Enduring Issues in Memory
The Sensory Registers • Visual and Auditory
Registers • Attention Short-Term Memory • Capacity of STM • Encoding in STM • Maintaining STM
Long-Term Memory • Capacity of LTM • Encoding in LTM • Serial Position Effect • Maintaining LTM • Types of LTM • Explicit and Implicit Memory
The Biology of Memory • Where Are Memories
Stored? • The Role of Sleep Forgetting • The Biology of Forgetting • Experience and Forgetting
Special Topics in Memory • Cultural Influences • Autobiographical Memory • Extraordinary Memory • Flashbulb Memories • Eyewitness Testimony • Recovered Memories
O V E R V I E W
Understanding Psychology, Ninth Edition, by Charles G. Morris and Albert A. Maisto. Published by Prentice Hall. Copyright © 2010 by Pearson Education, Inc.
Accounts of people with extraordinary memories raise many questions about the nature of memory itself: Why are some people so much better at remembering things than oth- ers? Why is it that remembering may sometimes be so simple (think how effortlessly baseball fans remember the batting aver- ages of their favorite players) and other times so difficult (as when we grope for answers on an exam)? Just how does mem- ory work, and what makes it fail?
Among the first to seek scientific answers to these questions was the 19th-century German psychologist Hermann Ebbinghaus. Using himself as a subject, Ebbinghaus composed lists of “non- sense syllables,” meaningless combinations of letters, such as PIB, WOL, or TEB. He memorized lists of 13 nonsense syllables each. Then, after varying amounts of time, he relearned each list of syllables. He found that the longer he waited after first learning a list, the longer it took to learn the list again. Most of the informa- tion was lost in the first few hours. Ebbinghaus’s contributions dominated memory research for many years.
Many contemporary psychologists, by contrast, perceive memory as a series of steps in which we process information, much as a computer stores and retrieves data (Ashcraft, 2006). Together, these steps form the information-processing model of memory. In this chapter you will find terms like encoding, storage, and retrieval, which are convenient ways of comparing human memory with computers. But we will also consider the social, emotional, and biological factors that make us human and that also distinguish our memories from those of computers.
Far more information bombards our senses than we can possibly process, so the first stage of information processing involves selecting some of this material to think about and remember. Therefore, we turn first to the sensory registers and to attention, the process that allows us to select incoming infor- mation for further processing.
ENDURING ISSUES IN MEMORY In this chapter, we will again encounter the “Enduring Issues” in psychology that were introduced in Chapter 1. We will explore the biological bases of memory (mind–body), the ways that memory differs among people and across cultures (diversity–universality), and the ways that memory changes in the first few years of life (stability–change). Finally, we will consider the extent to which memories can be changed by events outside the person as well as the importance of environmental cues in triggering memories (person–situation).
THE SENSORY REGISTERS What is the role of sensory registers?
Look slowly around the room. Each glance takes in an enormous amount of visual informa- tion, including colors, shapes, textures, relative brightness, and shadows. At the same time, you pick up sounds, smells, and other kinds of sensory data. All of this raw information
L E A R N I N G O B J E C T I V E S • Describe the role of the sensory
registers and the length of time information remains there. Distinguish between the icon and the echo.
• Compare Broadbent and Treisman’s theories of attention. Explain what is meant by the “cocktail-party phenomenon” and “inattentional blindness.”
information-processing model A computer- like model used to describe the way humans encode, store, and retrieve information.
memory The ability to remember the things that we have experienced, imagined, and learned.
Most of us remember certain days or moments more dis-tinctly than others. Your first day of school, your firstkiss, a special holiday, the loss of a loved one—these experiences may be etched so indelibly on your memory that it seems that they happened just yesterday, rather than many years in the past. But imagine if you had a distinct memory of not only your first day of school, but of the second one, too; as well as the third, fourth, fifth, and so on. Imagine if you recalled not just the most important events of your life, but, in addition, all of the tiny, insignificant details of each and every day: what the weather was like, what you ate for dinner, what you watched on television. Imagine these visions of the past—some ordinary and mundane, some comforting and pleasant, others, terribly painful and sad—ran through your head in a constant loop, a random compilation of all of the moments of your life assaulting your consciousness with ceaseless persistence. Jill Price, a 42- year-old woman who lives in California, need not imagine such a scenario; for Jill Price, this is life.
In her 2008 memoir, The Woman Who Can’t Forget, Jill Price recounts a life lived with what psychologist James L. McGaugh has diagnosed as hyperthymestic syndrome, or “overdeveloped memory.” If given a date over the course of the past thirty years, Price can typically recount what day of the week it was in addition to details about something that happened to her that day. More- over, according to Price, autobiographical memories, unpre- dictably summoned by various stimuli—a familiar smell, for example, or a song on the radio—constantly dominate her thoughts in a mechanism beyond her conscious control. As Price contends, her unusual powers of memory are more a burden than a blessing, forcing her to relive every argument, every disappoint- ment, every moment of despair she has ever known at arbitrary intervals. Indeed, as Price’s case illustrates, while the ability to remember has its merits, so too, it seems, does the ability to forget.
Understanding Psychology, Ninth Edition, by Charles G. Morris and Albert A. Maisto. Published by Prentice Hall. Copyright © 2010 by Pearson Education, Inc.
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flows from your senses into the sensory registers, which are like waiting rooms in which information enters and stays for only a short time. Whether we remember any of the information depends on which opera- tions we perform on it, as you will see throughout this chapter. Although there are registers for each of our senses, the visual and auditory registers have been studied most extensively.
Visual and Auditory Registers What would happen if auditory information faded as quickly as visual information fades?
Although the sensory registers have virtually unlimited capacity, infor- mation disappears from them quite rapidly (Cowan et al., 2005; Melcher,
2006; Rainer & Miller, 2002). A simple experiment can demonstrate how much visual information we take in—and how quickly it is lost. Bring a digital camera into a darkened room, and then take a photograph with a flash. During the split second that the room is lit up by the flash, your visual register will absorb a surprising amount of information about the room and its contents. Try to hold on to that visual image, or icon, as long as you can. You will find that in a few seconds, it is gone. Then compare your remembered image of the room with what you actually saw, as captured in the photograph. You will discover that your visual register took in far more information than you were able to retain for even a few seconds.
Classic experiments by George Sperling (1960) clearly demonstrate how quickly infor- mation disappears from the visual register. Sperling flashed groups of letters, organized into three rows, on a screen for just a fraction of a second. When the letters were gone, he sounded a tone to tell his participants which row of letters to recall: A high-pitched tone indicated that they should try to remember the top row of letters, a low-pitched tone meant that they should recall the bottom row, and a medium-pitched tone signaled them to recall the middle row. Using this partial-report technique, Sperling found that if he sounded the tone immediately after the letters were flashed, people could usually recall 3 or 4 of the let- ters in any of the three rows; that is, they seemed to have at least 9 of the original 12 letters in their visual registers. But if he waited for even 1 second before sounding the tone, his participants were able to recall only 1 or 2 letters from any single row—in just 1 second, then, all but 4 or 5 of the original set of 12 letters had vanished from their visual registers.
Visual information may disappear from the visual register even more rapidly than Sperling thought (Cowan, 1988; Smithson & Mollon, 2006). In everyday life, new visual information keeps coming into the register; and the new information replaces the old infor- mation almost immediately (in about a quarter of a second), a process often called masking.
Auditory information fades more slowly than visual information. The auditory equiv- alent of the icon, the echo, tends to last for several seconds, which, given the nature of speech, is certainly lucky for us. Otherwise, “You did it!” would be indistinguishable from “You did it!” because we would be unable to remember the emphasis on the first words by the time the last words were registered.
Attention Why does some information capture our attention, whereas other information goes unnoticed?
If information disappears from the sensory registers so rapidly, how do we remember anything for more than a second or two? One way is that we select some of the incoming information for further processing by means of attention. (See Figure 6–1.) Attention is the process of selectively looking, listening, smelling, tasting, and feeling (Egeth & Lamy, 2003; Knudsen, 2007). At the same time, we give meaning to the information that is coming in. Look at the
sensory registers Entry points for raw information from the senses.
attention The selection of some incoming information for further processing.
If you were to walk into this room, your eyes and your other sense organs would pick up many impressions of what is to be found here. How much of this information would you remember later?
Understanding Psychology, Ninth Edition, by Charles G. Morris and Albert A. Maisto. Published by Prentice Hall. Copyright © 2010 by Pearson Education, Inc.
page in front of you. You will see a series of black lines on a white page. For you to make sense of this jumble of data, you process the information in the sensory registers for meaning.
How do we select what we are going to pay attention to at any given moment, and how do we give that information meaning? Donald Broadbent (1958) suggested that a filtering process at the entrance to the nervous system allows only those stimuli that meet certain requirements to pass through. Those stimuli that do get through the filter are compared with what we already know, so that we can recognize them and figure out what they mean. If you and a friend are sitting in a restaurant talking, you filter out all other conversations taking place around you, a process known as the cocktail-party phenomenon (Cherry, 1966; Haykin & Chen, 2006). Although you later might be able to describe certain characteristics of those other conversations, such as whether the people speaking were men or women, according to Broadbent, you normally cannot recall what was being discussed, even at neighboring tables. Since you filtered out those other conversations, the processing of that information did not proceed far enough for you to understand what you heard.
Broadbent’s filtering theory helps explain some aspects of attention, but sometimes unattended stimuli do capture our attention. To return to the restaurant example, if someone nearby were to mention your name, your attention probably would shift to that conversation. Anne Treisman (1960, 1964, 2004) modified the filter theory to account for phenomena like this. She contended that the filter is not a simple on-and-off switch, but rather a variable control—like the volume control on a radio, which can “turn down” unwanted signals without rejecting them entirely. According to this view, although we may be paying attention to only some incoming information, we monitor the other sig- nals at a low volume. Thus, we can shift our attention if we pick up something particu- larly meaningful. This automatic processing can work even when we are asleep: Parents often wake up immediately when they hear their baby crying, but sleep through other, louder noises.
At times, however, our automatic processing monitor fails, and we can overlook even meaningful information. In research studies, for example, some people watching a video of a ball-passing game failed to notice a person dressed as a gorilla who was plainly visible for nearly 10 seconds (Mack, 2003). In other words, just because we are looking or listening to something, doesn’t mean we are attending to it. Psychologists refer to our failure to attend to something we are looking at as inattentionial blindness. Research has shown, for example, that attending to auditory information can reduce one’s ability to accurately process visual information, which makes driving while talking on a cell phone a distinctly bad idea (Pizzighello & Bressan, 2008)!
Figure 6–1 The sequence of information processing.
Forgetting through decay
Forgetting through interference or decay
External stimulus Attention
Raw information flows from the senses into the sensory registers.
High-capacity sensory registers briefly store information in the form of an icon or echo.
Information that is rehearsed in short-term memory is maintained there; otherwise, it decays rapidly.
Information that is actively processed and coded in short-term memory is transferred to long-term memory.
Information transferred from short-term memory to long- term memory becomes relatively permanent, comprising everything we “know”.
Information retrieved from long-term memory is transferred to short-term, or working memory, where it is available for use.
Attention directs the extraction of meaningful information from the sensory registers, transferring it to short- term memory.
Short-term memory, or working memory, holds the information we are thinking about or are aware of at any given moment, making it available for further processing.
This student is working attentively in spite of other activity in the classroom. If the teacher calls her name, though, the student’s atten- tion will be quickly diverted.
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CHECK YOUR UNDERSTANDING
1. Indicate whether the following statements are true (T) or false (F): a. ____________ The sensory registers have virtually unlimited capacity. b. ____________ Some kinds of information are stored permanently in the sensory
registers. c. ____________ Auditory information fades from the sensory registers more quickly
than visual information does. d. ____________ The filter theory as modified by Treisman holds that attention is like
an on-and-off switch.
L E A R N I N G O B J E C T I V E S • Define short-term memory (STM),
explain why it is called “working memory” and describe the way information is encoded in STM.
• Describe the capacity of STM including the role of chunking and interference, maintenance of information in STM, and the effect of stress on STM.
APPLY YOUR UNDERSTANDING
1. You are in a large, noisy group in which everyone seems to be talking at once. In order to concentrate on the conversation you are having with one of the people, you “tune out” all the other conversations that are going on around you. A few minutes later, someone nearby turns to you and says, “Did you hear what I was saying to John?” You have to admit that even though you were standing right next to her, you don’t know what she said. Your failure to remember that other conversation is an example of
a. selective attention. b. the partial-report technique. c. the cocktail-party phenomenon. d. masking.
2. A few minutes later in that same group, while talking to someone else, you suddenly hear someone nearby mention your name. This time your attention is immediately drawn to that other conversation. This is an example of
a. Broadbent’s filtering theory. b. the partial-report technique. c. the cocktail-party phenomenon. d. masking.
Answers:1. a.2. c.
SHORT-TERM MEMORY What are the two primary tasks of short-term memory?
Short-term memory (STM) holds the information that we are thinking about or are aware of at any given moment. When you listen to a conversation, when you watch a television show, when you become aware of a headache—in all these cases, you are using STM both to hold onto and to think about new information coming in from the sensory registers. Short- term memory has two primary tasks: to store new information briefly and to work on that (and other) information. Short-term memory is sometimes called working memory, to emphasize the active or working component of this memory system (Nairne, 2003; Neath, Brown, Poirier, & Fortin, 2005).
Capacity of STM How much information can be held in short-term memory?
Chess masters at tournaments demand complete silence while they ponder their next move. You shut yourself in a quiet room to study for final exams. As these examples illus- trate, STM can handle only so much information at any given moment. Research suggests
short-term memory (STM) Working memory; briefly stores and processes selected information from the sensory registers.
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that STM can hold about as much information as can be repeated or rehearsed in 1.5 to 2 seconds (Baddeley, 1986, 2002).
To get a better idea of the limits of STM, read the first row of letters in the list that fol- lows just once. Then close your eyes, and try to remember the letters in the correct sequence. Repeat the procedure for each subsequent row.
1. C X W 2. M N K T Y 3. R P J H B Z S 4. G B M P V Q F J D 5. E G Q W J P B R H K A
Like most other people, you probably found rows 1 and 2 fairly easy, row 3 a bit harder, row 4 extremely difficult, and row 5 impossible to remember after just one reading.
Now try reading through the following set of 12 letters just once, and see whether you can repeat them:
How many letters were you able to recall? In all likelihood, not all 12. But what if you had been asked to remember the following 12 letters instead?
TV FBI JFK YMCA
Could you remember them? Almost certainly the answer is yes. These are the same 12 letters as before, but here they are grouped into four separate “words.” This way of group- ing and organizing information so that it fits into meaningful units is called chunking (Cowan & Chen, 2009; Gobet, 2005; Gobet et al., 2001).
By chunking words into sentences or sentence fragments, we can process an even greater amount of information in STM (Baddeley, 1994; T. Carter, Hardy, & Hardy, 2001). For example, suppose that you want to remember the following list of words: tree, song, hat, sparrow, box, lilac, cat. One strategy would be to cluster as many of them as possible into phrases or sentences: “The sparrow in the tree sings a song”; “a lilac hat in the box”; “the cat in the hat.” But isn’t there a limit to this strategy? Would five sentences be as easy to
Chess players demand complete silence as they consider their next move. This is because there is a definite limit to the amount of information STM can handle at any given moment.
chunking The grouping of information into meaningful units for easier handling by short- term memory.Source: © The New Yorker Collection, 1997, Arnie Levin from cartoonbank.com. All Rights Reserved.
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rote rehearsal Retaining information in memory simply by repeating it over and over.
remember for a short time as five single words? No. As the size of any individual chunk increases, the number of chunks that can be held in STM declines (Fendrich & Arengo, 2004). STM can easily handle five unrelated letters or words at once, but five unrelated sen- tences are much harder to remember.
Keep in mind that STM usually has to perform more than one task at a time (Jonides, Lacey, & Nee, 2005). During the brief moments you spent memorizing the preceding rows of letters, you probably gave them your full attention. But normally you have to attend to new incoming information while you work on whatever is already present in short-term memory. Competition between these two tasks for the limited work space in STM means that neither task will be done as well as it could be. Try counting backward from 100 while trying to learn the rows of letters in our earlier example. What happens?
Now turn on some music and try to learn the rows of letters. You’ll find that the music doesn’t interfere much, if at all, with learning the letters. Interestingly, when two memory tasks are presented in different sensory modalities (for instance, visual and auditory), they are less likely to interfere with each other than if they are in the same modality (Cocchini, Logie, Sala, MacPherson, & Baddeley, 2002; Lehnert & Zimmer, 2008). This suggests the existence of domain-specific working memory systems that can operate at the same time with very little interference.
Not surprisingly, stress and worry have also been shown to be a detrimental to the operation of short-term memory (S. Hayes, Hirsch, & Mathews, 2008). This is particularly true when the task at hand involves mathematics, because the worry created by stress com- petes for working memory space, which would otherwise be allocated to solving the math problem (Beilock, 2008).
Encoding in STM Do we store material in short-term memory as it sounds or as it looks?
We encode verbal information for storage in STM phonologically—that is, according to how it sounds. This is the case even if we see the word, letter, or number on a page, rather than hear it spoken (Inhoff, Connine, Eiter, Radach, & Heller, 2004; Vallar, 2006). We know this because numerous experiments have shown that when people try to retrieve material from STM, they generally mix up items that sound alike (Sperling, 1960). A list of words such as mad, man, mat, cap is harder for most people to recall accurately than is a list such as pit, day, cow, bar (Baddeley, 1986).
But not all material in short-term memory is stored phonologically. At least some material is stored in visual form, and other information is retained on the basis of its mean- ing (R. G. Morrison, 2005). For example, we don’t have to convert visual data such as maps, diagrams, and paintings into sound before we can code them into STM and think about them. Moreover, research has shown that memory for images is generally better than mem- ory for words because we often store images both phonologically and as images, while words are usually stored only phonologically (Paivio, 1986). The dual coding of images accounts for the reason it is sometimes helpful to form a mental picture of something you are trying to learn (Sadoski, 2005; Sadoski & Paivio, 2001).
Maintaining STM How can we hold information in STM?
As we have said, short-term memories are fleeting, generally lasting a matter of seconds. However, we can hold information in STM for longer periods through rote rehearsal, also called maintenance rehearsal. Rote rehearsal consists of repeating information over and over, silently or out loud. Although it may not be the most efficient way to remember some- thing permanently, it can be quite effective for a short time.
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L E A R N I N G O B J E C T I V E S • Define long-term memory (LTM)
including the capacity of LTM and the way information is encoded in LTM. Explain the serial position effect.
• Differentiate rote rehearsal from elaborative rehearsal and explain the role of mnemonics and schemata as forms of elaborative rehearsal.
• Distinguish between episodic memories, semantic memories, procedural memories, emotional memories, explicit memories, and implicit memories. Explain how priming and the tip-of-the-tongue phenomenon shed light on memory.
long-term memory (LTM) The portion of memory that is more or less permanent, corresponding to everything we “know.”
LONG-TERM MEMORY What types of information are retained in long-term memory?
Our ability to store vast quantities of information for indefinite periods of time is essential if we are to master complex skills, acquire an education, or remember the personal experiences that contribute to our identity. Everything that we learn is stored in long-term memory (LTM): the words to a popular song; the meaning of justice; how to roller skate or draw a face; your enjoy- ment of opera or your disgust at the sight of raw oysters; and what you are supposed to be doing tomorrow at 4:00 P.M.
Capacity of LTM What is the limit of LTM?
We have seen that short-term memory can hold only a few items, normally only for a mat- ter of seconds. By contrast, long-term memory can store a vast amount of information for many years. In one study, for example, adults who had graduated from high school more than 40 years earlier were still able to recognize the names of 75% of their classmates (Lindsay & Read, 2006).
CHECK YOUR UNDERSTANDING
1. ____________ memory is what we are thinking about at any given moment. Its function is to briefly store new information and to work on that and other information.
2. ____________ enables us to group items into meaningful units. 3. Strings of letters and numbers are encoded ____________ in short-term memory. 4. ____________ rehearsal, or simply repeating information over and over, is an effective
way of retaining information for just a minute or two.
Answers:1. short-term.2. chunking.3. phonologically.4. rote.
APPLY YOUR UNDERSTANDING
1. You try to remember the letters CNOXNPEHFOBSN, but despite your best efforts you can’t seem to remember more than half of them. Then you are told that the letters can be rearranged as CNN FOX HBO ESPN (four TV channels). After that, you are able to remember all the letters even weeks later. Rearranging the letters into groups that are easier to retain in memory is known as
a. shadowing. b. chunking. c. rote rehearsal. d. cueing.
2. Your sister looks up a phone number in the phone book, but then can’t find the phone. By the time she finds the phone, she has forgotten the number. While she was looking for the phone, she apparently failed to engage in
a. rote rehearsal. b. parallel processing. c. phonological coding. d. categorizing.
Answers:1. b.2. a.
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Encoding in LTM How are most memories encoded in LTM?
Can you picture the shape of Florida? Do you know what a trumpet sounds like? Can you imagine the smell of a rose or the taste of coffee? Your ability to do most of these things means that at least some long-term memories are coded in terms of nonverbal images: shapes, sounds, smells, tastes, and so on (Cowan, 1988).
Yet, most of the information in LTM seems to be encoded in terms of meaning. If material is especially familiar (the words of the national anthem, for example), you may have stored it verbatim in LTM, and you can often retrieve it word for word when you need it. Generally speaking, however, we do not use verbatim storage in LTM. If someone tells you a long, rambling story, you may listen to every word, but you certainly will not try to remember the story verbatim. Instead,
you will extract the main points of the story and try to remember those. Even simple sen- tences are usually encoded in terms of their meaning. Thus, when people are asked to remem- ber that “Tom called John,” they often find it impossible to remember later whether they were told “Tom called John” or “John was called by Tom.” They usually remember the meaning of the message, rather than the exact words (R. R. Hunt & Ellis, 2003).
Serial Position Effect Which items in a list are hardest to remember?
When given a list of items to remember (such as a list of grocery items), people tend to do better at recalling the first items (primacy effect) and the last items (recency effect) in the list. They also tend to do poorest of all on the items in the middle of the list. (See Figure 6–2.)
The explanation for this serial position effect resides in understanding how short- and long-term memory work together. The recency effect occurs because the last items that were presented are still contained in STM and thus are available for recall. The primacy effect, on the other hand, reflects the opportunity to rehearse the first few items in the list— increasing their likelihood of being transferred to LTM.
Poor performance occurs on the items in the middle of the list because they were pre- sented too long ago to still be in STM, and because so many items requiring attention were presented before and after them that there was little opportunity for rehearsal. The serial position effect has been shown to occur under a wide variety of conditions and situations (Neath, 1993; Suhr, 2002; W. S. Terry, 2005).
Maintaining LTM What three processes are used to hold information in LTM?
Rote Rehearsal Rote rehearsal, the principal tool for holding information in STM, is also useful for holding information in LTM. Rote rehearsal is probably the standard method of storing conceptually meaningless material, such as phone numbers, Social Security numbers, security codes, computer passwords, birth dates, and people’s names.
Indeed, although everyone hates rote drill, there seems to be no escaping its use in mastering a wide variety of skills, from memorizing the alphabet to playing a work of Mozart on the piano or doing a back flip on the balance beam. Mastering a skill means achieving automaticity, or fluid, immediate performance. Expertise in typing, for example, involves the ability to depress the keys quickly and accurately without thinking about it. Automaticity is achieved only through tedious practice.
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Figure 6–2 The serial position effect. The serial position effect demonstrates how short- and long-term memory work together.
We can easily recall the first few items in a list because the opportunity to rehearse them increases the likelihood that they are transferred into long-term memory.
Items in the middle of the list are the hardest to recall because (a) they were presented too long ago to still be in short- term memory and (b) so many items came before and after them that there was little opportunity for rehearsal, limiting transfer into LTM.
We can easily
recall items near the end of
a list because they are still contained in short-term memory.
Position of item in list
Information in LTM is highly organized and cross-referenced, like a cataloging system in a library. The more carefully we organize information, the more likely we will be to retrieve it later.
serial position effect The finding that when asked to recall a list of unrelated items, performance is better for the items at the beginning and end of the list.
Research suggests, however, that repetition without any intention to learn generally has little effect on subsequent recall (Van-Hooff & Golden, 2002). You can probably prove this phenomenon to yourself: Stop here and try to imagine from memory the front side of a U.S. penny. Now look at Figure 6–3, and pick the illustration that matches your memory. For most people, this task is surprisingly difficult: Despite the repetition of seeing thou- sands of pennies, most people cannot accurately draw one, or even pick one out from among other, similar objects (Nickerson & Adams, 1979).
Elaborative Rehearsal As we have seen, rote rehearsal with the intent to learn is sometimes useful in storing information in LTM. But often, an even more effective proce- dure is elaborative rehearsal (Craik, 2002; Craik & Lockhart, 1972), the act of relating new information to something that we already know. Through elaborative rehearsal, you extract the meaning of the new information and then link it to as much of the material already in LTM as possible. We tend to remember meaningful material better than arbitrary facts; and the more links or associations of meaning you can make, the more likely you are to remem- ber the new information later.
Clearly, elaborative rehearsal calls for a deeper and more meaningful processing of new data than does simple rote rehearsal (Craik & Lockhart, 1972). Unless we rehearse material in this way, we often soon forget it. For example, have you ever been in a group in which people were taking turns speaking up—perhaps on the first day of class when all present are asked to introduce themselves briefly, or at the beginning of a panel discussion when the speakers are asked to do the same in front of a large audience? Did you notice that you forgot virtually everything that was said by the person who spoke just before you did? According to research, you failed to remember because you did not elab- oratively rehearse what that person was saying (C. F. Bond, Pitre, & Van Leeuwen, 1991). That person’s comments simply “went in one ear and out the other” while you were preoccupied with thinking about your own remarks.
In some situations, special techniques called mnemonics (pronounced ni-MON-iks) may help you to tie new material to information already in LTM. Some of the simplest mnemonic techniques are the rhymes and jingles that we often use to remember dates and other facts. Thirty days hath September, April, June, and November . . . enables us to recall how many days are in a month. With other simple mnemonic devices, words or sentences can be made out of the material to be recalled. We can remember the colors of the visible spectrum—red, orange, yellow, green, blue, indigo, and violet—by using their first letters to form the acronym ROY G. BIV.
Schemata A variation on the idea of elaborative rehearsal is the concept of schema (plural: schemata). A schema is a mental representation of an
Figure 6–3 A penny for your thoughts. Which of these accurately illustrates a real U.S. penny? The answer is on page 196.
LIBERTY LI BERTY
1995 1995 19951995 LIBERTY LIBERTY
IN GOD WE
IN GOD WE
elaborative rehearsal The linking of new information in short-term memory to familiar material stored in long-term memory.
mnemonics Techniques that make material easier to remember.
Elaborative rehearsal requires that you relate new material to informationalready stored in LTM. Sometimes, this requires thinking abstractly, visually,or conceptually about the things you want to remember. How would you use elaborative rehearsal to store the following information?
1. In Japanese, the word for difficult is muzukashii. 2. The p in pterodactyl is silent. 3. The square root of pi is approximately 1.772.
Now try to develop an elaborative rehearsal strategy for something you are try- ing to learn, say in this or another class you are taking.
Did using an elaborative rehearsal strategy increase your ability to recall the material? What types of elaborative rehearsal strategies did you devise? Which ones seem to work best for you? Why do you think that was the case?
schema (skee-mah; plural: schemata) A set of beliefs or expectations about something that is based on past experience.
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event, an object, a situation, a person, a process, or a relationship that is stored in memory and that leads you to expect your experience to be organized in certain ways. For example, you may have a schema for eating in a restaurant, for driving a car, or for attending a class lecture. A class lecture schema might include sitting down in a large room with seats arranged in rows, opening your notebook, and expecting the professor or lecturer to come in and address the class from the front of the room.
Schemata such as these provide a framework into which incoming information is fitted. Schemata also may color what you recall by prompting you to form a stereotype; that is, to ascribe certain characteristics to all members of a particular group. (We will explore the process of stereotyping in Chapter 14, “Social Psychology.”) Thus, becoming aware of your particular schemata is one way to improve your ability to remember. (See “Applying Psychology: Improving Your Memory” for more on improving your memory.)
To summarize, we have seen that the capacity of LTM is immense and material stored there may endure, more or less intact, for decades. By comparison, STM has a sharply limited capacity and information may disappear quickly from it. The sensory registers can take in an enormous volume of information, but they have no ability to process memories. Together, these three stages of memory—the sensory registers, STM, and LTM—comprise the information-processing view of memory, as reviewed in the “Summary Table: Memory as an Information-Processing System.” (Answer to question on page 195: The accurate illustration of a penny in Figure 6–3 is the third from the left.)
Types of LTM How do types of LTM differ?
The information stored in LTM can take many forms. However, most long-term memories can be classified into one of several types: episodic, semantic, procedural, and emotional memories.
Episodic memories (D. C. Rubin, 2006; Tulving, 2002, 2005) are memories for events experienced in a specific time and place. These are personal memories, rather than histori- cal facts. If you can recall what you ate for dinner last night or how you learned to ride a bike when you were little, then you are calling up episodic memories. Episodic memory is like a diary that lets you go back in time and space to relive a personal experience (Knierim, 2007). For Jill Price, profiled at the beginning of this chapter, every waking moment is char- acterized by a barrage of episodic memories.
MEMORY AS AN INFORMATION-PROCESSING SYSTEM
Means by Which Information Is Stored
Form in Which Information Is Stored
Storage Organization Storage Duration
Means by Which Information Is Retrieved
Factors in Forgetting
Sensory Register Visual and auditory registers
Raw sensory data
None From less than 1 second to only a few seconds
Reconsideration of registered information
Decay or masking
Rote or maintenance rehearsal
Visual and phonological representation
None Usually 15 to 20 seconds
Rote or maintenance rehearsal
Interference or decay
Rote rehearsal, elaborative rehearsal, schemata
Some nonverbal representations, mostly stored by meaning
Logical frameworks, such as hierarchies or categories
Perhaps for an entire lifetime
Retrieval cues linked to organized information
Retrieval failure or interference
episodic memories The portion of long- term memory that stores personally experienced events.
Semantic memories are facts and concepts not linked to a particular time. Semantic memory is like a dictionary or an encyclopedia, filled with facts and concepts, such as the meaning of the word semantic, the location of the Empire State Building, the value of 2 times 7, and the identity of George Washington.
Procedural memories are motor skills and habits (A. Johnson, 2003). They are not mem- ories about skills and habits; they are the skills and habits. Procedural memories have to do with knowing how: how to ride a bicycle, play a violin, make coffee, write your name, walk across a room, or slam on a car’s brakes. The information involved usually consists of a precise sequence of coordinated movements that are often difficult to describe in words. Repetition, and in many
semantic memories The portion of long-term memory that stores general facts and information.
What can you do to improve yourmemory? It’s the active decisionto get better and the number of hours you push yourself to improve that makes the difference. Regardless of your innate ability, anyone can improve their memory by doing the following.
1. Develop motivation. Without a strong desire to learn or remember some- thing, you probably won’t. But if you find a way to keep yourself alert and stimulated, you will have an easier time learning and remembering things.
2. Practice memory skills. To stay sharp, memory skills, like all skills, must be practiced and used. Memory experts recommend exercises such as crossword puzzles, acrostics, anagrams, Scrabble, Monopoly, Trivial Pursuit, and bridge. Practice testing on the material you want to learn is also helpful. Several studies have shown that repeated test- ing increases retention of material more than simply studying (A. K. Butler, Karpicke, & Roediger, 2008; Szpunar, McDermott, & Roediger, 2008).
3. Be confident in your ability to remember. Self-doubt often leads to anxiety, which, in turn, interferes with the ability to retrieve informa- tion from memory. Relaxation exer- cises, experts agree, may substantially boost your ability to retrieve infor- mation from memory.
4. Minimize distractions. Although some people can study for an exam and listen to the radio simultane- ously, most people find that outside distractions interfere with both learning and remembering. Look for a quiet, even secluded, setting before attempting to commit something to memory.
5. Stay focused. Paying close attention to details, focusing on your sur- roundings, emotions, and other ele- ments associated with an event, will help you remember it clearly.
6. Make connections between new material and other information already stored in your long-term memory. The more links you forge between new information and old information already in LTM, the more likely you are to remember the new material. Discuss things you want to remember with other peo- ple. Think about or write down ways in which the new information is related to things you already know.
7. Use mental imagery. Imagery works wonders as an aid to recalling infor- mation from memory. Whenever possible, form mental pictures of the items, people, words, or activi- ties you want to remember. If you have a sequence of stops to make, picture yourself leaving each place and heading for the next. To
remember that someone’s last name is Glass, you might imagine her holding a glass or looking through a glass.
8. Use retrieval cues. The more retrieval cues you have, the more likely it is that you will remember something. One way to establish automatic retrieval cues is to create routines and structure. For example, when you come in the door, put your house and car keys in the same place every time. Then when you ask yourself, “Where did I put my keys?” the fact that you have a spe- cial place for the keys serves as a retrieval cue.
9. Rely on more than memory alone. Write down the things you need to remember, and then post a note or list of those things somewhere obvi- ous, such as on your bulletin board or refrigerator door. Put all the dates you want to remember on a calendar, and then put the calendar in a con- spicuous place.
10. Be aware that your own personal schemata may distort your recall of events. People sometimes unknow- ingly “rewrite” past events to fit their current image or their desired image of themselves and their past decisions (Lyubomirsky & Ross, 1999; Mather, Shafir, & Johnson, 2000). Being on guard against such distortions may help you avoid them.
Improving Your Memory
procedural memories The portion of long- term memory that stores information relating to skills, habits, and other perceptual-motor tasks.
explicit memory Memory for information that we can readily express in words and are aware of having; these memories can be intentionally retrieved from memory.
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cases deliberate practice, are often required to master skills and habits, but once learned, they are rarely com- pletely lost.
Emotional memories are learned emotional responses to various stimuli: all of our loves and hates, our rational and irrational fears, our feelings of disgust and anxiety. If you are afraid of flying insects, become enraged at the sight of a Nazi flag, or are ashamed of something you did, you have emotional memories.
Explicit and Implicit Memory What are the differences between implicit and explicit memories?
Because of the differences among types of memories, psychologists distinguish between explicit memory, which includes episodic and semantic memories, and implicit memory, which includes proce- dural and emotional memories (D. L. Nelson, 1994). These terms reflect the fact that sometimes we are aware that we know something (explicit memory) and that sometimes we are not aware (implicit memory).
Serious interest in the distinction between explicit and implicit memory began as a result of experiments with amnesic patients. For example, Brenda Milner (Milner, Corkin, & Teuber, 1968) stud- ied the now-famous case of patient “H. M.” (Henry Molaison), a
young man who had severe, uncontrollable epileptic seizures. The seizures became life threatening, so that as a last resort, surgeons removed most of the afflicted area of his brain. The surgery greatly reduced the frequency and severity of seizures, but it left behind a new problem: H. M. could no longer form new memories. He could meet someone again and again, but each time it was as if he were meeting the person for the first time. Old memories were intact: He could remember things that he had learned long before the operation, but he could not learn anything new. Or so it seemed!
Then one day Milner asked H. M. to trace the outline of a star while looking in a mir- ror. This simple task is surprisingly difficult, but with practice most people show steady progress. Surprisingly, so did H. M. Each day he got better and better at tracing the star, just as a person with an undamaged brain would do—yet each day he had no recollection of ever having attempted the task. H. M.’s performance demonstrated not only that he could learn, but also that there are different kinds of memories. Some are explicit: We know things, and we know that we know them. And some are implicit: We know things, but that knowledge is unconscious. (See Table 6–1 for a summary of implicit and explicit memory.)
Additional support for the distinction between explicit and implicit memory is derived from clinical observations of the ways in which strong emotional experiences can affect behavior years later even without any conscious recollection of the experiences (Kihlström, 1999; Kihlström, Mulvaney, Tobias, & Tobis, 2000; Westen, 1998). In cases of war, abuse, or terrorism, emotional memories are sometimes so overwhelming and painful they can lead to a psychiatric disorder called posttraumatic stress disorder or PTSD (Lasiuk & Hegadoren, 2006; D. C. Rubin, Berntsen, & Bohni, 2008). (We will consider PTSD in more detail in Chapter 11, “Stress and Health Psychology.”)
The fact that strong emotional memories can affect behavior without conscious aware- ness seem at first to give credence to Freud’s notion of the unconscious mind—that repressed memories for traumatic incidents can still affect our behavior. But implicit
emotional memories Learned emotional responses to various stimuli.
implicit memory Memory for information that we cannot readily express in words and may not be aware of having; these memories cannot be intentionally retrieved from memory.
Types of Memory
Experts disagree about how many different kinds of memory there are.Recently, some psychologists have suggested that the classification ofmemories into different types is artificial and merely confuses matters. They suggest that we should consider memory a unitary thing.
What arguments can you come up with to support the practice of making distinctions among different kinds of memory?
Once skills such as playing tennis have been stored in our procedural memory, they are seldom lost.
memory research suggests instead that people store emotional experiences sepa- rately from the memories of the experience itself. Thus, we may feel anxiety about flying because of a traumatic plane ride in early childhood, yet we may not remember the experience that gives rise to that anxiety. Memory of the event is out of reach, not because (as Freud thought) it has been repressed, but because the episodic and emotional components of the experience were stored separately.
Priming Research on a phenomenon called priming also demonstrates the distinction between explicit and implicit memory. In priming, a person is exposed to a stimulus, usually a word or picture. Later, the person is shown a fragment of the stimulus (a few letters of a word or a piece of a picture) and is asked to complete it. The typical result is that people are more likely to com- plete fragments with items seen earlier than they are with other, equally plausi- ble items. For example, you might be shown a list of words, including the word tour. Later on, you might be shown a list of word fragments, including __ ou __, and be asked to fill in the blanks to make a word. In comparison to others who had not been primed by seeing the word tour, you are far more likely to write tour than you are four, pour, or sour, all of which are just as acceptable as tour. The earlier exposure to tour primes you to write that word.
The Tip-of-the-Tongue Phenomenon Everyone has had the experience of know- ing a word but not quite being able to recall it. This is called the tip-of-the-tongue phe- nomenon (or TOT) (R. Brown & McNeil, 1966; Hamberger & Seidel, 2003; B. L. Schwartz, 2002; Widner, Otani, & Winkelman, 2005). Although everyone experiences TOTs, these experiences become more frequent during stressful situations and as people get older (B. L. Schwartz & Frazier, 2005; K. K. White & Abrams, 2002). Moreover, other words—usually with a sound or meaning similar to the word you are seeking—occur to you while you are in the TOT state and these words interfere with and sabotage your attempt to recall the desired word. The harder you try, the worse the TOT state gets. The best way to recall a blocked word, then, is to stop trying to recall it! Most of the time, the word you were searching for will pop into your head, minutes or even hours after you stopped consciously searching for it (B. L. Schwartz, 2002). (If you want to experience TOT yourself, try naming Snow White’s seven dwarfs.)
The distinction between explicit and implicit memories means that some knowl- edge is literally unconscious. Moreover, as we shall soon see, explicit and implicit mem- ories also seem to involve different neural structures and pathways. However, memories typically work together. When we remember going to a Chinese restaurant, we recall not only when and where we ate and whom we were with (episodic memory), but also the nature of the food we ate (semantic memory), the skills we learned such as eating with chopsticks (procedural memory), and the embarrassment we felt when we spilled the tea (emotional memory). When we recall events, we typically do not experience these kinds of memories as distinct and separate; rather, they are integrally connected, just as
tip-of-the-tongue phenomenon (or TOT) Knowing a word, but not being able to immediately recall it.
Looking into a bakery window, perhaps smelling the aromas of the cakes inside, may prime the memory, triggering distinct memo- ries associated with those sights and smells, formed many years ago.
Table 6–1 TYPES OF MEMORIES
Semantic Episodic Procedural Emotional
Memories of facts and concepts
Memories of personally experienced events
Motor skills and habits
Learned emotional reactions
Example: recalling that Albany is the capital of New York
Example: recalling a trip to Albany
Example: ice skating
Example: recoiling at the sight of a rat
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L E A R N I N G O B J E C T I V E • Define long-term potentiation. Identify
the areas of the brain that play a role in the formation and storage of long-term memories. Describe the role of sleep in the formation of new memories.
long-term potentiation (LTP) A long-lasting change in the structure or function of a synapse that increases the efficiency of neural transmission and is thought to be related to how information is stored by neurons.
the original experiences were. Whether we will continue to remember the experiences accurately in the future depends to a large extent on what happens in our brain, as we will see in the next section.
CHECK YOUR UNDERSTANDING
1. The primacy effect accounts for why we remember items at the ___________ of a list, while the recency effect accounts for why we remember items at the ___________ of the list.
2. If information is learned through repetition, this process is ___________ rehearsal; if it is learned by linking it to other memories, this process is ___________ rehearsal.
3. A schema is a framework in memory into which new information is fit. Is this statement true (T) or false (F)?
4. Implicit memories consist of ___________ and ___________ memories, whereas explicit memories consist of ___________ and ___________ memories.
Answers:1. beginning; end.2. rote; elaborative.3. (T).4. procedural and emotional; episodic and semantic.
APPLY YOUR UNDERSTANDING
1. You run into an old friend who gives you his phone number and asks you to call. You want to be sure to remember the phone number, so you relate the number to things that you already know. “555” is the same as the combination to your bicycle lock. “12” is your brother’s age. And “34” is the size of your belt. This technique for getting information into long-term memory is called
a. rote rehearsal. b. relational rehearsal. c. elaborative rehearsal. d. episodic rehearsal.
2. He: “We’ve been to this restaurant before.” She: “I don’t think so.” He: “Didn’t we eat here last summer with your brother?” She: “That was a different restaurant, and I think it was last fall, not last summer.” This couple is trying to remember an event they shared and, obviously, their memories differ. The information they are seeking is most likely stored in
a. procedural memory. b. emotional memory. c. semantic memory. d. episodic memory.
Answers:1. c.2. d.
THE BIOLOGY OF MEMORY What role do neurons play in memory?
Research on the biology of memory focuses mainly on the question, How and where are memories stored? Simple as the question is, it has proved enormously difficult to answer and our answers are still not entirely complete.
Current research indicates that memories consist of changes in the synaptic connec- tions among neurons (Asrican, 2007; Kandel, 2001). When we learn new things, new con- nections are formed in the brain; when we review or practice previously learned things, old connections are strengthened. These chemical and structural changes can continue over a period of months or years (Abraham & Williams, 2008; Bekinschtein et al., 2008; Lu, Christian, & Lu, 2008), during which the number of connections among neurons increases as does the likelihood that cells will excite one another through electrical discharges, a process known as long-term potentiation (LTP).
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Although learning takes place in the brain, it is also influenced by events occurring elsewhere in the body. Two hormones in particular, epinephrine and cortisol, have been shown to affect long-term retention, especially for unpleasant experiences (Korol & Gold, 2007). Another hormone found to influence memory is ghrelin. Secreted from the lining of stomach when it is empty, ghrelin travels to the brain where it primarily stimulates recep- tors in the hypothalamus to signal hunger. However, some ghrelin also finds its way to the hippocampus, where studies with mice have shown it can enhance learning and memory (Diano et al., 2006; Olszewski, Schiöth, & Levine, 2008). As a result, the hungry mice are more likely to remember where they have found food in the past.
Mind–Body Effects of Stress on Body and Brain Epinephrine secretion is part of the “fight or flight” syndrome (see Chapter 11, “Stress and Health Psychology”), and has the effect of arousing the organism to action. However, the effect on memory of epinephrine and other stress-related hormones is not merely the result of general arousal. Apparently these hormones indirectly act on specific brain cen- ters, such as the hippocampus and the amygdala, that are critical for memory formation (Vermetten & Bremner, 2002). Increased blood levels of epinephrine probably also explain improved performance in humans under conditions of mild stress (L. Cahill & Alkire, 2003). Extreme stress, however, often interferes with both the learning and later recall of specific information. For example, research has demonstrated that when people are exposed to highly stressful events, their memory for the emotional aspect of the event may be enhanced (LaBar, 2007) but their ability to recall the nonemotional aspects of the event is disrupted (Payne et al., 2006). If you are studying for an exam, then, a little anxiety will probably improve your performance, but a high level of anxiety will work against you. ■
Where Are Memories Stored? Are STM and LTM found in the same parts of the brain?
Not all memories are stored in one place. Instead our brains appear to depend on large numbers of neurons distributed throughout the brain working in concert to form and store memories (Tsien, 2007). However, this characteristic does not mean that memories are ran- domly distributed throughout the brain. In fact, different parts of the brain are specialized for the storage of memories (Rolls, 2000). (See Figure 6–4.)
Short-term and working memory, for example, seem to be located primarily in the prefrontal cortex and temporal lobe (Izaki, Takita, & Akema, 2008; Rainer & Miller, 2002; Scheibel & Levin, 2004). Long-term semantic memories seem to be located primarily in the frontal and temporal lobes of the cortex, which interestingly, also play a prominent role in consciousness and awareness. Research shows increased activity in a particular area of the left temporal lobe—for example, when people are asked to recall the names of people. A nearby area shows increased activity when they are asked to recall the names of animals, and another neighboring area becomes active when they are asked to recall the names of tools (H. Damasio, Grabowski, Tranel, Hichwa, & Damasio, 1996). (See Figure 6–5.) Destruction of these areas of the cortex (through head injury, surgery, stroke, or disease) results in selective memory loss (e.g., H. Damasio et al., 1996).
Episodic memories also find their home in the frontal and temporal lobes (Jackson, 2004; Nyberg et al., 2003; Stevens & Grady, 2007). But some evidence shows that episodic and semantic memories involve different portions of these brain structures (Prince, Tsukiura, & Cabeza, 2007). In addition, because episodic memories depend on integrating different sensations (vision, audition, and so on) to create a personal memory experience, they also draw upon several distinct sensory areas of the brain. Thus, episodic memory is
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Figure 6–5 PET scanning shows increased activity in different areas of the brain when people are asked to recall the names of people, animals, and tools.
probably best thought of as the integration of memories that are located throughout the brain into a coherent personal experience (D. C. Rubin, 2006).
Procedural memories appear to be located primarily in the cerebellum (an area required for balance and motor coordination) and in the motor cortex (Gabrieli, 1998; Hermann et al., 2004).
Subcortical structures also play a role in long-term memory. For example, the hip- pocampus has been implicated in the functioning of both semantic and episodic memory (Eichenbaum & Fortin, 2003; Manns, Hopkins, & Squire, 2003; Rolls, 2000), as well as being involved in the ability to remember spatial relationships (Astur, Taylor, Marnelak, Philpott, & Sutherland, 2002; Bilkey & Clearwater, 2005). If the hippocampus is damaged, people can remember events that have just occurred (and are in STM), but their long-term recall of those same events is impaired. The amygdala, a structure that lies near the
Figure 6–4 The biological basis of memory. Many different parts of the brain are specialized for the storage of memories.
The frontal lobes store semantic and episodic memories.
The motor cortex is involved in storing procedural memories.
The cerebellum plays an important role in the storage of procedural memories.
The temporal lobe is involved in the formation and storage of long-term semantic and episodic memories and contributes to the processing of new material in short-term memory.
The hippocampus plays a pivotal role in the formation of new long-term semantic and episodic memories.
The prefrontal cortex is involved in the storage of short-term memories.
The amygdala is vital to the formation of new emotional memories.
hippocampus, seems to play a role in emotional memory that is similar to the role the hippocampus plays in episodic, semantic, and procedural memory (LaBar, 2007; Payne et al., 2006; Vermetten & Bremner, 2002). For example, damage to the amygdala reduces the ability to recall new emotional experiences, but it does not prevent the recall of emotional events that occurred prior to the damage, though they are often remembered as neutral facts, devoid of emotional content. This may explain why people with amygdala damage are sometimes unable to “read” facial expressions, even though they recognize the person’s face (Pegna, Caldara-Schnetzer, & Khateb, 2008; Pegna, Khateb, & Lazeyras, 2005).
The Role of Sleep In Chapter 4 (“States of Consciousness”), we noted that sleep appears to play an impor- tant role in the formation of new memories. One recent study of adolescents, for example, showed that sleeping less than 8 hours a night negatively impacted working memory (Gradisar, Terrill, Johnston, & Douglas, 2008). Studies like this have prompted neurosci- entists to explore precisely how sleep is involved in the formation and storage of new memories (Rasch & Born, 2008). Brain imaging with animals and humans shows that the same hippocampal neurons and patterns of neuron activity that accompany initial learn- ing are reactivated during subsequent deep sleep. Thus, it is not surprising that deep sleep after learning serves to strengthen new memories (M. P. Walker & Stickgold, 2006). More- over, high levels of neuron reactivation during sleep are associated with the formation of the strongest memories (McNaughton et al., 2003; Peigneux et al., 2004; Rasch, Büchel, Gais, & Born, 2007). Clearly, psychologists have a long way to go before they will fully understand the biology of memory, but progress is being made in this fascinating area.
CHECK YOUR UNDERSTANDING Match the following types of memory to the location in the brain where they appear to be stored: 1. ___ short-term memories a. frontal and temporal lobes 2. ___ long-term semantic and episodic
memories b. cerebellum and motor cortex
3. ___ procedural memories c. amygdala 4. ___ emotional memories d. prefrontal cortex and temporal lobe
Answers:1. d.2. a.3. b.4. c.
APPLY YOUR UNDERSTANDING
1. Oliver Sacks, the author of The Man Who Mistook His Wife for a Hat, describes Jimmie G., who was an otherwise healthy 49-year-old man whose long-term memory stopped changing when he was 19. New information in his short-term memory simply never got stored in long-term memory. Which part of his brain was most likely not working correctly?
a. the prefrontal cortex b. the hippocampus c. Broca’s area d. the occipital lobe
2. Imagine now that you encounter someone like Jimmie G., but in this case, the person cannot form new emotional memories. He has emotional reactions to things he encountered early in his life, but he has no such reactions to things he encountered more recently—no new loves or hates, no new fears, no new sources of anger or happiness. Which part of his brain is most likely not working correctly?
a. the amygdala b. the temporal lobe c. the prefrontal cortex d. the cerebellum Answers:1. b.2. a.
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204 Chapter 6
Figure 6–6 The progression of Alzheimer’s disease. A computerized brain scan taken of a single patient over time shows the spread of Alzheimer’s disease throughout the brain. Diseased tissue is shown as red and white. Notice how the damaged tissue replaces normal brain tissue shown here as blue.
FORGETTING What factors explain why we sometimes forget?
Why do memories, once formed, not remain forever in the brain? Part of the answer has to do with the biology of memory, and another part has to do with the experiences that we have before and after learning.
The Biology of Forgetting How does the deterioration of the brain help to explain forgetting?
According to the decay theory, memories deteriorate because of the passage of time. Most of the evidence supporting decay theory comes from experiments known as distractor stud- ies. For example, in one experiment, participants learned a sequence of letters, such as PSQ.
Then they were given a three-digit number, such as 167, and asked to count backwards by threes: 167, 164, 161, and so on, for up to 18 seconds (L. R. Peterson & Peterson, 1959). At the end of that period, they were asked to recall the three letters. The results of this test astonished the experimenters. The par- ticipants showed a rapid decline in their ability to remember the letters. Because the researchers assumed that counting backwards would not interfere with remembering, they could only account for the forgotten letters by noting that they had simply faded from short-term memory in a matter of seconds. Decay, then, seems to be at least partly responsible for forget- ting in short-term memory.
Information in LTM also can be lost if the storage process is disrupted. Head injuries often result in retrograde amnesia, a condition in which people cannot remember what happened to them shortly before their injury. In such cases, forgetting may occur because memories are not fully consolidated in the brain.
Severe memory loss is invariably traced to brain damage caused by accidents, surgery, poor diet, or disease (Roncadin, Guger, Archibald, Barnes, & Dennis, 2004). For example, chronic alcoholism can lead to a form of amnesia called Korsakoff ’s syndrome caused by a vitamin deficiency in the nutritionally poor diet that is typi- cal of people who abuse alcohol (Baddeley, 1987; Hildebrandt, Brokate, Eling, & Lanz, 2004). Other studies show the importance of the hippocampus to long-term memory formation. Studies of elderly people who are having trouble remembering new material, for instance, show alterations in hippocampal functioning and connectivity to other areas of the brain (Grady, McIntosh, & Craik, 2003). Brain scans (see Figure 6–6) also reveal hippocampus dam- age in people suffering from Alzheimer’s disease, a neurological disorder that causes severe memory loss (Rapp et al., 2006; Villain et al., 2008). (See Chapter 9,“Life-Span Development,” for more information about Alzheimer’s disease.)
L E A R N I N G O B J E C T I V E S • Describe the biological factors that
influence forgetting, including the phenomenon of retrograde amnesia.
• Differentiate between retroactive and proactive interference.
• Explain what is meant by “state- dependent memory” and the “reconstructive” nature of remembering.
decay theory A theory that argues that the passage of time causes forgetting.
retrograde amnesia The inability to recall events preceding an accident or injury, but without loss of earlier memory.
Source: © The New Yorker Collection, 1998, Mick Stevens from cartoonbank.com. All Rights Reserved.
Alzheimer’s may also involve below-normal levels of the neurotransmitter acetyl- choline in the brain. Indeed, some research suggests that drugs and surgical procedures that increase acetylcholine levels may serve as effective treatments for age-related mem- ory problems (Coyle, Geerts, Sorra, & Amatniek, 2007; McIntyre, Marriott, & Gold, 2003).
Experience and Forgetting What environmental factors contribute to our inability to remember?
Although sometimes caused by biological factors, forgetting can also result from inadequate learning. A lack of attention to critical cues, for example, is a cause of the forgetting commonly referred to as absentmindedness (D. L. Schacter, 1999). For exam- ple, if you can’t remember where you parked your car, most likely you can’t remember because you did- n’t pay attention to where you parked it.
Forgetting also occurs because, although we attended to the matter to be recalled, we did not rehearse the material enough. Merely “going through the motions” of rehearsal does little good. Prolonged, intense practice results in less forgetting than a few, halfhearted repetitions. Elaborative rehearsal can also help make new memories more durable. When you park your car in space G-47, you will be more likely to remember its location if you think, “G-47. My uncle George is about 47 years old.” In short, we cannot expect to remember infor- mation for long if we have not learned it well in the first place.
Interference Inadequate learning accounts for many memory failures, but learning itself can cause forgetting. This is the case because learning one thing can interfere with learning another. Information gets mixed up with, or pushed aside by, other information and thus becomes harder to remember. Such forgetting is said to be due to interference. As portrayed in Figure 6–7, there are two kinds of interference. In retroactive interference, new material interferes with information already in long-term memory. Retroactive interference occurs every day. For example, once you learn a new telephone number, you may find it difficult to recall your old number, even though you used that old number for years.
In the second kind of interference, proactive interference, old material interferes with new material being learned. Like retroactive interference, proactive interference is an everyday phenomenon. Suppose you always park your car in the lot behind the building where you work, but one day all those spaces are full, so you have to park across the street. When you leave for the day, you are likely to head for the lot behind the building—and may even be surprised at first that your car is not there. Learning to look for your car behind the building has interfered with your memory that today you parked the car across the street.
The most important factor in determining the degree of interference is the similarity of the competing items. Learning to swing a golf club may interfere with your ability to hit a baseball, but probably won’t affect your ability to make a free throw on the basketball courts. The more dissimilar something is from other things that you have already learned, the less likely it will be to mingle and interfere with other material in memory (G. H. Bower & Mann, 1992).
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Figure 6–7 Diagram of experiments measuring retroactive and proactive interference. In retroactive interference, the experimental group usually does not perform as well on tests of recall as those in the control group, who experience no retroactive interference from a list of words in Step 2. In proactive interference, people in the experimental group suffer the effects of proactive interference from the list in Step 1. When asked to recall the list from Step 2, they perform less well than those in the control group.
Step 1 Step 2 Step 3
Learn list of rivers
Learn list of rivers
Learn list of rivers
Learn list of mountains Experimental
group performs less well on recalling list
Experimental group performs
less well on recalling list of
Rest or engage in unrelated activity
Rest or engage in unrelated activity
Learn list of mountains
Learn list of mountains
retroactive interference The process by which new information interferes with information already in memory.
proactive interference The process by which information already in memory interferes with new information.
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206 Chapter 6
Situational Factors Whenever we try to memorize something, we are also unin- tentionally picking up information about the context in which the learning is taking place. That information becomes useful when we later try to retrieve the corresponding information from LTM. If those environmental cues are absent when we try to recall what we learned, the effort to remember is often unsuccessful. Context-dependent memory effects tend to be small, so studying in the same classroom where you are scheduled to take an exam will probably not do too much to improve your grade. Nev- ertheless, contextual cues are occasionally used by police who sometimes take wit- nesses back to the scene of a crime in the hope that they will recall crucial details that can be used to solve the crime.
Our ability to accurately recall information is also affected by internal cues, a phenom- enon known as state-dependent memory. Researchers have found that people who learn material in a particular physiological state tend to recall that material better if they return to the same state they were in during learning (de-l’Etoile, 2002; Kelemen & Creeley, 2003; Riccio, Millin, & Gisquet-Verrier, 2003). For example, if people learn material while under the influence of caffeine, recall of the material is slightly improved when they are again under the influence of caffeine (Kelemen & Creeley, 2003).
The Reconstructive Process Forgetting also occurs because of what is called the “reconstructive” nature of remembering. Earlier, we talked about how schemata are used in storing information in long-term memory. Bartlett proposed that people also use schemata to “reconstruct” memories (Bartlett, 1932; D. L. Schacter, Norman, & Koutstaal, 1998). This reconstructive process can lead to huge errors. Indeed, we are sometimes more likely to recall events that never happened than events that actually took place (Brainerd & Reyna, 1998)! The original memory is not destroyed; instead, people are sometimes unable to tell the difference between what actually happened and what they merely heard about or imag- ined (Garry & Polaschek, 2000; S. R. Schmidt, 2004; S. E. Taylor, Pham, Rivkin, & Armor, 1998).
We may also reconstruct memories for social reasons or personal self-defense (Feeney & Cassidy, 2003). Each time you tell someone the story of an incident, you may uncon- sciously make subtle changes in the details of the story. Consequently, these changes become part of your memory of the event. When an experience doesn’t fit our view of the world or ourselves, we tend, unconsciously, to adjust it or to blot it out of memory alto- gether (Bremner & Marmar, 1998). Such distortions of memory become critically impor- tant in criminal trials, in which a person’s guilt or innocence may depend on the testimony of an eyewitness—a topic we will return to later in this chapter.
FACTORS THAT AFFECT FORGETTING
Decay Information in memory deteriorates with the passage of time
Retrograde amnesia Storage of new information is disrupted; most often due to injury
Hippocampal damage Damage to the hippocampus interferes with the formation of new memories; often caused by brain injury, advanced aging or Alzheimer’s disease
Retroactive interference Learning new material interferes with information already stored in memory
Proactive interference Information already stored in memory interferes with learning new material
Situational factors Attempting to remember something in a different situation or internal state may negatively impact memory
Reconstruction Memories are reconstructed or replaced with incorrect information which is often more consistent with a current image or perception
SPECIAL TOPICS IN MEMORY What factors can influence how well you remember a specific incident?
Now that we have reviewed the various types of memory and how our memory for differ- ent events is stored in the brain, we will turn our attention to some special factors that affect memory.
Cultural Influences Are the memory tasks in Western schools different from those in cultures that pass on traditions orally?