In a series of experiments, we examine some effects of articulatory suppression in task switching. The results from Experiments 1a and 2a showed that switch costs in the articulatory suppression condition were larger than those in the control and tapping conditions when the switching cues were not provided. On the other hand, articulatory suppression did not have any effect on switch costs in Experiments 1b and 2b, where the switching cues were provided. In Experiment 3, using a computer-assisted experimentation, this pattern of data was replicated in a two-factor design with articulatory suppression and switching cues factors. The results indicate that a specific component in working memory, the phonological loop, might contribute to the performance in task switching, at least in situations where the external task cues were not available. The data reported here suggest that the phonological loop plays an important role in one of the executive control processes, and challenge the traditional idea that the slave systems are simply governed by the central executive in the working memory.

Recent task-switching studies in which a predictable task sequence has been used have indicated that verbal representation contributes to the control of task order information. The present study focused on the role of verbal representation in sequential task decisions, which are an important part of task order control, and examined the effects of articulatory suppression in a random-task-cuing paradigm with two different types of cues presented just before the presentation of a stimulus: a transition cue and a task cue. The former cue provided information only about switching or repeating the task, whereas the latter was associated directly with the identity of the task (i.e., indicating a parity or a magnitude task). In Experiment 1, in which transition cues guided task sequences, articulatory suppression impaired performance in both repetition and switch trials, thereby increasing the mixing costs. In Experiment 2, in which a task cue, rather than a transition cue, was presented to examine the influence of a cue-decoding process, articulatory suppression had no specific effect on task performance. Experiment 3, in which the transition cue and the task cue were randomly presented in the same block to equalize the memory load and task strategy for the two types of cues, confirmed that articulatory suppression significantly increased the mixing costs only in transition cue trials. The results from the three experiments indicated that the use of verbal representation is effective in sequential task decision-that is, in selecting a task set on the basis of transient task order information in both repetition and switch trials.

We examined the role of the phonological loop in task switching performance in a prevalently used research paradigm, that is, the alternating runs paradigm. This paradigm basically requires participants to alternate tasks on every second trial (i.e., AABBAABB). In this study, participants were required to alternate the letter and numerical decision tasks in cue-present and cue-absent conditions under control, articulatory suppression and foot tapping conditions. The results showed that error rates were larger and reaction times were longer in the articulatory suppression condition than in the control and tapping conditions for both switch and nonswitch trials in two cue conditions. These findings indicate that the phonological loop contributes to task performance not only in the switching trials but also in situations where the maintenance of task sequence information is required.

We conducted three experiments using a list paradigm to examine how articulatory suppression and response-stimulus interval (RSI) manipulation affected task switching. Experiments 1 and 2 tested task-switching performance under a short and long RSI and three concurrent task conditions (control, articulatory suppression, and tapping) without external task cues. The results indicated that alternation had a greater effect under articulatory suppression than under the control and tapping conditions, and that articulatory suppression costs were unrelated to the RSI. In Experiment 3, an external task cue was provided with each stimulus, and the negative effect of articulatory suppression on alternation cost was eliminated. These results indicated that articulatory suppression effects did not differ between conditions of short and long RSI and that the availability of verbal representations of task information was independent of RSI length. This paper discussed the possible roles played by the phonological loop in task-switching paradigms.

This paper considers the effect of articulatory suppression on a number-size consistency task to investigate the involvement of the phonological loop in situations involving potential interferences from task-irrelevant stimulus attributes. Participants were shown pairs of digits varying in numerical and physical sizes, and they were required to decide which digit was larger numerically or physically in the numerical-size and physical-size judgment tasks, respectively. Participants in the continuous-task group only performed the numerical-size judgment task. On the other hand, participants in the change-task group practiced the physical-size judgment task and then performed the numerical-size judgment task. The results showed that articulatory suppression had a negative effect on reaction time in the numerical-size judgment task only in the change-task group. This suggests that the phonological loop provides a useful aid for the control of action when participants are faced with interference in a difficult situation of maintaining the task goal.