Download Short-Term Memory

Memory
The Man with the 30 Second Memory
Cog Chp 4 - short Term/Working
Memory
1
Short Term Working Memory
(STWM)
A.K.A. – Primary memory, Immediate Memory, Shortterm store, Temporary Memory, Supervisory-Attention
System (SAS) and Working Memory (WM)
Cog Chp 4 - short Term/Working
Memory
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Short Term Memory
(STM) as a storage space.
Working Memory
(WM) as a place
where mental work is done
Cog Chp 4 - short Term/Working
Memory
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Serial Recall test – must remember the
words in the correct order
Free Recall test – may remember the
words in any order.
Cog Chp 4 - short Term/Working
Memory
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Capacity of Short Term Memory
John Jacobs (1887) used the Memory span test
with every letter in the alphabet and numbers
apart from “w” and “7” because they had two
syllables. He found out that people find it easier
to recall numbers rather than letters. The
average span for letters was 7.3 and for
numbers it was 9.3.
Cog Chp 4 - short Term/Working
Memory
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George Miller (1956) – free recall test of memory
for words and numbers.
- The Magic Number 7:
+/- 2
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Memory
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Memory Chunks – Seven Chunks of Memory
can be retained in STM.
Chunking – increases capacity of STM
BATCARBOYERA
- requires processing for meaning (recoding)
Cog Chp 4 - short Term/Working
Memory
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Herb Simon (1974) - Larger Chunks reduce
memory span.
Chunk Size
Memory Span
Unrelated words
6 or 7
Two Word Phrases
4
Eight Word Phrases
3
Cog Chp 4 - short Term/Working
Memory
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Pronunciation Time
Language Differences in digit span.
Mueller (2003) (Research Activity 4.1)
Shorter Pronunciation = Higher Digit Span
Cog Chp 4 - short Term/Working
Memory
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Maintenance Rehearsal:
Mentally repeating items in STM
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Memory
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Cowan et al. (2005) Running Memory Task
Method to control for rehearsal and Transfer
to Long Term Memory.
Presented unpredictable number of digits very
rapidly.
The Magical Mystery Four! - when rehearsal
is not allowed, Memory Span drops to 4.
Cog Chp 4 - short Term/Working
Memory
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Serial position effects
Better Memory for
1) first few words (Primacy Effect)
2) last few words in the list (Recency Effect).
Cog Chp 4 - short Term/Working
Memory
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Evidence
Present words too quickly to allow rehearsed Primacy effect disappears.
When rehearsal after presentation is eliminated (e.g.,
Brown- Peterson task) Recency Effect Disappears.
Primacy – early words rehearsed more -- moved
to LTM.
Recency - last words still in STM -- recovered
directly.
Cog Chp 4 - short Term/Working
Memory
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Duration of STM
Peterson & Peterson (1959)
Increasing the time of the secondary task
(counting backwards by 3’s) reduces Memory
Span.
Cog Chp 4 - short Term/Working
Memory
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Why is information lost from
STWM?
Brown-Peterson Studies
Distracter task (e.g., count backwards)
- eliminates rehearsal
- items are lost from STM
- recency effect disappears
If not attended to at least every 20 secs the memory
trace DECAYS and items lost from STM.
Cog Chp 4 - short Term/Working
Memory
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Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
After information enters STM, a copy may or
may not be sent to LTM. Soon, however, that
information will disappear from STM.
Two processes could cause information to disappear
from STM:
Decay and Displacement.
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
Decay: information that is not rehearsed disappears
as time passes.
Displacement: information being held in STM is
pushed out by newly arriving information.
Displacement is most likely to occur when the
capacity limit of STM has been reached (about 7
units of information).
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
B
R
D
Q
L
T
H
J
Displacement is most likely to occur when the
capacity limit of STM has been reached (about 7
units of information).
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
B
R
D
Q
L
T
H
J
Displacement is most likely to occur when the
capacity limit of STM has been reached (about 7
units of information).
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
B
R
D
Q
L
T
H
The original version of the Stage model emphasized
decay as the main cause of forgetting in STM. Their J
later version emphasized displacement. Here is a
study that compared decay to displacement and
showed a much greater effect of displacement.
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Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
You are read a list of 16 digits:
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
TONE
After the last digit, you hear a tone...
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Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
TONE
The tone is a signal to recall one of the digits. The
last digit before the tone (8) occurs only once at an
earlier point in the list.
This is called the “probe”.
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
TONE
Recall
The subject’s task is to recall the digit following the
probe.
Between the digit, 4, and the tone, two things happen:
(1) time passes, and
(2)
more
digits are presented. 24
Cog Chp
4 - short
Term/Working
Memory
STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
TONE
Recall
Which is more important in causing forgetting, time
or the additional digits?
The decay principle implies time; the displacement
principle implies digits.
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
Slow Presentation (Seconds)
+1+ 1 +1 +1 + 1 +1+ 1+ 1+ 1+ 1 +1 +1 = 12
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
TONE
Recall
Time and digits are correlated (confounded). To
separate them, Waugh & Norman used two rates of
presentation: slow (1 digit per second) and fast (4
digits per second).Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
1
Fast Presentation (Seconds)
+
1
+
1
=
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
3
TONE
More time passes between the digit and the tone with
slow presentation (12 seconds) than with fast
presentation (3 seconds). According to the decay
principle, the chances of recalling the digit should be
lower with slow thanCogwith
presentation.
Chp 4 -fast
short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
1
Fast Presentation (Seconds)
+
1
+
1
=
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
3
TONE
According to the displacement principle, the chances of
recalling the digit should be the same with fast and slow
presentation because the number of digits before the
tone is the same in both conditions.
Cog Chp 4 - short Term/Working
Memory
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STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
1
Fast Presentation (Seconds)
+
1
+
1
=
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
3
TONE
Waugh & Norman made this comparison with the probe
digit in each of the following positions: 3 (shown here),
5, 7, 9, 10, 12, 13, or 14.
Both decay and displacement predict an increase in recall
as the probe gets closer
theTerm/Working
tone.
Cog Chpto
4 - short
29
Memory
STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
1
Fast Presentation (Seconds)
+
1
+
1
=
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
3
TONE
Results
There was slightly (but not significantly) higher recall with
fast than with slow presentation when the probe was near
the beginning of the list. Recall dropped sharply as the
probe was moved from
the
endTerm/Working
toward the beginning. 30
Cog Chp
4 - short
Memory
STM
LTM
Forgetting from Short-Term Memory:
Decay or Displacement?
The Probe-Digit Procedure
(Waugh & Norman, 1965)
Probe
1
Fast Presentation (Seconds)
+
1
+
1
=
7 0 8 4 1 6 0 9 5 5 3 7 2 4 7 8
3
TONE
Conclusion
As time passes, what mainly causes forgetting
from short-term memory is exposure to additional
information, not the passage of time.
Cog Chp 4 - short Term/Working
Memory
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Participants poorer at recall when more items intervened.
◙ Retroactive interference
Rate of presentation did not effect recall
◙ Decay
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Memory
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Atkinson & Shiffrin (1968) Multistore Model
S
e
n
s
o
r
y
S
t
o
r
e
Retrieval
Short-Term
Memory
Long-Term
Memory
Encoding
Rehearsal
Loss
Cog Chp 4 - short Term/Working
Memory
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Short Term vs. Long-Term
Memory (LTM)
Capacity and Duration Difference
Double Dissociation?
Milner (1966) patient H.M normally working
short-term memory with an impaired long
term one. Shallice & Warrington (1970)
patient K.F. unimpaired long-term memory
performance while a severe impairment in
short-term memory.
Cog Chp 4 - short Term/Working
Memory
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Unitary-Store Approach
STM is just that fraction of LTM activated at any
given moment.
Ruchin (1999) – EPRs during serial recall test
Compared Pseudowords to real works
More activity with words than with pseudowords
People process semantic information (not just
sound) when words are presented.
Cog Chp 4 - short Term/Working
Memory
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Working Memory (WM)
(Baddley & Hitch)
Place where mental work is done.
- activates information from LTM into WM and
from WM to LTM.
Consists of two levels of processors
•
Central Executive
•
Helper Systems – modality specific memory stores
Cog Chp 4 - short Term/Working
Memory
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Central Executive (Boss)
- Directs the flow of Information
- limited capacity
- role is of attention rather than memory
- activation of info from LTM
Control Processes
- rehearsal
- coding for meaning
- integration of information
- decision making
Cog Chp 4 - short Term/Working
Memory
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Central Executive
- Resembles an attention System
- No storage ability
- Frontal Lobes Thought to play a large role.
Dysexecutive syndrome is a neurological
impairment of executive function, where
patients have trouble with complex thinking
and reasoning tasks.
Cog Chp 4 - short Term/Working
Memory
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Neurological Evidence
Three major executive processes based on different
parts of the Frontal Lobe.
Task Setting – simple planning
Monitoring – checking that the task is being
performed correctly.
Energization – sustained attention or concentration.
Cog Chp 4 - short Term/Working
Memory
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Storage and Temporary Maintenance of
information
Phonological Loop
Two structures
1. Phonological buffer
- holds verbal info for a few minutes
2. Subvocal rehearsal loop
(- everything we said about STM.)
Though to be important for verbal processing.
Cog Chp 4 - short Term/Working
Memory
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Phonological Loop
Phonological Similarity Effect - sound
based rehearsal.
Word Length Effect – not chunks, but
limited time duration
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Memory
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Holds acoustic
information
giving Central
Exec longer to
process it.
Central
Exec
Cog Chp 4 - short Term/Working
Memory
Phonological
loop
43
Visuospatial Sketch Pad
Holds images for further processing by central
Executive.
Both Slave systems have limited capacity but
Do not interfere with each other.
Cog Chp 4 - short Term/Working
Memory
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Visuo-Spatial Sketchpad
Capacity – About 4 Items
Vogel et al. (2001) Presented displays of
between 3 to 12 objects.
90ms later followed by either identical display
or identical with one object changed.
Performance good up to four objects then
begins to decline.
Cog Chp 4 - short Term/Working
Memory
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Are Visuo and Spatial Stores?
Visual task (is it the same object)
Spatial task (is it the same location)
Activated different areas of the Cortex
Gender Differences
Cog Chp 4 - short Term/Working
Memory
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Episodic Buffer – storage system that can hold
information from the phonological loop and
visuo-spatial sketchpad.
-General storage system for combining and
integrating information from other components
and from long-term memory.
- Limited capacity
Cog Chp 4 - short Term/Working
Memory
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Robbins et al. (1996)
Chess players (skilled and novice) had to select
moves from various chess positions.
Secondary Tasks
One group of participants engaged their central
executive by using their attention to generate
random letter sequences while trying to
memorize the positions of pieces.
Cog Chp 4 - short Term/Working
Memory
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Articulatory suppression task e.g. saying ‘seesaw” while trying to remember the positions.
Visuo-spatial sketchpad suppression task –
pressing keys on a keyboard in a clockwise
fashion.
After 10 seconds their memory was tested.
Participants in the articulatory suppression group
performed well.
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Memory
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Figure 4.4 Effects of secondary tasks on quality of chess-move
selection in stronger and weaker players. Adapted from Robbins et al.
(1996).
Episodic Buffer
No storage capacity
Acts as a glue to integrate information within
working memory
Cog Chp 4 - short Term/Working
Memory
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Working Memory Capacity
Information is stored briefly while processing
other information.
Working Memory Capacity = Ability to
combine processing and storage of
Information.
Cog Chp 4 - short Term/Working
Memory
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Measuring WM Capacity
Reading Span – Largest number of sentences
from which an individual can recall the final
words 50% of the time.
Operation Span (demo at 3:17) Dual task
(math and memory).
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Memory
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Memory
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WM Capacity is more strongly related to Fluid
than to Crystalized Intelligence!
This is a correlation!!
WM capacity could be causing higher IQ.
IQ could be causing higher WM Capacity.
Both could be related to come third factor!!
Cog Chp 4 - short Term/Working
Memory
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Attentional Control
Refers to individuals' capacity to choose what
they pay attention to and what they ignore.
e.g., Distractibility – The correlation between
WM Capacity and performance in a visual
search task is only found when distractors are
present.
Cog Chp 4 - short Term/Working
Memory
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e.g., Lapses in attention (vigilance tasks)
High WM capacity showed fewer lapses in
attention.
Allocation of Attention.
Low WM – inflexible, like spotlight
High WM – more flexible, divided attention.
Cog Chp 4 - short Term/Working
Memory
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Prosaccade and Antisaccade
Subjects view a fixation point and a visual
target is presented. Subjects are instructed to
make a saccade away from the target
(antisaccade) or to the target (prosaccade).
Prosaccade – no relation to WM capacity
Antisaccade – High WM were better.
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Memory
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Memory capacity
vs.
Cognitive control
capacity
“Greater working memory
capacity does not mean that
more items can be maintained
as active, but this is a result of
greater ability to control
attention,…ability to use
attention to avoid distraction.”
-Engle RW
The Answer is not that simple!
Dual-Component Model – Attention Control
is Important but so is LTM.
Multiple Regression Studies
Fluid Intelligence related to LTM, Attentional
Control and Working Memory Capacity!
Cog Chp 4 - short Term/Working
Memory
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