Asymmetric switch cost and backward inhibition: Carryover activation and inhibition in switching between tasks of unequal difficulty.

Asymmetric switch cost, observed when switching between tasks varying in difficulty, shows that the difference between repeat and switch trials is greater when switching to the easier task. Early explanations of this effect attributed this pattern to both positive priming of the difficult task and negative priming of the easier task, but more recent models have focused only on activation processes. The role of inhibition in asymmetric switch cost was examined using backward inhibition, a more direct measure of task-set inhibition. The results indicated asymmetric backward inhibition, with greater sequential inhibition of the easier task (i.e., easy-difficult-easy sequences). Switch costs, however, showed both typical and reversed asymmetry (greater cost when switching from the easy to the difficult task), depending on the relative difficulty of task pairs. This pattern of results indicates that switch costs are attributable to both activation and inhibition processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive control in set switching: Residual switch cost and task-set inhibition.

Executive processes necessary for flexible switching between different tasks were studied using a set switching paradigm that requires Ss to rapidly switch between different tasks across consecutive trials. Switch cost reflects poorer performance for task-switch trials than for consecutive same-task trials. 34 Ss (aged 18–48 yrs) participated in the study. Significant switch cost was observed even with considerable preparation time before a task-switch, an effect known as residual switch cost. The study tested the hypothesis that one process underlying residual switch cost is inhibition of the previous task-set. The authors used semantic categorization tasks to compare switch cost between alternating task series (ABA) and nonalternating series (ABC) in order to test the generality of a task-set inhibition effect previously observed with perceptual judgment tasks. The results yielded significant switch cost only for alternating tasks, in both response times and errors resulting from performance of the wrong task. Thus, resolving inhibition associated with previously abandoned task-sets may be the main process underlying residual switch costs, suggesting that task-set inhibition is an important executive control process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of recent practice on task switching.

Four experiments investigated the effect of recent selective practice on the cost of switching between 2 tasks afforded by letter-digit pairs: alphabet arithmetic and shape comparison. Experiments 1 and 2 found a greater cost associated with switching to the more recently practiced task: evidence that task-set inertia contributes to switching costs. Experiment 3 found this effect to be limited to trials on which a recently trained stimulus followed another such stimulus: a result problematic for all current theories of task-set priming. Experiment 4 showed that the effect of recent practice was eliminated by active preparation for a task switch: It appears that endogenous task-set preparation reduces the effects of task-set inertia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of repetition and foreknowledge in task-set reconfiguration.

To examine the roles of executive control and automatic activation in task switching, we manipulated foreknowledge as well as task transitions. In Experiments 1 and 2, performance with foreknowledge was faster than performance with no foreknowledge, but the amount of switch cost did not depend on foreknowledge. This result suggests that switch costs primarily reflect persisting activation rather than inadequate preparation. In Experiment 3, switch cost was greater with foreknowledge about task transitions alone than with foreknowledge about both task transition and identity, suggesting that foreknowledge about specific task identity did allow preparation for a switched task. We argue that task repetition and foreknowledge effects are independent. Although foreknowledge allows preparation for both repeated and switched tasks, repeating the same task has benefits over task switching regardless of foreknowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling Task Switching Without Switching Tasks: A Short-Term Priming Account of Explicitly Cued Performance.

Switch costs in task switching are commonly attributed to an executive control process of task-set reconfiguration, particularly in studies involving the explicit task-cuing procedure. The authors propose an alternative account of explicitly cued performance that is based on 2 mechanisms: priming of cue encoding from residual activation of cues in short-term memory and compound cue retrieval of responses from long-term memory. Their short-term priming account explains the repeated cue encoding benefit, switch cost, reduction in switch cost with preparation time, and other effects. The authors develop a mathematical model of their priming account and fit it to data from 3 experiments, demonstrating that a set of basic psychological processes can produce several effects--including putative switch costs--without switching tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in task switching.

Age differences in 2 components of task-set switching speed were investigated in 118 adults aged 20 to 80 years using task-set homogeneous (e.g., AAAA…) and task-set heterogeneous (e.g., AABBAABB…) blocks. General switch costs were defined as latency differences between heterogeneous and homogeneous blocks, whereas specific switch costs were defined as differences between switch and nonswitch trials within heterogeneous blocks. Both types of costs generalized over verbal, figural, and numeric stimulus materials; were more highly correlated to fluid than to crystallized abilities; and were not eliminated after 6 sessions of practice, indicating that they reflect basic and domain-general aspects of cognitive control. Most important, age-associated increments in costs were significantly greater for general than for specific switch costs, suggesting that the ability to efficiently maintain and coordinate 2 alternating task sets in working memory instead of 1 is more negatively affected by advancing age than the ability to execute the task switch itself. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of response repetition in task switching.

When switching between tasks, participants are sometimes required to use different response sets for each task. Thus, task switch and response set switch are confounded. In 5 experiments, the authors examined transitions of response within a linear 4-finger arrangement. A random baseline condition was compared with the cuing of specific response subsets grouped by hand or by finger equivalence, and these subsets were examined in both single task and task-switching designs. Results showed that part of the task switch cost is associated with switching between response sets. Furthermore, the analysis revealed a novel effect: When task switching and repetition trials are mixed, a bias towards switching the response and/or hand is found in task repetition trials. Response repetition is hindered when a task switch is expected, even for those trials when a switch of task does not occur. The results demonstrate executive processes involved in task set configuration closely depend on the motoric processing of the response set. The results are also important for current theories of task set control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control and interference in task switching—A review.

The task-switching paradigm offers enormous possibilities to study cognitive control as well as task interference. The current review provides an overview of recent research on both topics. First, we review different experimental approaches to task switching, such as comparing mixed-task blocks with single-task blocks, predictable task-switching and task-cuing paradigms, intermittent instructions, and voluntary task selection. In the 2nd part, we discuss findings on preparatory control mechanisms in task switching and theoretical accounts of task preparation. We consider preparation processes in two-stage models, consider preparation as an all-or-none process, address the question of whether preparation is switch-specific, reflect on preparation as interaction of cue encoding and memory retrieval, and discuss the impact of verbal mediation on preparation. In the 3rd part, we turn to interference phenomena in task switching. We consider proactive interference of tasks and inhibition of recently performed tasks indicated by asymmetrical switch costs and n-2 task-repetition costs. We discuss stimulus-based interference as a result of stimulus-based response activation and stimulus-based task activation, and response-based interference because of applying bivalent rather than univalent responses, response repetition effects, and carryover of response selection and execution. In the 4th and final part, we mention possible future research fields. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating the components of switch cost using two-to-two cue–task mapping.

In the task switch paradigm, a switch of task is typically accompanied by a change in task cue. It has been proposed that the performance deficit usually observed when switching tasks is actually the result of changing cues. To test this possibility, we used a 2:2 cue–task mapping in which each cue indicated 2 different tasks. With advance presentation of a cue, the cost associated with changing cues disappeared, though a substantial task switch cost remained. Without advance cues, the relative contributions of task switch cost and cue change cost differed by transition frequencies. The results suggest that task execution contributes to switch cost independent of cue changes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The dissipating task-repetition benefit in cued task switching: Task-set decay or temporal distinctiveness?

Decay of task-set activation, as commonly assumed in models of task switching, has been thought to be indexed by manipulating the response-to-cue interval (RCI) in a task-cuing paradigm. We propose an alternative account for RCI effects suggesting that episodic task retrieval is modulated by temporal distinctiveness, which we define as the ratio between previous RCI and current RCI. In Experiment 1, increasing RCI decreased the task-repetition benefit, but the slope of the RCI function depended on the range of RCIs rather than on the absolute duration of the RCI. In Experiment 2, the RCIs were blocked or random, and in Experiment 3, trial-wise predictability of RCIs was manipulated. RCI influenced the task-repetition benefit only when RCI changed from the previous to the current trial. Experiment 4 used two cues for each task and dissociated cue-repetition priming from task-repetition priming, suggesting that it is episodic task-set retrieval that is influenced by temporal distinctiveness. We discuss theoretical implications for persisting-task-set-activation theories and the relation to long-term decay, inhibition, and temporal preparation in task switching. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Task-set switching and long-term memory retrieval.

The authors tested the hypothesis of a close relationship between the intentional component of task-set switching ("advance reconfiguration;" R. D. Rogers & S. Monsell, 1995) and long-term memory (LTM) retrieval. Consistent with this hypothesis, switch costs are reported to be larger when the switched-to task involves high retrieval demands (i.e., retrieval of episodic information) than when it involves low retrieval demands (i.e., retrieval of semantic information). In contrast, switch costs were not affected by a primary-task difficulty manipulation unrelated to intentional retrieval demands (Experiment 2). Also, the retrieval-demand effect on switch costs was eliminated when time for advanced preparation or task cues explicitly specifying the task rules were provided (Experiment 3). Overall, results were consistent with the hypothesis that the intentional switch-cost component reflects the time demands of retrieving appropriate task rules from LTM. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic and intentional activation of task sets.

Four experiments examined automatic and intentional activation of task sets in a switching paradigm. Experiment 1 demonstrated incidental task sequence learning that was not accompanied by verbalizable task sequence knowledge. This learning did not affect task shift cost and may be attributed to automatic task-set activation. In Experiment 2, both shift cost and learning effect increased when the response–cue interval was short, indicating the influence of residual, persisting activation of the preceding task set. In Experiment 3, learning disappeared with a long cue–stimulus interval (CSI), which resulted in a strong preparation effect. This preparation, however, reduced reaction time level but was not specific to task shifts. Finally, experiment 4 showed that a within-subject CSI variation also leads to reduced shift costs. Together, the data suggest an activational account of task preparation and may have relevant implications for inhibitory accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cue-independent task-specific representations in task switching: Evidence from backward inhibition.

The compound-cue model of cognitive control in task switching explains switch cost in terms of a switch of task cues rather than of a switch of tasks. The present study asked whether the model generalizes to Lag 2 repetition cost (also known as backward inhibition), a related effect in which the switch from B to A in ABA task sequences is costlier than is the same switch in CBA task sequences. The model suggests that Lag 2 repetition cost should be absent from A′BA task sequences, in which A′ and A are different cues for the same task. The cost is robust on such sequences, which suggests that cue-independent, task-specific representations are necessary for explaining task-switching performance and that the compound-cue model has limited explanatory power. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hierarchical control of cognitive processes: Switching tasks in sequences.

[Correction Notice: An erratum for this article was reported in Vol 136(2) of Journal of Experimental Psychology: General (see record 2007-06470-005). Two task transitions were classified incorrectly in Table 7 (p. 634). Two task transitions were classified incorrectly in Table 7 (p. 634). The task transition at Serial Position 1 for sequence switches of the AABB sequence should be TR instead of TS. The task transition at Serial Position 1 for sequence switches of the ABBA sequence should be TS instead of TR. Two sections of text in the Results and Discussion section of Experiment 4 were affected by the misclassifications. The corrected text is provided for the Error rate analysis section (pp. 634-635) and the RT analysis section (p.635). These corrections do not alter any of the conclusions drawn from the original text.] Hierarchical control of cognitive processes was studied by examining the relationship between sequence- and task-level processing in the performance of explicit, memorized task sequences. In 4 experiments, switch costs in task-switching performance were perturbed by sequence initiation times that varied with sequence complexity, preparation time, and type of sequence transition (repetition or switch). Hierarchical control was inferred from these sequence initiation time effects and the recurrent finding of no switch cost at the first serial position across sequences, the point at which sequence-level processes are likely active in maintaining or instantiating a hierarchical control structure in working memory. These findings resonate with past research on motor programs and serial memory and provide new insights into the concepts of task set and control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increasing the difficulty of response selection does not increase the switch cost.

Several theories of task switching assume that basic task processes such as stimulus identification and response selection do not contribute to task-switch costs. This conclusion is mainly based on the finding that stimulus-identification manipulations have no influence on the size of the switch cost. The present study tested the influence of response-selection manipulations on the size of the switch cost. The authors manipulated the difficulty of response selection by using a semantically based response-side effect that is associated with numerical-judgement tasks, namely the Spatial Numerical Association of Response Codes (SNARC) effect. The authors observed a SNARC effect and a switch cost, but no interaction between the two: the task-switch cost did not differ between SNARC-compatible and -incompatible responses. The authors conclude that response selection does not contribute to the switch cost on the current trial, which provides further support for the idea that basic task processes and task-switch processes are separate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short cue presentations encourage advance task preparation: A recipe to diminish the residual switch cost.

In the task-switching literature, it has frequently been demonstrated that although advance task preparation reduces the switch cost, it never really eliminates the switch cost. This remaining residual switch cost received much attention, and it has been argued that advance preparation is restricted in nature. In the present study, the role of task-cue presentation in the establishment of the residual switch cost was investigated. In 4 experiments, the cue was removed during the preparation interval, and it was hypothesized that this would encourage participants to complete advance task preparation. The results of all 4 experiments provided support for this hypothesis: When the cue was presented for a short time and then removed, the residual switch cost completely disappeared. This was found for different cue types. Furthermore, Experiment 3 demonstrated that it was not the presence of the cue itself but merely differences in advance task preparation that caused the effects. This suggests that advance task preparation is not as restricted in nature as previously assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task preparation and task repetition: Two-component model of task switching.

The switch cost (the disadvantage of performing a new task vs. a repeated task) has been attributed to lack of preparation for the switched task or priming of the repeated task. These sources were examined by manipulating foreknowledge of task transition (repeat or switch), response-to-stimulus interval (RSI), and practice level. Regardless of foreknowledge, the cost decreased with RSI and practice. The reduction was greater with foreknowledge than with no foreknowledge, and the amount of switch cost did not depend on foreknowledge. These results suggest that the switch cost with foreknowledge may consist of both inadequate preparation and repetition benefit but the switch cost with no foreknowledge may reflect repetition benefit only. An ACT-R (adaptive control of thought-rational) model was proposed, accommodating both preparation and priming effect with 2 independent processes: conflict resolution among productions and decay of chunk activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task-set reconfiguration and perceptual processing: Behavioral and electrophysiological evidence.

Oriet and Jolic?ur (2003) proposed that an endogenous task-set reconfiguration process acts as a hard bottleneck during which even early perceptual processing is impossible. We examined this assumption using a psychophysiological approach. Participants were required to switch between magnitude and parity judgment tasks within a predictable task sequence while event-related potentials (ERPs) were recorded. Stimulus contrast and response stimulus interval (RSI) were manipulated. Behavioral data demonstrated typical task switch costs that decreased as RSI increased. However, whereas ERP analysis of visual ERP component latencies sensitively revealed the contrast effect, a switch-specific postponement of perceptual processing during task-set reconfiguration at short RSIs was not observed. The present findings indicate that the process of task-set reconfiguration does not constitute a hard bottleneck that delays perceptual processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Correction to Schneider and Logan (2006).

Reports an error in "Hierarchical Control of Cognitive Processes: Switching Tasks in Sequences" by Darryl W. Schneider and Gordon D. Logan (Journal of Experimental Psychology: General, 2006[Nov], Vol 135[4], 623-640). Two task transitions were classified incorrectly in Table 7 (p. 634). The task transition at Serial Position 1 for sequence switches of the AABB sequence should be TR instead of TS. The task transition at Serial Position 1 for sequence switches of the ABBA sequence should be TS instead of TR. Two sections of text in the Results and Discussion section of Experiment 4 were affected by the misclassifications. The corrected text is provided for the Error rate analysis section (pp. 634-635) and the RT analysis section (p.635). These corrections do not alter any of the conclusions drawn from the original text. (The following abstract of the original article appeared in record 2006-20327-009.) Hierarchical control of cognitive processes was studied by examining the relationship between sequence- and task-level processing in the performance of explicit, memorized task sequences. In 4 experiments, switch costs in task-switching performance were perturbed by sequence initiation times that varied with sequence complexity, preparation time, and type of sequence transition (repetition or switch). Hierarchical control was inferred from these sequence initiation time effects and the recurrent finding of no switch cost at the first serial position across sequences, the point at which sequence-level processes are likely active in maintaining or instantiating a hierarchical control structure in working memory. These findings resonate with past research on motor programs and serial memory and provide new insights into the concepts of task set and control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)