Impact of the nature and the rhythm of the secondary task on working memory spans
Sophie Portrat
Sophie.Portrat@u-bourgogne.fr
Material and procedure
All subjects were presented with the same series of letters (French consonants) of ascending length (from 1 to 8 letters to be remembered).
There was 3 series of each length. Seven stimuli to be process appeared between two letters. This stimuli which are numbers (from 1 to 10) were randomly presented above or below a horizontal line centered on screen.
Each letter a ppeared for 1500 ms. The inter-letter interval was kept constant to 9000 ms during which each stimuli was displayed on screen for 600 ms irrespective of the condition. On the regular rhythm condition, inter-stimuli interval was kept constant to 600 ms. In contrast, delays, in the syncopated rhythm condition, keeping a 600 ms main duration, were randomly selected between eight different values. (Figure 1)
Concerning the secondary task, subjects were asked to answer for each stimuli by said aloud “odd” or “even” for the parity judgment condition and
“top” or “down” for the spatial judgment. Irrespective of the condition, subjects were asked to read aloud letters and to maintain them until the word “rappel” appeared. They had to recall aloud all the letters in correct order. The testing finished when subject fail to recall the letters of all three series of one length (stop rule).
Introduction
Working memory is a system devoted to the coordination between processing and storage. Working memory span tasks require participants to maintain items in short term memory while performing some concurrent processing. According to the Time-Based Resource-Sharing Model (Barrouillet, Bernardin, & Camos, 2004), both components of these tasks require attention, which is a limited capacity resource. Thus, some sharing is needed. As soon as attention is switched away from the memory items, their activation suffers from a time-related decay. The refreshing of the decaying memory traces necessitates their retrieval through an attentional focusing (Cowan, 1999). And, when the processing component requires retrievals from long term memory, sharing attention is time based because a central bottleneck allows only one retrieval at a time. So, retrieval should have the most detrimental effect on concurrent maintenance. In other words, because of (1) the time based decaying of the memory items when attention is turn away by the concurrent processing component, and (2) only one retrieval can be perform at a time, working memory task needs a rapid and incessant switching of the focus of attention during the processing component. Therefore, participants can used short free pauses between two consecutive items to be process in order to reactivate memory items. In the TBRS model, the cognitive load of a given processing task, and thus its effect on maintenance corresponds to the amount of attention it requires. Thus, the less a task lets possibility to switch attention on memory items, the more disrupting its effect should be on memory performance. Alternatively, it could be suggested that the strategies of maintenance are disrupted by the appearance of items to be concurrently processed. The aim of the present study is to contrast these two hypotheses about the locus of the detrimental effect of processing component on the maintenance of items.
Discussion
According to the TBRS Model, working memory task involving retrievals in long term memory have a more detrimental effect on maintenance than one involving simple response selection.
On the contrary, the rhythm of appearance of processing episodes had no impact on recall performances. This result was also in accordance with the TBRS Model. In fact, the detrimental effect of a given task is due to the nature of interruptions on activities of maintenance but not to the rhythm of these interruptions.
However, the two tasks we used differ on the nature but most probably also on duration. Thus, is the observed difference due to the nature or the duration of the concurrent processing ? Further studies are needed to test this hypotheses.
References
1. Barrouillet P., Berna rdin S. & Camos V. (2004). Time constraints and resource sharing in adults’ working memory span.
Journal of Experimental Psychology : General, 133, 83-100.
2. Cowan N. (1999). An embedded-process model of working memory. In A. Miyake & P. Shah (Eds), Models of working memory : Mechanisms of active maintenance and executive control (pp. 62-101). Cambridge : Cambridge University Press.
3. Kemps E., De Rammelaere S. & Desmet T. (2000). The development of working memory : Exploring the complementary of two models. Journal of Experimental Child Psychology, 77, 89-109.
Hypotheses
The present study compared working memory spans in two tasks, involving either some retrievals on long term memory (parity judgment) or simply response selection. Moreover, in each task, these processes have to be perform either at a regular or a syncopated rhythm.
According to the TBRS model :
• Working memory span task involving retrievals should induce lower spans than task with response selection.
• Working memory span should not be affected by the rhythm of the secondary task.
Design
Eighteen adults were randomly assigned to one of the 4 experimental conditions in a between-subject design.
The nature of the secondary task was either a spatial judgment (involving response selection) or a parity judgment task (involving response selection AND retrieval in memory). The rhythm of items to be performed appearance was either regular or syncopated.
The span was the series in which letters were correctly recalled divided by 3 (Kemps, De Rammelaere & Desmet, 2000).
Results
•According to TBRS model, mean span in parity judgment task (3.24) was significantly lower than in spatial judgment (4.24), F(1,76) = 13.05, p <
.001. This effect was significant both in the regular and syncopated rhythm (Ps < .01 and .05 respectively).
•However, the rhythm did not affect the mean span (syncopated : 3.59 vs regular : 3.89), F(1,16) = 1.17 ; p < .28. There was not interaction between rhythm and nature of the processing, F < 1
3,35
4,43
3,13
4,05
2 2,5 3 3,5 4 4,5 5
Parity Judgment Spatial Judgment
Secondary Task
Spans
Regular Rhythm Syncopated Rhythm
Figure 2: Mean spans as a function of the nature (parity vs.spatial judgment) and rhythm (regular vs. syncopated) of completion of the secondary task.
“Top”
“Even”
“Top”
“Even”
(b) (a)
“B”
Figure 1: Experimental design, at (a) regular and (b) syncopated rhythm.
8 7
3 5 6
< 1500 ms > < 600 ms >
< - - - 9000 ms - - - >
R 2 10 B
8 7
3 5 6
< 1500 ms >
R 2
< 600 ms >
< - - - 9000 ms - - - >
10 B
Letter to be read and maintain Stimuli to be judge either for parity or location
“B”
<600 ms>
