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