1. Do Working Memory Spans
Depend only on Time?
Pierre Barrouillet
Valérie Camos
Sophie Portrat
Université de Bourgogne
LEAD - CNRS

2. Working Memory Span Tasks
They involve:
• Maintenance: items to be maintained and recalled
• Processing: some task, usually complex, such as reading
comprehension or problem solving

3. Working Memory Span Tasks
(6/3)+5=7? Operation span
(Turner & Engle, 1989)
Truck
(3+6)/3=2?
Deer
(8-6)x3=6?
Nail
Recall

4. Time-Based Resource-Sharing Model
The 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
4. Those processing components that require retrievals from LTM should have the
most detrimental effect on concurrent maintenance
5. When processing involves retrievals, sharing attention is time based because a
central bottleneck allows only one retrieval at a time

5. Time-Based Resource-Sharing Model
Rapid switching
Processing Maintenance

6. Switching mechanism and decay
Possible reactivation
of memory traces CL
Truck R R R R Deer
CL
Truck R R R R Deer
CL
Truck R R R R Deer

7. Cognitive Load is
The proportion of time during which a given activity captures attention
in such a way that the refreshment of memory traces is impeded.
Duration of attentional capture
CL =
Total time allowed
The more difficult the switching, the higher the cognitive load.

8. A metric for Cognitive Load
In tasks involving retrievals from LTM
The number of retrievals n
Their difficulty a
(the time they occupy central processes)
The total time allowed to perform them T
aN
CL =
T

9. Cognitive Load
as 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

10. Cognitive Load
as 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

11. Rate of Processing
Manipulating the Number of Retrievals / Time ratio
The Reading Digit Span Task
R8
31 Read aloud the successive screens
64 and recall the letters
K7
25
49
L3
68
24

12. Rate of Processing
Manipulating the Number of Retrievals / Time ratio
Either 6 or 10 digits to be read
Constant duration of the interletter intervals (6 s)
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
6 Digits 10 Digits

13. Rate of Processing
Manipulating the Number of Retrievals / Time ratio
Fixed number of digits to be read
Either 600 or 1000 ms per digit
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
Slow Fast
1000 ms 600 ms

14. Rate of Processing
Manipulating the Number of Retrievals / Time ratio
Varying
the number of digits to be read
and the time allowed to read them
• Either 4, 8, or 12 digits during 6, 8, or 10 seconds
• 9 different values of the critical ratio (from 0.4 to 2)

15. Rate of Processing
6
5,5
5
4,5
4
3,5
3
2,5
r = .965
2
1,5
1
0 0,5 1 1,5 2 2,5
Number of retrievals / Time ratio
Barrouillet, Bernardin, & Camos, JEP:G, 2004

16. 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)

17. Rate of processing rather than complexity
Lépine, Bernardin, & Barrouillet, EJCP, 2005
4,5
4
3,5
WM span
3
2,5
2
1,5
1
RS self-paced RLS slow RLS fast
Reading letters can have the same detrimental effect on spans as reading complex sentences !

18. Cognitive Load
as 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

19. Duration of the atomic steps of processing
Slower retrievals
Central processes occupied for a longer period
Higher CL
LOWER SPANS

20. Duration of the atomic steps of processing
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 letters
1 digit per second

21. Duration of the atomic steps of processing
4,5
4
*
WM span
3,5
3
2,5
2
4 Four IV
Slower retrievals occupy central processes for longer periods
and involve higher cognitive load.

22. Cognitive Load
as 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

23. Nature of the processes involved
Bernardin, Portrat, & Barrouillet, in press
Two different groups are presented with the same display
G 8 but perform different activities:
5
6
Location
Parity 1 2 “ Up, up, down, down”
“ Even, odd, even, odd …”
Retrievals from LTM required
3
Lower spans predicted
P

24. Nature of the processes involved
Bernardin, Portrat, & Barrouillet, in press
4,5
4
3,5
*
3
WM span
2,5
2
1,5
1
0,5
0
Location Parity
Retrievals from LTM more demanding than location judgments

25. Nature of the processes or time ???
Parity judgments involve lower spans but …
they probably take also longer !

26. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
WM spans as a function of the actual processing time within the interletter interval
4 7 2
T 9 K
Stimulus onset Response
Parity RT
Actual Processing Time = Σ RT
Location

27. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
 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

28. Spans as a function of the number of stimuli
and the nature of the task
6
Location
5.5
5
4.5
Mean span
4
3.5
3
2.5
2
4 6 8
Number of stimuli

29. Spans as a function of the number of stimuli
and the nature of the task
6
Location
5.5
Parity
5
4.5
Mean span
4
3.5
3
2.5
2
4 6 8
Number of stimuli

30. Actual duration of processing as a function of
the task and number of stimuli
4
3.5
Location
Actual duration of processing
3
2.5
2
1.5
1
0.5
0
4 6 8
Number of stimuli

31. Actual duration of processing as a function of
the task and number of stimuli
4
3.5 Parity
Location
Actual duration of processing
3
2.5
2
1.5
1
0.5
0
4 6 8
Number of stimuli

32. Nature or duration of the processes involved?
6.5
6
Observed location spans
5.5
Mean Span
5
4.5
4
3.5
3
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)

33. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
6.5
6
5.5
Mean Span
5
4.5
4
3.5
3
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)

34. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
6.5
6
Predicted span values for a
5.5 location task thatobserved
Parity spans would take
longer
Mean Span
5
4.5
4
3.5
3
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)

35. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
6.5
Mean location span
6
5.23
5.5
Mean parity span observed
4.48
Mean Span
5
4.5
Mean span predicted
4.48
4
3.5
3
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)

36. Nature or duration of the processes involved?
Barrouillet, Portrat, Bernardin, & Camos, in prep.
6.5
Mean location span
6
5.23
5.5
Mean parity span observed
4.48
Mean Span
5
4.5
Mean span predicted
4
4.48
3.5
3
1.5 2 2.5 3 3.5 4
Actual Interletter Processing Time (sec)

37. 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

38. Thanks to
Sophie Bernardin
Raphaëlle Lépine
Nathalie Gavens
LEAD - CNRS Université de Bourgogne