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8.1 How Memory Functions

Learning Objectives

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

  • Discuss the three basic functions of memory
  • Describe the stages of memory storage
  • Describe and distinguish between procedural and declarative memory and semantic and episodic memory


   Learning and memory operate together in order increase our ability for navigating the environment and survival. Learning refers to a change in behavior that results from acquiring knowledge about the world and memory is the process by which that knowledge is encoded, stored, and later retrieved. Memory represents an information processing system; therefore, we often compare it to a computer. Although a computer provides in many cases a useful analogy for human memory, there are still many differences which make our ability to encode, maintain and retrieve information unique. After Paul Broca’s 1861 discovery that disruption to a specific area in the left frontal cortex (Broca’s Area) leads to deficits in language production, researchers and medical professionals began to understand other mental functions such as sensation, perception, and voluntary movement are also mediated by specific areas of the brain. This concept is referred to as functional localization.

The importance of functional localization in the brain became clear, but did this also suggest there are specific area of the brain that are important for memory? There are several different types of memory, and certain regions of the brain are more important than other areas for some forms of memory.

Memory can be thought of as occurring for the most part on a linear continuum, meaning memory occurs in time organized stages. This process begins with the encoding of information, then through rehearsal that information is stored, and finally the information is retrieved.


A diagram shows three boxes, placed in a row from left to right, respectively titled “Encoding,” “Storage,” and “Retrieval.” One right-facing arrow connects “Encoding” to “Storage” and another connects “Storage” to “Retrieval.”Figure 8.01. Encoding involves the intake of information through the sensory receptors which allow further processing to take place. Storage is the retention of attended to information that has been encoded. Retrieval, or getting the information out of memory and back into awareness, refers to the access and recall of information that has been encoded and stored properly. 


   We get information into our brains through a process called encoding, which represents the act of taking in information and converting it to a usable mental form (Ashcraft & Radvansky, 2014). The previous chapter on sensation and perception describes in detail how transduction occurs through the various sense organs which is how information becomes available for encoding. Once we receive sensory information from the environment, the brain processes and organizes this information (i.e. what should be attended to, and will be passed on to later memory systems and what is not). Encoding information occurs through automatic processing which takes in much more information than we will actually be able to further maintain. Attentional processes later allow us to categorize information for further prioritize information in short-term memory stores.

If someone asks you what you ate for lunch today, more than likely you could recall this information quite easily. This is known as automatic processing, or the encoding of details like time, space, frequency, and the meaning of words. Automatic processing is usually done without any conscious awareness. Recalling the last time you studied for a test is another example of automatic processing. But what about the actual test material you studied? It probably required a lot of work and attention on your part in order to encode that information. This is known as effortful processing.


A photograph shows a person driving a car.When you first learn new skills such as driving a car, you have to put forth effort and attention to encode information about how to start a car, how to brake, how to handle a turn, and so on. Once you know how to drive, you can encode additional information about this skill automatically. (credit: Robert Couse-Baker)


   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!).

  1. The notes were sour because the seams split.
  2. The voyage wasn’t delayed because the bottle shattered.
  3. 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, 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. This exercise also demonstrates the effect of interference (a distracting task) which can reduce the amount of information that is encoded.

In terms of different methods of encoding information, Hermann Ebbinghaus pioneered the experimental study of memory in the 1880s by documenting what he referred to as the learning curve, and the forgetting curve. These curves are graphic representations of increases in learning related to the amount of exposure to a stimulus, and the amount of information lost (the amount fo information one is unable to accurately recall) over time, for the learning and forgetting curves respectively. The learning curve is used in two ways; to describe recall after presentation of the same task over time, and also to describe recall ability of a body of knowledge over time. Ebbinghaus revealed that different memory tasks can lead to differences in recall as found between performance on recall tasks and recognition tasks. Within recognition tasks, individuals only need to identify whether the information has been previously presented or not, compared to recall tasks where individuals are required to access the stored memory and report what they encoded leading to faster, more accurate responses for recognition tasks compared to recall tasks.

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? 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 accurately remembered more often compared to words encoded visually or acoustically suggesting semantic encoding involves a deeper level of processing than the shallower visual or acoustic encoding. Craik and Tulving concluded that the strength of the information being encoding depends on the depth of processing. Depth of processing suggests the more meaning and importance you assign to information as it is being encoded, the greater the chance that information will be correctly recalled later and the easier it will be to access that information.

The self-reference effect represents a 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). A generation effect has also been documented (Slameka & Graf, 1978) indicating information you generate or create is more likely to be accurately recalled compared to information you heard or read. Additionally, physical movement and acting out information with others has been shown to improve later recall (Noice & Noice, 2001), and more recent research has suggested incorporating associations with necessity for survival additionally tend to increase recall for words (Nairne, Thompson & Pandeirada, 2007).

Other influences on later memory recall include encoding specificity and the use of retrieval cues. Tulving and Thompson (1978; Unsworth, Spillers & Brewer, 2012) suggested information is encoded into memory not as isolated, individual items, but as pieces of a scene or action in a specific context. Therefore, encoding a context for the information to be remembered will lead to more accurate, and accessible information recall which is referred to as encoding specificity. Godden and Baddeley (1975) asked a group of scuba divers to memorize a list of words, half memorizing on land, and half memorizing words under water. During the later recall task, half of the people recalled the words in the same context as when it was encoded (on land or under water) and half recalled the information in the opposite context to where they encoded the information. Recall data for context demonstrated memory was better when the encoding and retrieval contexts were the same compared to when context was reversed. Finally, retrieval cues suggest information will be more readily available for memory recall when a useful prompt or reminder is associated with the encoding of the information. As an example of retrieval cues, Schab (1990) found participants who were presented with ambient odors such as chocolate during encoding later were able to recall information with greater accuracy compared to participants not cued with an odor. Could these techniques of encoding be beneficial to you as you attempt to later recall the concepts in this chapter?


   One of the most influential models to explain how memory is organized is the information-processing model (also known as the Atkinson–Shiffrin model or the multi-store model or the modal model or the Standard Theory of Memory, 1968). The model conceptualizes memory as a flow of encoded information through a series of stages: Sensory MemoryShort-Term Memory, and finally Long-Term Memory. Specifically, after encoding information, a short-term memory process known as working memory allows for maintenance and manipulation of different modalities of information before being transferred to long term memory.


A flow diagram consists of four boxes with connecting arrows. The first box is labeled “sensory input.” An arrow leads to the second box, which is labeled “sensory memory.” An arrow leads to the third box which is labeled “short-term memory (STM).” An arrow points to the fourth box, labeled “long-term memory (LTM),” and an arrow points in the reverse direction from the fourth to the third box. Above the short-term memory box, an arrow leaves the top-right of the box and curves around to point back to the top-left of the box; this arrow is labeled “rehearsal.” Both the “sensory memory” and “short-term memory” boxes have an arrow beneath them pointing to the text “information not transferred is lost.”Figure 8.02. According to the information-processing model, information passes through three distinct stages in a linear fashion in order for it to be stored in long-term memory. Rehearsal is used to build a stronger memory trace which is stored in long-term memory with sufficient rehearsal.


   In the information-processing model of human memory, stimuli from the environment are processed first in sensory memory: storage of brief sensory events, such as sights, sounds, and tastes. Sensory memory is extremely limited in maintaining information—up to a couple of seconds before information is further categorized for what will be processed in the next stage, short-term memory. We are constantly bombarded with sensory information through transduction from our various types of sensory receptors. We cannot absorb all of this information, or even most of it, and each distinct level of memory process acts as a filter as information moves from sensory memory, to short-term, and finally long-term memory where information is available for later recall. For example, what was your professor wearing the last class period? As long as the professor was dressed appropriately, most of the time the attire of a professor is not readily important and therefore is not usually considered important enough to rehearse and store in long-term memory. Sensory information about sights, sounds, smells, and even textures, which we do not view as valuable information, we discard. Think about driving for an hour or so. You are obviously absorbing the information around you as you drive as is evident by your ability to properly navigate to your destination, however you will most likely not be able to remember small specific details about your drive such as how many blue cars you passed or the names of all the street signs you passed along the way. If we view something as valuable, the information will move into our short-term memory system, but most information we process is filtered out in order to allow us to focus on what we categorize as important.

One study of sensory memory investigated the significance of valuable information on short-term memory storage. In one of the more well know experimental designs in psychology, 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 the figure below. 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, and not as easy as it seems.


Several names of colors appear in a font color that is different from the name of the color. For example, the word “red” is colored blue.Figure 8.03. The Stroop effect describes why it is difficult for us to name a color when the word and the color of the word are different.


   Short-term memory (STM) represents a temporary storage system that processes incoming sensory memory. Although some argue for no distinction between short-term and working memory (Cowen, 2008; Rose, Myerson, Roediger & Hale, 2010), for the sake of consistency with other introductory psychology text (Licht, Hull & Ballantyne, 2014) we will consider short-term memory a stage in the information processing model as well as a location where information is stored, and working memory as a collection of processes that allow us to maintain and manipulate information. The ability to maintain information longer than what is provided by sensory memory within working memory allows for rehearsal strategies or meaning to be assigned to information ensuring later accurate recall.

Working memory capacity is limited and operates on a bottleneck model of information processing. The bottleneck analogy refers to the flow of information through memory beginning from the base of a hypothetical bottle where large amounts of information are being processes through the senses, and as information is processed in working memory, the amount of information that is able to pass through the narrowing neck of the bottle and on to long term memory is drastically reduced (through the narrow neck of the bottle) in stored information compared to what was initially processed at the encoding stage.  Working memory processes exist right where the bottle becomes narrow allowing us to maintain information in working memory for about 20 seconds which will make the information more likely to end up securely stored in long-term memory. George Miller (1956), in his research on the capacity of memory which aided in the dawn of the field of cognitive psychology, 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.  More recent research re-evaluating working memory capacity suggests working memory capacity on average actually tends to be even lower at about four plus or minus one units of information suggesting a higher capacity found by Miller may have been related to the use of heuristics (discussed further below) such as chunking information (Cowan, 2001).

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). The conscious repetition of information known as rehearsal allows information to move from the temporary short term memory store into long-term memory, a process known as memory 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 below 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.


A series of numbers includes two rows, with six numbers in each row. From left to right, the numbers increase from four digits to five, six, seven, eight, and nine digits. The first row includes “9754,” “68259,” “913825,” “5316842,” “86951372,” and “719384273,” and the second row includes “6419,” “67148,” “648327,” “5963827,” “51739826,” and “163875942.”Figure 6. Work through this series of numbers using the recall exercise explained above to determine the longest string of digits that you can store.


   Note the longest string at which you got the series correct. As noted above, revisions to Miller’s seven plus or minus two capacity suggest on average, most people will have a working memory capacity of about 4 plus or minus one units when not using any kind of memory technique such as chunking. 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), but as discussed above, information processed with more depth of processing tend to be more readily available compared to more shallow encoding of information.


In humans, working memory is composed of various organized processes and consists of at least two individual mechanisms used to maintain and manipulate verbal and visuospatial information, a mediating mechanism that blends the different forms of information, and an overarching attention allocating mechanism that focuses the use of cognitive resources between the sub divisions of working memory. This structured organization of working memory processes was first proposed by Baddeley and Hitch (1974) and was initially proposed to be made up of three different sub-systems known as the visuospatial sketchpad, the episodic buffer, and the phonological loop. These three sub-systems are then coordinated by an attention directing mechanism known as the central executive.

According to the Baddeley (2000; Baddeley & Hitch, 1994) model, the phonological loop is mainly concerned with the processing and maintenance of verbal and auditory information. This mechanism has also been likened to what we understand as our inner monologue, which we use to recite and rehearse information in order to build a strong trace for later recall. We use the phonological loop while reading, trying to solve problems in our head, or learning new vocabulary. Studies have suggested on average people are able to actively manipulate about two seconds worth of verbal information without relying on repetition rehearsal (Baddeley, 2002).

The visuospatial sketchpad on the other hand represents a mechanism separate from the phonological loop that allows for the maintenance and manipulation of visual and spatial information. This system allows us to navigate in a room without your sight, reaching out to grab your coffee without spilling it all over your brand new khakis, and also aids in manipulation of spatial perspective. Using the visuospatial sketchpad we are able to envision a map of campus and determine what path to take to get to a lecture you would like to attend, or alternate routes to take in order to avoid congested traffic. Studies examining the visuospatial sketchpad demonstrated individuals have trouble trying to perform two visuospatial tasks at the same time suggesting this aspect of working memory is fairly demanding in terms of cognitive resource load (Repovš & Baddeley, 2006).

The central executive represents an attention allocating mechanism. Similar to a group leader or manager of lower level workers, the central executive is the process of determining which information to focus on, and therefore which working memory to utilize. The central executive additionally decides which information to ignore, and also has a limited capacity which explains people become less productive at individual tasks when performing many different tasks at once (texting, while eating and driving at the same time). The Eriksen Flanker task represents a widely used method in cognitive science to quantify the ability of the central executive to quickly and accurately suppress distractors in their recognition and response to target cues (ignore distractions) (Eriksen & Eriksen, 1974).

Finally, the episodic buffer acts as a mediating procedure that temporarily merges information from the phonological loop, the visuospatial sketchpad, and long-term memory, under the control of the central executive (Baddeley, 2000). This procedure forms an important bridge between information available in long-term memory and conscious awareness and allows us to form plans for the future, review past events and solve problems based on solutions that worked in the past. The episodic buffer additionally operates on a limited capacity of processing and allows individuals to use integrated units of information stored in long-term memory to imagine new concepts (Baddeley, 2012).


Figure 8.04. Representation of the components that make up the Baddeley model of working memory. The various parts are also presented over the relative brain areas hypothesized to mediate the phonological loop and visuospatial sketchpad. Adapted from Redshaw, 2009.


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. 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.


A diagram consists of three rows of boxes. The box in the top row is labeled “long-term memory”; a line from the box separates into two lines leading to two boxes on the second row, labeled “explicit (declarative)” and “implicit (non-declarative).” From each of the second row boxes, lines split and lead to two additional boxes. From the “explicit” box are two boxes labeled “episodic (experienced events)” and “semantic (knowledge and concepts).” From the “implicit” box are two boxes labeled “procedural (skills and actions)” and “emotional conditioning.”Figure 8.05. There are two components of long-term memory: explicit and implicit. Explicit memory includes episodic and semantic memory. Implicit memory includes procedural memory and things learned through conditioning.


Explicit memories (also referred to as declarative memories) are those we consciously try to remember and recall. Explicit memory has to do with the storage of facts and events and is the type of memory you are aware of having and can consciously express. For example, if you are studying for your chemistry exam, the material you are learning will be part of your explicit memory. Explicit memory has two parts: semantic memory and episodic memory.

Semantic memory has 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).

Often our most vivid episodic memories are associated with intense emotions. A flashbulb memory is a highly detailed, exceptionally vivid episodic memory of the circumstances surrounding a piece of surprising, consequential, or emotionally arousing news was heard. With flashbulb memories, individuals often recall the precise moment you learned of the event and specific details around it- where you were, who or what source informed you, what you did next, and how you felt. Notably, flashbulb memories are not first-hand memories of experiencing the event but rather the experiences associated with learning about an event (Hirst & Phelps, 2016). In addition, while memories seem intense and vivid, research suggests flashbulb memories are prone to inaccuracies and may lack specific important details (Hirst et al., 2015).

Implicit memories (also referred to as non-declarative memories) are memories that are not part of our consciousness. They are memories formed from behaviors. A common example of implicit memory is represented by what is known as repetition priming. Repetition priming represents a general form of implicit memory where a previous encounter with information facilitates later processing of the same information (Ashcraft & Radvansky, 2013). Repetition priming has been documented in a number of tasks such as word identification and lexical decision making tasks (Morton, 1979), word and picture naming tasks (Brown et al., 1991), and rereading fluency tasks (Masson, 1984). Within all these studies, prior experience to the stimuli leads to faster performance on a later task, even if the individual does not remember having encountered the stimuli before.

A classic demonstration of repetition priming described by Jacoby and Dallas (1981) who asked participants to study a list of familiar words, answering a question about each word as they moved through the task. Sometimes the questions asked participants about the physical form of the word as in “does the word contain the letter r?”, sometimes participants were asked about the sound of the word as in “does the word rhyme with train?”, and sometimes participants were asked about semantic characteristics of the word as in “is the word in the center of the nervous system?”. Related to Craik and Lockharts depth of processing theories (1972), Asking participants about the physical form of the word should create shallow information processing, while asking about the sound should create deeper processing and semantic questions should create the deepest levels of information processing. After the information was encoded, explicit memory was tested using a simple recognition and recall task. This task demonstrated that recognition and recall was highest for information that was coded at the deepest levels (semantic encoding), while the shallow coded information was less available for recall and recognition. In the implicit memory task, participants were presented the words one at a time for only 35 ms, followed by a row of asterisks as a mask. Participants had to report the words they say, demonstrating that participants did not need to remember which words they had seen earlier, they just had to identify what words were very briefly presented. On average, word identification was about 80% regardless of how they had been studies, in comparison to 65% of control words that had not been previously presented. This is a typical finding in implicit memory tasks in that even without conscious recollection of the stimuli that had been previously presented, there is a faster and more accurate response for words that were previously presented compared to those that were not.

An additional important implicit memory tasks created by Blakemore (1977) demonstrates implicit learning processes in amnesic patients. Being that patients such as H.M. who experienced bilateral damage to the hippocampus and lateral temporal lobes, and was unable to form new memories (anterograde amnesia), these patients were asked to complete a drawing exercise where they were to trace in inside guiding lines, specific shapes while watching their hands move in a mirror. Initially, this task is extremely difficult showing participants have lots of trouble staying within the lines. However, amnesic patients who have no recollect of completing the task before show significant improvement over time demonstrating clear implicit processes related to learning and memory.


Figure 8.06. H.M., a patient with anterograde amnesia completes and motor learning task in a mirror over a series of days. Improvement in the task over time represents evidence of implicit learning and memory. (adapted from Kalat, 2015)


Procedural memory is a type of implicit memory: it stores information about how to do things where you are able to perform actions without consciously monitoring the sub procedures that need to be pieced together in order to perform the task. It is the memory for skilled actions, such as how to brush your teeth, how to drive a car, and how to swim. 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.

Emotional Conditioning is also a type of implicit memory. Memories acquired through classical conditioning are also categorized as implicit such as the feelings of hunger you get when smelling the aroma of favorite food truck while walking by. Associations are created implicitly between stimuli that commonly occur together cueing thoughts of the associated stimuli when the first is encountered. Evidence of implicit memory can be found in studies using priming procedures, which are processes where individuals are measured on how they improve at tasks when being cued below conscious experience on how to respond to a task. Implicit memory also contributes to the illusion-of-truth effect where individuals are more likely to rate statements of being true if they had previously experience that statement regardless of whether it is true or not.


   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, 2009? 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.


A photograph shows Marilu Henner.

Marilu Henner’s super autobiographical memory is known as hyperthymesia. (credit: Mark Richardson)


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.


   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 at your job once you get there.

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. Or for 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 may 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. For example, 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 with their Mexico City branch. 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.


   Memory is a system or process that stores what we learn for future use.  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. The idea that information is processed through three memory systems is called the Information-Processing model of memory. First, environmental stimuli enter our sensory memory for a period of less than a second to a few seconds. Those stimuli that we notice and pay attention to then move into short-term memory (also called working memory). According to theInformation-Processing model, if we rehearse this information, then it moves into long-term memory for permanent storage. Other models like that of Baddeley and Hitch suggest there is more of a feedback loop between short-term memory and long-term memory. Long-term memory has a practically limitless storage capacity and is divided into implicit and explicit memory. Finally, retrieval is the act of getting memories out of storage and back into conscious awareness. This is done through recall, recognition, and relearning.



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




Review Questions: 

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

a. sensory memory

b. episodic memory

c. working memory

d. implicit memory


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

a. one or two bits of information

b. seven bits, plus or minus two

c. limited

d. essentially limitless


3. The three functions of memory are ________.

a. automatic processing, effortful processing, and storage

b. encoding, processing, and storage

c. automatic processing, effortful processing, and retrieval

d. encoding, storage, and retrieval


Critical Thinking Questions:

1. Compare and contrast implicit and explicit memory.

2. According to the Atkinson-Shiffrin model, name and describe the three stages of memory.

3. Compare and contrast the two ways in which we encode information.


Personal Application Questions: 

1. Describe something you have learned that is now in your procedural memory. Discuss how you learned this information.

2. Describe something you learned in high school that is now in your semantic memory.



acoustic encoding

automatic processing

declarative memory

effortful processing

episodic memory

explicit memory

Information-Processing Model

implicit memory

long-term memory (LTM)


memory consolidation






self-reference effect

semantic encoding

semantic memory

sensory memory

short-term memory (STM)


visual encoding

Answers to Exercises

Review Questions: 

1. C

2. D

3. D


Critical Thinking Questions:

1. Compare and contrast implicit and explicit memory.

2. According to the Atkinson-Shiffrin model, name and describe the three stages of memory.

3. Compare and contrast the two ways in which we encode information.



acoustic encoding: input of sounds, words, and music

automatic processing: encoding of informational details like time, space, frequency, and the meaning of words

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

effortful processing: encoding of information that takes effort and attentionencoding: input of information into the memory system

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

explicit memory: memories we consciously try to remember and recall

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

implicit memory: memories that are not part of our consciousness

long-term memory (LTM): continuous storage of information

memory: system or process that stores what we learn for future use

memory consolidation: active rehearsal to move information from short-term memory into long-term memory procedural memory: 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

recall: accessing information without cues

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

rehearsal: conscious repetition of information to be remembered

relearning: learning information that was previously learned

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

self-reference effect: tendency for an individual to have better memory for information that relates to oneself in comparison to material that has less personal relevance

semantic encoding: input of words and their meaning

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

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

short-term memory (STM): (also, working memory) holds about seven bits of information before it is forgotten or stored, as well as information that has been retrieved and is being used

storage: creation of a permanent record of information

visual encoding: input of images