THE “WORKING MEMORY”
APPROACH
• Baddeley & Hitch (1974)
– Use articulatory suppression to interfere
with some tasks, not others
B doesn’t precede A
B A
– Develop “Working Memory” model:
• Desk-top metaphor for STM
• Process & storage tradeoff
– (e.g., Posner & Rossman 1965)
• Multicomponent structure
COMPONENTS OF WORKING
MEMORY
(Baddeley, 1990)
(Random letter generation)
Central executive
(attentional control)
Phonological
store
Visual-spatial
sketchpad
(Repetitive
articulation)
(Repetitive
keying)
Concurrent Articulation and the
Phonological Store (Peterson &
Johnson, 1971)
No Concurrent Task
1
Visual
Auditory
Percent Correct
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Dissimilar
Similar
Type of List
Concurrent Articulation
1
Percent Correct
0.9
Visual
Auditory
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Dissimilar
Type of List
Similar
WORKING MEMORY AND CHESS
(Robbins, 1996)
Primary task: recall of
chess piece positions
Mean correct recall
Secondary tasks:
N None
P articulate “the, the..”
V execute 4x4 key pattern
CE generate random letters
N
P
V
CE
DISSOCIATING THE SKETCHPAD
FROM THE LOOP
• Instances of selective interference
(e.g., Brooks, 1968)
• Imaging evidence (Jonides, 1995)
– The n-back task
2-back:
M
P
F
P
verbal: match letter identity
+
+
Spatial: match location of dot in array
Dorsolateral Prefrontal lights up:
• Left side for verbal task
• Right side for spatial task
Prefrontal Activity Varies
with Memory Demand
Rypma, et al. (2002)
1, 3 or 6 letters in memory set
• Low memory-demand activity limited
to Ventrolateral Prefrontal Cortex
• High memory-demand also activates
Dorsolateral Prefrontal cortex
• Differences are largest for highperformance subjects
WM ACTIVITY and LTM
ENCODING
• Greater fMRI activity during WM trial
correlated with:
– better WM performance (Pessoa, et al.
2002
– Memory load for good performers
(Rypma, et a., 2002)
– Better subsequent LTM (Brewer, et al.
1988)
• Integrative WM tasks (e.g., item x
location) correlated with:
– Greater “remember” judgments
– Specific areas of “coupling” of PFC and
other cortical areas
– Greater memory-contingent PFC effect
for associative than item memory
(Howland, 2005)
– Baddeley’s “Episodic Buffer”?
WORKING MEMORY SPAN AND
COGNITIVE PERFORMANCE
• Daneman & Carpenter (1980)
– Reading Span, not digit span, correlates
with reading comprehension
The witness examined by the attorney…
The evidence examined by the attorney…
• Engle et al. (1995)
– Develop other “spans” (Operation Span)
– Argue it’s not “capacity” but skill at
controlling tasks and codes, inhibition,
etc.
– James’ “span of consciousness?”
Some Baddeley & Hitch 1974
trials
Repeat 2,5,8,3 rapidly
A doesn’t follow B
A B
D precedes G
G D
X follows Y
X Y
N doesn’t precede R
R N
Posner & Rossman 65
Demonstration
• Set 1: write down last two digits,
and add one ARAP, e.g. 91/92/93
– 26457381
– 75248619
– 13245768
• Set 2: write down last two digits,
and subtract 3 ARAP e.g. 91/88/85
– 54723169
– 71289435
– 65382147
should be greater errors in Set 2, as
difficulty of “work” in WM makes
storage/refreshing of PL harder
N-back demo
• 0-back series (target is “S”
– EDTWSVDDSGHRS
• 1-BACK (REPETITION)
– NKQQFTLCCWTSSQ
• 2-BACK (LAG OF 2)
– QXFXWTTWTJLJN