THE PHENOMENOLOGY
OF SHORT-TERM MEMORY
“There seems to be a presence-chamber in my mind
where full consciousness holds court, and where two
or three ideas are at the same time in audience, and
and antechamber full of more of less allied ideas,
which is situated just beyond the full ken of
consciousness. Out of this antechamber, the ideas
most readily allied to those in the presence-chamber
appear to be summoned in a mechanically logical
way, and have their turn of audience.”
-- Francis Galton (1883)
“The objects we feel in this directly intuited past differ
from properly recollected objects. An object which is
recollected, in the proper sense of the term, is one
which has been absent from consciousness
altogether, and now revived anew… But an object of
primary memory in not thus brought back; it was
never lost -- its date was never cut off in
consciousness from that of the immediately present
moment. In fact, it comes to us as belonging to the
rerward portion of the present space of time, and not
to the genuine past.”
-- William James (1890)
MEASURING THE DURATION OF
SHORT-TERM MEMORY
(Peterson & Peterson, 1959)
Task: rcall a 3-consonant trigram after a
brief interval of distraction (so, the
‘distractor” task)
XVK
294
..........
?
R e c a ll P r o b a b ility
“291, 288, uh, 285, 282..”
“x,v,..g?”
retention interval
3 to 18 seconds
0.6
0.5
0.4
0.3
0.2
0.1
0
3
6
9
12
15
Recall Delay (sec)
18
MEMORY STRUCTURES AND
PROCESSES IN
THE “MODAL MODEL”
(Atkinson & Shiffrin, 1968)
sensory
inputs
SENSORY REGISTERS
visual
auditory
tactile
SHORT-TERM STORE (STS)
temporary, working memory
control processes:
- rehearsal
- coding
- decisions
- retrieval strategies
LONG-TERM STORE (LTS)
permanent memory store
CLINICAL DISSOCIATIONS of
SHORT and LONG-TERM
MEMORY
• Damage to medial temporal lobes
– Hippocampus in particular
• The “classic amnestic syndrome”
– HM: surgical removal
– Clive Wearing: Encephalitis
– Other causes of the amnestic syndrome
CHARACTERISTICS OF
SHORT- AND LONG-TERM
MEMORY
(according to the “modal model”
of Atkinson & Shiffrin, 1968)
STM
LTM
• DURATION
< 30 sec
lifetime
• CAPACITY
~7 chunks
unlimited
• RETRIEVAL
serial
parallel
• FORGETTING
decay, dis- interference
placement
acousticsemantic
articulatory
• MAIN CODE
STM CAPACITY AND LTM
CODES
task: immediate serial recall (“memory span”)
Miller (1956): capacity of STM as
“about seven chunks”
1492177619451963...
FB
IJ
FK
FD
RL
BJ
STM CAPACITY AND
REHEARSAL TIME
Baddeley et al., 1975
Number of syllables
P r o p o r tio n C o r r e c t
1
2
3
4
5
Reading Rate
mumps
measles
leprosy
diphtheria
tuberculosis
2.2 words/sec
2.0
“
1.7
“
1.5
“
1.3
“
task: immediate serial recall of 6-item lists
1
0.8
0.6
0.4
1
2
3
4
5
Number of Syllabes
the word length effect
STM CAPACITY AND THE
RECENCY EFFECT
Task: free recall of word lists
P r o p o r tio n C o r r e c t
Primacy effect:
better recall of first few words
Recency effect:
better recall of last few words
Glanzer & Cunitz (1966): distraction
between study and test eliminates
recency effect:
0.8
No Distractor
0.6
30 Seconds
0.4
0.2
1
3
5
7
9
11
Serial Position
13
15
RETRIEVAL FROM STM
(Sternberg, 1966)
varied set of digits held in STM
2, 5, 8, 1
test digit: is it in the set?
yes
no
R T (m s e c )
2
7
650
600
550
YES
500
NO
450
400
1
2
3
4
5
Size of Memory Set
6
PROACTIVE INTERFERENCE
IN STM
(Keppel & Underwood, 1962)
things learned prior to study
can proactively interfere
with memory
STUDY PHASE
things learned between study
and test can retroactively
interfere with memory
R e c a ll P r o b a b ility
TEST PHASE
STM in the distractor task:
1
0.8
0.6
all trials
0.4
first trial
0.2
0
3
6
9
12
15
Recall Delay (sec)
18
DOMINANT CODES IN
STM AND LTM
Baddeley, 1966
Acoustically similar lists
mad, plan, nap, bag….
Semantically similar lists
big, large, huge, great…
Control lists
pen, day, wish, bill….
TYPE OF SERIAL
RECALL TASK:
% words in correct
position
A
S
C
STM: 5 words,
one trial, no delay
__%
__%
76%
LTM: 10 words,
four trials, delay
__%
__%
72%
DISSOCIATING VERBAL AND
VISUAL SKILLS
Hunt, 1985
task: reading comprehension scores
correlate performance with tests of...
vocabulary
+.67
grammar
+.63
mechanical
reasoning
+.33
spatial thinking
+.14
WAYS TO DISTINGUISH VERBAL
AND VISUAL CODES IN MEMORY
• PSYCHOMETRIC
– Patterns of correlations among
visual and verbal tasks (e.g.,
Hunt, 1985)
• NEUROLOGICAL
– Functional asymmetries of the
cerebral hemispheres:
• Left H: speech and language
• Right H: visual, spatial coding
– Brain activity during imaging
versus rehearsing
• EXPERIMENTAL
– Selective interference among
tasks (e.g., Brooks 1968)
VISUAL AND VERBAL CODES IN
STM (Logie, Zucco & Baddeley,
1990)
• STM tasks:
– Checkerboard array span
– Letter list span
• Concurrent tasks:
% Drop from Baseline
– Maintain visual image
– Mental arithmetic
70
adding
60
imaging
50
40
30
20
10
0
Visual Span
Letter Span
Primary Task
“MENTAL ROTATION” OF
BLOCK FORMS
(Shepard & Metzler, 1971)
task: decide if two figures are the same
the linear function
suggests a mental
process that’s
analogous to
physical rotation
R e s p o n s e tim e ( m s )
MENTAL ROTATION AND
DEAFNESS
(Emmory, Kosslyn & Bellugi, ‘93)
3700
3200
2700
Hearing
Deaf
2200
1700
1200
0
60
120
Degree of rotation
180
COMPONENTS OF WORKING
MEMORY
(Baddeley, 1990)
(Random letter generation)
Central executive
(attentional control)
Phonological
loop
Visual-spatial
sketchpad
(Repetitive
articulation)
(Repetitive
keying)
WORKING MEMORY AND
CHESS (Robbins, 1996)
Primary task: recall of
chess piece positions
Mean correct recall
(max = 20)
Secondary tasks:
N None
P articulate “the, the..”
V execute 4x4 key pattern
CE generate random letters
N
P
V
CE
INDIVIDUAL DIFFERENCES
IN WORKING MEMORY
• Establish the “working memory span”
– E.g., sentence span
Up to five of:
We were fifty miles out at sea before we lost
sight of land. TRAIL
Serial recall of final words
• Correlate with target cognitive task(s)
– Verbal SAT (+.59) Daneman & Carpenter ’80
– Distractibility in shadowing (Conway et al)
– Interference in STM Distractor task (Engle)