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10/30/07 CNTRICS St. Louis 2007 1
Measuring working memorycapacity and cognitive control
Randall W. Engle
Georgia Institute of Technology
All papers available at http://psychology.gatech.edu/renglelab/
10/30/07 CNTRICS St. Louis 2007 2
Outline
My question
My approach
My thoughts on WM as a system and specifically on WMC
Complex span tasks that ‘work’.Construct and predictive validity of WMC tasks
Evidence that WMC reflects individual differences in cognitive control
Take home message
10/30/07 CNTRICS St. Louis 2007 3
My initial question:
Why do complex span tasks predictperformance on higher-level tasks?
What is the nature of the mediating construct?
10/30/07 CNTRICS St. Louis 2007 4
Combination of psychometric and experimentalmethods. Cronbach (1957) and Underwood(1975).
Benefits and Limitations
My approach is inductive rather than deductive.
My approach
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My thoughts on working memory capacity:
Focus on limits in the NUMBER of items (7±2 or 4±1) is not helpful.Problem is in the interface between attention and retrieval frominactive memory and in the prevention of attention capture byrepresentations not relevant to the current task.Much of what we need to know to function, even in the modernworld, can be derived from largely automatic retrieval from LTMwithout need of WM.However, proactive interference can make automatic retrieval aproblem – when the wrong action is retrieved. So we need to havesome way to keep important information either in the primary memoryor easily accessible from secondary memory. – An American driving orcrossing the street in England.
10/30/07 CNTRICS St. Louis 2007 6
Other thoughts on WMC and Cognitive Control
Load from any source that captures attention can diminish thatcapability (e.g., intrusive thoughts and emotions). Load can turnhigh spans into low spans.
The construct is important to regulation of thought, emotion, andbehavior.
Question: Are cognitive declines associated withpsychopathology a result or a cause?
10/30/07 CNTRICS St. Louis 2007 7
Simple Span Reading Span Operation Span______ (WMC) (WMC)
B The tiger leapt to the ridge. B Is (3 x 1) – 1 = 3 ? B
N I’ll never forget my days of combat. N Is (10 / 2) + 1 = 6 ? N
K Andy was arrested for speeding. K Is (8 / 4) – 1 = 1 ? K
J The mirror cast a strange reflection. J Is (3 x 3) + 1 = 12 ? J
S Broccoli is a good source of nutrients. S Is (4 x 3) + 2 = 14 ? S
Verbal STM and WMC Tasks
10/30/07 CNTRICS St. Louis 2007 8
Simple span and complex spans reflect differentconstructs
Engle et al (1999, JEP:G)
OSPAN
RSPAN
CSPAN
BSPAN
FSPAND
FSPANS
.64
.78
.79
.74
.61
.70
WM
STM
gF
RAVENS
CATTELL
.77*
.63*
.61*
.67*
.79*
.71*
.81*
.85*
.29*
.91*
.74*
.41
.67
.49*
.12
COMMON
error
error
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Crystallized abilities
Fluid abilities
10/30/07 CNTRICS St. Louis 2007 10
Spatial WMC Tasks
???
???
???
Rotation-Arrow Span (set sizes 2 - 5)
Symmetry-Matrix Span (set sizes 2 - 5)
Navigation-Ball Span (set sizes 2 - 5)
G F
10/30/07 CNTRICS St. Louis 2007 11
WMC Construct is domain-general Engle et al (1999) and Kane et al (2004)
ReadSpan
NaviSpan
SymmSpan
CounSpan
OperSpan
RotaSpan
WM
.71
.73
.69
.82
.78
.84
ReadSpan
NaviSpan
SymmSpan
CounSpan
OperSpan
RotaSpan
WM-V
.75
.72
.76
.82
.79
.85
WM-S
Model A1 Model A2
.93
Χ2/df=1.72, CFI=1.0, NFI=.99,NNFI=.99, RMSEA=.02 Χ2/df=1.72, CFI=1.0, NFI=.99,NNFI=.99, RMSEA=.02
10/30/07 CNTRICS St. Louis 2007 12
Kane et al (2004)wordspan
lettspan
digtspan
operspan
readspan
counspan
symspan
rotaspan
ballspan
navispan
arrospan
matxspan
Storage-V
ExecAttn
Storage-S
inference
analogy
readcomp
remoassoc
syllogism
ravens
beta3
spacerela
rotablock
wasi
surfdevel
formbord
paperfold
Reason-V
Gf
Reason-S
.52*.29*
.25*
10/30/07 CNTRICS St. Louis 2007 13
WMC
operspan
readspan
counspan
Storage
word1a
word1b
word2aGf
ravens
cattell
PS
letter
pattern
digitsym
word2b
.60*
.07
.18
Conway et al (2002)
10/30/07 CNTRICS St. Louis 2007 14
WMcapacity
Higher-order tasks
Lower-order tasks
Reasoning
Process dissociation (C not A)
Vulnerability to PI
Dichotic listeningStroop
Object-based visual attention
Mind wandering
Antisaccade
Complex learning
Writing
Note taking
Vocabulary learning
Following directionsReading/listening comprehension
Don’t think of ‘white bears’ – intrusive thought
0
20
40
60
80
100
High Span Low Span
Perc
en
t R
ep
ort
ing
Nam
e
Conway, Cowan & Bunting
REDBLUE
GREENGREEN
REDGREENBLUERED
GREENRED
BLUEBLUE
10/30/07 CNTRICS St. Louis 2007 15
WMcapacity
Reasoning
Process dissociation (C not A)
Vulnerability to PI
Dichotic listeningStroop
Object-based visual attention
Mind wandering
Antisaccade
Complex learning
Writing
Note taking
Vocabulary learning
Following directionsReading/listening comprehension
Don’t think of ‘white bears’WMC as Trait Variable
Brain structures
Neurotransmitters
Genes
10/30/07 CNTRICS St. Louis 2007 16
WMcapacity
WMC as State Variable
Drugs(Peter Finn’s work)
Life Event Stress(Kitty Klein’s work)
Senile DementiaAltzheimer’s Type(Ginny Rosen’s work)
Sleep deprivation(Pilots and medical residents)
Stereotype threat(Toni Schmader’s and
Jennifer Richeson’s work)
Choking under pressure(Sian Beillock’s work with math problems)
10/30/07 CNTRICS St. Louis 2007 17
Dichotic listeningStroop
Antisaccade
Process dissociation (C not A)Vulnerability to PI
Object-basedvisual attention
Following directionsReading/listening comprehension
WMC
ReasoningComplex learning
WritingNote takingVocabulary learning
Don’t think of ‘white bears’
Individual Differences
Sleep deprivation
Drugs
Life Event Stress
Stereotype threat
SDAT
WMC as mediating construct
10/30/07 CNTRICS St. Louis 2007 18
Evidence that differences in WMC correspond to attentioncontrol:
Antisaccade TaskEriksen TaskAttention network task
The antisaccade task is a model for attention control and the regulation ofhighly prepotent behavior – behavioral inhibition.
Unsworth, Schrock & Engle (2004)
10/30/07 CNTRICS St. Louis 2007 19
Unsworth et al. (2004)
Trial Example (half speed) - watch the cross hairs!!
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Unsworth et al. (2004))
0
2
4
6
8
10
12
14
Prosaccade Antisaccade
Trial Type
Pe
rc
en
t e
rro
r
Low span
High span
10/30/07 CNTRICS St. Louis 2007 21
Heitz and Engle (2007 JEP:G)
Is WMC as measured by complex span tasks related to the speedof attention control?
Response deadline procedure (700-200 msec)
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Eriksen flanker task
Press left key if target is S and right key if target is H
.SSSSSHHHHHHHSHHSSHSS
Response deadline 200-700 msec
10/30/07 CNTRICS St. Louis 2007 23
HHSHH
HHSHH
HHSHH
Focus of attention as a function of time
time
10/30/07 CNTRICS St. Louis 2007 24
Heitz & Engle
Incompatible Bins - Low Discriminability
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 100 200 300 400 500 600 700 800
RT
Pro
po
rtio
n C
orr
ec
t
LS
HS
Look at accuracy as function of Rt bins
No difference between Hi and Lo WMC on compatible trials
10/30/07 CNTRICS St. Louis 2007 25
The Rate of Attention Control Model
High Span
S S H S S
S S H S S
S S H S S
S S H S S
S S H S S
S S H S S
Low Span
TIM
E
S S H S S
S S H S S
S S H S S
S S H S S
S S H S S
S S H S S
10/30/07 CNTRICS St. Louis 2007 26
HS/LS may not differ in the ability to constrainattentional field per se?
They do differ in the speed of that ability (rate ofattentional constraint)
10/30/07 CNTRICS St. Louis 2007 27
Value of combination of Experimental and Psychometricapproaches – Cronbach (1957)
1. Two WM tasks Ospan and Nback. Presumably they both measure thesame thing. Kane and Conway showed that both accounted forvariance in Raven but little of it was common.
2. One task, Stroop, clearly two versions measure different things. Onlyget WMC differences on incongruent trials in presence of congruenttrials – none with only incongruent trials.
3. Even subtle variation in a task will lead to big changes in what a taskmeasures. Unsworth & Engle (2006) Simple span and list length.
4. Distinction between Stability and Flexibility or Maintenance andUpdating.
10/30/07 CNTRICS St. Louis 2007 28
Complex span and gF
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
2 3 4 5
List Length
Co
rre
lati
on
wit
h g
F
Series1
10/30/07 CNTRICS St. Louis 2007 29
Simple span and gF
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
2 3 4 5 6 7
List-Length
Co
rre
lati
on
wit
h g
F
10/30/07 CNTRICS St. Louis 2007 30
Michael Posner’s Attention Networks - three ‘independent’ attention networks
Alerting – general readinessOrienting - to specific region of space or timeExecutive Control/Conflict
– Resolving conflict among responses– Associated with conflict tasks such as
Stroop and flanker
10/30/07 CNTRICS St. Louis 2007 31
Redick and Engle (2006)
Predict IDs in WMC would correspond toExecutive network but not sure about alertingor orienting– Different WMC Ss differentially control
attention on incompatible vs. compatibletrials
10/30/07 CNTRICS St. Louis 2007 32
Redick and Engle (2006)
31.49
63.12
121.57
40.63
51.30
88.36
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Alerting Network Orienting Network Executive Network
Attentional Networks
Dif
fere
nc
e s
co
re (
ms
)
Low Span High Span
No Cue― Double Cue
Alerting
Center Cue― Spatial Cue
Orienting
Incompatible― Compatible
Executive
10/30/07 CNTRICS St. Louis 2007 33
What we have called ‘working memory capacity’ reflectsindividual differences in ability to control the contents of thefocus of attention and plays a crucial role in the regulation ofcognition, emotion, and behavior.
I believe that construct reflects some aspect of functioning ofnormal frontal executive areas of the brain (PFC, anteriorcingulate).
There is growing evidence for a role of genetics in this system.
WMC construct is important for:(1) rapid access to task-relevant information particularly
in the presence of distraction and/or interference,(2) suppressing potentially interfering information AND
maintaining access to information, and(3) in the flexibility of attention allocation.
Take home message
10/30/07 CNTRICS St. Louis 2007 34
All papers available in downloadable pdf athttp://psychology.gatech.edu/renglelab/
Tasks available from same web site but you mustemail webmaster for password
10/30/07 CNTRICS St. Louis 2007 35
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
A-X A-nonX nonA-X nonA-nonX
Trial Type
Err
or
Ra
te
Low Span Short Low Span Long High Span Short High Span Long
10/30/07 CNTRICS St. Louis 2007 36
Sleep deprivation
10/30/07 CNTRICS St. Louis 2007 37
Effects of sleeplessness (30-36 hours) on flight performance
Gyroflight Sustained Operations Simulator (GSOS)
• Features 4-axis simulator motion and 3-channel visualsystem
• Models T-6 aircraft• Unique capability of presenting motion and visual
conflicts during an almost entirely automatedsimulator flight profile
10/30/07 CNTRICS St. Louis 2007 38
10 pilots studied (run in tandem)– 34.2 yrs (23-46)– 2806 flt hours (207-5800)
Pilot schedule– Training on evening of Day 1 (3 training flights)– Arrive at 0730/0800 on Day 2– Begin first session at 1200/1300– Continuous wakefulness until 1630/1730 on Day 3 (10
sessions)
Basic Methodology
1230 1530 1830 2130 0030 0330 0630 0930 1230 1530
Time of Session
10/30/07 CNTRICS St. Louis 2007 39
Difficulty of finding a task that predicts sleep-relatederror
Perceptual Vigilance task- Previous gold standard of fatigue
0000
Correlation (flight performance and PVT)=.44
Correlation (flight performance and OSPAN)=-.65
Results
10/30/07 CNTRICS St. Louis 2007 40
Schmader & Johns (2003)
10/30/07 CNTRICS St. Louis 2007 41
Beilock and Carr (2005)