Chapter 09.pdf

chapter

Memory

THEME:

Memory is not like a tape

recorder or a video camera:

Memories change as they

are stored and retrieved.

Key Questions

Is there more than one type of memory?

What causes forgetting?

What are the features of each type

of memory?

How accurate are everyday memories?

What happens in the brain when memo-

ries are formed?

Is there more than one type of long-term

memory?

How can memory be improved?

How is memory measured?

What are “photographic” memories?

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Memory

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Preview

“What the Hell’s Going on Here?”

It’s February and Steven is cross-country skiing on the ice

of Lake Michigan. He realizes he is very cold and decides

to turn back. In a few minutes comes a new realization: He

is lost. Wandering on the ice, he grows numb and very,

very tired.

Put yourself in Steven’s shoes, and you will appreciate

the shock of what happened next. Steven clearly recalls

wandering lost and alone on the ice. Immediately after

that, he remembers waking up in a ﬁ eld. But as he looked

around, Steven knew something was wrong. It was a

warm spring day! In his backpack he found running shoes,

swimming goggles, and a pair of glasses—all unfamiliar.

As he looked at his clothing—also unfamiliar—Steven

thought to himself, “What the hell’s going on here?”

Fourteen months had passed since he left to go skiing

(Loftus, 1980). How did he get to the ﬁ eld? Steven couldn’t

say. He had lost over a year of his life to total amnesia.

As Steven’s amnesia vividly shows, life without memory

would be meaningless. Imagine the terror of having all

your memories wiped out. You would have no identity,

no knowledge, and no life history (Behrend, Beike, &

Lampinen, 2004). You wouldn’t recognize friends or

family members. When you looked in a mirror, a stranger

would stare back at you. In a very real sense, we are our

memories.

This chapter discusses memory and forgetting. By

reading it you’ll almost certainly discover ways to improve

your memory.

Stages of Memory—Do You Have a

Mind Like a Steel Trap? Or a Sieve?

Do you remember what you had for breakfast this morning? Or

what happened on September 11, 2001? Of course you do. But

how is it possible for us to so easily travel back in time? Let’s begin

with a look at basic memory systems. An interesting series of

events must occur before we can say, “I remember.”

Many people think of memory as “a dusty storehouse of facts.”

In reality, memory is an active system that receives, stores, orga-

nizes, alters, and recovers information (Lieberman, 2004). In

some ways memory acts like a computer (

Retrieval

Storage

Figure 9.1). Incoming

information is ﬁ rst encoded, or changed into a usable form. This

step is like typing data into a computer. Next, information is

stored, or held in the system. (As we will see in a moment, human

memory can be pictured as three separate storage systems.) Fi-

nally, memories must be retrieved, or taken out of storage, to be

useful. If you’re going to remember all of the 9,856 new terms on

your next psychology exam, you must successfully encode, store,

and retrieve them.

What are the three separate memory systems just mentioned? Psy-

chologists have identiﬁ ed three stages of memory. To be stored for a

long time, information must pass through all three (

●

Encoding

● Figure 9.1 In some ways, a computer acts like a mechanical memory

system. Both systems process information, and both allow encoding, stor-

age, and retrieval of data.

Memory The mental system for receiving, encoding, storing,

organizing, altering, and retrieving information.

Encoding Converting information into a form in which it will

be retained in memory.

Storage Holding information in memory for later use.

Retrieval Recovering information from storage in memory.

Sensory memory The ﬁ rst stage of memory, which holds an

exact record of incoming information for a few seconds or less.

●

Figure 9.2).

Sensory Memory

Let’s say a friend asks you to pick up several things at a market.

How will you remember them? Information ﬁ rst enters sensory

memory, which can hold an exact copy of what you see or hear,

for a few seconds or less. For instance, look at a ﬂ ower and then

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CHAPTER 9

● Figure 9.2 Remembering is thought to involve at

least three steps. Incoming information is ﬁ rst held for a

second or two by sensory memory. Information selected

by attention is then transferred to temporary storage in

short-term memory. If new information is not rapidly

encoded or rehearsed, it is forgotten. If it is transferred

to long-term memory, it becomes relatively permanent,

although retrieving it may be a problem. The preceding

is a useful, but highly simpliﬁ ed, model of memory; it may

not be literally true of what happens in the brain (Eysenck

& Keane, 1995).

Successfully

coded for

storage in LTM

Long-term

memory

Incoming

information

Sensory

memory

Selective

attention

Short-term

memory

Forgotten

close your eyes. An icon (EYE-kon), or ﬂ eeting mental image, of

the ﬂ ower will persist for about one half second. Similarly, when

you hear information, sensory memory stores it as an echo for up

to 2 seconds (Schweickert, 1993). An echo is a brief ﬂ urry of activ-

ity in the auditory system. In general, sensory memory holds in-

formation just long enough to move it to the second memory sys-

tem (Neath, 2002).

something like this happen: Someone leaves a phone number on

your answering machine. You repeat the number to yourself as

you start to dial. Then the doorbell rings and you rush to see who

is there. When you return to the phone, you have completely for-

gotten the number. You listen to the message again and memorize

the number. This time as you begin to dial, someone asks you a

question. You answer, turn to the phone, and ﬁ nd that you have

forgotten the number. Notice again that STM can handle only

small amounts of information. It is very difﬁ cult to do more than

one task at a time in STM (Miyake, 2001).

Short-Term Memory

Not everything we see or hear stays in memory. Imagine that a ra-

dio is playing in the background as your friend reads her shopping

list. Will you remember what the announcer says, too? Probably

not, because selective attention (focusing on a selected portion of

sensory input) controls what information moves on to short-term

memory. Short-term memory (STM) holds small amounts of in-

formation for brief periods. By paying attention to your friend,

you will place her shopping list in short-term memory (while you

ignore the voice on the radio saying, “Buy Burpo Butter”).

How are short-term memories encoded? Short-term memories can

be stored as images. But more often they are stored phonetically

(by sound), especially in recalling words and letters (Neath, 2002).

If you are introduced to Tim at a party and you forget his name,

you are more likely to call him by a name that sounds like Tim

(Jim, Kim, or Slim, for instance), rather than a name that sounds

different, such as Bob or Mike. Your friend with the shopping list

may be lucky if you don’t bring home jam instead of ham and

soap instead of soup!

Short-term memory brieﬂ y stores small amounts of informa-

tion. When you dial a phone number or brieﬂ y remember a shop-

ping list, you are using STM. Notice that information is quickly

“dumped” from STM and forever lost. Short-term memory pre-

vents our minds from storing useless names, dates, telephone

numbers, and other trivia.

As you may have noticed when dialing a telephone, STM is

very sensitive to interruption, or interference. You’ve probably had

Working Memory

Short-term memory is often used for more than just storing infor-

mation. When STM is combined with other mental processes, it

provides an area of working memory where we do much of our

thinking. Working memory acts as a sort of “mental scratchpad.”

It brieﬂ y holds the information we need when we are thinking

and solving problems (Tuholski, Engle, & Baylis, 2001). When-

ever you do mental arithmetic, put together a puzzle, plan a meal,

follow directions, or read a book, you are using working memory

(Baddeley, 2003).

Long-Term Memory

If STM is so limited, how do we remember for longer periods of time?

Information that is important or meaningful is transferred to

long-term memory (LTM), which acts as a lasting storehouse for

knowledge. LTM contains everything you know about the

world—from aardvark to zucchini, math to MTV, facts to fantasy.

Yet there appears to be no danger of running out of room. LTM

can hold nearly limitless amounts of information. In fact, the

more you know, the easier it becomes to add new information to

memory. This is the reverse of what we would expect if LTM could

be “ﬁ lled up” (Eysenck & Keane, 1995). It is also one of many rea-

sons for getting an education.

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HUMAN DIVERSITY

Cows, Memories, and Culture

As noted, we are most likely to remember information that is per-

sonally meaningful. If you were on a farm and saw twenty cows

walk by, do you think you could remember the age, color, sex,

and condition of all of them? Unless you are a dairy farmer, doing

so would be quite a feat of memory. However, for a Maasai person

from East Africa, it would be easy. Livestock are very important in

Maasai culture; wealth among the Maasai is measured by the

number of cattle owned. Thus, the Maasai are prepared to code

and store information about cattle that would be difﬁ cult for many

people in the United States to remember.

Culture affects our memories in other interesting ways. For ex-

ample, American culture emphasizes individuals, whereas Chinese

culture emphasizes membership in groups. In a recent study,

European-American and Chinese adults were asked to recall

twenty memories from any time in their lives. As expected, Amer-

ican memories tended to be self-centered: Most people remem-

bered surprising events and what they did during the events. Chi-

nese adults, in contrast, remembered important social or historical

events and their own interactions with family members, friends,

and others (Wang & Conway, 2004). Thus, in the United States,

personal memories tend to be about “me”; in China they tend to

be about “us.”

Are long-term memories also encoded as sounds? They can be. But

typically, long-term memories are stored on the basis of meaning,

not sound. If you make an error in LTM, it will probably be related

to meaning. For example, if you are trying to recall the word barn

from a memorized list, you are more likely to mistakenly say shed

or farm than yarn or darn. If you can link information in STM to

knowledge already stored in LTM, it gains meaning. This makes it

easier to remember. As an example, try to memorize this story:

(LTM). As information enters the warehouse, it is ﬁ rst placed on

the desk. Because the desk is small, it must be quickly cleared off

to make room for new information. Unimportant items are sim-

ply tossed away. Meaningful or important information is placed

in the ﬁ les (LTM). (See “Cows, Memories, and Culture.”) When

we want to use knowledge from LTM to answer a question, the

information is returned to STM. Or, in our analogy, a folder is

taken out of the ﬁ les (LTM) and moved to the desk (STM), where it

can be used.

Now that you have a general picture of memory it is time to

explore STM and LTM in more detail. But ﬁ rst, here’s a chance to

rehearse what you’ve learned.

With hocked gems ﬁ nancing him, our hero bravely deﬁ ed all scornful

laughter. “Your eyes deceive,” he had said, “An egg, not a table, cor-

rectly typiﬁ es this unexplored planet.” Now three sturdy sisters sought

proof. Forging along, days became weeks as many doubters spread

fearful rumors about the edge. At last from nowhere welcome winged

creatures appeared, signifying momentous success. (Adapted from

Dooling & Lachman, 1971)

Icon A mental image or visual representation.

Echo A brief continuation of sensory activity in the auditory

system after a sound is heard.

Short-term memory (STM) The memory system used to hold

small amounts of information for relatively brief time periods.

Working memory Another name for short-term memory,

especially when it is used for thinking and problem solving.

Long-term memory (LTM) The memory system used for

relatively permanent storage of meaningful information.

This odd story emphasizes the impact that meaning has on

memory. People given the title of the story were able to remember

it far better than those not given a title. See if the title helps you as

much as it did them: “Columbus Discovers America.”

Dual Memory

Most of our daily memory chores are handled by STM and LTM.

To summarize their connection, picture short-term memory as a

small desk at the front of a huge warehouse full of ﬁ ling cabinets

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CHAPTER 9

“bins” into which separate items can be placed. Actually, a few

people can remember up to 9 bits, and for some types of informa-

tion 5 bits is the limit. Thus, an average of 7 information bits can

be held in short-term memory (Neath, 2002).

When all of the “slots” in STM are ﬁ lled, there is no room for

new information. Picture how this works at a party: Let’s say your

hostess begins introducing everyone who is there, “Chun, Dasia,

Marco, Roseanna, Cholik, Shawn, Kyrene . . .” “Stop,” you think to

yourself. But she continues, “Nelia, Jay, Efren, Frank, Marietta,

Jorge, Patty, Amit, Ricky.” The hostess leaves, satisﬁ ed that you

have met everyone. And you spend the evening talking with Chun,

Dasia, and Ricky, the only people whose names you remember!

KNOWLEDGE BUILDER

Memory Systems

REFLECT

Wave a pencil back and forth in front of your eyes while focusing

on something in the distance. The pencil’s image looks transpar-

ent. Why? (Because sensory memory brieﬂ y holds an image of the

pencil. This image persists after the pencil passes by.)

Think of a time today when you used short-term memory (such

as brieﬂ y remembering a phone number, an Internet address, or

someone’s name). How long did you retain the information? How

did you encode it? How much do you remember now?

How is long-term memory helping you read this sentence? If

the words weren’t already stored in LTM, could you read at all?

How else have you used LTM today?

Recoding

Before we continue, test your short-term memory again, this time

on letters. Read the following letters once, then look away and try

to write them in the proper order.

LEARNING CHECK

Match: A. Sensory memory B. STM C. LTM

1. _____ Working memory

2. _____ Holds information for a few seconds or less

T V I B M U S N Y M C A

3. _____ Stores an icon or echo

Notice that there are 12 letters, or “bits” of information. This

should be beyond the 7-item limit of STM. However, because the

letters are in four groups, or chunks of information, many students

are able to memorize them. Information chunks are made up of

bits of information grouped into larger units.

How does chunking help? Chunking recodes (reorganizes) infor-

mation into units that are already in LTM. For example, you may

have noticed that NY is the abbreviation for New York. If so, the

two bits N and Y became one chunk. In an experiment that used

lists like this one, people remembered best when the letters were

read as familiar meaningful chunks: TV, IBM, USN, YMCA (Bower

& Springston, 1970). If you recoded the letters this way, you prob-

ably remembered the entire list.

Chunking suggests that STM holds about 5 to 7 of whatever

units we are using. A single chunk could be made up of numbers,

letters, words, phrases, or familiar sentences (Barsalou, 1992). Pic-

ture STM as a small desk again. Through chunking, we combine

several items into one “stack” of information. This allows us to

place 7 stacks on the desk, where before there was only room for 7

separate items. While you are studying, try to ﬁ nd ways to link 2, 3,

or more separate facts or ideas into larger chunks, and your mem-

ory will improve. Psychologist Nelson Cowan (2001) believes that

STM may actually hold only 4 items, unless some chunking has oc-

curred. The clear message is that creating information chunks is the

key to making good use of your short-term memory.

4. _____ Permanent, unlimited capacity

5. _____ Temporarily holds small amounts of information

6. _____ Selective attention determines its contents

7. STM is improved by interruption, or interference, because at-

tention is more focused at such times. T or F?

CRITICAL THINKING

8. Why is sensory memory important to ﬁ lmmakers?

Short-Term Memory—Do You

Know the Magic Number?

To make good use of your memory, it is valuable to know more

about the characteristics of STM and LTM. It’s time to dig deeper

into the inner workings of our primary memory systems.

How much information can be held in short-term memory? For an

answer, read the following numbers once. Then close the book

and write as many as you can in the correct order.

8 5 1 7 4 9 3

This is called a digit-span test. It is a measure of attention and

short-term memory. If you were able to correctly repeat 7 digits,

you have an average short-term memory. Now try to memorize

the following list, reading it only once.

Rehearsing Information

How long do short-term memories last? They disappear very rapidly.

However, you can prolong a memory by silently repeating it, a

process called maintenance rehearsal. You have probably brieﬂ y

remembered an address or telephone number this way. In a sense,

rehearsing information allows you to “hear” it many times, not

just once (Nairne, 2002). The more times a short-term memory is

rehearsed, the greater its chances of being stored in LTM (Barsa-

lou, 1992).

7 1 8 3 5 4 2 9 1 6 3 4

This series was probably beyond your short-term memory capac-

ity. Psychologist George Miller found that short-term memory is

limited to the “magic number” 7 (plus or minus 2) information

bits (Miller, 1956). A bit is a single meaningful “piece” of informa-

tion, such as a digit. It is as if short-term memory has 7 “slots” or

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