Differential effects of articulatory suppression on cue-switch and task-switch trials in random task cueing with 2:1 mapping

Recent studies have revealed that verbal representations play an important role in various task-switching situations. This study examined whether verbal representations contribute to the actual switching process using random task cueing with two cues per task. This procedure allowed us to produce a trial in which the cue switched, but the task repeated, thereby separating the cue-switching process from the actual task-switching process. Participants performed colour or shape judgements that were initiated by an arbitrary symbol cue (Experiments 1 and 2) or a kanji cue (Experiment 3) under control, articulatory-suppression, and foot-tapping conditions. In Experiments 1 and 2 with the arbitrary cues, articulatory suppression impaired performance in only the cue-switch condition. In Experiment 3, in which a kanji cue indicated the upcoming task name, articulatory suppression did not have any effects. These results suggest that the involvement of verbal representations in random task cueing is based on the cue-switching process rather than on the task-switching process.     

Effects of response-stimulus interval manipulation and articulatory suppression on task switching

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.     

Effects of response–stimulus interval manipulation and articulatory suppression on task switching

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.     

Verbal representation in task order control: An examination with transition and task cues in random task switching

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.     

Differential effects of cue changes and task changes on task-set selection costs

A task-switching paradigm with a 2:1 mapping between cues and tasks was used to separate cue-switching processes (indexed through pure cue-switch costs) from actual task-switching processes (indexed through additional costs in case of cue and task changes). A large portion of total switch costs was due to cue changes (Experiments 1 and 2), and cue-switch costs but not task-switch costs were sensitive to effects of practice (Experiment 1) and preparation (Experiment 2). In contrast, task-switch costs were particularly sensitive to response-priming effects (Experiments 1 and 2) and task-set inhibition (Experiment 3). Results suggest two processing stages relevant during task-set selection: cue-driven retrieval of task rules from long-term memory and the automatic application of rules to a particular stimulus situation.     

Separating cue encoding from target processing in the explicit task-cuing procedure: are there "true" task switch effects?

Six experiments were conducted to separate cue encoding from target processing in explicitly cued task switching to determine whether task switch effects could be separated from cue encoding effects and to determine the nature of the representations produced by cue encoding. Subjects were required to respond to the cue, indicating which cue was presented (Experiments 1, 3a, and 4a) or which task was cued (Experiments 2, 3b, and 4b), before performing the cued task on the target. Cue encoding was successfully separated from target processing when the cue response indicated which task was cued but not when it indicated which cue was presented. Task switch effects were found when this separation was successful, suggesting that there are "true" task switch effects independent of cue encoding. Analysis of the conditions required for successful separation suggested that cue encoding results in a semantic categorical representation of the task to be performed rather than verbal or phonological representations of individual cues. Implications for the authors' past modeling of task-switching performance are discussed.     

The surface structure and the deep structure of sequential control: What can we learn from task span switch costs?

A large component of response time switch costs in the cued task-switching paradigm is linked to cue changes without task changes, suggesting costs might reflect passive priming rather than endogenous control. In contrast, the task span procedure requires subjects to guide task selection via sequences of memorized task cues and therefore may be better suited to reflect endogenous switch processes (Logan, 2004). The present experiments combined the task span procedure with a 2:1 mapping between cues and tasks, allowing separation of cue-switch costs from true task-switch costs. Replicating findings with the cued task-switching paradigm, results showed both substantial cue-switch costs and actual task-switch costs (Experiments 1 and 2) as well as sensitivity of cue-switch costs, but not of task-switch costs, to opportunity for preparation (Experiment 2). Apparently, simple action plans use “surface level” phonological or articulatory codes that contain no task information. These results suggest that the distinction between cue-related and task-related processes is critical no matter whether tasks are cued exogenously or endogenously.     

Effect of articulatory suppression on task‐switching performance: Implications for models of working memory

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.     

Cognitive control in cued task switching with transition cues: Cue processing,task processing,and cue–task transition congruency

We investigated the processes underlying performance during cued task switching with transition cues. To this end, transition cueing and explicit cueing were compared in a design controlling for sequential effects in the two preceding trials in order to further examine the contribution of cue processes, task processes, and cue–task transition congruency during transition cueing. The study confirmed that the task-switch cost in transition cueing is larger than the task-switch cost in explicit cueing and showed that this larger switch cost is mainly due to cue processing. We also successfully decomposed performance in transition cueing into cue processing, task processing, and cue–task transition congruency on both a theoretical (Experiment 1) and an empirical basis (Experiments 2–3). Our empirical dissociation also demonstrates that cue–task transition congruency affects performance during both cue processing and task processing. We discuss the importance of our findings in relation to the different theories on task switching.     

Effect of articulatory suppression on task-switching performance: implications for models of working memory

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.     

On the role of verbalization during task set selection: Switching or serial order control?

Recent task-switching work in which paper-and-pencil administered single-task lists were compared with task-alternation lists has demonstrated large increases in task-switch costs with concurrent articulatory suppression (AS), implicating a crucial role for verbalization during switching (Baddeley, Chincotta, & Adlam, 2001; Emerson & Miyake, 2003). Experiment 1 replicated this result, using computerized assessment, albeit with much smaller effect sizes than in the original reports. In Experiment 2, AS interference was reduced when a sequential cue (spatial location) that indicated the current position in the sequence of task alternations was given. Finally, in Experiment 3, switch trials and no-switch trials were compared within a block of alternating runs of two tasks. Again, AS interference was obtained mainly when the endogenous sequencing demand was high, and it was comparable for no-switch and switch trials. These results suggest that verbalization may be critical for endogenous maintenance and updating of a sequential plan, rather than exclusively for the actual switching process.     

The effects of advance location cueing on latencies in a single-letter recognition task

Summary This study investigates facilitating effects of foreknowledge of position in single-letter recognition tasks with latency as the dependent variable. Three kinds of cue are used: symbolic cues, location cues and neutral cues. For the effects of symbolic and location cues the following predictions are derived from the literature: increasing benefits with increasing SOAs for symbolic cues and constant benefits with increasing SOAs for location cues.Cue-detection times and letter-recognition times with the different cues were determined in three experiments. In the experiments the same general paradigm was used. In Experiment 1 cue-detection times appeared to differ as a function of cue eccentricity; in Experiments 2 and 3 cues were adjusted in such a way that cue-detection times were about the same. Cues reliably indicated the target position in Experiments 1 and 2; in Experiment 3 cue validity was reduced to 50%.The cueing results conformed partly to the predictions. All experiments suggested a small benefit under symbolic cueing and a larger benefit under location cueing. Except for the smallest SOA used, for both types of cue benefits were invariant over SOAs. The implications of these results in relation to other single-letter recognition studies are briefly discussed.     

The role of item similarity in part-list cueing impairment

The presentation of a subset of studied items as retrieval cues can have detrimental effects on recall of the remaining (target) items. In three experiments we examined whether such part-list cueing impairment depends on the similarity between cue and target items. Item similarity was manipulated by making use of pre-experimental semantic similarities between cue and target items (Experiments 1 and 2), or was episodically induced through a similarity-encoding task, in which participants were asked to interrelate cue and target items in a meaningful way (Experiment 3). In all three experiments reliable part-list cueing impairment arose when the similarity between cues and targets was low, but no impairment was found when the similarity between cues and targets was high. Inhibitory as well as non-inhibitory explanations of the findings are discussed.     

The impact of verbal instructions on goal-directed behaviour

It is common to use verbal instructions when performing complex tasks. To evaluate how such instructions contribute to cognitive control, mixing costs (as a measure of sustained concentration on task) were evaluated in two task-switching experiments combining the list and alternating runs paradigms. Participants responded to bivalent stimuli according to a characteristic explicitly defined by a visually presented instructional cue. The processing of the cue was conducted under four conditions across the two experiments: Silent Reading, Reading Aloud, Articulatory Suppression, and dual mode (visual and audio) presentation. The type of cue processing produced a substantial impact on the mixing costs, where its magnitude was greatest with articulatory suppression and minimal with reading aloud and dual mode presentations. Interestingly, silently reading the cue only provided medium levels of mixing cost. The experiments demonstrate that relevant verbal instructions boost sustained concentration on task goals when maintaining multiple tasks.     

Interactions Between Exogenous Auditory and Visual Spatial Attention

Six experiments were carried out to investigate the issue of cross-modality between exogenous auditory and visual spatial attention employing Posner's cueing paradigm in detection, localization, and discrimination tasks. Results indicated cueing in detection tasks with visual or auditory cues and visual targets but not with auditory targets (Experiment 1). In the localization tasks, cueing was found with both visual and auditory targets. Inhibition of return was apparent only in the within-modality conditions (Experiment 2). This suggests that it is important whether the attention system is activated directly (within a modality) or indirectly (between modalities). Increasing the cue validity from 50% to 80% influenced performance only in the localization task (Experiment 4). These findings are interpreted as being indicative for modality-specific but interacting attention mechanisms. The results of Experiments 5 and 6 (up/down discrimination tasks) also show cross-modal cueing but not with visual cues and auditory targets. Furthermore, there was no inhibition of return in any condition. This suggests that some cueing effects might be task dependent.     

Attentional capture by items that match episodic long-term memory representations

A remarkable ability of the human visual system is the implementation of attentional control settings (ACSs) that govern what stimuli capture or hold attention. We provide evidence that ACSs can be specified by episodic long-term memory representations. In all experiments, participants memorized 30 images of objects that they then monitored for in an attention task, inducing an episodic-based ACS. In Experiments 1a and 1b, only studied cues in a cueing task captured attention. We confirmed these cueing effects reflect capture by testing for inhibition of return in Experiment 2a, and controlled for perceptual masking by cues in Experiment 2b. In Experiment 3 we determined that ACSs are specifically supported by episodic retrieval, by dividing studied images into two sets and designating one as the targets in a rapid serial visual presentation task: Only target-set matching distractors produced a spatial blink (captured attention). These results extend our understanding of the representations specifying ACSs.     

Inner speech as a retrieval aid for task goals: the effects of cue type and articulatory suppression in the random task cuing paradigm

Articulatory suppression has been shown to increase switch costs in the list paradigm (e.g., [J. Exp. Psychol.: General 130 (2001) 641, J Memory Language 48 (2003) 148]). The present dual-task study examined whether this effect generalizes to the random task cuing paradigm. Participants performed color or shape judgments according to explicit word cues (COLOR or SHAPE) or less transparent letter cues ( C for the color task and S for the shape task). In the word cue condition, the switch cost was equivalent for the articulatory suppression and the control (no dual-task) conditions, but, in the letter cue condition, the switch cost was significantly greater for the articulatory suppression condition than for the control condition. These results suggest that inner speech may be recruited as a tool for retrieving and activating the relevant task goal when the task cue is not transparent and hence imposes nonnegligible retrieval demand.     

Masked stimuli modulate endogenous shifts of spatial attention

Unconscious stimuli can influence participants’ motor behavior but also more complex mental processes. Recent research has gradually extended the limits of effects of unconscious stimuli. One field of research where such limits have been proposed is spatial cueing, where exogenous automatic shifts of attention have been distinguished from endogenous controlled processes which govern voluntary shifts of attention. Previous evidence suggests unconscious effects on mechanisms of exogenous shifts of attention. Here, we applied a cue-priming paradigm to a spatial cueing task with arbitrary cues by centrally presenting a masked symmetrical prime before every cue stimulus. We found priming effects on response times in target discrimination tasks with the typical dynamic of cue-priming effects (Experiments 1 and 2) indicating that central symmetrical stimuli which have been associated with endogenous orienting can modulate shifts of spatial attention even when they are masked. Prime–Cue Congruency effects of perceptual dissimilar prime and cue stimuli (Experiment 3) suggest that these effects cannot be entirely reduced to perceptual repetition priming of cue processing. In addition, priming effects did not differ between participants with good and poor prime recognition performance consistent with the view that unconscious stimulus features have access to processes of endogenous shifts of attention.     

The homophone effect in semantic access tasks using kanji words: its relation to the articulatory suppression effect

The present study examined whether articulatory suppression influences homophone effects in semantic access tasks using Japanese kanji words. In Experiment 1, participants were required to decide whether visually presented word pairs were synonyms. This experiment replicated the homophone effect observed in previous research that showed more false positive errors in response to nonsynonym homophone pairs than to controls. The present study found that this homophone effect was also obtained under an articulatory suppression condition. In Experiment 2, participants performed a semantic decision task, in which they had to judge whether a visually presented target word was an exemplar of a definition that was shown immediately before presentation of the target word. The homophone effect observed in previous studies was replicated--that is, longer response times and more false positive errors were associated with homophones of correct exemplars than with nonhomophone control words. This homophone effect was also obtained under an articulatory suppression conditions. These results suggest that the phonological processing that produces the homophone effects in semantic access tasks using Japanese kanji words does not include articulatory mechanisms.     

Suppression effects on musical and verbal memory

Three experiments contrasted the effects of articulatory suppression on recognition memory for musical and verbal sequences. In Experiment 1, a standard/comparison task was employed, with digit or note sequences presented visually or auditorily while participants remained silent or produced intermittent verbal suppression (saying "the") or musical suppression (singing "la"). Both suppression types decreased performance by equivalent amounts, as compared with no suppression. Recognition accuracy was lower during suppression for visually presented digits than during that for auditorily presented digits (consistent with phonological loop predictions), whereas accuracy was equivalent for visually presented notes and auditory tones. When visual interference filled the retention interval in Experiment 2, performance with visually presented notes but not digits was impaired. Experiment 3 forced participants to translate visually presented music sequences by presenting comparison sequences auditorily. Suppression effects for visually presented music resembled those for digits only when the recognition task required sensory translation of cues.