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years, a very old person”), dates (1944 was “near the end of World War II”), and
cross-country racing times for various distances (3492 was “3 minutes and 49.2
seconds, nearly a world’s record for the mile”).
In a neighborhood park in London, a family plays a giant outdoor game of chess.
Do you think chess masters could recall the configurations on this giant board as
easily as they can from their perspective on a table? This question has never been
put to test.
Julio Etchart / Alamy Stock Photo
The value of chunking is also evidenced by the way people retain information in
their areas of expertise. Study the arrangement of pieces on the chessboard shown
in Figure 6.4, and in 5 seconds memorize as much of it as you can. Chances are,
you’ll be able to reproduce approximately seven items. Yet after looking at the same
arrangement for 5 seconds, chess masters can reproduce all the pieces and their
row-and-column positions almost without error. It’s not that chess masters are born
with computer-like minds. When chess pieces are placed randomly on the board,
chess masters are no more proficient than the rest of us. But when the arrangement
is taken from an actual game between good players, masters naturally chunk the
configurations of individual pieces into familiar patterns such as the “Romanian Pawn
Defense” and “Casablanca Bishop’s Gambit” (Chase & Simon, 1973; De Groot, 1965;
Gobet, 2016). Researchers estimate that chess masters can store up to 50,000 such
chunks in memory (Gobet & Simon, 1996).
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Description
Figure 6.4 The Value of Chunking
From years of experience, experts in all domains—including computer
programmers, figure skaters, servers, bridge players, ballet dancers, gamers, and
professional actors—exhibit these advantages in their STM performance (Sala &
Gobet, 2017; Vicente & Wang, 1998). Similarly, research demonstrates that in a
comparison of musician and nonmusician memory performance, musicians highly
outperform nonmusicians on tonal stimuli and moderately outperform nonmusicians
on verbal stimuli (Talamini, Altoè, Carretti, & Grassi, 2017). Furthermore, there are
hippocampal differences between musicians and nonmusicians, as illustrated in
Figure 6.5. Specifically, musicians have denser hippocampi than do nonmusicians.
Description
Figure 6.5 Functional and Structural Differences in Musicians’ vs. Nonmusicians’
Hippocampi
Source: Groussard M, La Joie R, Rauchs G, Landeau B, Chételat G,
Viader F, et al. (2010) When Music and Long-Term Memory Interact:
Effects of Musical Expertise on Functional and Structural Plasticity in the
Hippocampus. PLoS ONE 5(10): e13225.
Duration
Memory is an important function of the brain, not just for knowledge and directions
but also for socialization. Unfortunately, most people experience moments when
memory limitations hinder their ability to perform. Imagine, for example, having the
job of a short order cook on a busy night. Servers are lined up, yelling food orders
into the air as fast as popping popcorn. Flames are rising from the grill, timers are
ringing, water is boiling, music is playing in the background, everyone is yelling, and
you are supposed to be able to tune all of that out and keep the orders straight. What
happens if you forget to leave off the onions? What happens if you forget the name of
the new server who walked off after saying, “I need this on the fly”? And if you use the
wheat noodles by accident when someone has requested a gluten-free substitution,
the consequences could be dire. Many strategies can help, but those who work in the
food service industry have to juggle a lot of information at once—ingredients and
steps for making a variety of menu items, food and workplace safety rules, charges
for each table, names of patrons and coworkers, and cues from customers that
they’re getting impatient. Have you ever been on the other side, receiving the wrong
order for your meal? It may be an inconvenience, but perhaps this chapter will give
you a reason to be a bit more forgiving.
Experiences with forgetting are common because short-term memory is limited
not only in the amount of information it can store—the cook brings in tons of sensory
information when an order is called out—but also in the length of time it can hold that
information. What is the duration of short-term memory? That is, how long does a
memory trace last if a person does not actively rehearse or repeat it? To measure
how rapidly information is forgotten, Lloyd Peterson and Margaret Peterson (1959)
asked subjects to recall a set of unrelated consonants such as MJK. So that subjects
could not rehearse the material, they were given a number and instructed to count
backward from that number by 3s: 564, 561, 558, 555, and so on. After varying
lengths of time, subjects were cued to recall the consonants. After 18 seconds,
performance plummeted to below 10 percent (illustrated in Figure 6.6). So, from the
time the server sends the order to the cook, to the time the cook is able to collect the
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ingredients, it is quite possible that 18 seconds have passed and what you ordered to
accompany your steak is forgotten.
Description
Figure 6.6 Duration of Short-Term Memory
Source: Peterson, L., & Peterson, M. J. (1959). Short-term retention of
individual verbal items. Journal of Experimental Psychology, 58(3), 193–
198. https://doi.org/10.1037/h0049234
Knowing the fleeting nature of short-term memory, we can prevent forgetting by
repeating information silently or aloud. A short order cook can silently repeat the
order while collecting the ingredients. Repetition extends the 20-second duration of
short-term memory in the same way that chunking expands its four- to seven-item
capacity.
The retention benefits of sheer repetition, also called maintenance rehearsal,
were first demonstrated by Hermann Ebbinghaus (1885/1913), a German philosopher
who was a pioneer in memory research. Using himself as a subject, Ebbinghaus
created a list of all possible nonsense syllables consisting of a vowel inserted
between two consonants. Syllables that formed words were then eliminated—which
left a list of unfamiliar items (e.g., RUX, VOM, QEL, MIF), each written on a separate
card. To study the effects of rehearsal, Ebbinghaus would turn over the cards, one at
a time, and say each syllable aloud to the ticking rhythm of a metronome. Then, after
reading the items once, he would start again and go through the cards in the same
order. This procedure was repeated until he could anticipate each syllable before
turning over the card. Ebbinghaus found that he could recall a list of seven syllables
after a single reading (there’s that magical number again) but that he needed more
practice for longer lists. The more often he repeated the items, the more he could
recall. Other studies have confirmed the point: “Rehearsal” can be used to “maintain”
an item in short-term memory for an indefinite period of time.
maintenance rehearsal. The use of sheer repetition to keep information in shortterm memory.
Functions of Short-Term Memory
The limitations of short-term memory may seem to be a handicap, but in fact they
are economic and adaptive. As with clearing outdated papers off a desk or purging
old images from your phone, it helps to forget what is no longer useful. Otherwise,
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your mind would be cluttered with every sensation, every name, address, and morsel
of trivia that ever entered the stream of your consciousness. If short-term memory
had unlimited capacity, you would constantly be distracted—possibly with devastating
results. When we discuss psychological disorders, for example, we’ll learn that
people who suffer from schizophrenia are often incoherent, jumping from one topic to
the next as they speak, in part because they cannot filter out distractions.
Working Memory
In the computer we call the human mind, short-term memory is a mental
workspace, like the screen. On a computer, material displayed on the screen may be
entered on a keyboard, downloaded, or retrieved from previously saved files.
Similarly, STM contains both new sensory input and material that is pulled from longterm storage. All cognitive psychologists agree that people have fleeting memories
that are limited in their capacity and duration (Coltheart, 1999; Gathercole, 2001).
However, many researchers are critical of the traditional view that STM is a passive
storage depot that merely holds information until it fades or is transferred to a
permanent warehouse (Crowder, 1993).
To conceptualize short-term memory as an active mental workspace where
information is processed, Alan Baddeley (1992) and others prefer to use the term
working memory. According to Baddeley, our working memory consists of a “central
executive” processor and two specialized storage-and-rehearsal systems—one for
auditory input, the other for visual and spatial images. However, according to Nelson
Cowan (2016), this is just one of nine definitions for working memory. Cowan argues
that Baddeley has provided the storage and processing definition of working memory.
Within this definition, the working memory system is critical for intelligent functioning
because a person must store the information while simultaneously processing said
information. This requires attention. To interpret spoken or written language, for
example, you have to remember the early part of a statement after it has receded into
the past. Similarly, to solve an arithmetic problem, you have to keep track of the
different steps you take—as in remembering to carry the 1 when adding 45 and 55.
Now, think about all of the processes you require of your brain during a routine drive
to class. What can you really pay attention to? The traffic signs? A text message that
just came in? The new song on the radio? Chances are that if your attention is
focused on the new song, and then refocused on the text message alert, you aren’t
able to remember whether or not you stopped at that last stop sign. But at least you
do remember some of the new song and that a text message just came in, right?
Figure 6.7 illustrates how Cowan (2016) believes information moves from sensory to
activation in short-term memory.
working memory. Term used to describe short-term memory as an active
workspace where information is accessible for current use.
Description
Figure 6.7 Cowan’s Model of Memory
iStock.com/LeoPatrizi
Unsworth and Spillers (2010) also investigated the contribution of working
memory to intelligence and concluded that the ability to retrieve information from
long-term memory is also important. For example, to interpret a language we aren’t
fluent in, we must search our long-term memory for the words as they are read or
spoken, and then connect those words with their meaning. This view of working
memory is what Cowan calls the inclusive working memory definition. Regardless of
the various definitions for working memory, research supports the notion that working
memory contains separate systems for auditory and visual input—and that the
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system as a whole is highly adaptive (Andrade, Baddeley, & Hitch, 2002; Cowan,
2016; Miyake & Shah, 1999).
The Serial-Position Effect
Research also suggests that it may be useful to distinguish between short-term
and long-term memory. Whenever people try to memorize a list, they inevitably recall
items from the beginning and end of the list better than those sandwiched in the
middle. The enhanced recall of early items in a sequence is called primacy, the
advantage for the later items is called recency, and the combined pattern is known as
the serial-position curve. This result was discovered in the 1890s by Mary Whiton
Calkins, the first female president of the American Psychological Association
(Madigan & O’Hara, 1992). Since that time, researchers have consistently observed
the same effect.
serial-position curve. A U-shape pattern indicating the tendency to recall more
items from the beginning and end of a list than from the middle.
What explains the serial-position effect? It appears that different factors are
responsible for primacy and recency. Primacy is easy to understand. Imagine
receiving a list of words and trying to recall them for a test: chair, artichoke, bicycle,
frame, teacher, and so on. Chances are, you’ll later recall the first word because you
repeated it to yourself over and over again. You must divide your attention in half for
the second word as you try to hold two in memory, divide your attention into thirds for
the third item, and so on, through the list. In other words, primacy occurs because the
first few words receive more attention and rehearsal than later ones—and are more
likely to be transferred into long-term memory.
Explaining the recency effect is trickier. On the basis of the information-processing
model described earlier, researchers argued that the last items in a list are easier to
recall because they are still fresh in short-term working memory when the test begins.
Initially, studies supported this explanation. For example, Murray Glanzer and Anita
Cunitz (1966) presented two groups of subjects with 15 words to memorize. One
group was tested right after the presentation; the second was distracted for 30
seconds and then tested. Figure 6.8 shows that subjects who were tested
immediately after the presentation exhibited the usual effect: The first items were
recalled by rehearsal, the last ones had not yet faded, and those in the middle slipped
through the cracks. But there was no recency effect in the delayed-testing group—
only primacy. After 30 seconds and no opportunity for rehearsal, the last few items
vanished from working memory.
This explanation of the serial-position curve seems convincing, but there’s a
problem with it: Mack and colleagues (2017) argue that research in support of the
serial-position effect tends to present items at one every 5 to 20 seconds. This
presentation doesn’t generalize to all circumstances. The researchers believed that
the primacy and recency findings would be stronger if replicated under different
conditions—specifically, more time between item presentation and outside of a
controlled lab. Therefore, Mack and colleagues (2017) decided to use an iPhone
recall app titled RECAPP, which allowed the experimenter to control the items and
their rate of presentation in a setting closer to the real world. Across three
experiments, and a span of several consecutive days, participants were presented
with a list of words at the rate of one word per hour via RECAPP. An hour after the
last word was presented, participants were given a free recall test—a measure of
memory performance absent cues to help retrieval. The results demonstrated a weak
serial-position effect. Items presented first or last were not much more or less likely to
be recalled. While this study did not strongly support the serial-position effect, it does
not debunk it, either. According to Mack and colleagues (2017), participants used
different strategies to help cue their recall of items, and these strategies might have
depended on the length of the lists and time between exposure and recall. Some
strategies may have been better than others. In the next section, we discuss some
strategies participants may have used—elaborative rehearsal, for example—to
increase their memory performance.
free recall. A type of explicit-memory task in which a person must reproduce
information without the benefit of external cues (e.g., an essay exam).
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Description
Figure 6.8 The Serial-Position Effect
Source: Glanzer, M., & Cunitz, A. R. (1966). Two storage mechanisms
in free recall. Journal of Verbal Learning & Verbal Behavior, 5(4), 351–
360. https://doi.org/10.1016/S0022-5371(66)80044-0
LONG-TERM MEMORY
LEARNING OBJECTIVES
Juxtapose the belief that memories are forever with the belief that memories
eventually become extinct.
Describe the transfer of information from short-term memory into long-term
memory.
Explain memory retrieval, forgetting, and retrieval failure.
Tell the story of H.M., and include why his story is so important.
Create an argument for why people claim that “memory is reconstructive.”
Do you remember your fourth birthday, the name of your first-grade teacher, or the
smell of floor wax in the corridors of your elementary school? Can you describe a
dream you had last night or recite the words of the national anthem? To answer these
questions, you would have to retrieve information from the mental warehouse of longterm memory. Like the hard drive on a computer, LTM is a relatively enduring storage
system that has the capacity to retain vast amounts of information for long periods of
time. This section examines long-term memories of the recent and remote past—how
they are encoded, stored, retrieved, forgotten, and even reconstructed in the course
of a lifetime.
Encoding
Information can be kept alive in short-term working memory by rote repetition, or
maintenance rehearsal. But to transfer something into long-term memory, you would
find it much more effective to use elaborative rehearsal—a strategy that involves
thinking about the material in a more meaningful way and associating it with other
knowledge that is already in LTM. The more deeply you process something, the more
likely you are to recall it at a later time.
elaborative rehearsal. A technique for transferring information into long-term
memory by thinking about it in a deeper way.
To demonstrate this process, Fergus Craik and Endel Tulving (1975) showed
subjects a list of words, one at a time, and for each asked them for (a) a simple visual
judgment that required no thought about the words themselves (“Is—printed in capital
letters?”); (b) an acoustic judgment that required subjects to at least pronounce the
letters as words (“Does—rhyme with small?”); or (c) a more complex semantic
judgment that compelled subjects to think about the meaning of the words (“Does the
word fit the sentence ‘I saw a—in the pond’?”). Subjects did not realize that their
memory would be tested later. Yet words that were processed at a “deep” level, in
terms of meaning, were more easily recognized than those processed at a “shallow”
level (illustrated in Figure 6.9). This strategy could have been used in the RECAPP
experiment discussed earlier. When presented with a word to remember, participants
could have used the word in a sentence or looked up the definition. So, when you are
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studying, try to process the information at a deeper level by focusing on its true
meaning and how it applies to the real world.
Description
Figure 6.9 Elaborative Rehearsal
Source: Adapted from Craik, F. I. M., & Tulving, E. (1975). Depth of
processing and the retention of words in episodic memory. Journal of
Experimental Psychology: General, 104(3), 268–294.
https://doi.org/10.1037/0096-3445.104.3.268
Does making complex semantic judgments, compared to simple visual judgments,
activate different regions of the brain? Is it possible to see physical traces of deep
processing? Using fMRI technology, John Gabrieli et al. (1996) devised a study
similar to Craik and Tulving’s in which subjects were shown stimulus words on a
computer and were instructed to determine whether the words were concrete or
abstract (a semantic judgment) or simply whether they were printed in uppercase or
lowercase letters (a visual judgment). As in past research, subjects later recalled
more words for which they had made semantic rather than visual judgments. In
addition, however, the brain-imaging measures showed that processing the words in
semantic terms triggered more activity in a part of the frontal cortex of the languagedominant left hemisphere.
Memorizing—definitions, math formulas, poems, or historical dates—usually
requires conscious effort and practice. In 1885, Ebbinghaus read through a list of
nonsense syllables 0, 8, 16, 24, 32, 42, 53, or 64 times and checked his memory for
the items 24 hours later. As predicted, the more learning time he spent the first day,
the better his memory was on the second day.
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Figure 6.10 The Value of Chunking (Blank Board)
But there’s more. Ebbinghaus and others found that retention is increased through
“overlearning”—that is, continued rehearsal even after the material seems to have
been mastered (Driskell, Willis, & Copper, 1992; Semb, Ellis, & Araujo, 1993; Shibata
et al., 2017). In fact, Shibata and colleagues (2017) discovered that overlearning
solidifies connections in the brain, which protects the newly mastered material from
interference. When we master new information, it is at risk of being overshadowed by
the next set of information we must learn. Overlearning prevents this overshadowing.
Shibata and colleagues’ work demonstrates how this happens in the brain with
neuronal adjustments to stabilize mastered materials when overlearning is
implemented.
Long-term memory is also better when the practice is spread over a long period of
time than when it is crammed in all at once, a phenomenon known as the “spacing
effect” (Dempster, 1988). Harry Bahrick and Lynda Hall (1991) thus found that adults
retained more of their high school math skills when they had later practiced the math
in college—and when that practice was extended over semesters rather than
condensed into a single year. When you think about it, this spacing effect makes
adaptive sense. Names, faces, and events that recur over long intervals of time
rather than in concentrated brief periods are probably, in real life, more important to
remember (Anderson & Schooler, 1991). Therefore, another technique you can use
to help you study is to revisit the material often. Take note of the items you missed,
and read the material again. Try to figure out why you provided an incorrect answer.
Next, talk to your instructor about why you missed it and ask for help. Then, take the
practice quiz a second time. Repeat the process until it’s time for your exam.
Storage
Whether the encoding process is effortful or automatic, cognitive psychologists
have long been interested in the format, the content, and the neural bases of longterm memory as it is represented in the brain.
Formats of Long-Term Memory
In long-term memory, information is stored in two forms or “codes”: semantic and
visual. Semantic coding is easy to demonstrate. When we process verbal information
—such as a spoken phrase, a speech, a written sentence, or a story—what we store
is the meaning of the information, not specific words. For example, Jacqueline Sachs
(1967) had subjects listen to a voice-recorded passage. She then presented a series
of sentences (e.g., “He sent a letter about it to Galileo, the great Italian scientist”) and
asked if they were the same as or different from those of the original passage.
Subjects correctly rejected sentences that changed the meaning (“Galileo, the great
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Italian scientist, sent him a letter about it”), but they did not reject sentences with the
same meaning that were worded differently (“A letter about it was sent by him to
Galileo, the great Italian scientist”). The reason: They had stored the semantic
content of the passage—not an exact, word-for-word representation. In fact, people
often read “between the lines” and recall hearing not just what was said but what was
implied. For example, subjects who heard that a paratrooper “leaped out the door”
often recalled later that he “jumped out of the plane.” And mock jurors who heard a
witness testify that “I ran up to the alarm” later assumed the witness had said, “I rang
the alarm” (Harris & Monaco, 1978).
Although verbal information is stored in a semantic form, visual inputs and many
long-term memories (including some of our most cherished childhood recollections)
are stored as visual images. In visual coding, a mental picture of an object or a scene
is generated—a process that has implications for how people retrieve the information.
To demonstrate, Stephen Kosslyn (1980) showed subjects drawings like the boat in
Figure 6.11. Later, he asked the subjects to visualize each drawing, to focus on the
right or left side of it, and then, as quickly as possible, to indicate whether a specific
object was present by pressing a YES or NO button that stopped a clock. If the
drawing is stored in a visual manner, reasoned Kosslyn, then it should take longer for
subjects to “scan” their image for an answer when the object is located away from the
subject’s focus of attention. That is exactly what happened. When subjects were
mentally focused on the left rather than the right side of the drawing, for example, it
took them longer to determine that a flag was present on the right side of the boat. In
more recent experiments using PET scans, Kosslyn and others (1999) found that
when subjects shut their eyes and tried to visualize patterns of stripes, parts of the
visual cortex were activated—the same as when they actually viewed the stripes.
Moulton and Kosslyn (2009) argue that mental imagery is a simulation that allows
humans to “generate specific predictions based upon past experience” (p. 1273).
Description
Figure 6.11 Visual Coding
Source: Stephen M. Kosslyn. (2005). Mental images and the Brain,
Cognitive Neuropsychology, 22:3-4, 333-347, DOI:
10.1080/02643290442000130
Mental images play an important role in long-term memory. Popular books on how
to improve your memory advise people to use imagery, and research shows that this
advice is well founded. As an illustration, try to memorize the following list of word
pairs so that the first word triggers your memory of the second: lawyer-chair,
snowflake-mountain, shoes-milk, dog-bicycle, chef-pickle, student-sandwich, boyflag. You might try to master the list by silently repeating the items over and over—
maintenance rehearsal. But now take a different approach: For each item, form an
image in your “mind’s eye” that contains the two words of each pair interacting in
some way. For example, imagine a brown dog chasing a bicycle or a student eating a
foot-long sandwich. This method should improve performance (Bower & Winzenz,
1970; Paivio, 1969). Consistent with the notion that imagery facilitates memory,
concrete words that are easy to visualize (fire, tent, statue, zebra) are recalled more
easily than abstract words that are difficult to represent in a picture (infinite, freedom,
process, future). To remember something, it’s better to encode it in both semantic and
visual forms than in either alone (Paivio, 1986).
LEARNING CHECK
Numbers Game
How good is your memory for numbers? When you check your answers, you may
have a better idea!
(Answers: 1. b; 2. c; 3. a; 4. b.)
Contents of Long-Term Memory
Increasingly it seems that we have more than one type of long-term memory
(Kesner & Rolls, 2015; Rolls, 2000). Following Endel Tulving (1985), researchers now
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commonly distinguish two types, as illustrated in Figure 6.12. One is procedural
memory, a “know how” memory that consists of our stored knowledge of well-learned
habits and skills—such as how to drive, swim, type, ride a bike, and tie shoelaces.
The second type is declarative memory, which consists of both semantic memories
for facts about the world—such as who LeBron James is, what a dollar is worth, what
you need to access the iCloud, and what the word gravity means—and episodic
memories that we have about ourselves—such as who our parents are, where we
went to school, and what our favorite movie is (Tulving, 2002). This distinction is
important, as we’ll see later, because people with amnesia are often unable to recall
declarative memories of facts and events (Kensinger & Giovanello, 2006), yet they
still retain many of the skills they had learned and committed to procedural memory.
procedural memory. Stored long-term knowledge of learned habits and skills.
declarative memory. Stored long-term knowledge of facts about ourselves and
the world.
Figure 6.12 Types of Long-Term Memory
iStock.com/vgajic; iStock.com/Gargolas
With all that’s stored in long-term memory—habits; skills; verbal information; and
knowledge of words, names, dates, faces, pictures, personal experiences, and the
like—it’s amazing that anything can ever be retrieved from this vast warehouse.
Surely our knowledge must be organized in memory, perhaps the way books are filed
in a library. One popular view is that memories are stored in a complex web of
associations, or semantic networks. According to proponents of this view, items in
memory are linked together by semantic relationships, as illustrated in Figure 6.13.
When one item is brought to mind, the pathways leading to meaningfully related
items are primed—thus increasing the likelihood that they too will be retrieved
(Anderson, 1983; Collins & Loftus, 1975; Jones, Willits, & Dennis, 2015).
semantic network. A complex web of semantic associations that link items in
memory such that retrieving one item triggers the retrieval of others as well.
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