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Running head: Practice Effect on Dual Task Activties








The Effects of Practice on Dual Task Activities, Both With and Without Articulatory Suppression

Ingrid Campbell

The University of the West Indies, Mona




















            In order to assess the impact of practice on dual-task endeavours one experiment is described in which participants were asked to complete regular switching between addition and subtraction under practice condition with or without articulatory suppression. The results higlighted that the arithmetic list requiring switching showed more improvements than the blocked lists. Also the control group overall had greater improvements than the experimental. These imply that control group’s improvements can be accounted for by the process of task automatisation, As their task were easier to master than that of the experimental group.



Cognitive Psychology is primarily concerned with how the brain processes information. The field’s roots are planted in the 1950s in the same time period that Broadbent began  researching auditory attention, argued we are constantly presented with stimuli but because of the limited capacity which analyse incoming messages, a filter sifts through the messages, allowing only that which is deemed relevant to go on to higher order processing. Later Treisman using the shadow technique found participants could recall words from their unattended ear. This pushed her to argue that stimuli were not exactly filtered and disregarded, but were attenuated and as a result some of the “unattended” information would seep into higher order processing. Contrasting Broadbent’s and Treisman’s theories of early selection were Deutsch and Deutsch, who stated that all stimuli made it to higher order processing at which point selection—which is evidenced by the response we produce—takes place. Building on this foundation, other have sought to understand what conditions permits us to do more than one thing simultaneously. Wickens, McLeod, Treisman and Davies contend that when tasks differ significantly whether it be in their modalities, processing stage or even in the means of response, we are more likely to successfully complete the task because their [the task] differences ensure minimal interference. Secondly, Spelke, HIrst and Neisser in teaching two participants to take dictation while reading short stores for comprehension demonstrates that with enough practice even complex dual task can be mastered. Along with task similarity and practice dual task success also depends on the task difficulty. Duncan and Sullivan demonstrate that participants found it more challenging to complete a dual tasks activity when the tasks increased in difficulty (Eysenck & Keane, 2000).

With regards to memory psychologist have taken particular interest in short-term memory which processes incoming information or information in need of immediate attention. In 1974 Baddeley and Hitch proposed that this long standing idea be replaced with working memory. Their new model consisted of a phonological loop that stores information in a speech based patter; a visuo-spatial sketchpad that concentrated on storing information via imagery; and an unbound important central executive, which presides over both the loop and sketchpad. Baddeley and Hitch posit all components of the model have some amount of autonomy and limited capacity. Consequently when two tasks put demand on the same component simultaneously, this impairs the likelihood of successful completion. Baddeley and Hitch’s central executive component of working memory resembles attention very closely and it is mirrored in his assumption which resembles task similarity (ibid). 

            Based on this theory David Allport in 1994 conducted research requiring participants to switch between tasks. He claimed that indeed there is no central executive because regardless of how long the delay was between tasks there was always a switching cost. His claim renewed interest switching and In response Allport and others Baddelely, Chincotta and Adlam’s 2001 paper Working Memory and the Central Action Evidence From Task Switching, sought to better understand the function of working memory in tasks involving regular switching. Their study consisted of 7 experiments using Jersild’s list paradigm in which the switching condition involved alternating between adding and subtracting and the block condition required consecutive additions followed by consecutive subtraction. Their results showed that when the ‘+’ and ‘-’ signs are present articulatory suppression (the months of the year) had no significant effects on switching performance, yet when the signs were not present and participants had to rely, presumably, on the phonological loop performance slowed significantly. Though there was minor effect on the block task it was not as considerable as on the alternating task. Baddeley et al then sought to find out the impact of simple articulatory suppression (the) on switching tasks that required endogenous control. Surprisingly they found even simple articulatory suppression impaired performance on switching task. The then when on to test the effect of practice on the task and found that practice no significant differences between the groups

            We are primarily interested in determining the effect of practice on switching tasks with and without articulatory suppression. Allport contends that studies which show great improvement on complex dual tasks require skills that are usually highly practised and implying some amount of automatisation. Therefore the question remains how does articulatory suppression impact this improvement? In our experiment Jersild’s list paradigm was used to carry out both the switching condition—alternating between adding and subtracting—and the block task—consisting of consecutive additions which were followed by consecutive subtractions of ‘1’. The time it took participants to add or subtract ‘1’ from the column of single digits alone as well as while engaged in articulatory suppression was recorded.  Our basic design therefore requires participants to perform the block or alternating task either with or without articulatory suppression. Thus allowing us, via contrasting two conditions, to pinpoint the effect of practice both with and without the suppressive techniques

             All switching tasks were conducted under endogenous controls and such reason proposes the control group will show greater improvements than the experimental group. Similarly the switching condition will show more improvements than the block condition. Considering the nature of the task and the conditions it is suspected that there will be some amount of interaction between the conditions and the tasks, meaning some of the improvements registered will be dependent on whether they were performing the switching or the blocked task.



            The Participants were 33 undergraduate students who volunteered their time during the 8 and 9am tutorial session of a third year psychology course.



            The arithmetic task comprised of 7 list each consisting of 40 computations requiring ‘1’ to be either added (e.g. 6+1) or subtracted (e.g. 7-1) from single digits (1-9), which were selected at random.  Each sheet consisted of 8 columns, of 40 computations, with a line drawn through the middle to distinguish the upper half consisted solely of additional problems, while the lower half consisted of subtraction, for the block task. For the alternating condition computations within the column alternated between addition and subtraction for both halves.

            A time piece equipped with second time was used to measure task duration.



Fifteen participants were randomly assigned to the control group and likewise 18 to the experiment group. Both groups completed the arithmetic tasks while engaged in simple articulatory suppression. This condition required the participants to say aloud the, the, the at a one per second rate in time with a metronome, However, the control group completed the initial and final arithmetic task list while saying ‘the’ to the metronome but did not engage in articulatory suppression during the 5 trials in between. The experimental group did the arithmetic task along with the articulatory suppression for both the initial and final list, along with the 5 trials in between.

Participants worked in pairs. The experiments was carried out over a two week period where the first week, for both groups, one partner functioned as the experimenter while the other complete the computations while switching. In the second week the experimenter partner was now the participant partner completing the computation in the block manner.

 The participants were allowed enough practice in order to produce one ‘the’ per second in time with the mentronome for each of the arithmetic tasks that were performed along with articulatory suppression. After that which was deemed enough practice—about 6 thes—the experimenter gave the instruction GO which signalled the beginning of the task. Participants were watched closely and indicated when the last computation was completed.

The time taken to complete the arithmetic problem as measured with a time piece, while the number of errors on the secondary task, identified by an omission were recorded.


The timed data was collected and manipulated. It was shown that incorrect arithmetic and articulatory omission posed not significant effect on the results which are shown in Table 1.

Table 1. Time It Took  to Complete The Arithmetic Task For Initial and Final Runs and the Change in the two Conditions for the Control and Experimental Group for both Switching and Block Conditions.



Baseline (sec)

Outcome (sec)

Practice Effect (sec)

Control Group


120 (40)

79 (29)



50 (20)

36 (5)


Experimental Group


86 (34)

72 (26)



37 (5)

30 (5)



The large standard deviations for the baseline switching condition in both the control and experimental groups indicate their distributions would have a large overlap leaving us to infer that there is no statistically significant difference between the 120 (SD=40) and the 86(SD =34) seconds respectively . At the baseline the block computations for the control group, 50(SD=20)) seconds, was much slower than that of the 37(SD= 5) seconds of experimental group. Further representation of the change between the baseline and the outcome tasks is presented in Figure 1.


Figure 1. The Effects of Practice on Switching With and Without Articulatory Suppression

The result showed that the control group had far greater improvements in the time it took to complete the switching task that the experimental group. Where as the control group shaved 41(s) of their performance the experimental group only shaved 14(s) of their performance. The control group also outperformed the experimental group on the block task by a 7(s) differential. This suggests that articulator suppression greatly impairs performance improvement on the switching task and although there was some impairment on the block task it was not as sizable as in the switching task. The timed data was also submitted to an analysis of variance (ANOVA) of which the results are summarised in table 2.




Table 2: ANOVA Showing Main Effects of Condition and Task Along With The Interaction Between the them.




Condition (control vs. experiment)



Task (switch vs. block)



Interaction (condition x task)




Analysis illustrate significant main effects for the Condition, F(1, 29)= 4.88, p=0.03; therefore we deduce that the differences in the practice trials, whether articulatory suppression was used as concurrent tasks or not, produced significant differences in the time it took to complete the task on the final run. Equally so the main effects for the Task, F(1, 29)= 5.13, p=0.03, showed that there was significant differences between the alternating and block situation. On the other hand, though figure 1 seem to show that there is some interaction the interaction effect F(1,29) = 1.16, p = 0.21 showed that it was significant enough to constitute such. Therefore were infer that the differences between the control and the experimental group did not depend on whether it was a switching or block task being performed.


There was no significant difference between the control and the experimental group on the baseline switching task. However, the baseline block task for the control group was slower than the experimental counterpart. For both groups the switching task showed considerable improvements with practice while the block task did not improve as much. There were significant results for Level A—the condition—and Level B—the task—but not for the interaction between them.

The control group baseline block condition was particularly surprising because similar experiments conducted by Baddeley et al (2001) showed the baseline block task on both conditions were virtually indistinguishable. As we can see no other faults it is assumed that this development is simply a function of possible problems with the experimental conditions. We posit that the expected large improvements of the switching task as compared to the block task is as a result of the because of the block tasks relatively fast times from the outset leaving little room for improvement. 

            Also expected was the control group’s substantial improvements in comparison to the experimental group. Considering that the only difference between the them was whether or not the practice trial had involved simple articulatory suppression. This leads us to reason that the phonological loop had an important role in lists’ completion. Central Capacity theories would argue that for the control group the ‘plus, minus, plus, minus…’ sequence or even the one necessary switch for the block task did not put heavy burden on the loop’s capabilities. But that in the experimental condition where these were confounded with the the placed a heavy load on lists. This increase effort produces physiological arousal which I known to interfere with performance on unfamiliar tasks. Therefore by the time the participant in the experimental group got to the final arithmetic list he or she would be much less familiar with the list than those in the control group who had not the suppressive technique hinder the familiarity process. Modular Theories argue that similar between the loops way of keeping track of progress and the saying aloud of the leads to some amount of interference between the them. The control was able to perform the task without interference from the suppression. This unrestrained practice possibly, a As a result by the time the control group were once again faced with completing the task with suppression the arithmetic list had become somewhat engrained and unconscious that so that attention was not as divided as it was before the practice trials began. Both the central and modular theories contend that control group did much better with practice because they were allowed a certain level of familiarity with, automatisation or unconscious ingraining, of the arithmetic procedure that the experimental group was not afforded. As such the later’s potential move from controlled to automatic processing was greatly impaired by the constant confounding of the articulatory suppression with the ‘plus, minus, plus, minus…’ track in the loop.

The phonological loop’s activity of keeping track of the rapid changes in arithmetic procedures, produces inevitable cost (Allport, 1994), in our experiment this was evidenced by the huge time differential between the alternating and the block tasks.  

Surprisingly enough, the lack of interaction between the condition and the task is evidence that the difference in the control and experimental groups is not a consequence of whether it was the block or alternating task being performed.  The block task was placed in the experiment as to constant to ensure that it was the switching that was improving suggests to us that the switching in an of itself cannot account for the significant differences between the two conditions. Therefore we are left to infer that the differences of the two conditions (control and block) is a function of their differences in the practice trials.

            Our population of 33 participants only had 4 males. It is believed that men are more arithmetically inclined than females (Santrock, 2000). Even though our experiment was not measuring mathematical competencies, based on this assumptions the unequal gender distribution possibly produced larger mean scores than could have been. Therefore there exists the possibility that the tasks were slower than those a balanced population would produce. Using psychology students who are acutely aware of the experimental implications is one shortcoming of this study. It is believe that they are more concerned than the general public with producing the ‘right’ results leading to unnecessary levels of stress while completing the tasks and it is widely understood that high stress levels do confound test results. Futhermore in Baddeley et all (2001) they carried out practice trials before the baseline run to reduce the chances of participant settling down effect on his data. We employed no such measures so we can assume that there is some settling down effect contamination our data. The manner in which the experiment was set, whereby the experimenter one week was the participant the next may have confused the participant who had to perform the block task after one week of switching. This may have explin the slower than expected bloc task. There are several experimental conditions that may have posed a problem. Ideal testing condition dictate that participants be fully aware and wake, isolated and comfortable. In our experiment the control and experimental group were tested at 8 and 9 am respectively. This early session in which participant may have been a bit sleepy may also account for the slow time of the block task. Furthermore our experiment was conducted in an air conditioned free class room situated near vehicular and pedestrian traffic. We can only speculate how much of these environmental variable had seeped their way into our data. On the other hand out experiment ensured that no one person did any two task therefore reducing—not eliminating--the chances of over learning any one procedure resulting in tainted results

The concluded study has found out that it does not require extended practice to produce automatisation of simple task. However the more difficult a task is or becomes the longer automatisation takes to occur.  We believe that next step is to determine how much practice is necessary on varying specified tasks to produce a stage of complete automatic responses to these said tasks.


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