Models of Memory

211
The Nature of Memory
try to do so, implicit memory has been said to involve “retention without remembering” (Roediger, Guynn, & Jones, 1995).
Models of Memory
We remember some information far better than other information. Suppose your
friends throw a surprise party for you. When you enter the room, you might barely
notice the flash of a camera. Later, you cannot recall it at all. And you might forget in
a few seconds the name of a person you met at the party. But if you live to be a hundred, you will never forget where the party took place or how surprised and pleased
you were. Why do some things stay in memory forever, whereas others barely make an
impression? Each of four ways of thinking about memory, called models of memory,
provides a somewhat different explanation. Let’s see what the levels-of-processing,
transfer-appropriate processing, parallel distributed processing, and informationprocessing models have to say about memory.
The levels-of-processing model suggests that memory
depends on the extent to which you encode and process information when you first
encounter it. Consider, for example, the task of remembering a phone number you
just heard on the radio. If you were unable to write it down, you would probably
repeat the number over and over to yourself until you could get to a phone. This
repetition process is called maintenance rehearsal. It can be an effective method
for encoding information temporarily, but what if you need to remember something
for hours, months, or years? In that case, you would be better off using elaborative
rehearsal, a process in which you relate new material to information you already
have stored in memory. For example, instead of trying to remember a new person’s
name by simply repeating it to yourself, you could try thinking about how the name
is related to something you know well. So if you are introduced to a man named
Jim Crews, you might think, “He is as tall as my Uncle Jim, who always wears a crew
cut.”
Study after study has shown that memory is improved when people use elaborative
rehearsal rather than maintenance rehearsal (Jahnke & Nowaczyk, 1998). According to
the levels-of-processing model, the reason is that material is processed more “deeply”
when elaborative rehearsal is used (Lockhart & Craik, 1990; Roediger & Gallo, 2001).
The more you think about new information, organize it, and relate it to something you
already know, the “deeper” the processing, and the better your memory of the information becomes. Teachers use this idea when they ask students not only to define a
new word but also to use it in a sentence. Figuring out how to use the new word takes
deeper processing than does merely defining it. (The next time you come across an
unfamiliar word in this book, don’t just read its definition. Try to use the word in a
sentence by coming up with an example of the concept that is related to your knowledge and experience.)
Levels of Processing
levels-of-processing model A model
of memory suggesting that differences
in how well something is remembered
reflect the degree or depth of mental
processing.
maintenance rehearsal A memorization method that involves repeating information over and over to keep it in
memory.
elaborative rehearsal A memorization
method that relates new information to
information already stored in memory.
transfer-appropriate processing model
A model suggesting that memory depends on how the encoding process
matches up with what is later retrieved.
Transfer-Appropriate Processing Level of processing is not the only factor that
affects memory. Another critical factor, suggested by the transfer-appropriate processing model of memory, is how the encoding process matches up with what is
later retrieved. In one study, for example, half the students in a class were told that
their next exam would contain multiple-choice questions. The rest of the students
were told to expect essay questions. Only half the students actually got the type of
exam they expected, however. These students did much better on the exam than those
who took an unexpected type of exam. Apparently, in studying for the exam, the two
groups used encoding strategies that were most appropriate to the type of exam they
expected. Those who tried to retrieve the information in a way that did not match
their encoding method had a harder time (d’Ydewalle & Rosselle, 1978). Results such
as these indicate that how well the encoding method transfers to the retrieval task is
just as important as the depth of processing.
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Chapter 6
Sensory memory
Briefly retains the
information picked up
by the sensory organs
(information lost after
about one second)
EXTERNAL
STIMULI
FIGURE
Short-term memory
Temporarily holds
information in
consciousness
(information stored for
about 18 seconds)
This traditional information-processing
model describes three stages in the
memory system.
Parallel Distributed Processing A third way of thinking about memory is based
on parallel distributed processing (PDP) models (Rumelhart & McClelland,
1986). These models of memory suggest that new experiences do more than provide
specific facts that are stored and later retrieved one at a time. Those facts are also combined with what you already know, so that each new experience changes your overall
understanding of the world and how it operates. For example, when you first arrived
at college, you learned lots of specific facts, such as where classes are held, what time
the library closes, and where to get the best pizza. Over time, these and many other
facts about college life form a network of information that creates a more general
understanding of how the whole college system works. The development of this
network makes experienced students not only more knowledgeable than new students,
but also more sophisticated. It allows them to, say, allocate their study time in order to
do well in their most important courses and to plan a schedule that doesn’t conflict
with work commitments and maybe even avoids early morning classes—and certain
professors.
Using this network concept, PDP models of memory see each unit of knowledge as
connected with every other unit. The connections between units become stronger as
they are experienced together more frequently. In other words, your knowledge about
the world is distributed across a network of associations that all operate at the same
time, in parallel. This network allows you to quickly and efficiently draw inferences and
generalizations about the world. For example, because of your network of associations,
just seeing the word chair allows you to know immediately what a chair looks like, what
it is used for, where it tends to be located, who might buy one, and the like. PDP models of memory explain this process very effectively.
The information-processing model is probably the
most influential and comprehensive model of memory. It suggests that for information
to be firmly implanted in memory, it must pass through three stages of mental processing: sensory memory, short-term memory, and long-term memory (see Figure 6.2).
In sensory memory, information from the senses—sights or sounds, for example—is
held very briefly before being lost. But if information in sensory memory is attended
to, analyzed, and encoded as a meaningful pattern, we say that it has been perceived
(see the chapter on sensation and perception). Information in sensory memory that
has been perceived can now enter short-term memory. If nothing further is done with
it, that information will disappear in less than twenty seconds. However, if the information in short-term memory is further processed, it may be encoded into long-term
memory, where it may remain indefinitely.
The act of reading illustrates all three stages of memory processing. As you read any
sentence in this book, light energy reflected from the page reaches your eyes, where it
is converted to neural activity and registered in your sensory memory. If you pay attention to these visual stimuli, your perception of the patterns of light can be held in shortterm memory. This stage of memory holds the early parts of the sentence so that they
can be integrated and understood as you read the rest of the sentence. As you read, you
are constantly recognizing words by matching your perceptions of them with the patterns and meanings you have stored in long-term memory. In other words, all three
stages of memory are necessary for you to understand a sentence.
“In Review: Models of Memory” summarizes the four memory models we have discussed. Each of these models provides an explanation of why we remember some things
Information Processing
doing
2
learn
Long-term memory
Can retain information
for long periods of time,
often for life
6.2
Three Stages of Memory
by
Memory
SENSORY MEMORY AT
WORK In a darkened room,
ask a friend to hold a small
flashlight and move it very slowly in a
circle. You will see a moving point of
light. If it appears to have a “tail,” like a
comet, that is your sensory memory of
the light before it fades. Now ask your
friend to move the light faster. You
should now see a complete circle of light,
because as the light moves, its impression
on your sensory memory does not have
time to fade before the circle is completed. A similar process allows us to see
“sparkler circles.”