Post on 27-Jul-2015
Do Working Memory SpansDepend only on Time?
Valérie Camos
Pierre BarrouilletUniversité de Bourgogne
LEAD - CNRS
Working Memory Span Tasks
• Maintenance: items to be maintained and recalled
• Processing: some task, usually complex, such as reading comprehension or problem solving
They involve:
Working Memory Span Tasks
(6/3)+5=7?
Truck
(3+6)/3=2?
Deer
(8-6)x3=6?
Nail
Recall
Operation span(Turner & Engle, 1989)
Time-Based Resource-Sharing ModelThe main proposals
Barrouillet, Bernardin, & Camos, JEP:G, 2004
1. Processing and maintenance require attention which is a limited resource (some sharing is needed)
2. As soon as attention is switched away from the memory items, their activation suffers from a time-related decay
3. Refreshing the decaying memory traces necessitates their retrieval through attentional focusing (as proposed by Cowan, 1999)
4. When processing component requires retrievals from LTM, it should have the most detrimental effect on concurrent maintenance
5. In this case, sharing attention is time based because a central bottleneck allows only one retrieval at a time
Time-Based Resource-Sharing Model
Processing Maintenance
Rapid switching
Switching mechanism and decay
R R R RTruck Deer
CL
R R R RTruck Deer
CL
R R R RTruck Deer
CL
Possible reactivation of memory traces
Cognitive Load is
CL =Duration of attentional capture
Total time allowed
The proportion of time during which a given activity captures attention in such a way that the refreshment of memory traces is impeded.
A metric for Cognitive Load In tasks involving retrievals from LTM
The number of retrievals nTheir difficulty a
(the time they occupy central processes)
The total time allowed to perform them T
CL =a N
T
Cognitive Loadas defined by the Time-Based Resource-Sharing model
depends on
rate of processing rather than complexity
duration of the atomic steps of processing
nature of the processes involved
Cognitive Loadas defined by the Time-Based Resource-Sharing model
depends on
rate of processing rather than complexity
duration of the atomic steps of processing
nature of the processes involved
R 8 3 1 6 4 K7 2 5 4 9 L63
842
Rate of ProcessingManipulating the Number of Retrievals / Time ratio
The Reading Digit Span Task
Read aloud the successive screens and recall the letters
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
6 Digits 10 Digits
Rate of ProcessingManipulating the Number of Retrievals / Time ratio
Either 6 or 10 digits to be read
Constant duration of the interletter intervals (6 s)
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
Slow1000 ms
Fast600 ms
Rate of ProcessingManipulating the Number of Retrievals / Time ratio
Fixed number of digits to be read
Either 600 or 1000 ms per digit
• Either 4, 8, or 12 digits during 6, 8, or 10 seconds
• 9 different values of the critical ratio (from 0.4 to 2)
Rate of ProcessingManipulating the Number of Retrievals / Time ratio
Varying the number of digits to be read
and the time allowed to read them
1
1,5
2
2,5
3
3,5
4
4,5
5
5,5
6
0 0,5 1 1,5 2 2,5
Number of retrievals / Time ratio
R2 = .932
Rate of Processing
Barrouillet, Bernardin, & Camos, JEP:G, 2004
Mea
n S
pa n
Rate of processing rather than complexity Lépine, Bernardin, & Barrouillet, EJCP, 2005
In undergraduate students who remembered series of digits:
• Traditional Reading Span (self paced)
• Reading Letter Span (slow: 1200 ms per letter)
• Reading Letter Span (fast: 600 ms per letter)
1
1,5
2
2,5
3
3,5
4
4,5
RS self-paced RLS slow RLS fast
Reading letters can have the same detrimental effect on spans as reading complex sentences !
Rate of processing rather than complexityLépine, Bernardin, & Barrouillet, EJCP, 2005
WM
spa
n
Cognitive Loadas defined by the Time-Based Resource-Sharing model
depends on
rate of processing rather than complexity
duration of the atomic steps of processing
nature of the processes involved
Duration of the atomic steps of processing
Slower retrievals
Central processes occupied for a longer period
Higher CL
LOWER SPANS
A reading digit span with digits presented …
4 Four IV
442 ms 446 ms 625 ms
Reading digit spans should be lower when digits are presented in roman
Reading numbers (1 to 9) while maintaining letters1 digit per second
Duration of the atomic steps of processing
2
2,5
3
3,5
4
4,5
4 Four IV
Slower retrievals occupy central processes for longer periods and involve higher cognitive load.
*
Duration of the atomic steps of processing
WM
spa
n
Cognitive Loadas defined by the Time-Based Resource-Sharing model
depends on
rate of processing rather than complexity
duration of the atomic steps of processing
nature of the processes involved
Parity“ Even, odd, even, odd …”
Location“ Up, up, down, down”
Retrievals from LTM requiredLower spans predicted
G 8
5
6
1 2
3P
Two different groups are presented with the same display but perform different activities:
Nature of the processes involvedBernardin, Portrat, & Barrouillet, in press
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
Location Parity
*
Retrievals from LTM more demanding than location judgments
Nature of the processes involvedBernardin, Portrat, & Barrouillet, in press
WM
spa
n
Nature of the processes or time ???
Parity judgments involve lower spans but …
they probably take also longer !
Nature or duration of the processes involved?
T K4 7
92
Location
Actual Processing Time RT
WM spans as a function of the actual processing time within the interletter interval
Parity
Stimulus onset Response
RT
Nature or duration of the processes involved?
Series of ascending length of 1 to 7 letters to be remembered (3 series of each length)
Interletter intervals 6400 ms
Either 4, 6, or 8 stimuli to be processed in each interval
Responses by pressing keys
2 Tasks x 3 Rates = 6 groups of 16 adults
Spans as a function of the number of stimuli and the nature of the task
2
2.5
3
3.5
4
4.5
5
5.5
6
4 6 8
Number of stimuli
Mea
n s
pan
Location
2
2.5
3
3.5
4
4.5
5
5.5
6
4 6 8
Number of stimuli
Mea
n s
pan
Location
Parity
Spans as a function of the number of stimuli and the nature of the task
Actual duration of processing as a function of the task and number of stimuli
0
0.5
1
1.5
2
2.5
3
3.5
4
4 6 8Number of stimuli
Act
ual
du
rati
on o
f p
roce
ssin
g
Location
Actual duration of processing as a function of the task and number of stimuli
0
0.5
1
1.5
2
2.5
3
3.5
4
4 6 8Number of stimuli
Act
ual
du
rati
on o
f p
roce
ssin
g
Location
Parity
Nature or duration of the processes involved?
3
3.5
4
4.5
5
5.5
6
6.5
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)
Mean
Sp
an
Observed location spans
Nature or duration of the processes involved?
3
3.5
4
4.5
5
5.5
6
6.5
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)
Mean
Sp
an
Nature or duration of the processes involved?
3
3.5
4
4.5
5
5.5
6
6.5
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)
Mean
Sp
an
Predicted span values for a location task that would take
longer
Parity spans observed
Nature or duration of the processes involved?
3
3.5
4
4.5
5
5.5
6
6.5
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)
Mean
Sp
an
Mean location span5.23
Mean span predicted4.34
Mean parity span observed4.48
Nature or duration of the processes involved?
3
3.5
4
4.5
5
5.5
6
6.5
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)
Mean
Sp
an
Mean location span5.23
Mean span predicted4.34
Mean parity span observed4.48
Tasks have no effect on spans beyond their duration
Do working memory spans depend only on time?
Working memory spans depend on the time during which the processing component
captures attention
Thanks to
Sophie BernardinRaphaëlle LépineNathalie GavensSophie Portrat
LEAD - CNRS Université de Bourgogne