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Chapter 5
Short-Term and Working Memory
What Is Memory?
• Memory: processes involved in retaining,
retrieving, and using information about
stimuli, images, events, ideas, and skills after
the original information is no longer present
Attention
Recall
•Atkinson and Shiffrin’s (1968) model.
It’s the modal model because almost all
subsequent models are modifications of it.
Control processes allow you to “steer” memory.
Modal Model of Memory
• Control processes: active processes that can
be controlled by the person
– Rehearsal
– Strategies used to make a stimulus more
memorable
– Strategies of attention
Caption: What happens in different
parts of Rachel’s memory as she is
(a and b) looking up the phone
number, (c) calling the pizza shop,
and (d) memorizing the number. A
few days later, (e) she retrieves the
number from long-term memory to
order pizza again. Darkened parts
of the modal model indicate which
processes are activated for each
action that Rachel takes.
Modal Model of Memory: Sensory Memory
• Short-lived sensory memory registers all or
most information that hits our visual receptors
– Information decays very quickly
• Persistence of vision: retention of the
perception of light
– Sparkler’s trail of light
– Frames in film
Modal Model of Memory: Sensory Memory
• Measuring the capacity and duration of
sensory memory (Sperling, 1960)
– Array of letters flashed quickly on a screen
– Participants asked to report as many as
possible
Sperling’s Partial
Report (1960)
Full Report Method:
Suggested that the visual
icon (iconic memory)
contains 30-40% of the
original image.
Partial report indicated
that the visual icon
contains 82% of the
original image
Modal Model of Memory: Sensory Memory
• Whole report: participants asked to report as
many as could be seen
– Average of 4.5 out of 12 letters (37.5%)
• Partial report: participants heard tone that told
them which row of letters to report
– Average of 3.3 out of 4 letters (82.5%)
– Participants could report any of the rows
Caption: Results of Sperling’s (1960) partial report experiments. The
decrease in performance is due to the rapid decay of iconic
memory (sensory memory in the modal model).
Modal Model of Memory: Short-Term Memory
• Stores small amounts of information for a
brief duration
• Includes both new information received from
the sensory stores and information recalled
from long-term memory
Modal Model of Memory: Short-Term Memory
• Short-term memory, when rehearsal is
prevented, is about 15-20 seconds
Serial-position curve (Murdoch, 1962).
- Specific changes can affect one without the
other.
Modal Model of Memory: Short-Term Memory
• Proactive interference (PI): occurs when
information learned previously interferes with
learning new information
Coding methods
- All forms of memory utilize all three coding
strategies
Caption: Results of Peterson and Peterson’s (1959) duration of STM
experiment. (a) The result originally presented by Peterson and Peterson,
showing a large drop in memory for letters with a delay of 18 seconds
between presentation and test. These data are based on the average
performance over many trials. (b) Analysis of Peterson and Peterson’s
results by Keppel and Underwood, showing little decrease in performance
if only the first trial is included.
Modal Model of Memory: Short-Term Memory
•
Capacity of short-term memory
– Digit span: how many digits a person can
remember
•
• Typical result: 5-8 items
• But what is an item?
Chunking: small units can be combined into larger
meaningful units
– Chunk is a collection of elements strongly
associated with one another but weakly
associated with elements in other chunks
Modal Model of Memory: Short-Term Memory
• Ericcson et al. (1989)
– Trained a college student with average
memory ability to use chunking
• S.F. had an initial digit span of 7
– After 230 one-hour training sessions, S.F.
could remember up to 79 digits
• Chunking them into meaningful units
Modal Model of Memory: Short-Term Memory
• Chase and Simon (1973)
– Memory for chess pieces on a board
– Chess masters and beginners
– Pieces positioned for a real chess game or
randomly positioned
Modal Model of Memory: Short-Term Memory
• How is information coded in STM?
– Coding: the way information is represented
– Physiological: how stimulus is represented
by the firing of neurons
– Mental: how stimulus or experience is
represented in the mind
Modal Model of Memory: Short-Term Memory
• Auditory coding – Conrad (1964)
– Participants briefly saw target letters and
were asked to write them down
– Errors most often occurred with letters that
sounded alike
– STM is auditory
Modal Model of Memory: Short-Term Memory
• Visual coding – Della Sala (1999)
– Presented visual information that is difficult
to verbalize
– Participants could recreate patterns of up
to 9 items
– STM is also visual
Modal Model of Memory: Short-Term Memory
• Semantic coding – Wickens et al. (1976)
– Participants listened to three words, counted
backwards for 15 seconds, and attempted to
recall the three words
• Four trials, different words on each trial
Wickens’s Experiment Demonstrating
Semantic Coding in STM.
Caption: Results of Wickens et al.’s (1976) proactive inhibition experiment. (a)
Fruit group, showing reduced performance on trials 2, 3, and 4 caused at
least partially by proactive interference (indicated by dark points). (b)
Professions group, showing reduced performance on trials 2 and 3 but
improved performance on trial 4. The increase in performance on trial 4
represents a release from proactive interference caused by the change of
category from professions to fruits.
Working Memory
• Similar concept to short-term memory
• Working memory (WM): limited capacity system
for temporary storage and manipulation of
information for complex tasks such as
comprehension, learning, and reasoning
Working Memory
• Working memory differs from STM
– STM holds information for a brief period of
time
– WM is concerned with the processing and
manipulation of information that occurs during
complex cognition
Caption: Diagram of the three main components of Baddeley and
Hitch’s (1974; Baddeley 2000) model of working memory: the
phonological loop, the visuospatial sketch pad, and the central
executive.
Phonological Loop
• Phonological similarity effect
– Letters or words that sound similar are
confused
• Word-length effect
– Memory for lists of words is better for short
words than for long words
– Takes longer to rehearse long words and to
produce them during recall
Phonological Loop
• Articulatory suppression
– Prevents one from rehearsing items to be
remembered
• Reduces memory span
• Eliminates word-length effect
• Reduces phonological similarity effect for
reading words
Visuospatial Sketch Pad
• Brooks (1968)
– Memorize sentence and then consider each
word (mentally)
– Response is either
• Phonological: say “yes” if it is a noun and
“no” if it is not
• Visuospatial: point to Y if word is a noun
and N if word is not
It’s probably easier to
perform two tasks
simultaneously if they
don’t use common
resources.
Memorize sentence, then
(1) say “Yes” or “No” or
(2) point to Y or N.
Speaking takes longer.
“John ran to the store to buy some oranges.”
Visuospatial Sketch Pad
• Brooks (1968)
– Visualize a capital letter F, starting at the top
left corner
– Response is either
• Phonological: say “out” if it is an exterior
corner and “in” if it is an interior corner
• Visuospatial: point to “out” if it is an exterior
corner and “in” if it is an interior corner
Memorize shape, then
visualize it and
outline it (1) saying
“Yes” each time you
turn an outside corner
or “No” each time you
turn an inside corner
or (2) point to Y or N.
Pointing takes longer.
Working Memory
• WM is set up to process different types of
information simultaneously
• WM has trouble when similar types of
information are presented at the same time
The Central Executive
• Attention controller
– Focus, divide, switch attention
• Controls suppression of irrelevant information
Caption: Baddeley’s revised working memory model, which contains
the original three components plus the episodic buffer.
WM and the Brain
• Prefrontal cortex responsible for processing
incoming visual and auditory information
– Monkeys without a prefrontal cortex have
difficulty holding information in WM
WM and the Brain
• Funahashi et al. (1989)
– Single cell recordings from monkey’s
prefrontal cortex during a delay-response
task
WM and the Brain
• Neurons responded when stimulus was flashed
in a particular location and during delay
• Information remains available via these neurons
for as long as they continue firing
Caption: Results of an experiment showing the response of neurons
in the monkey’s PF cortex during an attentional task. Neural
responding is indicated by an asterisk (*). (a) A cue square is
flashed at a particular position, causing the neuron to respond. (b)
The square goes off , but the neuron continues to respond during
the delay. (c) The fixation X goes off , and the monkey
demonstrates its memory for the location of the square by moving
its eyes to where the square was
Caption: Some of the areas in the cortex that have been shown by
brain imaging research to be involved in working memory. The
colored dots represent the results of more than 60 experiments
that tested working memory for words and numbers (red), objects
(blue), spatial location (orange), and problem-solving (green).
CogLab Exercises
• Sternberg Search
• Phonological Similarity
• Modality Effect
• Implicit Learning