Think of all the information streaming through your sensory channels at this very moment. Your eyes may be focused on this sentence, but you are also collecting data through your peripheral vision. You may be hearing noises (the hum of a fan), smelling odors (dinner cooking in the kitchen), tasting foods (if you are snacking), and even feeling things (your back pressed against a chair). Many of these sensory stimuli never catch your attention, but some are being registered in your sensory memory, the first stage of the information-processing model (Infographic 6.1).

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LO 4 Describe sensory memory.

The bulk of information entering sensory memory comes and goes like the images on a movie screen. A few things catch your attention—the beautiful eyes of Mila Kunis, the sound of her voice, and perhaps the color of her shirt—but not much more before the frame switches and you’re looking at another image. Information floods our sensory memory through multiple channels—what we see enters through one channel, what we taste through another, and so on.

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ICONIC MEMORY: “MORE IS SEEN THAN CAN BE REMEMBERED” Interested in how the brain processes data entering the visual channel, Harvard graduate student George Sperling (1960) designed an experiment to determine how much information can be detected in a brief exposure to visual stimuli. Sperling set up a screen that flashed multiple rows of letters for one-twentieth of a second, and then asked participants to report what they saw. His first goal was to determine how many letters the participants could remember when an array of letters (for example, three rows of four letters) was flashed briefly; he found that, on average, the participants only reported four letters. But Sperling wasn’t sure if this meant they were only able to store one row at a time in their memory, or if they stored all the rows at once, but just not long enough to recite them before they were forgotten.

Sperling was convinced that “more is seen than can be remembered” (1960, p. 1), so he devised a clever method called partial report to provide evidence. As with the original experiment, he briefly flashed an array of letters (for example, three rows of four letters), with all rows visible. But instead of having the participants report what they remembered from all the rows, he asked them to report what they remembered from just one row at a time (Infographic 6.1). Here’s how the study went: The array of letters was flashed, and once it disappeared, a tone was sounded. When participants heard a high-pitched tone, they were to report the letters in the top row; with a medium-pitched tone, the letters in the middle row; and with a low-pitched tone, the letters in the bottom row. The participants were only asked to give a partial report, that is, to report on just one of the rows, but they did not know which row ahead of time. In this version of the study, the participants doubled their performance, recalling approximately 76% of the letters (Sperling, 1960). Sperling’s research suggests that the visual impressions in our sensory memory, also known as iconic memory, are photograph-like in their accuracy but dissolve in less than a second. Given the short duration of iconic memory, can you predict what would happen to the participants’ performance if there were a delay before they reported what they saw?

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Stare at the photo of the child laughing and then shut your eyes. Does an image of the child linger in your mind’s eye for just a moment? How long do you think this iconic memory lasts?

EIDETIC IMAGERY Perhaps you have heard friends talk about someone who claims to have a “photographic memory” that can record and store images with the accuracy of a camera: “My cousin Dexter can look at a textbook page, remember exactly what it says in a few seconds, and then recall the information days later, seeing the pages exactly as they were.” That may be what Dexter claims, but is there scientific evidence to back up such an assertion? We doubt it.

According to some reports, though, researchers have documented a phenomenon that comes fairly close to photographic memory. It’s called eidetic imagery (ī-ˈde-tik), and those who have this ability can “see” an image or object for as long as several minutes after it has been removed from sight, describing its parts with amazing specificity. However, the details they “see” are not always accurate, and thus their memories are not quite “photographic.” Eidetic imagery is rare and usually only occurs in young children (Searleman, 2007, March 12).

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ECHOIC MEMORY Exact copies of the sounds we hear linger longer than visual impressions; echoic memory (ə-kō-ik) can last from about 1 to 10 seconds (Lu, Williamson, & Kaufman, 1992; Peterson, Meagher, & Ellsbury, 1970), and it can capture very subtle changes in sound. Research has shown that the introduction of a single tone played for 300 milliseconds initiates changes in cortical activity (Inui et al., 2010). Even if you are not aware of it, your auditory system is picking up slight changes in stimuli and storing them in echoic memory for a brief moment, so you don’t have to pay attention to every incoming sound. Perhaps you have had the following experience: During class, your instructor notices a classmate daydreaming and tries to bring her back to reality: “Olivia, could you please restate the question for us?” Her mind was indeed wandering, but amazingly she can recall the instructor’s last sentence, responding, “You asked us if brain scans should be allowed as evidence in courtrooms.” For this, Olivia can thank her echoic memory.

Although brief, sensory memory is critical to the creation of memories. Without it, how would information enter the memory system in the first place? We have discussed iconic and echoic memory, which register sights and sounds, but memories can also be rich in smells, tastes, and touch. Remember, data received from all the senses are held momentarily in sensory memory. The bulk of research has focused on iconic and echoic memories, but psychologists propose that we also have similar sensory stores for the other senses.

LO 5 Summarize short-term memory.

When information enters your sensory memory, it does not linger. So where does it go next? If not lost in the overwhelming array of sensory stimuli, the data proceed to short-term memory, the second stage in the information-processing model proposed by Atkinson and Shiffrin (1968). The amount of time information is maintained and processed in short-term memory depends on how much you are distracted by other cognitive activities, but the duration can be about 30 seconds (Atkinson & Shiffrin, 1968). You can stretch short-term memory further with maintenance rehearsal, a technique of repeating what you want to remember over and over in your mind. With maintenance rehearsal, it is theoretically possible to hold information there as long as desired. It comes in handy when you need to remember a series of numbers or letters (for example, phone numbers or zip codes). Imagine this: While strolling down the street, you witness a hit-and-run accident: a truck runs a red light, smashes into a car, and then speeds away. As the truck zooms off, you manage to catch a glimpse of the license plate number, “PRZ-7659,” but how will you remember it long enough before reaching the 911 operator? If you’re like most people, you will say the plate number to yourself over and over, either aloud or in your mind, using maintenance rehearsal.

But maintenance rehearsal does not work so well if you are distracted. In a classic study examining the duration of short-term memory, most participants were unable to recall three-letter combinations beyond 18 seconds while performing another task (Peterson & Peterson, 1959; Figure 6.3). The task (counting backward by 3s) interfered with their natural inclination to mentally repeat the letter combinations; in other words, they were limited in their ability to use maintenance rehearsal. What this study reveals is that short-term memory has a limited capacity.

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At any given moment, you can only concentrate on a tiny percentage of the data flooding your sensory memory. Items that capture your attention can move into your short-term memory, but most everything else disappears faster than you can say the word “memory.” Please remember this when you are texting during class or watching TV while studying; if your goal is to remember what you should be concentrating on, you need to give it your full attention.

Multitasking, whether it involves texting, using Facebook, or IMing, inevitably requires a shift in attention, and this is hard work for the brain, which has to engage and disengage different networks (Clapp, Rubens, Sabharwal, & Gazzaley, 2011). Keep this in mind the next time you consider using your smart phone behind the wheel. Texting while driving increases the likelihood of crashing or coming close to crashing by 23 times (Olson, Hanowski, Hickman, & Bocanegra, 2009), and studies show that using a cell phone impairs driving to the same degree as drunkenness (Strayer & Watson, 2012, March).

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LO 6 Give examples of how we can use chunking to improve our memory span.

Now that we have established how important attention is for your success and safety, let’s return to the memory stage to which it is so intimately tied: short-term memory. We mentioned that people frequently try to remember numbers and letters by repeating them over and over in their minds. This maintenance rehearsal is useful, but how many items can we realistically hold in our short-term memory at one time? Using a task called the Digit Span test (Figure 6.4), cognitive psychologist George Miller (1956) determined that most people can retain only five to nine digits: He called this the “magical number seven, plus or minus two.” Indeed, most people can only attend to about five to nine items at one time (Cowan, Chen, & Rouder, 2004; Cowan, Nugent, & Elliott, 2000). But what exactly constitutes an “item?” Must it be a single-digit number? Not necessarily; we can expand short-term memory by packing more information into the items we need to remember.

Consider this example: Your friend has just gotten a new phone number, which she tells you as the elevator door is closing between you. How are you going to remember her number long enough to create a new entry in your cell phone? You could try memorizing all 10 digits in a row (8935550172), but a better strategy is to break the number into more manageable pieces (893-555-0172). Here, you are using chunking, Miller’s name for grouping numbers, letters, or other types of information into meaningful subsets, or “chunks.” Can you think of situations in which you might chunk information to help you remember it more easily?

Short-term memory can only hold so much, but we can increase its storage potential by chunking. The fact that short-term memory is actively processing information and is flexible in this regard suggests that it may be more than just a stage in which information is briefly stored. Indeed, many psychologists believe that short-term memory is more than an inactive storage facility.

LO 7 Explain working memory and how it compares with short-term memory.

Subsequent conceptualizations of the information-processing model include a concept known as working memory (Baddeley & Hitch, 1974), which refers to what is going on in short-term memory. Working memory is the active processing through which we maintain and manipulate information in the memory system. Let’s use an analogy of a “bakery” and what goes on inside it. Think of short-term memory as the bakery, that is, the place that hosts your current thoughts and whatever your brain is working on at this very moment. According to this conceptualization, working memory is analogous to the making of bread, cakes, and pastries inside the bakery.

But not everyone agrees on the distinctions between short-term and working memory (Cowan, 2008; Rose, Myerson, Roediger, & Hale, 2010). Some psychologists do not differentiate between short-term and working memory, and use the terms interchangeably. For our purposes, we will identify “short-term memory” as a stage in the original information-processing model as well as the “location” where information is temporarily held, and “working memory” as the activities and processing occurring within.

Now let’s take a closer look at the model of working memory originally proposed by psychologists Alan Baddeley and Graham Hitch (1974), which has been updated and revised over the years (Baddeley, 2002). According to this model, the purpose of working memory is to actively maintain information, aiding the mind as it performs complex cognitive tasks. To accomplish this, working memory has four components with specific functions: the phonological loop, the visuospatial sketchpad, the central executive, and the episodic buffer (Baddeley, 2002; Figure 6.5).

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PHONOLOGICAL LOOP The phonological loop is responsible for working with verbal information for brief periods of time; when exposed to verbal stimuli, we “hear” an immediate corollary in our mind. This component of working memory is what we use, for example, when we are reading, trying to solve problems, or learning new vocabulary. Most of us can only manipulate about 2 seconds’ worth of verbal material in this loop without actively trying to repeat it (Baddeley, 2000; Baddeley & Hitch, 1994). Imagine you are trying to remember the passcode for your debit card. You know it is somehow related to your first zip code, so you retrieve your zip code from long-term memory. You then “hear” the five numbers played in your phonological loop as you desperately try to remember your passcode (I remember it was 02138). Once you figure out your passcode, the numbers of your zip code are no longer needed, and they slip quietly back into your long-term memory.

VISUOSPATIAL SKETCHPAD The visuospatial sketchpad is where visual and spatial data are briefly stored and manipulated, including information about your surroundings and where things are in relation to each other and you. This working memory component allows you to close your eyes and reach for the coffee mug you just set down. We can also use information from long-term memory in our visuospatial sketchpad. Imagine you are standing at the entrance to the mall, determined to make your shopping excursion short and sweet. Thinking back to the last time you were there, you bring forth a mental image of how the stores are laid out. Excellent! You now have a map of the mall in your visuospatial sketchpad, which allows you to make more strategic decisions (Victoria’s Secret? No, JCPenney is closer). But as you start considering the items you need to buy, the memory of the mall layout begins to slide back into your long-term memory. Studies by Baddeley and colleagues show that we have difficulty trying to perform even two visuospatial tasks at the same time (Baddeley, 1999, 2006).

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CENTRAL EXECUTIVE The central executive has responsibilities similar to those of the chief executive in any organization—it directs attention, makes plans, and coordi-nates activities (Baddeley, 2002). Part of its role is to determine what information is important, and to help organize and manipulate consciousness. Why is it that we cannot actually text, eat, and safely drive all at once? Like a juggler, the central executive can only catch and toss one ball at a time. We may think we are doing all three tasks at once, but we are really just swapping the alternatives in and out at a fast pace.

EPISODIC BUFFER The episodic buffer is the part of working memory where information from the phonological loop, visuospatial sketchpad, and long-term memory can be brought together temporarily, under the direction of the central executive (Baddeley, 2000). The episodic buffer forms the bridge between memory and conscious awareness. It enables us to assign meaning to past events, solve problems, and make plans for the future.

As you know, working memory is limited in its capacity and duration. So how do we maintain so much information over the years? What aspect of memory makes it possible to memorize thousands of vocabulary words, scores of names and facts, and lyrics to your favorite songs? Enter long-term memory.

Items that enter short-term memory have two possible fates: Either they fade away or they move into long-term memory (Figure 6.6). Think of how much information is stored in your long-term memory: funny jokes, important conversations, images of faces, multiplication tables, and so many vocabulary words—between 30,000 (Lessmoellmann, 2006, October/November) and 60,000 words (Pinker, 1994) for the average English speaker. Could it be that long-term memory has an endless holding capacity? It may be impossible to answer this question, but for all practical purposes our long-term memory has no limits. And the memories stored there, such as street names from your childhood, may even last a lifetime (Schmidt, Peeck, Paas, & van Breukelen, 2000).

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LO 8 Describe long-term memory.

EXPLICIT MEMORY Long-term memory can be described in a variety of ways, but psychologists often distinguish between two categories: explicit and implicit. Explicit memory is the type of memory you are aware of having and can consciously express in words or declare: Roses are red, guacamole is made with avocados; I wore bootcut jeans yesterday. Tulving (1972) proposes two forms of explicit memory: semantic and episodic. Semantic memory pertains to general facts about the world (the sky is blue; the United States holds presidential elections every four years). But there is also a type of memory you can call your own. This personal form is called episodic memory (e-pə-sä-dik). It is your record of the memorable experiences, or “episodes,” in your life, including when and where they occurred (Tulving, 1985).

FLASHBULB MEMORIES Often our most vivid episodic memories are associated with intense emotion. Think about an emotionally charged experience from your past: receiving news that a loved one has died, getting engaged, or being the victim of an assault. If recollecting these events feels like watching a 4-D movie, you might be experiencing what psychologists call a flashbulb memory, a detailed account of circumstances surrounding an emotionally significant or shocking, sometimes historic, event (Brown & Kulik, 1977). Some people remember what they were doing when they heard about the terrorist attacks of September 11, 2001, or the horrific events that unfolded at Sandy Hook Elementary School in Newtown, Connecticut, on December 14, 2012. They recall where they were, who or what source relayed the news, how it made them feel, what they did next, and other random details about their experience (Brown & Kulik, 1977).

Because flashbulb memories seem so strong, vivid, and rich in detail, we often place great confidence in them, but research suggests that we should be cautious about doing this. Flashbulb memories sometimes include inaccuracies or lack some specific details (Neisser, 1991; Talarico & Rubin, 2003).

IMPLICIT MEMORY Unlike explicit memory, which can easily flow into conscious thought, implicit memory is difficult to bring into awareness and express. It is a memory for something you know or know how to do, but which might be automatic or unconscious. Many of the physical activities we take for granted, such as playing an instrument, driving a car, and dribbling a basketball, use a special type of implicit memory called procedural memory, that is, the memory of how to carry out an activity without conscious control or attention. After his illness, Clive Wearing could still pick up a piece of music and play it on the piano. He had no recollection of learning to sight-read or play, yet he could execute these skills like the professional he had always been (Vennard, 2011, November 21). Therefore, Clive’s procedural memory was still working.

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Memories acquired through classical conditioning are also implicit. Let’s say you enjoy eating food at McDonald’s and the very sight of the golden arches makes you salivate like one of Pavlov’s dogs. Somewhere along the line, you formed an association, a memory linking the appearance of that restaurant to juicy hamburgers and creamy shakes, but the association does not require your conscious awareness (Cowan, 1988). It is implicit.

How does the process of moving data into the memory system create long-term memories? Some activities work well for keeping information in short-term memory (maintenance rehearsal, for example). Others involve moving information from short-term memory to long-term memory. Let’s take a look at some of these processes, kicking off our discussion with a little test.

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You just completed a miniversion of “Random Words,” Dorothea’s favorite event in the World Memory Championships. Dorothea won a gold medal in this category, committing 244 words to memory in 15 minutes. What’s her secret? She uses mnemonic (nih-ˈmän-ik) devices—techniques for improving memory. You have probably used several mnemonic devices in your own life. For example, have you ever relied on the first-letter technique, such as Every Good Boy Deserves Fudge, to learn the line notes of the treble clef scale? Or perhaps you have used an acronym, such as ROY G BIV, to remember the colors of the rainbow (Figure 6.7)? Chunking, which we discussed earlier, is also a mnemonic technique. As you can see in Infographic 6.2 mnemonic devices and other memory strategies can enhance retention of material as you study.

METHOD OF LOCI One of the mnemonics Dorothea relies on most is the method of loci (lō-ˌsī, meaning “places”). Here’s how it works: When presented with a series of words to remember, Dorothea takes them on a mental journey through the place she knows best: her bedroom and bathroom. Walking through her room, she puts the items-to-be-remembered at predetermined spots along the way. Let’s say she is trying to remember the seven words from above. Dorothea visualizes herself entering her bedroom. The first thing she comes upon is the bed, so she might imagine a cute puppy playing with the pillow. Then she encounters a bedside table, which suddenly becomes a bus stop with a bus parked in front. She walks over to the sofa, climbs onto it, and begins to sing. The next object on her path is a box, but not an ordinary box, because it’s weeping tears of sadness. Next in her path is a mirror that she shatters to pieces with a soccer ball. When she gets to the sink, she kicks it with her foot. Finally, she imagines aliens climbing out of the toilet, causing her to panic. If she needs to remember the items, she retraces the journey, stopping at each point to observe the image she left there.

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You can use the method of loci, too. Just pick a familiar route—through your favorite restaurant, college campus, even your own body—and mentally place things you need to remember at points along the way. For remembering short lists, memory champion Dominic O’Brien suggests tagging items to preestablished points along the body (O’Brien, 2005). Suppose you need to pick up five items at the grocery: milk, eggs, olive oil, bananas, and cherries. Choose some body parts and then visually connect them to the items you need. For example, your hair is slicked back in olive oil; your nose is a big long banana; you can’t see because someone threw eggs in your eyes; cherries dangle from your ears like earrings; and you have a milk mustache.

HIERARCHICAL STRUCTURES Another way to boost your memory is to arrange the material you are trying to memorize into a hierarchy, or a system of meaningful categories and subcategories. In a classic study, researchers found that if participants were given a list of words that followed a hierarchical structure, they were better able to recall the words than participants learning the same words not organized in any meaningful way. In fact, the participants who had learned the words using the hierarchy were able to recall three times as many words as the other group (Bower, Clark, Lesgold, & Winzenz, 1969).

try this
Try to remember the various divisions of the nervous system. Sketch a diagram like the one here (this is from Figure 2.2 from Chapter 2) showing the relationships among the concepts, starting with the most general and ending with the most specific.

AUTOMATIC AND EFFORTFUL PROCESSING As you recall from earlier in the chapter, the levels of processing framework suggests that stronger memories result when you think about information on a deep level. Dorothea and her rivals came to the championships expecting to use effortful processing. As the name implies, effortful processing is not only intentional but also requires work (Hartlage et al., 1993; Hasher & Zacks, 1979). Some types of effortful processing, such as maintenance rehearsal, are useful for extending the amount of time you can hold onto information in short-term memory. Others employ patterns and meaning to encode information for longer storage. For example, Dorothea links hundreds of elaborate images (like the puppy playing on the pillow, or aliens rising out of the toilet) on a mental journey—not an easy task to perform in 15 minutes. Her effortful processing occurs at a deep level, and as the levels of processing framework suggests, results in more successful learning and retention of information.

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We should note that some encoding occurs through automatic processing—that is, with little or no conscious effort or awareness (Hartlage, Alloy, Vázquez, & Dykman, 1993; Hasher & Zacks, 1979). For example, when Dorothea walked into the conference room at the World Memory Championships, she processed all sorts of information without even trying—like the fact that most of the people milling around the room were men and that the team from China was wearing matching orange-and-white tracksuits. She did not make an effort to pick up on these details, but she remembers them nevertheless. Her memory system absorbed the data automatically.

ELABORATIVE REHEARSAL AND VISUALIZATION Effortful processing is evident in elaborative rehearsal, the method of connecting incoming information to knowledge in long-term memory. Here, we can see that the level of processing occurs at a deep level, which suggests the encoding of information will be more successful. Dorothea’s mental walks involve this type of deeper processing (elaborative rehearsal) because she takes new information and puts it in the familiar framework of her home. By picturing the journey and the objects-to-be-remembered in her mind’s eye, Dorothea is taking advantage of visualization, another effective encoding strategy. People tend to remember verbal information better when it’s accompanied by vivid imagery. Some research suggests, for example, that children recall news stories better when they see them presented on television, as opposed to reading about them in a printed article (Walma van der Molen & van der Voort, 2000).

DISTRIBUTED PRACTICE What other strategies might improve encoding and help you move information into long-term memory? You’ve probably heard this before, but you should avoid cramming for long periods of time without breaks (also referred to as massed practice). Research dating back to the 1800s shows that distributed practice—spreading out study sessions, with breaks in between—is much more effective than packing information into your brain all at once (Ebbinghaus, 1885/1913; Rohrer & Taylor, 2006). When researchers asked students to learn a new mathematical skill, they found that participants who practiced the new skill in two sessions (separated by a week) did better on a practice test (4 weeks later) than those who spent the same amount of time practicing in one session (Pashler, Rohrer, Cepeda, & Carpenter, 2007). Surprisingly, how students apply distributed practice to studying may be associated with their culture and beliefs (Schommer-Aikins & Easter, 2008). But when it comes to studying groups, there are no hard-and-fast rules that apply to every member. Each individual should be viewed as such—an individual. Keep this in mind as you read on.

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across the WORLD

SLEEP AND MEMORY We have touched on many strategies for boosting memory, from chunking to visualization to distributed practice. If we could leave you with one final piece of advice, it would be the following: SLEEP. Exactly how sleep promotes memory is still not completely understood, but there is no question that good sleep makes for better processing of memories (Born, Rasch, & Gais, 2006; Diekelmann & Born, 2010; Marshall & Born, 2007). Even periods of “wakeful resting” can be of benefit. Participants who experienced a 15-minute period of wakeful resting (sitting in a darkened quiet room) displayed better retention of newly learned material than did participants who played a game for 15 minutes. Wakeful resting seems to allow newly learned material to be encoded better, and thus retained in memory longer (Dewar, Alber, Butler, Cowan, & Della Sala, 2012). What might this mean for you? Make sure you allow yourself some quiet time following the learning of new material. Don’t end your study sessions with an activity that might interfere with your encoding. Of course, it takes more than good rest to succeed in college; you need to be able to analyze, apply, and synthesize material, not just remember it.

“Wow, that’s a lot to remember,” you may be saying. Hopefully, you can retain it with the help of some of the mnemonic devices we have presented. You might also take a wakeful resting break in preparation for the next section, which focuses on the topic of memory retrieval.

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Question 1

1. 10 seconds

2. 30 seconds

3. 45 seconds

4. 60 seconds

Question 2

1. sensory memory.

2. working memory.

3. phonological loop.

4. flashbulb memory.

Question 3

Question 4

1. phonological loop.

2. sensory memory.

3. implicit memory.

4. flashbulb memory.

Question 5