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A neutral stimulus, or N, S, is represented by a white rate. A horizontal arrow
leads to the right to the unconditioned response. The unconditioned response, or U,
C, R, is represented by a smiling baby. A statement reads as follows, When Little
Albert sees a white rat, a neutral stimulus, he is unafraid and curious.
Stage Two is labeled, During Conditioning.
A neutral stimulus, represented by a white rat, and an unconditioned stimulus,
represented by a loud noise result in a crying baby. A statement reads as follows,
Every time Little Albert is shown a white rat, a neutral stimulus, he hears the loud
sound, the unconditioned stimulus, and cries with fear, unconditioned response.
Stage Three is labeled, After Conditioning.
The neutral stimulus has now become a conditioned stimulus. The white rat now
results in a crying baby. A statement reads as follows, After several pairings of rat
and loud sound, there is no loud sound but when Little Albert sees the white rat, the
conditioned stimulus, he cries with fear, the conditioned response.
Back to Figure
A Skinner box is a laboratory apparatus used to study animal behavior, especially
operant conditioning and classical conditioning. A Skinner box allows experimenters
to study behavior conditioning by teaching a subject animal to perform certain
actions, such as pressing a lever, in response to specific stimuli, such as a light or
sound signal. When the subject correctly performs the behavior, the chamber
mechanism delivers food or other reward.
A photograph of the Skinner box is shown on the left. A white rat is visible within
the box. On the right-hand side of the diagram is an illustration of the output method
for the Skinner box. A cylindrical drum contains a roll of paper. The paper is drawn
from the drum and a pen is positioned on an arm and records changes in behavior
over time. The sample in the illustration shows that at first the animal was not
responding. Then one response occurred. Then a series of rapid responses, which
appear like a flight of steps on the read-out. A Reinforcement Blip then occurs before
the response rate rises again.
Back to Figure
An author introduction reads as follows. These curves show the response patterns
typically produced by different schedules of reinforcement. The steeper the curve, the
higher the response rate, the slash marks on each curve indicate the delivery of a
reinforcement. As illustrated, the rate of responding is higher under ratio than interval
schedules.
The time in minutes is plotted on the X-drive, with a range from zero to 80, at
intervals of 10. The number of responses is plotted on the Y-drive, with a range from
zero to 1000, at intervals of 250.
The trends for each of the response patterns are as follows.
1. Fixed Ratio. A steep curve is formed from 100 respondents at 5 minutes up to
900 respondents at 22 minutes. There are 6 slash marks representing a
reinforcement delivery.
2. Variable Ratio. A steep curve is formed from 100 respondents at 15 minutes
up to 900 respondents at 25 minutes. There are 4 slash marks representing a
reinforcement delivery.
3. Fixed Interval. A shallow curve is formed from 100 respondents at 17 minutes
up to 750 respondents after 80 minutes. There are 6 slash marks representing a
reinforcement delivery.
4. Variable Interval. A shallow curve is formed from 100 respondents at 22
minutes up to 450 respondents at 80 minutes. There are 8 slash marks
representing a reinforcement delivery.
Back to Figure
An author introduction reads as follows. Tolman trained rats to run a maze like the
one shown here. But after their training, he blocked the most direct routes to the goal
box, Block A and Block B. Operating as if they had a cognitive map, the animals
rerouted themselves around the blocked routes and took the best available detours.
The maze is formed from a small start box and a large box containing a food box
in the southeast corner. There are 3 routes from the start box to the box containing
the food box, as follows.
1. Route 1. An orange arrow represents Route 1 and is a direct route along the
central path between the start box and the food box.
2. Route 2. A green arrow represents Route 2. The route diverts onto a pathway
to the left before rejoining the central pathway. Route 2 is a middle route in terms
of distance.
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3. Route 3. A blue arrow represents Route 3. The route diverts onto a long
pathway to the right before rejoining the central pathway. Route 3 is the longest
route.
Back to Figure
An author introduction reads as follows. In 1930, Tolman and Honzik put rats into
a maze and measured how quickly they reached the goal box. Those rewarded with
food improved; those without reward did not. A third group received no food until the
11th day. As the rats in this third group explored the maze, they developed a cognitive
map or mental picture of the layout of the maze. In this way, as soon as the rats in
this last group became aware of the food, they used this cognitive map to run their
way through the maze just as quickly as the group of rats that had been rewarded
with food all along. These animals had exhibited latent learning, learning that is not
observable until there is a reason to demonstrate it, for instance, food was placed in
the maze.
The days are plotted on the X-axis of the graph, with a range from 1 to 17, at
intervals of 2 days. The average errors in the maze are plotted on the Y-axis, with a
range from zero to 10, at intervals of 2. There are 3 data lines as follows.
No reward. The number of errors stays stable.
Regularly rewarded. Gradual improvement over time.
No reward until day 11. Gradual improvement in number of errors until
marked improvement at day 11.
The full estimated data points are presented in the following table. The numbers
represent the numbers of errors.
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6 MEMORY
Reeldeal Images / Alamy Stock Photo
Learning Objectives
Relate your own memory successes and failures to the successes and
failures of your favorite technology; in what ways can you blame the
technology, and in what ways can you blame the user for failures?
Connect sensation to memory; determine the importance of iconic and
echoic memory.
Examine scientifically supported methods to enlarge the capacity of
short-term memory.
Juxtapose the belief that memories are forever with the belief that
memories eventually become extinct.
Consider the research on autobiographical memory and apply it to
your own life.
WHAT’S YOUR PREDICTION: CAN A FALSE
MEMORY BE CREATED?
The Situation
You sign up for a study of memory, and when you appear for the session, the
experimenter says that you’ll hear several lists of words via an audio recording. Listen
carefully. After each list, you will hear either a tone or a knocking sound to signal
whether you should spend the next 2 minutes writing down the words in that list or
working on some arithmetic problems. After the first list, you’ll hear a second list, a
third list, and so on, until you’re finished. You have no questions, so the session
begins.
The experimenter turns on the recording and you hear a male voice reciting a
word every 1.5 seconds. Try it: bed, rest, awake, tired, dream, wake, night, blanket,
doze, slumber, snore, pillow, peace, yawn, drowsy. Got it? Now look away, take out a
sheet of paper, and take 2 minutes to write down as many of these words as you can.
Okay, time’s up. Here’s the next list: note, sound, piano, sing, radio, band, melody,
horn, concert, instrument, jazz, symphony, orchestra, art, rhythm. Again, try to recall
as many words as you can.
After completing all the lists, you are told that your ability to recognize the original
words will now be tested. You’ll receive a set of 96 words, some of which appeared
earlier. For each word, you should indicate whether it is new (never presented before)
or old (presented earlier). Next, for each word you recognize as old, you’re asked:
Are you sure you vividly recall hearing the speaker say that word on the recording?
Try it. Cover the preceding paragraph and circle each of the following words that you
recognize from before: tooth, beach, sleep, art, traffic, pillow, kitten, music.
As a participant in this experiment, you know that some of the test items are new,
others old. What you don’t know is that some of the new items were meaningfully
related to words that did appear in the original lists. The experimenters referred to
these as “lures.” The question is, how easy was it to tell the difference?
Make a Prediction
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Think about the recognition test. Participants were reshown some of the same
words they had been presented with just minutes earlier. So how well could they
recognize these items? And will they ever “remember” hearing the lure words not on
the list? To get you started, the percentage of old items correctly identified as old is
presented below. As you can see, participants recognized 79 percent of these words
—57 percent of which they were absolutely sure about. Using these numbers as a
guideline and the table below, predict how often (0–100 percent) the participants
falsely recognized and were sure about the lures that were never actually presented.
The Results
In this study, Henry Roediger and Kathleen McDermott (1995) were curious to
determine whether they could get people to create “false memories” of words not
previously heard. So, what did you predict? How often did participants “recognize”
lure words compared to the percentage of old items correctly and confidently
recognized? The results were striking. As shown below, participants could not tell the
difference between words that were on the list and those that were not.
What Does It All Mean?
To appreciate what happened in this experiment, take another look at the test
materials and your own responses. After hearing (or reading) sleep-related words
such as bed and yawn and music-related words such as jazz and instrument, didn’t
you think that you had also heard (read) sleep and music—words that fit but were not
actually on the list? Most people do. During a talk that Henry Roediger gave a few
years after the study, titled “Creating False Memories in the Classroom,” he
reproduced this result with an audience of psychology professors. Many other
researchers have obtained this same result, with some investigating the role that
even culture can play in constructing false memories (Wang et al., 2021).
Psychologists liken human memory to a computer that faithfully records
information for later use. This study reveals, however, that there is much more to the
story. As we’ll see in this chapter, remembering is an active process, and we
sometimes construct memories in light of our own beliefs, wishes, needs, contextual
factors, and information received from outside sources.
“Indelible in the hippocampus is the laughter.” Christine Blasey Ford said this
during her Senate Judiciary Committee testimony about her remembered
experiences with Supreme Court nominee Judge Brett Kavanaugh when they were
high school students in suburban Maryland. Blasey Ford remembered many details of
an attempted sexual assault by Kavanaugh. Kavanaugh remembered nothing of the
sort. To corroborate his account, Kavanaugh produced a detailed calendar of his daily
activities from the presumed year in question—1982. Blasey Ford had no calendar,
just the lasting traumatic memory of that night, albeit she could not remember the
exact date the incident happened, how she got to the house party where the alleged
sexual assault occurred, or how she got home. Their testimonies reflected
divisiveness not only between the two accounts, but also between political parties,
opinions about binge drinking, and current thinking about how memories are (and are
not) formed during trauma and why victims don’t immediately report their assaults
and accused assailants to police. Blasey Ford supporters tweeted #IBelieveChristine.
Kavanaugh supporters wrote letters emphatically praising his character and
respectful treatment of women.
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Christine Blasey Ford is sworn in prior to giving testimony before the U.S. Senate
Judiciary Committee on Capitol Hill, September 27, 2018, in Washington, D.C. Blasey
Ford, a professor at Palo Alto University and a research psychologist at the Stanford
University School of Medicine, had accused Supreme Court nominee Brett
Kavanaugh of sexually assaulting her during a party in 1982, when they were high
school students.
Pool / Pool/Getty Images News/Getty Images
The American people will never know what happened between Blasey Ford and
Kavanaugh, but their testimony raised some important questions. One question was,
why do some people believe Blasey Ford yet others believe Kavanaugh? Research
on registered psychologists demonstrates that these differences in trusting the
accuser can be influenced by the psychologist’s sex and traumatic history (Page &
Morrison, 2018). Even among 292 mental health professionals, “female psychologists
believed disclosures regardless of their personal trauma history, while male
psychologists with a personal history of trauma believed disclosures significantly
more than male psychologists without personal trauma history” (p. 1). Furthermore,
women and persons with higher “rape empathy” and lower “rape myth acceptance”
have more belief in accusers than men and persons with lower rape empathy and
higher rape myth acceptance (Nason et al., 2018).
A second question was, is it possible that both people are telling their truth? The
short answer is yes. Human memory is often the subject of controversy. Sometimes
we seem able to recall a face, a voice, the contents of a lecture, a foreign language, a
news event, a first date, graduation, or the death of a loved one with precision and
certainty. Yet, at other times, memory is limited, flawed, and biased—as when we
forget an address we just looked up, the items on the grocery list we left at home,
coursework from last semester, or the name of someone we met recently. We could
swear we remember an important event like it was yesterday, and recall that event,
but unbeknownst to us, our recollection of the event’s details is imprecise and
sometimes fabricated. How are experiences stored in the brain and then later
retrieved? What causes us to preserve some events but not others? How accurate
are our recollections of the past? To answer these questions, cognitive psychologists
study memory, the process by which information is retained for later use (Baddeley,
1999; Schacter, 2001).
memory. The process by which information is retained for later use.
AN INFORMATION-PROCESSING MODEL
LEARNING OBJECTIVES
Relate your own memory successes and failures to the successes and failures of
your favorite technology; in what ways can you blame the technology, and in what
ways can you blame the user for failures?
Compare human memory to the workings of a computer.
Determine the differences among sensory, short-term, and long-term
memory.
Aristotle and Plato likened memory to the stamping of an impression into a block
of wax. Others, more recently, have compared memory to a switchboard, storage
box, workbench, library, layered stack, and videorecorder. Today, cognitive
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psychologists like to compare the human mind to a computer and memory to an
information-processing system. Your computer receives input from a keyboard,
touchscreen, or mouse; it converts the symbols and clicks into a special numeric
code; it saves the information on a hard drive or in the cloud; it then retrieves the data
to be displayed on a screen. If the computer crashes, if there’s not enough storage
space on the hard drive or in the cloud, if the file was deleted, or if you enter the
wrong retrieval command, the information becomes inaccessible, or “forgotten.”
Using the computer as a model, memory researchers seek to trace the flow of
information as it is mentally processed. In this information-processing model, a
stimulus that registers on our senses can be remembered only if it (a) draws
attention, which brings it into consciousness; (b) is encoded, or transferred to storage
sites in the brain; and (c) is retrieved for use at a later time (Atkinson & Shiffrin,
1968). How might this model relate to your favorite photo app? First, you direct your
camera to the stimulus of interest, say a group of you and your friends at a concert.
This is the draws attention phase. You take six different pictures, because the first
five weren’t very good. Second, you save the sixth photo. This is the
encoding/storage phase. Third, you pull up the photo up a few hours later to post it on
social media—retrieval.
information-processing model. A model of memory in which information must
pass through discrete stages via the processes of attention, encoding, storage, and
retrieval.
Within this information-processing approach, three types of memory have been
distinguished: sensory, short term, and long term. Sensory memory stores all stimuli
that register on the senses, holding literal copies for a brief moment ranging from a
fraction of a second to 3 seconds. Sensations that do not draw attention tend to
vanish. Those things we “pay attention to” are transferred to short-term memory
(STM), another temporary storage system that can hold seven—plus or minus two—
items of information for about 20 seconds. Although STM fades quickly, information
can be held for a longer period of time through repetition and rehearsal. When people
talk about attention span, they are referring to short-term memory. Finally, long-term
memory (LTM) is a somewhat permanent storage system that can hold vast
quantities of information for many years. Science writer Isaac Asimov once estimated
that LTM takes in a quadrillion separate bits of information in the course of a lifetime.
When people talk about memory, long-term memory is typically what they have in
mind.
sensory memory. A memory storage system that records information from the
senses for up to three seconds.
short-term memory (STM). A memory storage system that holds about seven
items for up to 20 seconds before the material is transferred to long-term memory or
is forgotten.
long-term memory (LTM). A relatively permanent memory storage system that
can hold vast amounts of information for many years.
As you read this chapter, you’ll see that memory researchers ask two types of
questions. First, how are memories stored? Is there a single unitary system, as some
believe, or are there multiple memory systems, each uniquely dedicated to storing
certain types of information? Second, to what extent are our memories of the past
faithful to reality? We will see that researchers have exposed some serious flaws and
biases in human memory—what Daniel Schacter (2001) has called the “sins” of
memory. Thus, you’ll notice this recurring theme: Human beings are both competent
and incompetent, and both objective and subjective, in their processing of
information.
THE SENSORY REGISTER
LEARNING OBJECTIVES
Connect sensation to memory; determine the importance of iconic and echoic
memory.
Create an argument for whether or not fleeting traces of sensation linger in
the mind even after the removal of a stimulus.
Compare and contrast iconic and echoic memory.
Take a flashlight into a dark room, turn it on, shine it on a wall, and wave it quickly
in a circular motion. What do you see? If you twirl it fast enough, the light will appear
to leave a glowing trail, and you’ll see a continuous circle. The reason: Even though
the light illuminates only one point in the circle at a time, your visual system stores a
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“snapshot” of each point as you watch the next point. The visual image is called an
icon, and the snapshot it stores is called iconic memory (Neisser, 1967).
iconic memory. A fleeting sensory memory for visual images that lasts only a
fraction of a second.
Iconic Memory
People typically don’t realize that a fleeting mental trace lingers after a stimulus is
removed from view. Nor did cognitive psychologists realize it until George Sperling’s
(1960) ingenious series of experiments. Sperling instructed subjects to stare at the
center of a blank screen. Then he flashed an array of letters for one-twentieth of a
second and asked subjects to name as many of the letters as possible. Take a quick
glance at Figure 6.1, and try it for yourself. You’ll probably recall about a handful of
letters. In fact, Sperling found that no matter how large the array was, subjects could
name only four or five items. Why? One possibility is that people can register just so
much visual input in a single glance—that 12 letters is too much to see in so little
time. A second possibility is that all letters registered, but the image faded before
subjects could report them all. Indeed, many subjects insisted they were able to “see”
the whole array but then forgot some of the letters before they could name them.
Description
Figure 6.1 Testing for Iconic Memory
Source: Adapted from Sperling, G. (1960). The information available in
brief visual presentations. Psychological Monographs: General and
Applied, 74(11), 1–29. https://doi.org/10.1037/h0093759
Did the information that was lost leave a momentary trace, as subjects had
claimed, or did it never register in the first place? To test these alternative
hypotheses, Sperling devised the “partial-report technique.” Instead of asking
subjects to list all the letters, he asked them to name only one row in each array—a
row that was not determined until after the array was shown. In this procedure, each
presentation was immediately followed by a tone signaling which letters to name: A
high-pitched tone indicated the top line; a medium pitch, the middle line; a low pitch,
the bottom line. If they saw the entire array, subjects should have been able to report
all the letters in a prompted row correctly—regardless of which row was prompted.
Sperling was right: Subjects correctly recalled 3.3 letters per row. In other words, 10
letters (9.9), not 4 or 5, were instantly registered in consciousness before fading, held
briefly in iconic memory. To determine how long this type of memory lasts, Sperling
next varied the time between the letters and the tone that signaled the row to be
recalled. As depicted in Figure 6.2, the visual image started to fade as the interval
was increased to one-third of a second and had vanished almost completely twothirds of a second later. Since this study, researchers have found that, when it comes
to pictures of objects or scenes, words, sentences, and other visual stimuli presented
briefly, people form “fleeting memories” that last for just a fraction of a second
(Coltheart, 1999).
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Description
Figure 6.2 Duration of Iconic Memory
Source: Adapted from Sperling, G. (1960). The information available in
brief visual presentations. Psychological Monographs: General and
Applied, 74(11), 1–29. https://doi.org/10.1037/h0093759
Echoic Memory
A similar phenomenon exists for auditory stimuli. The next time you listen to
music, notice after you turn it off how an “echo” of the sound seems to reverberate
inside your head. This auditory sensory register is called echoic memory. Just how
much auditory input is stored in echoic memory, and for how long? In a study
modeled after Sperling’s, Christopher Darwin and colleagues (1972) put headphones
on subjects and all at once played three sets of spoken letters—in the right ear, in the
left ear, and in both ears at once. Subjects then received a visual signal indicating
which set to report. Using this study and others, researchers have found that echoic
memory holds only a few items but lasts for 2 or 3 seconds, and perhaps even longer,
before activation in the auditory cortex fades (Cowan, 1988; Lu, Williamson, &
Kaufman, 1992; Sams, Hari, Rif, & Knuutila, 1993).
echoic memory. A brief sensory memory for auditory input that lasts only 2 or 3
seconds.
Whether a sensory memory system stores information for one-third of a second or
for 3 seconds, you might wonder: What’s the point of having a “memory” that is so
quick to decay? To answer this question, try to imagine what your perceptions of the
world would be like without sensory memories. Without the visual icon, for instance,
you would lose track of what you see with every blink of the eye—as if you were
viewing the world through a series of snapshots rather than on a continuous film.
Similarly, it would be hard to understand spoken language without the persistent
traces of echoic memory. Speech would be heard as a series of staccato sounds
rather than as connected words and phrases. One case study that features a person
with stroke demonstrates the importance of echoic memory. Without his echoic
memory intact, the person could not “recall a single syllable he had heard one second
before” (Kojima, Karino, Yumoto, & Funayama, 2012, p. 133).
SHORT-TERM MEMORY
LEARNING OBJECTIVES
Examine scientifically supported methods to enlarge the capacity of short-term
memory.
Identify the limits of our short-term memory.
List the functions that are served by short-term memory.
Explain the serial-position curve and why it occurs.
Try to imagine yourself behind the steering wheel of a car. As you drive, with the
window down, your body is bombarded by sensations: the vibration under your feet
from the terrain beneath the tires; the sound of your music overshadowed by horns
honking; a siren blaring, and vehicles screeching to a stop; a faint aroma of freshly
brewed coffee being overwhelmed by the smell of exhaust fumes; and the sight of
skyscrapers, traffic lights, street vendors, delivery trucks bouncing over bumps in the
road, while pedestrians scramble to reach the other side.
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Those are just the sensations you register all while keeping track of speed,
balance, turn signals, and safety. Most stimuli surrounding your journey will never
reach consciousness and, instead, will be “forgotten” immediately. You might even
wonder if you stopped at the stop sign a few streets back. The key is attention. As
noted earlier, sensations that do not capture our attention tend to evaporate quickly,
whereas those we notice are transferred to short-term memory—a somewhat more
lasting but limited storage facility. People are selective in their perceptions and can
instantly direct their attention to stimuli that are interesting, adaptive, or important.
While driving the car, you are so busy avoiding pedestrians and other vehicles that
you focus on those objects to the exclusion of everything else.
From the sensory register, the brain encodes information—that is, it converts the
information into a form that can be stored in short-term memory. A stimulus may be
encoded in different ways. After you read this sentence, for example, you might recall
a picture of the letters and their placement on the page (visual encoding), the sounds
of the words themselves (acoustic encoding), or the meaning of the sentence as a
whole (semantic encoding). Research shows that people typically encode this type of
information in acoustic terms. Thus, when subjects are presented with a string of
letters and immediately asked to recall them, they make more “sound-alike” errors
than “look-alike” errors. For example, subjects mis-recall an F as an S or X, but not
as an E or B (Conrad, 1964). Subjects are also more likely to confuse words that
sound alike (man, can) than words that are similar in meaning (big, huge)—further
indicating that we tend to encode verbal information in acoustic terms rather than in
semantic terms (Baddeley, 1966).
The information-processing model of memory regards attention as a necessary
first step. In tennis and other tasks, people selectively tune in to stimuli that are
adaptive, interesting, and important. Here, Naomi Osaka of Japan plays a shot during
practice.
Scott Barbour / Stringer/Getty Images Sport/Getty Images
Capacity
Attention limits what information comes under the spotlight of short-term memory
at any given time. To the extent that one stimulus captures our attention, others may
be ignored— sometimes with startling effects on memory. For example, research on
eyewitness testimony shows that when a criminal displays a weapon, witnesses are
less able to identify the culprit than if no weapon is present (Hope & Wright, 2007;
Kocab & Sporer, 2016; Steblay, 1992). Why? One reason is that the witness’s eyes
fixate on the weapon, particularly when it comes as a surprise, thereby drawing
attention away from the face (Pickel, 1999, 2009). To demonstrate, Elizabeth Loftus
and colleagues (1987) showed subjects slides of a customer who walked up to a
bank teller and pulled out either a gun or a checkbook. By recording eye movements,
these researchers found that subjects spent more time looking at the gun than at the
checkbook. The result: impairment in their ability to identify the criminal in a lineup.
Limited by attentional resources, short-term memory can hold only a small
number of items. How small a number? The accompanying “Try This!” activity
illustrates the limited capacity of short-term memory. By presenting increasingly long
lists of items, researchers seek to identify the point at which subjects can no longer
recall without error. In tasks like this one, the average person can store seven or so
list items (usually between five and nine)—regardless of whether the items are
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numbers, letters, words, or names. This limit seemed so consistent that George Miller
(1956) described the human STM capacity by the phrase “the magical number seven,
plus or minus two.” Over the years, other studies have shown that our short-term
storage capacity is more limited than Miller had suggested—and that the magical
number is more like four plus or minus two (Cowan, 2000, 2010).
TRY THIS!
Memory-Span Task
To appreciate the limited capacity of short-term memory, TRY THIS: Read the top
row of digits in Figure 6.3, one per second, then look away and repeat them back in
order. Next, try the second row, the third row, and so on, until you make a mistake.
The average person’s memory span can hold seven items of information.
Description
Figure 6.3 Memory Span Test
Once short-term memory is filled to capacity, whatever that number may be, the
storage of new information requires that existing contents be discarded or
“displaced.” Thus, if you’re trying to memorize historical dates, chemical elements, or
a list of vocabulary words, you may find that the fifth or sixth item pushes out those
earlier on the list. It’s like the view you get on a computer screen. As you fill the
screen with more and more new information, old material scrolls out of view. This
limited capacity seems awfully disabling. But is it absolutely fixed, or can we
overcome it?
According to Miller, short-term memory can accommodate only seven items, and
that number may be smaller, but there’s a hitch: Although an item may consist of one
letter or digit, these items can be grouped into chunks of words, sentences, and large
numbers—thus enabling us to use our storage capacity more efficiently. To see the
effects of chunking on short-term memory, read the following letters, pausing at each
space; then look up and name as many of the letters as you can in correct order: CN
NIB MMT VU SA. Since this list contains 12 discrete letters, you probably found the
task quite frustrating. Now try this next list, again pausing between spaces: CNN IBM
MTV USA. Better, right? This list contains the same 12 letters. But because the
letters are “repackaged” into familiar groups, you had to store only 4 chunks, not 12—
well within our “magical” capacity (Bower, 1970).
Chunking enables us to improve our STM span by using our capacity more
efficiently. We may be limited to seven or so chunks, but we can learn to increase the
size of those chunks. To demonstrate, a group of researchers trained two male
university students, both long-distance runners and of average intelligence, for
several months. For an hour a day, three or four days a week, these students were
asked to recall random strings of numbers. If they recalled a sequence correctly,
another digit was added to the next sequence and the task was repeated. If they
made a mistake, the number of digits in the next sequence was reduced by one.
Their improvement was astonishing. Before practicing, their memory span was four to
seven digits. After six months, they were up to 80 items (Ericsson & Chase, 1982;
Ericsson, Chase, & Faloon, 1980). In one session, for example, the experimenter
read the following numbers in order:
chunking. The process of grouping distinct bits of information into larger wholes,
or chunks, to increase short-term-memory capacity.
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After 2 minutes of concentration, the subject repeated all 73 digits, in groups of
three and four. How did he do it? Given no special instruction, the subject developed
his own elaborate strategy: He converted the random numbers into ages (“89.3
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