encoding the events of our lives—attending to the world, trying to understand it. Normally this presents no problem, as our days are filled with routine occurrences, so we don’t need to pay attention to everything. But if something does happen that seems strange—during your daily walk across campus, you see a giraffe—then we pay close attention and try to understand why we are seeing what we are seeing.

Right after your typical walk across campus (one without the appearance of a giraffe), you would be able to remember the events reasonably well if you were asked. You could say whom you bumped into, what song was playing from a radio, and so on. However, suppose someone asked you to recall the same walk a month later. You wouldn’t stand a chance. You would likely be able to recount the basics of a typical walk across campus, but not the precise details of that particular walk. Yet, if you had seen a giraffe during that walk, the event would have been fixed in your mind for a long time, probably for the rest of your life. You would tell your friends about it, and, on later occasions when you saw a giraffe, you might be reminded of the day you saw one on campus. Psychologists have long pinpointed distinctiveness—having an event stand out as quite different from a background of similar events—as a key to remembering events (Hunt, 2003).

What are the most effective ways to ensure that important memories are well encoded? Even a simple sentence is easier to recall when it is meaningful (Anderson, 1984). Read the following sentences (Bransford & McCarrell, 1974), then look away and count backwards from 30 by threes to zero, and then try to write down the sentences (no peeking back at this page!).

• The notes were sour because the seams split.
• The voyage wasn’t delayed because the bottle shattered.
• The haystack was important because the cloth ripped.

How well did you do? By themselves, the statements that you wrote down were most likely confusing and difficult for you to recall. Now, try writing them again, using the following prompts: bagpipe, ship christening (shattering a bottle over the bow of the ship is a symbol of good luck), and parachutist. Next count backwards from 40 by fours, then check yourself to see how well you recalled the sentences this time. You can see that the sentences are now much more memorable because each of the sentences was placed in context. Material is far better encoded when you make it meaningful.

There are three types of encoding. The encoding of words and their meaning is known as semantic encoding . It was first demonstrated by William Bousfield (1935) in an experiment in which he asked people to memorize words. The 60 words were actually divided into 4 categories of meaning, although the participants did not know this because the words were randomly presented. When they were asked to remember the words, they tended to recall them in categories, showing that they paid attention to the meanings of the words as they learned them.

Visual encoding is the encoding of images, and acoustic encoding  is the encoding of sounds, words in particular. To see how visual encoding works, read over this list of words: car, level, dog, truth, book, value . If you were asked later to recall the words from this list, which ones do you think you’d most likely remember? You would probably have an easier time recalling the words car, dog, and book , and a more difficult time recalling the words level, truth, and value . Why is this? Because you can recall images (mental pictures) more easily than words alone. When you read the words car, dog, and book you created images of these things in your mind. These are concrete, high-imagery words. On the other hand, abstract words like level, truth, and value are low-imagery words. High-imagery words are encoded both visually and semantically (Paivio, 1986), thus building a stronger memory.

Now let’s turn our attention to acoustic encoding. You are driving in your car and a song comes on the radio that you haven’t heard in at least 10 years, but you sing along, recalling every word. In the United States, children often learn the alphabet through song, and they learn the number of days in each month through rhyme: “ Thirty days hath September, / April, June, and November; / All the rest have thirty-one, / Save February, with twenty-eight days clear, / And twenty-nine each leap year.” These lessons are easy to remember because of acoustic encoding. We encode the sounds the words make. This is one of the reasons why much of what we teach young children is done through song, rhyme, and rhythm.

Which of the three types of encoding do you think would give you the best memory of verbal information? Some years ago, psychologists Fergus Craik and Endel Tulving (1975) conducted a series of experiments to find out. Participants were given words along with questions about them. The questions required the participants to process the words at one of the three levels. The visual processing questions included such things as asking the participants about the font of the letters. The acoustic processing questions asked the participants about the sound or rhyming of the words, and the semantic processing questions asked the participants about the meaning of the words. After participants were presented with the words and questions, they were given an unexpected recall or recognition task.

Words that had been encoded semantically were better remembered than those encoded visually or acoustically. Semantic encoding involves a deeper level of processing than the shallower visual or acoustic encoding. Craik and Tulving concluded that we process verbal information best through semantic encoding, especially if we apply what is called the self-reference effect. The self-reference effect is the tendency for an individual to have better memory for information that relates to oneself in comparison to material that has less personal relevance (Rogers, Kuiper & Kirker, 1977). Could semantic encoding be beneficial to you as you attempt to memorize the concepts in this module?

The process of encoding is selective, and in complex situations, relatively few of many possible details are noticed and encoded. The process of encoding always involves recoding —that is, taking the information from the form it is delivered to us and then converting it in a way that we can make sense of it. For example, you might try to remember the colors of a rainbow by using the acronym ROY G BIV (red, orange, yellow, green, blue, indigo, violet). The process of recoding the colors into a name can help us to remember. However, recoding can also introduce errors—when we accidentally add information during encoding, then remember that new material as if it had been part of the actual experience (as discussed below).

Psychologists have studied many recoding strategies that can be used during study to improve retention. First, research advises that, as we study, we should think of the meaning of the events (Craik & Lockhart, 1972), and we should try to relate new events to information we already know. This helps us form associations that we can use to retrieve information later. Second, imagining events also makes them more memorable; creating vivid images out of information (even verbal information) can greatly improve later recall (Bower & Reitman, 1972). Creating imagery is part of the technique Simon Reinhard uses to remember huge numbers of digits, but we can all use images to encode information more effectively. The basic concept behind good encoding strategies is to form distinctive memories (ones that stand out), and to form links or associations among memories to help later retrieval (Hunt & McDaniel, 1993). Using study strategies such as the ones described here is challenging, but the effort is well worth the benefits of enhanced learning and retention.

We emphasized earlier that encoding is selective: people cannot encode all information they are exposed to. However, recoding can add information that was not even seen or heard during the initial encoding phase. Several of the recoding processes, like forming associations between memories, can happen without our awareness. This is one reason people can sometimes remember events that did not actually happen—because during the process of recoding, details got added. One common way of inducing false memories in the laboratory employs a word-list technique (Deese, 1959; Roediger & McDermott, 1995). Participants hear lists of 15 words, like door, glass, pane, shade, ledge, sill, house, open, curtain, frame, view, breeze, sash, screen, and shutter. Later, participants are given a test in which they are shown a list of words and asked to pick out the ones they’d heard earlier. This second list contains some words from the first list (e.g., door, pane, frame ) and some words not from the list (e.g., arm, phone, bottle ). In this example, one of the words on the test is window , which—importantly—does not appear in the first list, but which is related to other words in that list. When subjects were tested, they were reasonably accurate with the studied words ( door , etc.), recognizing them 72% of the time. However, when window was on the test, they falsely recognized it as having been on the list 84% of the time (Stadler, Roediger, & McDermott, 1999). The same thing happened with many other lists the authors used. This phenomenon is referred to as the DRM (for Deese-Roediger-McDermott) effect. One explanation for such results is that, while students listened to items in the list, the words triggered the students to think about window , even though window  was never presented. In this way, people seem to encode events that are not actually part of their experience.

Because humans are creative, we are always going beyond the information we are given: we automatically make associations and infer from them what is happening. But, as with the word association mix-up above, sometimes we make false memories from our inferences—remembering the inferences themselves as if they were actual experiences. To illustrate this, Brewer (1977) gave people sentences to remember that were designed to elicit pragmatic inferences . Inferences, in general, refer to instances when something is not explicitly stated, but we are still able to guess the undisclosed intention. For example, if your friend told you that she didn’t want to go out to eat, you may infer that she doesn’t have the money to go out, or that she’s too tired. With pragmatic inferences, there is usually one particular inference you’re likely to make. Consider the statement Brewer (1977) gave her participants: “The karate champion hit the cinder block.” After hearing or seeing this sentence, participants who were given a memory test tended to remember the statement as having been, “The karate champion broke the cinder block.” This remembered statement is not necessarily a logical inference (i.e., it is perfectly reasonable that a karate champion could hit a cinder block without breaking it). Nevertheless, the pragmatic conclusion from hearing such a sentence is that the block was likely broken. The participants remembered this inference they made while hearing the sentence in place of the actual words that were in the sentence (see also McDermott & Chan, 2006).

Encoding—the initial registration of information—is essential in the learning and memory process. Unless an event is encoded in some fashion, it will not be successfully remembered later. However, just because an event is encoded (even if it is encoded well), there’s no guarantee that it will be remembered later.

Once the information has been encoded, we somehow have to retain it. Our brains take the encoded information and place it in storage. Storage is the creation of a permanent record of information.

But A-S is just one model of memory. Others, such as Baddeley and Hitch (1974), have proposed a model where short-term memory itself has different forms. In this model, storing memories in short-term memory is like opening different files on a computer and adding information. The type of short-term memory (or computer file) depends on the type of information received. There are memories in visual-spatial form, as well as memories of spoken or written material, and they are stored in three short-term systems: a visuospatial sketchpad, an episodic buffer, and a phonological loop. According to Baddeley and Hitch, a central executive part of memory supervises or controls the flow of information to and from the three short-term systems.

Sensory Memory

In the Akinson-Shiffrin model , stimuli from the environment are processed first in sensory memory : storage of brief sensory events, such as sights, sounds, and tastes. It is very brief storage—up to a couple of seconds. We are constantly bombarded with sensory information. We cannot absorb all of it, or even most of it. And most of it has no impact on our lives. For example, what was your professor wearing the last class period? As long as the professor was dressed appropriately, it does not really matter what she was wearing. Sensory information about sights, sounds, smells, and even textures, which we do not view as valuable information, we discard. If we view something as valuable, the information will move into our short-term memory system.

One study of sensory memory researched the significance of valuable information on short-term memory storage. J. R. Stroop discovered a memory phenomenon in the 1930s: you will name a color more easily if it appears printed in that color, which is called the Stroop effect. In other words, the word “red” will be named more quickly, regardless of the color the word appears in, than any word that is colored red. Try an experiment: name the colors of the words you are given in Figure 7. Do not read the words, but say the color the word is printed in. For example, upon seeing the word “yellow” in green print, you should say “green,” not “yellow.” This experiment is fun, but it’s not as easy as it seems.

Short-Term Memory

Short-term memory (STM)  is a temporary storage system that processes incoming sensory memory; sometimes it is called working memory. Short-term memory takes information from sensory memory and sometimes connects that memory to something already in long-term memory. Short-term memory storage lasts about 20 seconds. George Miller (1956), in his research on the capacity of memory, found that most people can retain about 7 items in STM. Some remember 5, some 9, so he called the capacity of STM 7 plus or minus 2.

Think of short-term memory as the information you have displayed on your computer screen—a document, a spreadsheet, or a web page. Then, information in short-term memory goes to long-term memory (you save it to your hard drive), or it is discarded (you delete a document or close a web browser). This step of rehearsal , the conscious repetition of information to be remembered, to move STM into long-term memory is called   consolidation .

You may find yourself asking, “How much information can our memory handle at once?” To explore the capacity and duration of your short-term memory, have a partner read the strings of random numbers (Figure 8) out loud to you, beginning each string by saying, “Ready?” and ending each by saying, “Recall,” at which point you should try to write down the string of numbers from memory.

Note the longest string at which you got the series correct. For most people, this will be close to 7, Miller’s famous 7 plus or minus 2. Recall is somewhat better for random numbers than for random letters (Jacobs, 1887), and also often slightly better for information we hear (acoustic encoding) rather than see (visual encoding) (Anderson, 1969).

Long-term Memory

Long-term memory (LTM) is the continuous storage of information. Unlike short-term memory, the storage capacity of LTM has no limits. It encompasses all the things you can remember that happened more than just a few minutes ago to all of the things that you can remember that happened days, weeks, and years ago. In keeping with the computer analogy, the information in your LTM would be like the information you have saved on the hard drive. It isn’t there on your desktop (your short-term memory), but you can pull up this information when you want it, at least most of the time. Not all long-term memories are strong memories. Some memories can only be recalled through prompts. For example, you might easily recall a fact— “What is the capital of the United States?”—or a procedure—“How do you ride a bike?”—but you might struggle to recall the name of the restaurant you had dinner when you were on vacation in France last summer. A prompt, such as that the restaurant was named after its owner, who spoke to you about your shared interest in soccer, may help you recall the name of the restaurant.

Long-term memory is divided into two types: explicit and implicit (Figure 9). Understanding the different types is important because a person’s age or particular types of brain trauma or disorders can leave certain types of LTM intact while having disastrous consequences for other types. Explicit memories are those we consciously try to remember and recall. For example, if you are studying for your chemistry exam, the material you are learning will be part of your explicit memory. (Note: Sometimes, but not always, the terms explicit memory and declarative memory are used interchangeably.)

Implicit memories are memories that are not part of our consciousness. They are memories formed from behaviors. Implicit memory is also called non-declarative memory.

Procedural memory  is a type of implicit memory: it stores information about how to do things. It is the memory for skilled actions, such as how to brush your teeth, how to drive a car, how to swim the crawl (freestyle) stroke. If you are learning how to swim freestyle, you practice the stroke: how to move your arms, how to turn your head to alternate breathing from side to side, and how to kick your legs. You would practice this many times until you become good at it. Once you learn how to swim freestyle and your body knows how to move through the water, you will never forget how to swim freestyle, even if you do not swim for a couple of decades. Similarly, if you present an accomplished guitarist with a guitar, even if he has not played in a long time, he will still be able to play quite well.

Explicit memory has to do with the storage of facts and events we personally experienced. Explicit (declarative) memory has two parts: semantic memory and episodic memory. Semantic means having to do with language and knowledge about language. An example would be the question “what does argumentative mean?” Stored in our semantic memory is knowledge about words, concepts, and language-based knowledge and facts. For example, answers to the following questions are stored in your semantic memory:

• Who was the first President of the United States?
• What is democracy?
• What is the longest river in the world?

Episodic memory is information about events we have personally experienced. The concept of episodic memory was first proposed about 40 years ago (Tulving, 1972). Since then, Tulving and others have looked at scientific evidence and reformulated the theory. Currently, scientists believe that episodic memory is memory about happenings in particular places at particular times, the what, where, and when of an event (Tulving, 2002). It involves recollection of visual imagery as well as the feeling of familiarity (Hassabis & Maguire, 2007).

Everyday Connections: Can You Remember Everything You Ever Did or Said?

Episodic memories are also called autobiographical memories. Let’s quickly test your autobiographical memory. What were you wearing exactly five years ago today? What did you eat for lunch on April 10, 2019? You probably find it difficult, if not impossible, to answer these questions. Can you remember every event you have experienced over the course of your life—meals, conversations, clothing choices, weather conditions, and so on? Most likely none of us could even come close to answering these questions; however, American actress Marilu Henner, best known for the television show Taxi, can remember. She has an amazing and highly superior autobiographical memory (Figure 10).

Very few people can recall events in this way; right now, only 12 known individuals have this ability, and only a few have been studied (Parker, Cahill & McGaugh 2006). And although hyperthymesia normally appears in adolescence, two children in the United States appear to have memories from well before their tenth birthdays.

If you’re interested in learning more, watch these Part 1 and Part 2 video clips on superior autobiographical memory from the television news show 60 Minutes .

In this video, Hank Green explains several research studies that helped us better understand implicit memories.

You can view the transcript for “Why Is Riding a Bike “Just Like Riding a Bike?”” here (opens in new window) .

Think It Over

• Describe something you have learned that is now in your procedural memory. Discuss how you learned this information.
• Describe something you learned in high school that is now in your semantic memory.

So you have worked hard to encode (via effortful processing) and store some important information for your upcoming final exam. How do you get that information back out of storage when you need it? The act of getting information out of memory storage and back into conscious awareness is known as retrieval . This would be similar to finding and opening a paper you had previously saved on your computer’s hard drive. Now it’s back on your desktop, and you can work with it again. Our ability to retrieve information from long-term memory  is vital to our everyday functioning. You must be able to retrieve information from memory in order to do everything from knowing how to brush your hair and teeth, to driving to work, to knowing how to perform your job once you get there.

Memory Cues

What factors determine what information can be retrieved from memory? One critical factor is the type of hints, or cues , in the environment. You may hear a song on the radio that suddenly evokes memories of an earlier time in your life, even if you were not trying to remember it when the song came on. Nevertheless, the song is closely associated with that time, so it brings the experience to mind.

The general principle that underlies the effectiveness of retrieval cues is the encoding specificity principle  (Tulving & Thomson, 1973): when people encode information, they do so in specific ways. For example, take the song on the radio: perhaps you heard it while you were at a terrific party, having a great, philosophical conversation with a friend. Thus, the song became part of that whole complex experience. Years later, even though you haven’t thought about that party in ages, when you hear the song on the radio, the whole experience rushes back to you. In general, the encoding specificity principle states that, to the extent a retrieval cue (the song) matches or overlaps the memory trace of an experience (the party, the conversation), it will be effective in evoking the memory. A classic experiment on the encoding specificity principle had participants memorize a set of words in a unique setting. Later, the participants were tested on the word sets, either in the same location they learned the words or a different one. As a result of encoding specificity, the students who took the test in the same place they learned the words were actually able to recall more words (Godden & Baddeley, 1975) than the students who took the test in a new setting. In this instance, the physical context itself provided cues for retrieval. This is why it’s good to study for midterms and finals in the same room you’ll be taking them in.

One caution with this principle, though, is that, for the cue to work, it can’t match too many other experiences (Nairne, 2002; Watkins, 1975). Consider a lab experiment. Suppose you study 100 items; 99 are words, and one is a picture—of a penguin, item 50 in the list. Afterwards, the cue “recall the picture” would evoke “penguin” perfectly. No one would miss it. However, if the word “penguin” were placed in the same spot among the other 99 words, its memorability would be exceptionally worse. This outcome shows the power of distinctiveness : one picture is perfectly recalled from among 99 words because it stands out. Now consider what would happen if the experiment were repeated, but there were 25 pictures distributed within the 100-item list. Although the picture of the penguin would still be there, the probability that the cue “recall the picture” (at item 50) would be useful for the penguin would drop correspondingly. Watkins (1975) referred to this outcome as demonstrating the cue overload principle . That is, to be effective, a retrieval cue cannot be overloaded with too many memories. For the cue “recall the picture” to be effective, it should only match one item in the target set (as in the one-picture, 99-word case).

To sum up how memory cues function: for a retrieval cue to be effective, a match must exist between the cue and the desired target memory; furthermore, to produce the best retrieval, the cue-target relationship should be distinctive.

Types of Retrieval

There are three ways you can retrieve information out of your long-term memory storage system: recall, recognition, and relearning. Recall  is what we most often think about when we talk about memory retrieval: it means you can access information without cues. For example, you would use recall for an essay test. Recognition happens when you identify information that you have previously learned after encountering it again. It involves a process of comparison. When you take a multiple-choice test, you are relying on recognition to help you choose the correct answer. Here is another example. Let’s say you graduated from high school 10 years ago, and you have returned to your hometown for your 10-year reunion. You may not be able to recall all of your classmates, but you recognize many of them based on their yearbook photos.

The third form of retrieval is relearning , and it’s just what it sounds like. It involves learning information that you previously learned. Whitney took Spanish in high school, but after high school she did not have the opportunity to speak Spanish. Whitney is now 31, and her company has offered her an opportunity to work in their Mexico City office. In order to prepare herself, she enrolls in a Spanish course at the local community center. She’s surprised at how quickly she’s able to pick up the language after not speaking it for 13 years; this is an example of relearning.

Recall and Recognition

Psychologists measure memory performance by using production tests (involving recall) or recognition tests (involving the selection of correct from incorrect information, e.g., a multiple-choice test). For example, with our list of 100 words, one group of people might be asked to recall the list in any order (a free recall test), while a different group might be asked to circle the 100 studied words out of a mix with another 100, unstudied words (a recognition test). In this situation, the recognition test would likely produce better performance from participants than the recall test.

We usually think of recognition tests as being quite easy, because the cue for retrieval is a copy of the actual event that was presented for study. After all, what could be a better cue than the exact target (memory) the person is trying to access? In most cases, this line of reasoning is true; nevertheless, recognition tests do not provide perfect indexes of what is stored in memory. That is, you can fail to recognize a target staring you right in the face, yet be able to recall it later with a different set of cues (Watkins & Tulving, 1975). For example, suppose you had the task of recognizing the surnames of famous authors. At first, you might think that being given the actual last name would always be the best cue. However, research has shown this not necessarily to be true (Muter, 1984). When given names such as Tolstoy, Shaw, Shakespeare, and Lee, subjects might well say that Tolstoy and Shakespeare are famous authors, whereas Shaw and Lee are not. But, when given a cued recall test using first names, people often recall items (produce them) that they had failed to recognize before.

For example, in this instance, a cue like George Bernard ________ often leads to a recall of “Shaw,” even though people initially failed to recognize Shaw as a famous author’s name. Yet, when given the cue “William,” people may not come up with Shakespeare, because William is a common name that matches many people (the cue overload principle at work). This strange fact—that recall can sometimes lead to better performance than recognition—can be explained by the encoding specificity principle. As a cue, George Bernard _________ matches the way the famous writer is stored in memory better than does his surname, Shaw, does (even though it is the target). Further, the match is quite distinctive with George Bernard ___________, but the cue William _________________ is much more overloaded (Prince William, William Yeats, William Faulkner, will.i.am).

The phenomenon we have been describing is called the recognition failure of recallable words , which highlights the point that a cue will be most effective depending on how the information has been encoded (Tulving & Thomson, 1973). The point is, the cues that work best to evoke retrieval are those that recreate the event or name to be remembered, whereas sometimes even the target itself, such as Shaw in the above example, is not the best cue. Which cue will be most effective depends on how the information has been encoded.

Retrieval and Reconstruction

Whenever we think about our past, we engage in the act of retrieval. We usually think that retrieval is an objective act because we tend to imagine that retrieving a memory is like pulling a book from a shelf, and after we are done with it, we return the book to the shelf just as it was. However, research shows this assumption to be false; far from being a static repository of data, the memory is constantly changing. In fact, every time we retrieve a memory, it is altered. For example, the act of retrieval itself (of a fact, concept, or event) makes the retrieved memory much more likely to be retrieved again, a phenomenon called the testing effect or the retrieval practice effect (Pyc & Rawson, 2009; Roediger & Karpicke, 2006). However, retrieving some information can actually cause us to forget other information related to it, a phenomenon called retrieval-induced forgetting (Anderson, Bjork, & Bjork, 1994). Thus the act of retrieval can be a double-edged sword—strengthening the memory just retrieved (usually by a large amount) but harming related information (though this effect is often relatively small).

Retrieval of distant memories is reconstructive. We weave the concrete bits and pieces of events in with assumptions and preferences to form a coherent story (Bartlett, 1932). For example, if during your 10th birthday, your dog got to your cake before you did, you would likely tell that story for years afterward. Say, then, in later years you misremember where the dog actually found the cake, but repeat that error over and over during subsequent retellings of the story. Over time, that inaccuracy would become a basic fact of the event in your mind. Just as retrieval practice (repetition) enhances accurate memories, so will it strengthen errors or false memories (McDermott, 2006). Sometimes memories can even be manufactured just from hearing a vivid story. Consider the following episode, recounted by Jean Piaget, the famous developmental psychologist, from his childhood:

One of my first memories would date, if it were true, from my second year. I can still see, most clearly, the following scene, in which I believed until I was about 15. I was sitting in my pram . . . when a man tried to kidnap me. I was held in by the strap fastened round me while my nurse bravely tried to stand between me and the thief. She received various scratches, and I can still vaguely see those on her face. . . . When I was about 15, my parents received a letter from my former nurse saying that she had been converted to the Salvation Army. She wanted to confess her past faults, and in particular to return the watch she had been given as a reward on this occasion. She had made up the whole story, faking the scratches. I therefore must have heard, as a child, this story, which my parents believed, and projected it into the past in the form of a visual memory. . . . Many real memories are doubtless of the same order. (Norman & Schacter, 1997, pp. 187–188)

Piaget’s vivid account represents a case of a pure reconstructive memory. He heard the tale told repeatedly, and doubtless told it (and thought about it) himself. The repeated telling cemented the events as though they had really happened, just as we are all open to the possibility of having “many real memories … of the same order.” The fact that one can remember precise details (the location, the scratches) does not necessarily indicate that the memory is true, a point that has been confirmed in laboratory studies, too (e.g., Norman & Schacter, 1997).

Review the concepts from this section on encoding, storage, and retrieval in the following CrashCourse video:

You can view the transcript for “How We Make Memories: Crash Course Psychology #13” here (opens in new window) .

Check out these resources on memory and learning

• Book: Brown, P.C., Roediger, H. L. & McDaniel, M. A. (2014). Make it stick: The science of successful learning. Cambridge, MA: Harvard University Press. https://www.amazon.com/Make-Stick-Science-Successful-Learning/dp/0674729013
• Web: Retrieval Practice, a website with research, resources, and tips for both educators and learners around the memory-strengthening skill of retrieval practice. http://www.retrievalpractice.org/

Parts of the Brain Involved with Memory

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

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

Many scientists believe that the entire brain is involved with memory. However, since Lashley’s research, other scientists have been able to look more closely at the brain and memory. They have argued that memory is located in specific parts of the brain, and specific neurons can be recognized for their involvement in forming memories. The main parts of the brain involved with memory are the amygdala, the hippocampus, the cerebellum, and the prefrontal cortex (Figure 13).

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

Link to Learning

Hippocampus.

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

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

Cerebellum and Prefrontal Cortex

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

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

Neurotransmitters

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

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

Learn more about flashbulb memories in this brief video.

A flashbulb memory  is an exceptionally clear recollection of an important event (Figure 14). Where were you when you first heard about the 9/11 terrorist attacks? Most likely you can remember where you were and what you were doing. In fact, a Pew Research Center (2011) survey found that for those Americans who were age 8 or older at the time of the event, 97% can recall the moment they learned of this event, even a decade after it happened.

Dig Deeper: Inaccurate and False Memories

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

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

Some people attributed Bush’s wrong recall of the event to conspiracy theories. However, there is a much more benign explanation: human memory, even flashbulb memories, can be frail. In fact, memory can be so frail that we can convince a person an event happened to them, even when it did not. In studies, research participants will recall hearing a word, even though they never heard the word. For example, participants were given a list of 15 sleep-related words, but the word “sleep” was not on the list. Participants recalled hearing the word “sleep” even though they did not actually hear it (Roediger & McDermott, 2000). The researchers who discovered this named the theory after themselves and a fellow researcher, calling it the Deese-Roediger-McDermott paradigm.

Forgetting and Other Memory Problems

• Compare and contrast the two anterograde and retrograde amnesia
• Explain encoding failure and give examples of common memory errors, such as transience, absentmindedness, blocking, misattribution, suggestibility, bias, persistence, and interference.
• Describe the unreliability of eyewitness testimony
• Explain the misinformation effect

You may pride yourself on your amazing ability to remember the birthdates and ages of all of your friends and family members, or you may be able recall vivid details of your 5th birthday party at Chuck E. Cheese’s. However, all of us have at times felt frustrated, and even embarrassed, when our memories have failed us. There are several reasons why this happens.

the outstanding fact about K.C.’s mental make-up is his utter inability to remember any events, circumstances, or situations from his own life. His episodic amnesia covers his whole life, from birth to the present. The only exception is the experiences that, at any time, he has had in the last minute or two. (Tulving, 2002, p. 14)

Anterograde Amnesia

There are two common types of amnesia: anterograde amnesia and retrograde amnesia (Figure 15). Anterograde amnesia is commonly caused by brain trauma, such as a blow to the head. With anterograde amnesia , you cannot remember new information, although you can remember information and events that happened prior to your injury. The hippocampus is usually affected (McLeod, 2011). This suggests that damage to the brain has resulted in the inability to transfer information from short-term to long-term memory; that is, the inability to consolidate memories.

Retrograde Amnesia

Retrograde amnesia is loss of memory for events that occurred prior to the trauma. People with retrograde amnesia cannot remember some or even all of their past. They have difficulty remembering episodic memories. What if you woke up in the hospital one day and there were people surrounding your bed claiming to be your spouse, your children, and your parents? The trouble is you don’t recognize any of them. You were in a car accident, suffered a head injury, and now have retrograde amnesia. You don’t remember anything about your life prior to waking up in the hospital. This may sound like the stuff of Hollywood movies, and Hollywood has been fascinated with the amnesia plot for nearly a century, going all the way back to the film Garden of Lies from 1915 to more recent movies such as the Jason Bourne trilogy starring Matt Damon. However, for real-life sufferers of retrograde amnesia, like former NFL football player Scott Bolzan, the story is not a Hollywood movie. Bolzan fell, hit his head, and deleted 46 years of his life in an instant. He is now living with one of the most extreme cases of retrograde amnesia on record.

Encoding Failure

Sometimes memory loss happens before the actual memory process begins, which is encoding failure. We can’t remember something if we never stored it in our memory in the first place. This would be like trying to find a book on your e-reader that you never actually purchased and downloaded. Often, in order to remember something, we must pay attention to the details and actively work to process the information (effortful encoding). Lots of times we don’t do this. For instance, think of how many times in your life you’ve seen a nickel. Can you accurately recall what the front of a U.S. nickel looks like? When researchers Raymond Nickerson and Marilyn Adams (1979) asked this question, they found that most Americans don’t know which one it is. The reason is most likely encoding failure. Most of us never encode the details of the nickel. We only encode enough information to be able to distinguish it from other coins. If we don’t encode the information, then it’s not in our long-term memory, so we will not be able to remember it.

Memory Errors

Psychologist Daniel Schacter (2001), a well-known memory researcher, offers seven ways our memories fail us. He calls them the seven sins of memory and categorizes them into three groups: forgetting, distortion, and intrusion (Table 1).

Let’s look at the first sin of the forgetting errors: transience , which means that memories can fade over time. Here’s an example of how this happens. Nathan’s English teacher has assigned his students to read the novel To Kill a Mockingbird . Nathan comes home from school and tells his mom he has to read this book for class. “Oh, I loved that book!” she says. Nathan asks her what the book is about, and after some hesitation she says, “Well . . . I know I read the book in high school, and I remember that one of the main characters is named Scout, and her father is an attorney, but I honestly don’t remember anything else.” Nathan wonders if his mother actually read the book, and his mother is surprised she can’t recall the plot. What is going on here is storage decay: unused information tends to fade with the passage of time.

In 1885, German psychologist Hermann Ebbinghaus analyzed the process of memorization. First, he memorized lists of nonsense syllables. Then he measured how much he learned (retained) when he attempted to relearn each list. He tested himself over different periods of time from 20 minutes later to 30 days later. The result is his famous forgetting curve (Figure 18). Due to storage decay, an average person will lose 50% of the memorized information after 20 minutes and 70% of the information after 24 hours (Ebbinghaus, 1885/1964). Your memory for new information decays quickly and then eventually levels out.

Are you constantly losing your cell phone? Have you ever driven back home to make sure you turned off the stove? Have you ever walked into a room for something, but forgotten what it was? You probably answered yes to at least one, if not all, of these examples—but don’t worry, you are not alone. We are all prone to committing the memory error known as absentmindedness. These lapses in memory are caused by breaks in attention or our focus being somewhere else.

Cynthia, a psychologist, recalls a time when she recently committed the memory error of absentmindedness .

When I was completing court-ordered psychological evaluations, each time I went to the court, I was issued a temporary identification card with a magnetic strip which would open otherwise locked doors. As you can imagine, in a courtroom, this identification is valuable and important and no one wanted it to be lost or be picked up by a criminal. At the end of the day, I would hand in my temporary identification. One day, when I was almost done with an evaluation, my daughter’s day care called and said she was sick and needed to be picked up. It was flu season, I didn’t know how sick she was, and I was concerned. I finished up the evaluation in the next ten minutes, packed up my tools, and rushed to drive to my daughter’s day care. After I picked up my daughter, I could not remember if I had handed back my identification or if I had left it sitting out on a table. I immediately called the court to check. It turned out that I had handed back my identification. Why could I not remember that? (personal communication, September 5, 2013)

When have you experienced absentmindedness?

“I just went and saw this movie called Oblivion , and it had that famous actor in it. Oh, what’s his name? He’s been in all of those movies, like The Shawshank Redemption and The Dark Knight trilogy. I think he’s even won an Oscar. Oh gosh, I can picture his face in my mind, and hear his distinctive voice, but I just can’t think of his name! This is going to bug me until I can remember it!” This particular error can be so frustrating because you have the information right on the tip of your tongue. Have you ever experienced this? If so, you’ve committed the error known as blocking : you can’t access stored information (Figure 19).

Now let’s take a look at the three errors of distortion: misattribution, suggestibility, and bias. Misattribution happens when you confuse the source of your information. Let’s say Alejandro was dating Lucia and they saw the first Hobbit movie together. Then they broke up and Alejandro saw the second Hobbit movie with someone else. Later that year, Alejandro and Lucia get back together. One day, they are discussing how the Hobbit books and movies are different and Alejandro says to Lucia, “I loved watching the second movie with you and seeing you jump out of your seat during that super scary part.” When Lucia responded with a puzzled and then angry look, Alejandro realized he’d committed the error of misattribution.

What if someone is a victim of rape shortly after watching a television program? Is it possible that the victim could actually blame the rape on the person she saw on television because of misattribution? This is exactly what happened to Donald Thomson.

Australian eyewitness expert Donald Thomson appeared on a live TV discussion about the unreliability of eyewitness memory. He was later arrested, placed in a lineup and identified by a victim as the man who had raped her. The police charged Thomson although the rape had occurred at the time he was on TV. They dismissed his alibi that he was in plain view of a TV audience and in the company of the other discussants, including an assistant commissioner of police. . . . Eventually, the investigators discovered that the rapist had attacked the woman as she was watching TV—the very program on which Thomson had appeared. Authorities eventually cleared Thomson. The woman had confused the rapist’s face with the face that she had seen on TV. (Baddeley, 2004, p. 133)

The second distortion error is suggestibility. Suggestibility is similar to misattribution, since it also involves false memories, but it’s different. With misattribution you create the false memory entirely on your own, which is what the victim did in the Donald Thomson case above. With suggestibility, it comes from someone else, such as a therapist or police interviewer asking leading questions of a witness during an interview.

Memories can also be affected by bias , which is the final distortion error. Schacter (2001) says that your feelings and view of the world can actually distort your memory of past events. There are several types of bias: Stereotypical bias involves racial and gender biases. For example, when Asian American and European American research participants were presented with a list of names, they more frequently incorrectly remembered typical African American names such as Jamal and Tyrone to be associated with the occupation basketball player, and they more frequently incorrectly remembered typical White names such as Greg and Howard to be associated with the occupation of politician (Payne, Jacoby, & Lambert, 2004). Egocentric bias involves enhancing our memories of the past (Payne et al., 2004). Did you really score the winning goal in that big soccer match, or did you just assist? Hindsight bias happens when we think an outcome was inevitable after the fact. This is the “I knew it all along” phenomenon. The reconstructive nature of memory contributes to hindsight bias (Carli, 1999). We remember untrue events that seem to confirm that we knew the outcome all along.

Have you ever had a song play over and over in your head? How about a memory of a traumatic event, something you really do not want to think about? When you keep remembering something, to the point where you can’t “get it out of your head” and it interferes with your ability to concentrate on other things, it is called persistence . It’s Schacter’s seventh and last memory error. It’s actually a failure of our memory system because we involuntarily recall unwanted memories, particularly unpleasant ones (Figure 20). For instance, you witness a horrific car accident on the way to work one morning, and you can’t concentrate on work because you keep remembering the scene.

Alternatively, some memories may be forgotten because we deliberately attempt to keep them out of mind . Over time, by actively trying not to remember an event, we can sometimes successfully keep the undesirable memory from being retrieved either by inhibiting the undesirable memory or generating diversionary thoughts (Anderson & Green, 2001). Imagine that you slipped and fell in your high school cafeteria during lunch time, and everyone at the surrounding tables laughed at you. You would likely wish to avoid thinking about that event and might try to prevent it from coming to mind. One way that you could accomplish this is by thinking of other, more positive, events that are associated with the cafeteria. Eventually, this memory may be suppressed to the point that it would only be retrieved with great difficulty (Hertel & Calcaterra, 2005).

Interference

Sometimes information is stored in our memory, but for some reason it is inaccessible. This is known as interference, and there are two types: proactive interference and retroactive interference  (Figure 21). Have you ever gotten a new phone number or moved to a new address, but right after you tell people the old (and wrong) phone number or address? When the new year starts, do you find you accidentally write the previous year? These are examples of proactive interference: when old information hinders the recall of newly learned information. Retroactive interference happens when information learned more recently hinders the recall of older information. For example, this week you are studying Freud’s Psychoanalytic Theory. Next week you study the humanistic perspective of Maslow and Rogers. Thereafter, you have trouble remembering part of Freud’s theory, his Psychosexual Stages of Development, because you can only remember Maslow’s Hierarchy of Needs.

Dig Deeper: Preserving Eyewitness Memory: The Elizabeth Smart Case

Applications of faulty memory: elizabeth loftus and the misinformation effect.

Cognitive psychologist Elizabeth Loftus has conducted extensive research on memory. She has studied false memories as well as recovered memories of childhood sexual abuse. Loftus also developed the misinformation effect paradigm , which holds that after exposure to incorrect information, a person may misremember the original event.

According to Loftus, an eyewitness’s memory of an event is very flexible due to the misinformation effect. To test this theory, Loftus and John Palmer (1974) asked 45 U.S. college students to estimate the speed of cars using different forms of questions (Figure 23). The participants were shown films of car accidents and were asked to play the role of the eyewitness and describe what happened. They were asked, “About how fast were the cars going when they (smashed, collided, bumped, hit, contacted) each other?” The participants estimated the speed of the cars based on the verb used.

This video explains the misinformation effect.

You can view the transcript for “The Misinformation Effect” here (opens in new window) .

Participants who heard the word “smashed” estimated that the cars were traveling at a much higher speed than participants who heard the word “contacted.” The implied information about speed, based on the verb they heard, had an effect on the participants’ memory of the accident. In a follow-up one week later, participants were asked if they saw any broken glass (none was shown in the accident pictures). Participants who had been in the “smashed” group were more than twice as likely to indicate that they did remember seeing glass. Loftus and Palmer demonstrated that a leading question encouraged them to not only remember the cars were going faster, but to also falsely remember that they saw broken glass.

Studies have demonstrated that young adults (the typical research subjects in psychology) are often susceptible to misinformation, but that children and older adults can be even more susceptible (Bartlett & Memon, 2007; Ceci & Bruck, 1995). In addition, misinformation effects can occur easily, and without any intention to deceive (Allan & Gabbert, 2008). Even slight differences in the wording of a question can lead to misinformation effects. Subjects in one study were more likely to say yes when asked “Did you see the broken headlight?” than when asked “Did you see a broken headlight?” (Loftus, 1975).

Other studies have shown that misinformation can corrupt memory even more easily when it is encountered in social situations (Gabbert, Memon, Allan, & Wright, 2004). This is a problem particularly in cases where more than one person witnesses a crime. In these cases, witnesses tend to talk to one another in the immediate aftermath of the crime, including as they wait for police to arrive. But because different witnesses are different people with different perspectives, they are likely to see or notice different things, and thus remember different things, even when they witness the same event. So when they communicate about the crime later, they not only reinforce common memories for the event, they also contaminate each other’s memories for the event (Gabbert, Memon, & Allan, 2003; Paterson & Kemp, 2006; Takarangi, Parker, & Garry, 2006).

The misinformation effect has been modeled in the laboratory. Researchers had subjects watch a video in pairs. Both subjects sat in front of the same screen, but because they wore differently polarized glasses, they saw two different versions of a video, projected onto a screen. So, although they were both watching the same screen, and believed (quite reasonably) that they were watching the same video, they were actually watching two different versions of the video (Garry, French, Kinzett, & Mori, 2008).

In the video, Eric the electrician is seen wandering through an unoccupied house and helping himself to the contents thereof. A total of eight details were different between the two videos. After watching the videos, the “co-witnesses” worked together on 12 memory test questions. Four of these questions dealt with details that were different in the two versions of the video, so subjects had the chance to influence one another. Then subjects worked individually on 20 additional memory test questions. Eight of these were for details that were different in the two videos. Subjects’ accuracy was highly dependent on whether they had discussed the details previously. Their accuracy for items they had not previously discussed with their co-witness was 79%. But for items that they had discussed, their accuracy dropped markedly, to 34%. That is, subjects allowed their co-witnesses to corrupt their memories for what they had seen.

Improving Memory

Putting It All Together: Improving Your Memory

A central theme of this chapter has been the importance of the encoding and retrieval processes, and their interaction. To recap: to improve learning and memory, we need to encode information in conjunction with excellent cues that will bring back the remembered events when we need them. But how do we do this? Keep in mind the two critical principles we have discussed: to maximize retrieval, we should construct meaningful cues that remind us of the original experience, and those cues should be distinctive and not associated with other memories . These two conditions are critical in maximizing cue effectiveness (Nairne, 2002).

In 2013, Simon Reinhard sat in front of 60 people in a room at Washington University, where he memorized an increasingly long series of digits. On the first round, a computer generated 10 random digits—6 1 9 4 8 5 6 3 7 1—on a screen for 10 seconds. After the series disappeared, Simon typed them into his computer. His recollection was perfect. In the next phase, 20 digits appeared on the screen for 20 seconds. Again, Simon got them all correct. No one in the audience (mostly professors, graduate students, and undergraduate students) could recall the 20 digits perfectly. Then came 30 digits, studied for 30 seconds; once again, Simon didn’t misplace even a single digit. For a final trial, 50 digits appeared on the screen for 50 seconds, and again, Simon got them all right. In fact, Simon would have been happy to keep going. His record in this task—called “forward digit span”—is 240 digits!

When most of us witness a performance like that of Simon Reinhard, we think one of two things: First, maybe he’s cheating somehow. (No, he is not.) Second, Simon must have abilities more advanced than the rest of humankind. After all, psychologists established many years ago that the normal memory span for adults is about 7 digits, with some of us able to recall a few more and others a few less (Miller, 1956). That is why the first phone numbers were limited to 7 digits—psychologists determined that many errors occurred (costing the phone company money) when the number was increased to even 8 digits. But in normal testing, no one gets 50 digits correct in a row, much less 240. So, does Simon Reinhard simply have a photographic memory? He does not. Instead, Simon has taught himself simple strategies for remembering that have greatly increased his capacity for remembering virtually any type of material—digits, words, faces and names, poetry, historical dates, and so on. Twelve years earlier, before he started training his memory abilities, he had a digit span of 7, just like most of us. Simon has been training his abilities for about 10 years as of this writing, and has risen to be in the top two of “memory athletes.” In 2012, he came in second place in the World Memory Championships (composed of 11 tasks), held in London. He currently ranks second in the world, behind another German competitor, Johannes Mallow. In this section, we will explain the general principles by which you can improve your own memory.

• Recognize and apply memory-enhancing strategies, including mnemonics, rehearsal, chunking, and peg-words

Ways to Enhance Memory

Memory-enhancing strategies.

What are some everyday ways we can improve our memory, including recall? To help make sure information goes from short-term memory to long-term memory, you can use memory-enhancing strategies . One strategy is rehearsal , or the conscious repetition of information to be remembered (Craik & Watkins, 1973). Think about how you learned your multiplication tables as a child. You may recall that 6 x 6 = 36, 6 x 7 = 42, and 6 x 8 = 48. Memorizing these facts is rehearsal.

Another strategy is chunking : you organize information into manageable bits or chunks (Bodie, Powers, & Fitch-Hauser, 2006). Chunking is useful when trying to remember information like dates and phone numbers. Instead of trying to remember 5205550467, you remember the number as 520-555-0467. So, if you met an interesting person at a party and you wanted to remember his phone number, you would naturally chunk it, and you could repeat the number over and over, which is the rehearsal strategy.

You could also enhance memory by using elaborative rehearsal : a technique in which you think about the meaning of the new information and its relation to knowledge already stored in your memory (Tigner, 1999). For example, in this case, you could remember that 520 is an area code for Arizona and the person you met is from Arizona. This would help you better remember the 520 prefix. If the information is retained, it goes into long-term memory.

Mnemonic devices  are memory aids that help us organize information for encoding (Figure 25). They are especially useful when we want to recall larger bits of information such as steps, stages, phases, and parts of a system (Bellezza, 1981). Brian needs to learn the order of the planets in the solar system, but he’s having a hard time remembering the correct order. His friend Kelly suggests a mnemonic device that can help him remember. Kelly tells Brian to simply remember the name Mr. VEM J. SUN, and he can easily recall the correct order of the planets: M ercury, V enus, E arth, M ars, J upiter, S aturn, U ranus, and N eptune. You might use a mnemonic device to help you remember someone’s name, a mathematical formula, or the seven levels of Bloom’s taxonomy.

If you have ever watched the television show Modern Family , you might have seen Phil Dunphy explain how he remembers names:

The other day I met this guy named Carl. Now, I might forget that name, but he was wearing a Grateful Dead t-shirt. What’s a band like the Grateful Dead? Phish. Where do fish live? The ocean. What else lives in the ocean? Coral. Hello, Co-arl. (Wrubel & Spiller, 2010)

It seems the more vivid or unusual the mnemonic, the easier it is to remember. The key to using any mnemonic successfully is to find a strategy that works for you.

Some other strategies that are used to improve memory include expressive writing and saying words aloud. Expressive writing helps boost your short-term memory, particularly if you write about a traumatic experience in your life. Masao Yogo and Shuji Fujihara (2008) had participants write for 20-minute intervals several times per month. The participants were instructed to write about a traumatic experience, their best possible future selves, or a trivial topic. The researchers found that this simple writing task increased short-term memory capacity after five weeks, but only for the participants who wrote about traumatic experiences. Psychologists can’t explain why this writing task works, but it does.

What if you want to remember items you need to pick up at the store? Simply say them out loud to yourself. A series of studies (MacLeod, Gopie, Hourihan, Neary, & Ozubko, 2010) found that saying a word out loud improves your memory for the word because it increases the word’s distinctiveness. Feel silly, saying random grocery items aloud? This technique works equally well if you just mouth the words. Using these techniques increased participants’ memory for the words by more than 10%. These techniques can also be used to help you study.

Using Peg-Words

Consider the case of Simon Reinhard. In 2013, he sat in front of 60 people in a room at Washington University, where he memorized an increasingly long series of digits. On the first round, a computer generated 10 random digits—6 1 9 4 8 5 6 3 7 1—on a screen for 10 seconds. After the series disappeared, Simon typed them into his computer. His recollection was perfect. In the next phase, 20 digits appeared on the screen for 20 seconds. Again, Simon got them all correct. No one in the audience (mostly professors, graduate students, and undergraduate students) could recall the 20 digits perfectly. Then came 30 digits, studied for 30 seconds; once again, Simon didn’t misplace even a single digit. For a final trial, 50 digits appeared on the screen for 50 seconds, and again, Simon got them all right. In fact, Simon would have been happy to keep going. His record in this task—called “forward digit span”—is 240 digits!

Simon Reinhard’s ability to memorize huge numbers of digits. Although it was not obvious, Simon Reinhard used deliberate mnemonic devices to improve his memory. In a typical case, the person learns a set of cues and then applies these cues to learn and remember information. Consider the set of 20 items below that are easy to learn and remember (Bower & Reitman, 1972).

• is a gun. 11 is penny-one, hot dog bun.
• is a shoe. 12 is penny-two, airplane glue.
• is a tree. 13 is penny-three, bumble bee.
• is a door. 14 is penny-four, grocery store.
• is knives. 15 is penny-five, big beehive.
• is sticks. 16 is penny-six, magic tricks.
• is oven. 17 is penny-seven, go to heaven.
• is plate. 18 is penny-eight, golden gate.
• is wine. 19 is penny-nine, ball of twine.
• is hen. 20 is penny-ten, ballpoint pen.

It would probably take you less than 10 minutes to learn this list and practice recalling it several times (remember to use retrieval practice!). If you were to do so, you would have a set of peg words on which you could “hang” memories. In fact, this mnemonic device is called the peg word technique . If you then needed to remember some discrete items—say a grocery list, or points you wanted to make in a speech—this method would let you do so in a very precise yet flexible way. Suppose you had to remember bread, peanut butter, bananas, lettuce, and so on. The way to use the method is to form a vivid image of what you want to remember and imagine it interacting with your peg words (as many as you need). For example, for these items, you might imagine a large gun (the first peg word) shooting a loaf of bread, then a jar of peanut butter inside a shoe, then large bunches of bananas hanging from a tree, then a door slamming on a head of lettuce with leaves flying everywhere. The idea is to provide good, distinctive cues (the weirder the better!) for the information you need to remember while you are learning it. If you do this, then retrieving it later is relatively easy. You know your cues perfectly (one is gun, etc.), so you simply go through your cue word list and “look” in your mind’s eye at the image stored there (bread, in this case).

This peg word method may sound strange at first, but it works quite well, even with little training (Roediger, 1980). One word of warning, though, is that the items to be remembered need to be presented relatively slowly at first, until you have practice associating each with its cue word. People get faster with time. Another interesting aspect of this technique is that it’s just as easy to recall the items in backwards order as forwards. This is because the peg words provide direct access to the memorized items, regardless of order.

How did Simon Reinhard remember those digits? Essentially he has a much more complex system based on these same principles. In his case, he uses “memory palaces” (elaborate scenes with discrete places) combined with huge sets of images for digits. For example, imagine mentally walking through the home where you grew up and identifying as many distinct areas and objects as possible. Simon has hundreds of such memory palaces that he uses. Next, for remembering digits, he has memorized a set of 10,000 images. Every four-digit number for him immediately brings forth a mental image. So, for example, 6187 might recall Michael Jackson. When Simon hears all the numbers coming at him, he places an image for every four digits into locations in his memory palace. He can do this at an incredibly rapid rate, faster than 4 digits per 4 seconds when they are flashed visually, as in the demonstration at the beginning of the module. As noted, his record is 240 digits, recalled in exact order. Simon also holds the world record in an event called “speed cards,” which involves memorizing the precise order of a shuffled deck of cards. Simon was able to do this in 21.19 seconds! Again, he uses his memory palaces, and he encodes groups of cards as single images.

How to Study Effectively

Based on the information presented in this chapter, here are some strategies and suggestions to help you hone your study techniques (Figure 26). The key with any of these strategies is to figure out what works best for you.

• Use elaborative rehearsal : In a famous article, Craik and Lockhart (1972) discussed their belief that information we process more deeply goes into long-term memory. Their theory is called levels of processing . If we want to remember a piece of information, we should think about it more deeply and link it to other information and memories to make it more meaningful. For example, if we are trying to remember that the hippocampus is involved with memory processing, we might envision a hippopotamus with excellent memory and then we could better remember the hippocampus.
• Apply the self-reference effect : As you go through the process of elaborative rehearsal, it would be even more beneficial to make the material you are trying to memorize personally meaningful to you. In other words, make use of the self-reference effect. Write notes in your own words. Write definitions from the text, and then rewrite them in your own words. Relate the material to something you have already learned for another class, or think how you can apply the concepts to your own life. When you do this, you are building a web of retrieval cues that will help you access the material when you want to remember it.
• Don’t forget the forgetting curve : As you know, the information you learn drops off rapidly with time. Even if you think you know the material, study it again right before test time to increase the likelihood the information will remain in your memory. Overlearning can help prevent storage decay.
• Rehearse, rehearse, rehearse : Review the material over time, in spaced and organized study sessions. Organize and study your notes, and take practice quizzes/exams. Link the new information to other information you already know well.
• Be aware of interference : To reduce the likelihood of interference, study during a quiet time without interruptions or distractions (like television or music).
• Keep moving : Of course you already know that exercise is good for your body, but did you also know it’s also good for your mind? Research suggests that regular aerobic exercise (anything that gets your heart rate elevated) is beneficial for memory (van Praag, 2008). Aerobic exercise promotes neurogenesis: the growth of new brain cells in the hippocampus, an area of the brain known to play a role in memory and learning.
• Get enough sleep : While you are sleeping, your brain is still at work. During sleep the brain organizes and consolidates information to be stored in long-term memory (Abel & Bäuml, 2013).
• Make use of mnemonic devices : As you learned earlier in this chapter, mnemonic devices often help us to remember and recall information. There are different types of mnemonic devices, such as the acronym. An acronym is a word formed by the first letter of each of the words you want to remember. For example, even if you live near one, you might have difficulty recalling the names of all five Great Lakes. What if I told you to think of the word Homes? HOMES is an acronym that represents Huron, Ontario, Michigan, Erie, and Superior: the five Great Lakes. Another type of mnemonic device is an acrostic: you make a phrase of all the first letters of the words. For example, if you are taking a math test and you are having difficulty remembering the order of operations , recalling the following sentence will help you: “Please Excuse My Dear Aunt Sally,” because the order of mathematical operations is Parentheses, Exponents, Multiplication, Division, Addition, Subtraction. There also are jingles, which are rhyming tunes that contain keywords related to the concept, such as i before e, except after c .
• Create a mnemonic device to help you remember a term or concept from this module.
• What is an effective study technique that you have used? How is it similar to/different from the strategies suggested in this module?

In this chapter, you learned to

• explain the process of memory
• explain and give examples of forgetting and memory failure
• recognize and apply memory-enhancing strategies

Memory is the set of processes used to encode, store, and retrieve information over different periods of time. Interestingly, our memory is prone to errors and we sometimes remember things that never happened, misconstrue things that did, and forget things we shouldn’t.

More and more memory researchers are digging deeper to better understand the place where memories are stored in the brain, also known as engrams. Fascinating new studies delve into memory reconsolidation, in which researchers more or less re-train a memory so that subjects no longer have the same memory trace. You can imagine the applications of this in helping someone with a phobia or post-traumatic stress disorder, for example, in reducing the efficacy of their fear memory.

Memory is important to our daily functioning and well-being, and it is of particular interest for students (like yourself!) because there is a lot to be remembered and little time to learn it all. You read about Ebbinghaus’ forgetting curve and memory decay and discovered some techniques to counteract forgetfulness, such as using mnemonics, chunking, the peg-word system, and elaborative rehearsal. A 2008 study sought to determine which type of studying is most effective in learning new words and concepts. The study, by Jeffrey D. Karpicke and Henry L. Roediger III, had students learn forty pairs of Swahili words and their meanings in English. After learning all forty words one time through, they were split into 4 groups for the rest of the learning phase:

• A group that studied all 40 words and got tested on all 40 words
• A group that studied only the words they didn’t know already, then were tested on all 40 words
• A group that studied all 40 words, but were tested only on the words they didn’t know
• A group that studied only the words they didn’t know already, then were tested on only the words they didn’t know already

Which way would be your preferred method for learning the new words? Do you ever study this way? A common study technique is to practice with flashcards, then put away the words you already know (similar to groups 2 or 4). Which group do you think learned the words the best a week later? It turns out that when tested one week later, both the first and second groups remembered about 80% of the words, while the third and fourth groups (that were tested only on the words they didn’t already know) only remembered about 35% of the words. This is a significant difference! This study demonstrated the importance of testing and the importance of retrieval practice in learning. This is why you may not want to complain too much if your instructor gives you a pop quiz, and also why it’s a good idea to force yourself to recall information and quiz yourself on the things you learn. [1]

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set of processes used to encode, store, and retrieve information over different periods of time

holds about seven bits of information before it is forgotten or stored, as well as information that has been retrieved and is being used

type of declarative memory that contains information about events we have personally experienced, also known as autobiographical memory

type of declarative memory about words, concepts, and language-based knowledge and facts

episodic memories of your life

input of information into the memory system

creation of a permanent record of information

act of getting information out of long-term memory storage and back into conscious awareness

input of words and their meaning

input of images

input of sounds, words, and music

taking the information from the form it is delivered to us and then converting it in a way that we can make sense of it

memory model that states we process information through three systems: sensory memory, short-term memory, and long-term memory

storage of brief sensory events, such as sights, sounds, and tastes

repetition of information to be remembered

the neural processes that occur between an experience and the stabilization of the memory

continuous storage of information

memories we consciously try to remember and recall

type of long-term memory of facts and events we personally experience

memories that are not part of our consciousness

type of long-term memory for making skilled actions, such as how to brush your teeth, how to drive a car, and how to swim

The hypothesis that a retrieval cue will be effective to the extent that information encoded from the cue overlaps or matches information in the engram or memory trace.

The principle stating that the more memories that are associated to a particular retrieval cue, the less effective the cue will be in prompting retrieval of any one memory.

accessing information without cues

identifying previously learned information after encountering it again, usually in response to a cue

learning information that was previously learned

A term indicating the change in the nervous system representing an event; also, memory trace.

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

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

Vivid personal memories of receiving the news of some momentous (and usually emotional) event.

loss of long-term memory that occurs as the result of disease, physical trauma, or psychological trauma

loss of memory for events that occur after the brain trauma

loss of memory for events that occurred prior to brain trauma

loss of information from long-term memory

memory error in which unused memories fade with the passage of time

lapses in memory that are caused by breaks in attention or our focus being somewhere else

memory error in which you cannot access stored information

memory error in which you confuse the source of your information

effects of misinformation from external sources that leads to the creation of false memories

how feelings and view of the world distort memory of past events

failure of the memory system that involves the involuntary recall of unwanted memories, particularly unpleasant ones

old information hinders the recall of newly learned information

information learned more recently hinders the recall of older information

after exposure to additional and possibly inaccurate information, a person may misremember the original event

technique to help make sure information goes from short-term memory to long-term memory

organizing information into manageable bits or chunks

thinking about the meaning of new information and its relation to knowledge already stored in your memory

memory aids that help organize information for encoding

information that is thought of more deeply becomes more meaningful and thus better committed to memory

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8.3 Problems with Memory

Learning objectives.

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

• Compare and contrast the two types of amnesia
• Discuss the unreliability of eyewitness testimony
• Discuss encoding failure
• Discuss the various memory errors
• Compare and contrast the two types of interference

You may pride yourself on your amazing ability to remember the birthdates and ages of all of your friends and family members, or you may be able to recall vivid details of your 5th birthday party at Chuck E. Cheese’s. However, all of us have at times felt frustrated, and even embarrassed, when our memories have failed us. There are several reasons why this happens.

Amnesia is the loss of long-term memory that occurs as the result of disease, physical trauma, or psychological trauma. Endel Tulving (2002) and his colleagues at the University of Toronto studied K. C. for years. K. C. suffered a traumatic head injury in a motorcycle accident and then had severe amnesia. Tulving writes,

the outstanding fact about K.C.'s mental make-up is his utter inability to remember any events, circumstances, or situations from his own life. His episodic amnesia covers his whole life, from birth to the present. The only exception is the experiences that, at any time, he has had in the last minute or two. (Tulving, 2002, p. 14)

Anterograde Amnesia

There are two common types of amnesia: anterograde amnesia and retrograde amnesia ( Figure 8.10 ). Anterograde amnesia is commonly caused by brain trauma, such as a blow to the head. With anterograde amnesia , you cannot remember new information, although you can remember information and events that happened prior to your injury. The hippocampus is usually affected (McLeod, 2011). This suggests that damage to the brain has resulted in the inability to transfer information from short-term to long-term memory; that is, the inability to consolidate memories.

Many people with this form of amnesia are unable to form new episodic or semantic memories, but are still able to form new procedural memories (Bayley & Squire, 2002). This was true of H. M., which was discussed earlier. The brain damage caused by his surgery resulted in anterograde amnesia. H. M. would read the same magazine over and over, having no memory of ever reading it—it was always new to him. He also could not remember people he had met after his surgery. If you were introduced to H. M. and then you left the room for a few minutes, he would not know you upon your return and would introduce himself to you again. However, when presented the same puzzle several days in a row, although he did not remember having seen the puzzle before, his speed at solving it became faster each day (because of relearning) (Corkin, 1965, 1968).

Retrograde Amnesia

Retrograde amnesia is loss of memory for events that occurred prior to the trauma. People with retrograde amnesia cannot remember some or even all of their past. They have difficulty remembering episodic memories. What if you woke up in the hospital one day and there were people surrounding your bed claiming to be your spouse, your children, and your parents? The trouble is you don’t recognize any of them. You were in a car accident, suffered a head injury, and now have retrograde amnesia. You don’t remember anything about your life prior to waking up in the hospital. This may sound like the stuff of Hollywood movies, and Hollywood has been fascinated with the amnesia plot for nearly a century, going all the way back to the film Garden of Lies from 1915 to more recent movies such as the Jason Bourne spy thrillers. However, for real-life sufferers of retrograde amnesia, like former NFL football player Scott Bolzan, the story is not a Hollywood movie. Bolzan fell, hit his head, and deleted 46 years of his life in an instant. He is now living with one of the most extreme cases of retrograde amnesia on record.

Link to Learning

View the video story about Scott Bolzan's amnesia and his attempts to get his life back to learn more.

Memory Construction and Reconstruction

The formulation of new memories is sometimes called construction , and the process of bringing up old memories is called reconstruction . Yet as we retrieve our memories, we also tend to alter and modify them. A memory pulled from long-term storage into short-term memory is flexible. New events can be added and we can change what we think we remember about past events, resulting in inaccuracies and distortions. People may not intend to distort facts, but it can happen in the process of retrieving old memories and combining them with new memories (Roediger & DeSoto, 2015).

Suggestibility

When someone witnesses a crime, that person’s memory of the details of the crime is very important in catching the suspect. Because memory is so fragile, witnesses can be easily (and often accidentally) misled due to the problem of suggestibility. Suggestibility describes the effects of misinformation from external sources that leads to the creation of false memories. In the fall of 2002, a sniper in the DC area shot people at a gas station, leaving Home Depot, and walking down the street. These attacks went on in a variety of places for over three weeks and resulted in the deaths of ten people. During this time, as you can imagine, people were terrified to leave their homes, go shopping, or even walk through their neighborhoods. Police officers and the FBI worked frantically to solve the crimes, and a tip hotline was set up. Law enforcement received over 140,000 tips, which resulted in approximately 35,000 possible suspects (Newseum, n.d.).

Most of the tips were dead ends, until a white van was spotted at the site of one of the shootings. The police chief went on national television with a picture of the white van. After the news conference, several other eyewitnesses called to say that they too had seen a white van fleeing from the scene of the shooting. At the time, there were more than 70,000 white vans in the area. Police officers, as well as the general public, focused almost exclusively on white vans because they believed the eyewitnesses. Other tips were ignored. When the suspects were finally caught, they were driving a blue sedan.

As illustrated by this example, we are vulnerable to the power of suggestion, simply based on something we see on the news. Or we can claim to remember something that in fact is only a suggestion someone made. It is the suggestion that is the cause of the false memory.

Eyewitness Misidentification

Even though memory and the process of reconstruction can be fragile, police officers, prosecutors, and the courts often rely on eyewitness identification and testimony in the prosecution of criminals. However, faulty eyewitness identification and testimony can lead to wrongful convictions ( Figure 8.11 ).

How does this happen? In 1984, Jennifer Thompson, then a 22-year-old college student in North Carolina, was brutally raped at knifepoint. As she was being raped, she tried to memorize every detail of her rapist’s face and physical characteristics, vowing that if she survived, she would help get him convicted. After the police were contacted, a composite sketch was made of the suspect, and Jennifer was shown six photos. She chose two, one of which was of Ronald Cotton. After looking at the photos for 4–5 minutes, she said, “Yeah. This is the one,” and then she added, “I think this is the guy.” When questioned about this by the detective who asked, “You’re sure? Positive?” She said that it was him. Then she asked the detective if she did OK, and he reinforced her choice by telling her she did great. These kinds of unintended cues and suggestions by police officers can lead witnesses to identify the wrong suspect. The district attorney was concerned about her lack of certainty the first time, so she viewed a lineup of seven men. She said she was trying to decide between numbers 4 and 5, finally deciding that Cotton, number 5, “Looks most like him.” He was 22 years old.

By the time the trial began, Jennifer Thompson had absolutely no doubt that she was raped by Ronald Cotton. She testified at the court hearing, and her testimony was compelling enough that it helped convict him. How did she go from, “I think it’s the guy” and it “Looks most like him,” to such certainty? Gary Wells and Deah Quinlivan (2009) assert it’s suggestive police identification procedures, such as stacking lineups to make the defendant stand out, telling the witness which person to identify, and confirming witnesses choices by telling them “Good choice,” or “You picked the guy.”

After Cotton was convicted of the rape, he was sent to prison for life plus 50 years. After 4 years in prison, he was able to get a new trial. Jennifer Thompson once again testified against him. This time Ronald Cotton was given two life sentences. After serving 11 years in prison, DNA evidence finally demonstrated that Ronald Cotton did not commit the rape, was innocent, and had served over a decade in prison for a crime he did not commit.

Watch this first video about Ronald Cotton who was falsely convicted and then watch this second video about the task of his accuser to learn more about the fallibility of memory.

Ronald Cotton’s story, unfortunately, is not unique. There are also people who were convicted and placed on death row, who were later exonerated. The Innocence Project is a non-profit group that works to exonerate falsely convicted people, including those convicted by eyewitness testimony. To learn more, you can visit http://www.innocenceproject.org.

Preserving Eyewitness Memory: The Elizabeth Smart Case

Contrast the Cotton case with what happened in the Elizabeth Smart case. When Elizabeth was 14 years old and fast asleep in her bed at home, she was abducted at knifepoint. Her nine-year-old sister, Mary Katherine, was sleeping in the same bed and watched, terrified, as her beloved older sister was abducted. Mary Katherine was the sole eyewitness to this crime and was very fearful. In the following weeks, the Salt Lake City police and the FBI proceeded with caution with Mary Katherine. They did not want to implant any false memories or mislead her in any way. They did not show her police line-ups or push her to do a composite sketch of the abductor. They knew if they corrupted her memory, Elizabeth might never be found. For several months, there was little or no progress on the case. Then, about 4 months after the kidnapping, Mary Katherine first recalled that she had heard the abductor’s voice prior to that night (he had worked exactly one day as a handyman at the family’s home) and then she was able to name the person whose voice it was. The family contacted the press and others recognized him—after a total of nine months, the suspect was caught and Elizabeth Smart was returned to her family.

The Misinformation Effect

Cognitive psychologist Elizabeth Loftus has conducted extensive research on memory. She has studied false memories as well as recovered memories of childhood sexual abuse. Loftus also developed the misinformation effect paradigm , which holds that after exposure to additional and possibly inaccurate information, a person may misremember the original event.

According to Loftus, an eyewitness’s memory of an event is very flexible due to the misinformation effect. To test this theory, Loftus and John Palmer (1974) asked 45 U.S. college students to estimate the speed of cars using different forms of questions ( Figure 8.12 ). The participants were shown films of car accidents and were asked to play the role of the eyewitness and describe what happened. They were asked, “About how fast were the cars going when they (smashed, collided, bumped, hit, contacted) each other?” The participants estimated the speed of the cars based on the verb used.

Participants who heard the word “smashed” estimated that the cars were traveling at a much higher speed than participants who heard the word “contacted.” The implied information about speed, based on the verb they heard, had an effect on the participants’ memory of the accident. In a follow-up one week later, participants were asked if they saw any broken glass (none was shown in the accident pictures). Participants who had been in the “smashed” group were more than twice as likely to indicate that they did remember seeing glass. Loftus and Palmer demonstrated that a leading question encouraged them to not only remember the cars were going faster, but to also falsely remember that they saw broken glass.

Controversies over Repressed and Recovered Memories

Other researchers have described how whole events, not just words, can be falsely recalled, even when they did not happen. The idea that memories of traumatic events could be repressed has been a theme in the field of psychology, beginning with Sigmund Freud, and the controversy surrounding the idea continues today.

Recall of false autobiographical memories is called false memory syndrome . This syndrome has received a lot of publicity, particularly as it relates to memories of events that do not have independent witnesses—often the only witnesses to the abuse are the perpetrator and the victim (e.g., sexual abuse).

On one side of the debate are those who have recovered memories of childhood abuse years after it occurred. These researchers argue that some children’s experiences have been so traumatizing and distressing that they must lock those memories away in order to lead some semblance of a normal life. They believe that repressed memories can be locked away for decades and later recalled intact through hypnosis and guided imagery techniques (Devilly, 2007).

Research suggests that having no memory of childhood sexual abuse is quite common in adults. For instance, one large-scale study conducted by John Briere and Jon Conte (1993) revealed that 59% of 450 men and women who were receiving treatment for sexual abuse that had occurred before age 18 had forgotten their experiences. Ross Cheit (2007) suggested that repressing these memories created psychological distress in adulthood. The Recovered Memory Project was created so that victims of childhood sexual abuse can recall these memories and allow the healing process to begin (Cheit, 2007; Devilly, 2007).

On the other side, Loftus has challenged the idea that individuals can repress memories of traumatic events from childhood, including sexual abuse, and then recover those memories years later through therapeutic techniques such as hypnosis, guided visualization, and age regression.

Loftus is not saying that childhood sexual abuse doesn’t happen, but she does question whether or not those memories are accurate, and she is skeptical of the questioning process used to access these memories, given that even the slightest suggestion from the therapist can lead to misinformation effects. For example, researchers Stephen Ceci and Maggie Brucks (1993, 1995) asked three-year-old children to use an anatomically correct doll to show where their pediatricians had touched them during an exam. Fifty-five percent of the children pointed to the genital/anal area on the dolls, even when they had not received any form of genital exam.

Ever since Loftus published her first studies on the suggestibility of eyewitness testimony in the 1970s, social scientists, police officers, therapists, and legal practitioners have been aware of the flaws in interview practices. Consequently, steps have been taken to decrease suggestibility of witnesses. One way is to modify how witnesses are questioned. When interviewers use neutral and less leading language, children more accurately recall what happened and who was involved (Goodman, 2006; Pipe, 1996; Pipe, Lamb, Orbach, & Esplin, 2004). Another change is in how police lineups are conducted. It’s recommended that a blind photo lineup be used. This way the person administering the lineup doesn’t know which photo belongs to the suspect, minimizing the possibility of giving leading cues. Additionally, judges in some states now inform jurors about the possibility of misidentification. Judges can also suppress eyewitness testimony if they deem it unreliable.

“I’ve a grand memory for forgetting,” quipped Robert Louis Stevenson. Forgetting refers to loss of information from long-term memory. We all forget things, like a loved one’s birthday, someone’s name, or where we put our car keys. As you’ve come to see, memory is fragile, and forgetting can be frustrating and even embarrassing. But why do we forget? To answer this question, we will look at several perspectives on forgetting.

Encoding Failure

Sometimes memory loss happens before the actual memory process begins, which is encoding failure. We can’t remember something if we never stored it in our memory in the first place. This would be like trying to find a book on your e-reader that you never actually purchased and downloaded. Often, in order to remember something, we must pay attention to the details and actively work to process the information (effortful encoding). Lots of times we don’t do this. For instance, think of how many times in your life you’ve seen a penny. Can you accurately recall what the front of a U.S. penny looks like? When researchers Raymond Nickerson and Marilyn Adams (1979) asked this question, they found that most Americans don’t know which one it is. The reason is most likely encoding failure. Most of us never encode the details of the penny. We only encode enough information to be able to distinguish it from other coins. If we don’t encode the information, then it’s not in our long-term memory, so we will not be able to remember it.

Memory Errors

Psychologist Daniel Schacter (2001), a well-known memory researcher, offers seven ways our memories fail us. He calls them the seven sins of memory and categorizes them into three groups: forgetting, distortion, and intrusion ( Table 8.1 ).

Let’s look at the first sin of the forgetting errors: transience , which means that memories can fade over time. Here’s an example of how this happens. Nathan’s English teacher has assigned his students to read the novel To Kill a Mockingbird . Nathan comes home from school and tells his mom he has to read this book for class. “Oh, I loved that book!” she says. Nathan asks her what the book is about, and after some hesitation she says, “Well . . . I know I read the book in high school, and I remember that one of the main characters is named Scout, and her father is an attorney, but I honestly don’t remember anything else.” Nathan wonders if his mother actually read the book, and his mother is surprised she can’t recall the plot. What is going on here is storage decay: unused information tends to fade with the passage of time.

In 1885, German psychologist Hermann Ebbinghaus analyzed the process of memorization. First, he memorized lists of nonsense syllables. Then he measured how much he learned (retained) when he attempted to relearn each list. He tested himself over different periods of time from 20 minutes later to 30 days later. The result is his famous forgetting curve ( Figure 8.14 ). Due to storage decay, an average person will lose 50% of the memorized information after 20 minutes and 70% of the information after 24 hours (Ebbinghaus, 1885/1964). Your memory for new information decays quickly and then eventually levels out.

Are you constantly losing your cell phone? Have you ever driven back home to make sure you turned off the stove? Have you ever walked into a room for something, but forgotten what it was? You probably answered yes to at least one, if not all, of these examples—but don’t worry, you are not alone. We are all prone to committing the memory error known as absentmindedness , which describes lapses in memory caused by breaks in attention or our focus being somewhere else.

Cynthia, a psychologist, recalls a time when she recently committed the memory error of absentmindedness.

When I was completing court-ordered psychological evaluations, each time I went to the court, I was issued a temporary identification card with a magnetic strip which would open otherwise locked doors. As you can imagine, in a courtroom, this identification is valuable and important and no one wanted it to be lost or be picked up by a criminal. At the end of the day, I would hand in my temporary identification. One day, when I was almost done with an evaluation, my daughter’s day care called and said she was sick and needed to be picked up. It was flu season, I didn’t know how sick she was, and I was concerned. I finished up the evaluation in the next ten minutes, packed up my briefcase, and rushed to drive to my daughter’s day care. After I picked up my daughter, I could not remember if I had handed back my identification or if I had left it sitting out on a table. I immediately called the court to check. It turned out that I had handed back my identification. Why could I not remember that? (personal communication, September 5, 2013)

When have you experienced absentmindedness?

“I just streamed this movie called Oblivion , and it had that famous actor in it. Oh, what’s his name? He’s been in all of those movies, like The Shawshank Redemption and The Dark Knight trilogy. I think he’s even won an Oscar. Oh gosh, I can picture his face in my mind, and hear his distinctive voice, but I just can’t think of his name! This is going to bug me until I can remember it!” This particular error can be so frustrating because you have the information right on the tip of your tongue. Have you ever experienced this? If so, you’ve committed the error known as blocking : you can’t access stored information ( Figure 8.15 ).

Now let’s take a look at the three errors of distortion: misattribution, suggestibility, and bias. Misattribution happens when you confuse the source of your information. Let’s say Alejandra was dating Lucia and they saw the first Hobbit movie together. Then they broke up and Alejandra saw the second Hobbit movie with someone else. Later that year, Alejandra and Lucia get back together. One day, they are discussing how the Hobbit books and movies are different and Alejandra says to Lucia, “I loved watching the second movie with you and seeing you jump out of your seat during that super scary part.” When Lucia responded with a puzzled and then angry look, Alejandra realized she’d committed the error of misattribution.

What if someone is a victim of rape shortly after watching a television program? Is it possible that the victim could actually blame the rape on the person she saw on television because of misattribution? This is exactly what happened to Donald Thomson.

Australian eyewitness expert Donald Thomson appeared on a live TV discussion about the unreliability of eyewitness memory. He was later arrested, placed in a lineup and identified by a victim as the man who had raped her. The police charged Thomson although the rape had occurred at the time he was on TV. They dismissed his alibi that he was in plain view of a TV audience and in the company of the other discussants, including an assistant commissioner of police. . . . Eventually, the investigators discovered that the rapist had attacked the woman as she was watching TV—the very program on which Thomson had appeared. Authorities eventually cleared Thomson. The woman had confused the rapist's face with the face that she had seen on TV. (Baddeley, 2004, p. 133)

The second distortion error is suggestibility. Suggestibility is similar to misattribution, since it also involves false memories, but it’s different. With misattribution you create the false memory entirely on your own, which is what the victim did in the Donald Thomson case above. With suggestibility, it comes from someone else, such as a therapist or police interviewer asking leading questions of a witness during an interview.

Memories can also be affected by bias , which is the final distortion error. Schacter (2001) says that your feelings and view of the world can actually distort your memory of past events. There are several types of bias:

• Stereotypical bias involves racial and gender biases. For example, when Asian American and European American research participants were presented with a list of names, they more frequently incorrectly remembered typical African American names such as Jamal and Tyrone to be associated with the occupation basketball player, and they more frequently incorrectly remembered typical White names such as Greg and Howard to be associated with the occupation of politician (Payne, Jacoby, & Lambert, 2004).
• Egocentric bias involves enhancing our memories of the past (Payne et al., 2004). Did you really score the winning goal in that big soccer match, or did you just assist?
• Hindsight bias happens when we think an outcome was inevitable after the fact. This is the “I knew it all along” phenomenon. The reconstructive nature of memory contributes to hindsight bias (Carli, 1999). We remember untrue events that seem to confirm that we knew the outcome all along.

Have you ever had a song play over and over in your head? How about a memory of a traumatic event, something you really do not want to think about? When you keep remembering something, to the point where you can’t “get it out of your head” and it interferes with your ability to concentrate on other things, it is called persistence . It’s Schacter’s seventh and last memory error. It’s actually a failure of our memory system because we involuntarily recall unwanted memories, particularly unpleasant ones ( Figure 8.16 ). For instance, you witness a horrific car accident on the way to work one morning, and you can’t concentrate on work because you keep remembering the scene.

Interference

Sometimes information is stored in our memory, but for some reason it is inaccessible. This is known as interference, and there are two types: proactive interference and retroactive interference ( Figure 8.17 ). Have you ever gotten a new phone number or moved to a new address, but right after you tell people the old (and wrong) phone number or address? When the new year starts, do you find you accidentally write the previous year? These are examples of proactive interference : when old information hinders the recall of newly learned information. Retroactive interference happens when information learned more recently hinders the recall of older information. For example, this week you are studying about memory and learn about the Ebbinghaus forgetting curve. Next week you study lifespan development and learn about Erikson's theory of psychosocial development, but thereafter have trouble remembering Ebbinghaus's work because you can only remember Erickson's theory.

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• Authors: Rose M. Spielman, William J. Jenkins, Marilyn D. Lovett
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• Book title: Psychology 2e
• Publication date: Apr 22, 2020
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• Book URL: https://openstax.org/books/psychology-2e/pages/1-introduction
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Study Find First in Human Evidence of How Memories Form

Summary: Researchers have identified the characteristics of over 100 memory-sensitive neurons that play a key role in how memories are recalled in the brain.

Source: UT Southwestern Medical Center

In a discovery that could one day benefit people suffering from traumatic brain injury, Alzheimer’s disease, and schizophrenia, UT Southwestern researchers have identified the characteristics of more than 100 memory-sensitive neurons that play a central role in how memories are recalled in the brain.

Bradley Lega, M.D., Associate Professor of Neurological Surgery, Neurology, and Psychiatry, said his findings, published in the journal  NeuroImage , may point to new deep brain-stimulation therapies for other brain diseases and injuries.

“It sheds important light on the question, ‘How do you know you are remembering something from the past versus experiencing something new that you are trying to remember?'” said Dr. Lega, a member of the Peter O’Donnell Jr. Brain Institute.

The most significant finding was that firing occurs with different timing relative to other brain activity when memories are being retrieved. This slight difference in timing, called “phase offset,” has not been reported in humans before. Together, these results explain how the brain can “re-experience” an event, but also keep track of whether the memory is something new or something previously encoded.

“This is some of the clearest evidence to date showing us how the human brain works in terms remembering old memories versus forming new memories,” Dr. Lega said.

His study identified 103 memory-sensitive neurons in the brain’s hippocampus and entorhinal cortex that increase their rate of activity when memory encoding is successful. The same pattern of activity returned when patients attempted to recall these same memories, especially highly detailed memories.

This activity in the hippocampus may have relevance to schizophrenia because hippocampal dysfunction underlies schizophrenics’ inability to decipher between memories and hallucinations or delusions. The neurons identified by Dr. Lega are an important piece of the puzzle for why this happens, said Carol Tamminga, M.D., Professor and Chair of Psychiatry and a national expert on schizophrenia.

“Hallucinations and delusions in people with a psychotic illness are actual memories, processed through neural memory systems like ‘normal’ memories, even though they are corrupted. It would be important to understand how to use this ‘phase offset’ mechanism to modify these corrupted memories,” Dr. Tamminga said.

An opportunity to learn more about human memory arose from surgeries where electrodes that were implanted in epilepsy’s patients’ brains to map the patients’ seizures could also be used to identify neurons involved in memory. In this study, 27 epilepsy patients who had the electrodes implanted at UT Southwestern and a Pennsylvania hospital participated in memory tasks to generate data for brain research.

The data analysis does not conclusively prove, but adds new credibility to important memory model called Separate Phases at Encoding And Retrieval (SPEAR) that scientists developed from rodent studies.

“It’s never been nailed down. It’s one thing to have a model; it is another thing to show evidence that this is what’s happening in humans,” Dr. Lega said.

The SPEAR model, which predicts the “phase offset” reported in the study, was developed to explain how the brain can keep track of new-versus-old experiences when engaged in memory retrieval. Previously, the only evidence in support of SPEAR came from rodent models.

Dr. Tamminga holds the Stanton Sharp Distinguished Chair in Psychiatry.

About this memory research news

Author: Press Office Source: UT Southwestern Medical Center Contact: UT Southwestern Medical Center Image: The image is in the public domain

Original Research: Open access. “ Neurons in the human medial temporal lobe track multiple temporal contexts during episodic memory processing ” by Hye Bin Yoo et al. NeuroImage

Neurons in the human medial temporal lobe track multiple temporal contexts during episodic memory processing

Episodic memory requires associating items with temporal context, a process for which the medial temporal lobe (MTL) is critical. This study uses recordings from 27 human subjects who were undergoing surgical intervention for intractable epilepsy. These same data were also utilized in Umbach et al. (2020).

We identify 103 memory-sensitive neurons in the hippocampus and entorhinal cortex, whose firing rates predicted successful episodic memory encoding as subjects performed a verbal free recall task. These neurons exhibit important properties. First, as predicted from the temporal context model, they demonstrate reinstatement of firing patterns observed during encoding at the time of retrieval.

The magnitude of reinstatement predicted the tendency of subjects to cluster retrieved memory items according to input serial position. Also, we found that spiking activity of these neurons was locked to the phase of hippocampal theta oscillations, but that the mean phase of spiking shifted between memory encoding versus retrieval.

This unique observation is consistent with predictions of the “Separate Phases at Encoding And Retrieval (SPEAR)” model. Together, the properties we identify for memory-sensitive neurons characterize direct electrophysiological mechanisms for the representation of contextual information in the human MTL.

I have twice severe TBI by 2 accidents, both caused lost of memory especially the new one. Fortunately my skill to combine the stored brain data into a novel form that called invention is still working by the unbroken parts.

Yeah since too much stress put your heart into a lot of work.

I am currently dealing with a deranged group of former friends who have sold me out in order to conduct secret mind experimentation for behavior control on women whom they have stalked through the invasion of my bodily privacy.

But the initial inquiry stems from 23 years investigating my father, before they ultimately euthanized him nearly to death in 2013.

The use of cellular memory is among my many concerns.

I’ve had epilepsy since i was 18 I’m 34 now I’ve lost around half my life in memory i don’t remember having my first son and when i do remember stuff it’s as if it just happenedin the way it feels…but then again i start talking sometimes and start saying stuff i didn’t know i knew and i look out up and it’s right….weird it seems that i just lost my conscious memory and kept my subconscious memory

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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.

Stanford researchers observe memory formation in real time

By Alan Toth

Why is it that someone who hasn’t ridden a bicycle in decades can likely jump on and ride away without a wobble, but could probably not recall more than a name or two from their 3rd grade class?

This may be because physical skills — dubbed motor memories by neuroscientists — are encoded differently in our brains than our memories for names or facts.

Now, a new study by scientists with the Wu Tsai Neurosciences Institute is revealing exactly how motor memories are formed and why they are so persistent. It may even help illuminate the root causes of movement disorders like Parkinson’s disease.

“We think motor memory is unique,” said Jun Ding , an associate professor of neurosurgery and of neurology. “Some studies on Alzheimer’s disease included participants who were previously musicians and couldn’t remember their own families, but they could still play beautiful music. Clearly, there’s a huge difference in the way that motor memories are formed.”

Memories are thought to be encoded in the brain in the pattern of activity in networks of hundreds or thousands of neurons, sometimes distributed across distant brain regions. The concept of such a memory trace — sometimes called a memory engram — has been around for more than a century, but identifying exactly what an engram is and how it is encoded has proven extremely challenging. Previous studies have shown that some forms of learning activate specific neurons, which reactivate when the learned memory is recalled. However, whether memory engram neurons exist for motor skill learning remains unknown.

Ding and postdoctoral scholars Richard Roth and Fuu-Jiun Hwang wanted to know how these engram-like groups of cells get involved in learning and remembering a new motor skill.

“When you’re first learning to shoot a basketball, you use a very diverse set of neurons each time you throw, but as you get better, you use a more refined set that’s the same every time,” said Roth. “These refined neuron pathways were thought to be the basis of a memory engram, but we wanted to know exactly how these pathways emerge.”

In their new study, published July 8, 2022 in Neuron , the researchers trained mice to use their paws to reach food pellets through a small slot. Using genetic wizardry developed by the lab of Liqun Luo , a Wu Tsai Neurosciences Institute colleague in the Department of Biology, the researchers were able to identify specific neurons in the brain’s motor cortex — an area responsible for controlling movements — that were activated during the learning process. The researchers tagged these potential engram cells with a fluorescent marker so they could see if they also played a role in recalling the memory later on.

When the researchers tested the animals’ memory of this new skill weeks later, they found that those mice that still remembered the skill showed increased activity in the same neurons that were first identified during the learning period, showing that these neurons were responsible for encoding the skill: the researchers had observed the formation of memory engrams.

But how do these particular groups of neurons take on responsibility for learning a new task in the first place? And how do they actually improve the animal’s performance?

To answer these questions, the researchers zoomed in closer. Using two-photon microscopy to observe these living circuits in action, they observed the so-called “engram neurons” reprogram themselves as the mice learned. Motor cortex engram cells took on new synaptic inputs — potentially reflecting information about the reaching movement — and themselves formed powerful new output connections in a distant brain region called the dorsolateral striatum — a key waystation through which the engram neurons can exert refined control over the animal’s movements. It was the first time anyone had observed the creation of new synaptic pathways on the same neuron population — both at the input and the output levels — in these two brain regions.

The ability to trace new memories forming in the mouse brain allowed the research team to weigh in on a long-standing debate about how skills are stored in the brain: are they controlled from one central memory trace, or engram, or is the memory redundantly stored across many different brain areas? Though this study cannot discount the idea of centralized memory, it does lend credibility to the opposing theory. Another fascinating question is whether the activation of these engram neurons is required for the performance of already learned motor tasks. The researchers speculated that by suppressing the activity of neurons that had been identified as part of the motor cortex memory engram, the mice probably still would be able to perform the task.

“Think of memory like a highway. If 101 and 280 are both closed, you could still get to Stanford from San Francisco, it would just take a lot longer,” said Ding.   

These findings suggest that, in addition to being dispersed, motor memories are highly redundant. The researchers say that as we repeat learned skills, we are continually reinforcing the motor engrams by building new connections — refining the skill. It’s what is meant by the term muscle memory — a refined, highly redundant network of motor engrams used so frequently that the associated skill seems automatic.

Ding believes that this constant repetition is one reason for the persistence of motor memory, but it’s not the only reason. Memory persistence may also be affected by a skill being associated with a reward, perhaps through the neurotransmitter dopamine. Though the research team did not directly address it in this study, Ding’s previous work in Parkinson’s disease suggests the connection.

“Current thinking is that Parkinson’s disease is the result of these motor engrams being blocked, but what if they’re actually being lost and people are forgetting these skills?” said Ding. “Remember that even walking is a motor skill that we all learned once, and it can potentially be forgotten.”

It’s a question that the researchers hope to answer in a follow-up study, because it may be the key to developing effective treatments for motor disorders. If Parkinson’s disease is the result of blocked motor memories, then patients should be able to improve their movement abilities by practicing and reinforcing these motor skills. On the other hand, if Parkinson’s destroys motor engrams and inhibits the creation of new ones — by targeting motor engram neurons and their synaptic connection observed in the team’s new study — then a completely different approach must be taken to deliver effective treatments.

“Our next goal is to understand what’s happening in movement disorders like Parkinson’s,” Ding said. “Obviously, we’re still a long way from a cure, but understanding how motor skills form is critical if we want to understand why they’re disrupted by disease.”

The research was published July 8 in Neuron: https://doi.org/10.1016/j.neuron.2022.06.006

Study authors were Fuu-Jiun Hwang, Richard H. Roth, Yu-Wei Wu, Yue Sun, Destany K. Kwon, Yu Liu, and Jun B. Ding.

The research was supported by the National Institutes of Health (NIH) and National Institute for Neurological Disease and Stroke (NINDS); the Klingenstein Foundation's Aligning Science Across Parkinson’s initiative; and GG gift fund, the Stanford School of Medicine Dean’s Postdoctoral Fellowship; and Parkinson’s Foundation Postdoctoral Fellowship.

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Earliest Memories Start at Age Two and a Half, Study Finds

Joni Sweet is an experienced writer who specializes in health, wellness, travel, and finance.

Nick Blackmer is a librarian, fact-checker, and researcher with more than 20 years’ experience in consumer-oriented health and wellness content. He keeps a DSM-5 on hand just in case.

Key Takeaways

• New research shows that our earliest memories may begin at age 2.5, about a year sooner than previously thought.
• How far back you can remember depends on a long line-up of factors, including your culture, gender, family, and the way in which you’re asked to recall memories.
• You may be able to remember further back when asked repeatedly over time what your earliest memory is.

How far back can you remember? The answer might be even earlier than you think, according to new research.

In a study recently published in the journal Memory , researchers found that people could recall things that happened to them from as far back at age 2.5 years old on average—about a year earlier than previously estimated.

The research also suggests that there’s actually a “pool of potential memories” that people can pull from, rather than a fixed beginning, and you may be able to recall even older memories when interviewed repeatedly about them.

Here’s what the latest research says about how far back our memory actually goes and why it matters for the narrative of your life.

For this study, researcher Carole Peterson, PhD , professor in the department of psychology at Memorial University of Newfoundland, reviewed previous research on childhood amnesia and analyzed data collected in her laboratory over the last two decades to better understand early memories .

The data showed that people’s earliest memories can often be traced back to age 2.5. Scientists previously believed that a person’s memory clock started at around 3.5 years old.  

David Copeland, PhD

It might be difficult to pinpoint the one true ‘earliest memory’ for anyone.

“This article explored the idea of infantile amnesia—this is an idea that researchers have considered for years and it states that people do not remember much (or anything) from their first 2 to 3 years of life,” explains David Copeland, PhD , associate professor of psychology at the University of Nevada, Las Vegas. “This line of research is suggesting that we might have memories a little bit earlier than that.”

The research also found that just how far back any one individual’s memory goes depends on a variety of factors, such as: 

• nationality
• home environment (urban vs. rural)
• how your parent recalls their memories
• intelligence
• birth order
• the size of your family

Cassandra Fallon, LMFT

This study will lend validation to people that even from a young age, children do see and are impacted by their environment, the people in them, and events around them.

“This study will lend validation to people that even from a young age, children do see and are impacted by their environment, the people in them, and events around them,” says Cassandra Fallon, LMFT , a therapist at Thriveworks.

Fallon continues, “The fact that recalling memories is a challenge and that this study gives permission for this to be acceptable is helpful for validating that we may not ever know some details, like dates and times, but that it does not take away from the fact that we experienced or felt what we did and that it impacts us.”

Another important factor in how far you can remember is how you’re asked to recall your earliest memory, the study found. Your earliest memory may not be permanently fixed. Instead, extensive interviews and multiple follow-ups over the span of months or years could help you pull even earlier recollections from your memory bank in some cases.

“This aligns with what I observe in my clinic. I advise my patients to create timelines of their life, and this helps them access early memories,” says Leela Magavi, MD , psychiatrist and regional medical director at  Community Psychiatry  in Newport Beach, California. “They are often surprised by how much they can remember once they complete this activity.”

The research concluded there’s fluidity in retrieving early experiences and that one’s earliest memory may actually be malleable.

“In other words, it might be difficult to pinpoint the one true ‘earliest memory’ for anyone,” adds Copeland.

Why Early Memories Matter

Regardless of how far back they go, your earliest memories may provide therapeutic opportunities.

“Early memories often align with individuals’ core values, fears, hopes, and dreams. Learning about early memories can allow individuals to nurture their inner child and heal from the stressful or traumatic situations they have endured throughout their life,” says Dr. Magavi. “It can also help them gain clarity and embrace what matters the most to them.”

Leela Magavi, MD

Early memories often align with individuals’ core values, fears, hopes, and dreams. Learning about early memories can allow individuals to nurture their inner child and heal from the stressful or traumatic situations they have endured throughout their life.

Early memories—even those that have been reconstructed from external sources beyond what’s in our minds—can also play an important role in constructing the overall narrative of your life, says Copeland.

“For example, whether someone truly remembers the experience of falling off of a tricycle at age 3 or they learn about it from family members’ stories or from seeing pictures, it might not matter—as long as the event actually happened, it can be a part of one’s life narrative,” he says. “Someone might use it as a theme in their life of overcoming difficulties ever since they were young.”

Overall, these early memories help us to better understand ourselves, which can help us lead more fulfilling lives.

“The better we know ourselves, both attributes and challenges, the better we are able to make changes or maintain awareness for consistency. It is a powerful thing to know our strengths to continue using them and to know our weaknesses so that we can grow and learn to become a better become better version of ourselves,” says Fallon.

She adds: “This improves self-confidence, eases anxiety, reduces depression, and builds our grit, determination, and resiliency to handle anything life throws at us.”

What This Means For You

Your earliest memories can teach you a lot about yourself. Just how far back you can recall depends on a variety of factors, but new research shows that our memory bank may start at age 2.5 on average.

Repeatedly being interviewed about your earliest memories may allow you to remember things that happened at an even younger age. But experts say the age at which your earliest memory occurred doesn’t matter quite as much as putting that information into the context of your life and finding ways to grow from it. These memories, when placed into our overall narratives, provide opportunities to heal from trauma and handle the obstacles of life. 

Peterson C. What is your earliest memory? It depends .  Memory . 2021;29(6):811-822. doi:10.1080/09658211.2021.1918174

By Joni Sweet Joni Sweet is an experienced writer who specializes in health, wellness, travel, and finance.

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Chapter 8 psych.

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Researchers investigate memory recall in healthy, older adults

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Even among healthy people, a faltering memory is often an expected part of aging - but it's not inevitable.

Some individuals exhibit remarkable maintenance of memory function throughout late adulthood, whereas others experience significant memory decline. Studying these differences across individuals is critical for understanding the complexities of brain aging, including how to promote resilience and longevity." Alexandra Trelle, Postdoctoral Research Fellow, Stanford University

Building on studies that have focused on young populations, Trelle and colleagues are investigating memory recall in healthy, older adults as part of the Stanford Aging and Memory Study. In new research, published May 29 in eLife , this team has found that memory recall processes in the brains of older adults can look very similar to those previously observed in the brains of young adults. However, for those seniors who had more trouble remembering, evidence for these processes was noticeably diminished.

By gaining a better understanding of memory function in older adults, these researchers hope to someday enable earlier and more precise predictions of when memory failures signal increased risk for dementia.

A striking similarity

When Anthony Wagner, the Lucie Stern Professor in the Social Sciences at Stanford's School of Humanities and Sciences, was a graduate student at Stanford in the '90s, he conducted some of the first fMRI studies of memory formation. At that time, state-of-the-art imaging and analysis technologies only allowed measurement of the magnitude of activity from a centimeter-and-a-half section of the brain.

In contrast, the current study measured activity from the whole brain at high-resolution, and analyses not only focused on the magnitude of activity but also on the memory information that is contained in patterns of brain activity.

"It's exciting to have basic science tools that allow us to witness when a memory is being replayed in an individual mind and to draw on these neural processes to explain why some older adults remember better than others," said Wagner, who is senior author of the paper. "As a graduate student, I would never have predicted that we would do this kind of science someday."

In the experiment, 100 participants between the ages of 60 and 82 had their brains scanned as they studied words paired with pictures of famous people and places. Then, during a scanned memory test, they were prompted with words they had seen and asked to recall the associated picture. The memory test was designed to assess one's ability to remember specific associations between elements of an event, a form of memory that is often disproportionately affected by aging.

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In the scans, the researchers observed that the brain processes that support remembering in older adults resemble those in younger populations: when people remember, there is an increase in hippocampal activity - a brain structure long known to be important for remembering events - along with the reinstatement of activity patterns in the cortex that were present when the event was initially experienced. That is, remembering entails neural time travel, replaying patterns that were previously established in the brain.

"It was striking that we were able to replicate this moment-to-moment relationship between hippocampal activity, replay in the cortex, and memory recall, which has previously been observed only in healthy younger adults," said Trelle, who is lead author of the paper. "In fact, we could predict whether or not an individual would remember at a given moment in time based on the information carried in patterns of brain activity."

The researchers found that, on average, recall ability declined with age. Critically, however, regardless of one's age, stronger hippocampal activity and replay in the cortex was linked to better memory performance. This was true not only for the memory test conducted during the scan but also memory tests administered on a different day of the study. This intriguing finding suggests that fMRI measures of brain activity during memory recall are tapping into stable differences across individuals, and may provide a window into brain health.

Only the beginning

This research lays the foundation for many future investigations of memory in older adults in the Stanford Aging and Memory Study cohort. These will include work to further detail the process of memory creation and recall, studies of change in memory performance over time, and research that pairs fMRI studies with other kinds of health data, such as changes in brain structure and the build-up of proteins in the brain that are linked to Alzheimer's disease.

The ultimate aim is to develop new and sensitive tools to identify individuals who are at increased risk for Alzheimer's disease before significant memory decline occurs.

"We're beginning to ask whether individual differences in the ability to mentally travel back in time can be explained by asymptomatic disease that impacts the brain and predicts future clinical diagnosis," said Wagner. "We're hopeful that our work, which requires rich collaborations across disciplines, will inform clinical problems and advance human health."

Stanford University

Trelle, A.N., et al. (2020) Hippocampal and cortical mechanisms at retrieval explain variability in episodic remembering in older adults. eLife . doi.org/10.7554/eLife.55335 .

Posted in: Medical Science News | Medical Research News | Healthcare News

Tags: Aging , Alzheimer's Disease , Brain , Cortex , Dementia , Diagnostics , Imaging , Neurology , Radiology , Research , Seniors , Tsai

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Internet Use Affects Memory, Study Finds

By Patricia Cohen

• July 14, 2011

The widespread use of search engines and online databases has affected the way people remember information, researchers are reporting .

The scientists, led by   Betsy Sparrow, an assistant professor of psychology at Columbia, wondered whether   people were more likely to remember information that could be easily retrieved from a computer, just as students are more likely to recall facts they believe will be on a test.

Dr. Sparrow and her collaborators, Daniel M. Wegner of Harvard and Jenny Liu of the University of Wisconsin, Madison, staged four different memory experiments. In one, participants typed 40 bits of trivia — for example, “an ostrich’s eye is bigger than its brain” — into a computer. Half of the subjects believed the information would be saved in the computer; the other half believed the items they typed would be erased.

The subjects were significantly more likely to remember information if they thought they would not be able to find it later. “Participants did not make the effort to remember when they thought they could later look up the trivia statement they had read,” the authors write.

A second experiment was aimed at determining whether computer accessibility affects precisely what we remember. “If asked the question whether there are any countries with only one color in their flag, for example,” the researchers wrote, “do we think about flags — or immediately think to go online to find out?”

In this case, participants were asked to remember both the trivia statement itself and which of five computer folders it was saved in. The researchers were surprised to find that people seemed better able to recall the folder.

“That kind of blew my mind,” Dr. Sparrow said in an interview.

The experiment explores an aspect of what is known as transactive memory — the notion that we rely on our family, friends and co-workers as well as reference material to store information for us.

“I love watching baseball,” Dr. Sparrow said. “But I know my husband knows baseball facts, so when I want to know something I ask him, and I don’t bother to remember it.”

The Internet’s effects on memory are still largely unexplored, Dr. Sparrow said, adding that her experiments had led her to conclude that the Internet has become our primary external storage system.

“Human memory,” she said, “is adapting to new communications technology.”

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Memory is complicated. A new study co-authored by Jeopardy! contestant Monica Thieu looks at how two different memory systems might give some people an edge with recalling facts.

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Yoga Boosts Memory and Brain Function Study Shows

Concerned about keeping your full memory capacity and cognitive functioning as you get older?

Well, if you are a yoga practitioner, there is good news. A 2020 meta-analysis shows that for people without cognitive impairment, regular yoga practice can offer significant benefits on both memory and cognitive function.

As the number of yoga studies proliferates, a growing number of meta-analyses are able to chart the effects of yoga on one factor across not just one, but multiple studies.

The 2020 meta-analysis included 12 studies with a total of 912 participants, 73.9% female. Eleven of the studies were randomized controlled trials, which is the highest standard for reliable research evidence. Of the subjects, about one third had some degree of cognitive impairment, while two thirds did not.

When results were compiled across all 12 studies, they showed significant beneficial effects on a number of cognitive factors, including improved memory, better executive function, and enhanced attention and processing speed.

Which type of yoga was used? The studies involved had a wide variety of yoga practices, but they had one thing in common: a meditative focus while doing the postures.

This study adds to the evidence from previous studies on the benefits of yoga for cognitive and mental-emotional health.

A study published in the journal Mindfulness, for example, showed that both yoga and meditation can boost mood and increase cognitive performance.

Yoga and Meditation Study

Researchers at the University of Waterloo in Canada recruited a predominantly Caucasian, college-educated sample of adult women between the ages of 18 and 48 (mean 27.71 sd= 8.32) to participate in the study. To be included, women were required to have between 4 months and five years of hatha yoga experience.

Each participant completed a series of questionnaires about physical activity and their yoga and meditation experience. They were then asked to complete three 25-minute counterbalanced sessions of hatha yoga, meditation, and a control task of reading one or more “yoga culture” magazines. Yoga sessions included mindfulness meditation, followed by postures and concluding with savasana (corpse pose), and were taught by a certified yoga instructor. During each class, participants were repeatedly reminded to focus on breath and bodily sensations and balance effort with ease.

Guided meditation practice was taught in the supine position. During these meditation sessions women were asked to become non-judgmental observers of their experience, and were led through a present-focused awareness exercise where they were asked to pay attention to their thoughts and emotions with openness and acceptance. This was followed by a body scan during which they were asked to note feelings and bodily sensations.

Cognitive function was assessed using the Stroop interference task – a standardized measure of executive function and inhibitory control. Mood was evaluated using a short form of the adult version of the Profile of Mood States (POMS).

Research Says Yoga and Meditation Boost Mood and Cognitive Function

The study’s results showed that, for a sample of healthy, experienced female yoga practitioners, 25 minutes of either hatha yoga or mindfulness meditation significantly improved executive function. Interestingly, this effect was not detected 5 minutes after yoga and meditation practice but was found after a 10-post-session delay. Improvements in cognitive function did not differ significantly between yoga and meditation, but there was a slight trend toward greater positive change following hatha yoga.

Similarly, both yoga and meditation yielded similar improvements in mood, with yoga demonstrating slightly greater mood enhancement benefits than meditation. Neither cognitive performance nor mood were impacted by reading “yoga culture” magazines.

The results of this study are consistent with prior research with diverse samples of participants who associate yoga and meditation with greater positive mood and enhanced executive function. Regarding their inability to detect reliable changes in cognitive performance 5 minutes following yoga and meditation, researchers suggest that there may be yoga- or meditation-induced sedative effects immediately following practice that may render cognitive benefits indiscernible in the short term.

Because this study was constrained to a sample of predominantly Caucasian, well-educated women in early to middle adulthood, more research will be needed to determine whether enhancement of mood and cognitive function is experienced among diverse groups of participants.

Luu, K & Hall PA (2016). Examining the acute effects of hatha yoga and mindfulness meditation on executive function and mood. Mindfulness . DOI 10.1007/s12671-016-0661-2

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How much are students willing to pay for subscriptions?

Subscription-based services such as Amazon Prime, Apple Music and Disney+ have grown in both popularity and price throughout the past several years, tacking on dollars to students’ spending.

In a study done by C+R Research in 2022, consumers estimated spending an average of $86 per month on subscriptions. In reality, consumers spent an average of $219, or 2.5 times their average original estimate.

Several educational apps such as Duolingo, Kahoot and Quizlet have instituted subscriptions that make new and existing features part of paid tiers. Companies start charging for subscriptions at low prices, then raise them as they try to find the highest price most customers will pay, BYU finance professor Taylor Nadauld said.

For the language learning app Duolingo’s premium subscription, “I would probably pay $10 more from what it is now,” BYU student Cindy Hernandez said. She said she would pay this amount because the app helps her learn and she finds that valuable.

However, Hernandez would not pay an additional $10 a month for an app such as Apple Music.

“I’m not really learning anything from it. It’s just kind of a comfort,” she said.

Companies rely on subscriptions because it makes revenue more consistent, Nadauld said. When a customer signs up, they are less likely to stop paying for the service.

“It’s a little harder to get someone to pay you every single time they use a product,” he said, “than it is to get them to pay you once and then hope that they keep paying you.”

 If customers feel they are paying more than what a service is worth, they might cancel, Nadauld said.

“If I was really invested in it, the most I’d be willing to pay is probably about $10. Maybe up to $12 depending on specifically what the subscription is and whether or not they’re making any improvements,” BYU student Cael Erickson said of monthly subscriptions. Erickson does not pay for any subscriptions, but said he would be most likely to pay for a music-streaming app.

In addition to maintaining customers, companies who operate a subscription business model can be acquired at a higher price because their revenue model is more stable and forecastable, Nadauld said.

While subscription-based business models may not be what’s best for consumers, “it’s best for the company in terms of making them more attractive as an acquisition target,” Nadauld said.

Subscription models are likely here to stay, he said, but new technologies will arrive that will help people manage their various subscriptions.

“So ironically, people will get one more subscription that helps them manage all of their other subscriptions. That’s what I think is gonna happen,” he said.

Subscription tracking services include Rocket Money , PocketGuard and Trim , among others. While many of these services offer free features, they offer paid features as well.

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