Academic journal article Memory & Cognition

Verbal Representation in Task Order Control: An Examination with Transition and Task Cues in Random Task Switching

Academic journal article Memory & Cognition

Verbal Representation in Task Order Control: An Examination with Transition and Task Cues in Random Task Switching

Article excerpt

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.

Goal-directed behavior is founded on mechanisms that select and execute an appropriate task set, using relevant stimulus and response features conformable to that goal (Mayr, 2003). The nature and functions of task sets have been intensively examined with a task-switching paradigm (Monsell, 2003), in which participants are required to repeat the same task or to switch from one task to another. Generally, performance in task switching is worse (i.e., requires more time and is less accurate) than that in task repetition (e.g., Allport, Styles, & Hsieh, 1994; Meiran, 1996; Rogers & Monsell, 1995). A large body of literature exists on the task-switching paradigm. However, in this study, we focused on a specific issue suggested by previous studies-namely, that verbal representations are useful mediators for efficient task-switching performance, especially in predictable and sequential task switching (Baddeley, Chincotta, & Adlam, 2001; Bryck & Mayr, 2005; Emerson & Miyake, 2003; Saeki & Saito, 2004a, 2004b; Saeki, Saito, & Kawaguchi, 2006).

One procedure that includes predictable and sequential task switching is the list paradigm, in which participants are required to repeat the same task or to switch between two tasks alternately in separate blocks (Jersild, 1927). The difference between reaction times (RTs) and errors in the task-switching block and those in the task repetition block is referred to as the alternation cost (Rubin & Meiran, 2005). Recent studies in which the list paradigm has been used have examined the role of verbal representations in task switching through an articulatory suppression technique, which requires participants to continuously articulate task-irrelevant words that interfere with their use of speech-based verbal representation. The findings showed that articulatory suppression increased the alternation cost only when an external switching cue was not presented (Baddeley et al., 2001; Emerson & Miyake, 2003; Saeki & Saito, 2004a); thus, articulatory suppression impaired performance in the switching block when participants had to maintain both current and future task information to alternately switch tasks. On the basis of these findings, it is assumed that verbal representations are usually used to maintain task information. More specifically, Baddeley et al. …

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