Can the task-cuing paradigm measure an endogenous task-set reconfiguration process?

In 6 task-cuing experiments, with 2 cues per task, the authors varied cue-stimulus interval to investigate G. D. Logan and C. Bundesen's (2003) claim that when cue repetition is controlled for, task-switch cost and its reduction with preparation are largely eliminated and hence cannot index an endogenous control process. Experiment 1 replicates their result, but Experiments 2 and 3, with similar designs, demonstrate a substantial task-switch cost, reducing with increasing cue-stimulus interval. Experiments 4 to 6 show that the critical difference is the probability of a task change: If it is kept low enough to discourage reconfiguration of task set unless and until the cue signals a task change, robust evidence for anticipatory task-set reconfiguration is obtained, even in Experiment 6, modeled closely on Logan and Bundesen's. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Task-switching performance with 1:1 and 2:1 cue–task mappings: Not so different after all.

When task-switching studies use the task-cuing procedure with a 1:1 cue–task mapping, task switching and cue switching are confounded, which is problematic for interpreting switch costs. The use of a 2:1 cue–task mapping is a potential solution to this problem, but it is possible that introducing more cues may also introduce marked changes in task-switching performance. In 5 experiments involving 160 subjects, the authors compared performance with 1:1 and 2:1 mappings across several methodological changes. Differences in switch costs between mappings were small and, in most analyses, nonsignificant. In all experiments, both mappings yielded significant reductions in switch cost across cue–target interval, and there were significant cue-switching effects with the 2:1 mapping. A model of cue encoding fit the data from both mappings about equally well. Overall, task-switching performance was more similar than it was different between mappings, leading the authors to suggest that the use of a 2:1 mapping is a viable solution to the problem associated with a 1:1 mapping. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Response Selection Difficulty and Asymmetrical Costs of Switching Between Tasks and Stimuli: No Evidence for an Exogenous Component of Task-Set Reconfiguration.

Four task-switching experiments examined the notion of an exogenous component of task-set reconfiguration (i.e., a process needed to shift task set that is not initiated in the absence of a task-associated figuration stimulus). The authors varied the complexity and familiarity of stimulus-response (SR) mapping rules to produce differentially time-consuming reconfiguration demands. Tasks with more complex or less familiar rules did not display increased switch costs, given that stimulus repetitions were excluded from the analysis. These results do not support the idea of exogenous reconfiguration. Moreover, stimulus repetitions inflated task-switch costs and did so disproportionately for tasks with increased response selection difficulty, thereby demonstrating that insufficient control of the sequence of stimuli may yield results that mimic those predicted by exogenous reconfiguration accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task switching versus cue switching: Using transition cuing to disentangle sequential effects in task-switching performance.

Recent methodological advances have allowed researchers to address confounds in the measurement of task-switch costs in task-switching performance by dissociating cue switching from task switching. For example, in the transition-cuing procedure, which involves presenting cues for task transitions rather than for tasks, cue transitions (cue switches and cue repetitions) and task transitions (task switches and task repetitions) can be examined in a complete factorial design. Transition cuing removes the confound between cue transitions and first-order task transitions, but it introduces a confound between cue transitions and longer task sequences. In the present study, transition cuing was studied with two cues per transition (REPEAT and AGAIN for task repetitions; SWITCH and CHANGE for task switches), enabling a partial deconfounding of cue transitions and task sequences. Two experiments revealed robust sequential effects, with higher order task transitions affecting performance when cue transitions were held constant and with cue transitions affecting performance when task sequences were held constant. Methodological and theoretical implications of these findings for research on task switching are discussed. (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)     

Focal/nonfocal cue effects in prospective memory: Monitoring difficulty or different retrieval processes?

We investigated whether focal/nonfocal effects (e.g., Einstein et al., 2005) in prospective memory (PM) are explained by cue differences in monitoring difficulty. In Experiment 1, we show that syllable cues (used in Einstein et al., 2005) are more difficult to monitor for than are word cues; however, initial-letter cues (in words) are similar in monitoring difficulty to word cues (Experiments 2a and 2b). Accordingly, in Experiments 3 and 4, we designated either an initial letter or a particular word as a PM cue in the context of a lexical decision task, a task that presumably directs attention to focal processing of words but not initial letters. We found that the nonfocal condition was more likely than the focal condition to produce costs to the lexical decision task (task interference). Furthermore, when task interference was minimal or absent, focal PM performance remained relatively high, whereas nonfocal PM performance was near floor (Experiment 4). Collectively, these results suggest that qualitatively different retrieval processes can support prospective remembering for focal versus nonfocal cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heightened conflict in cue-target translation increases backward inhibition in set switching.

Backward inhibition (BI) is a performance cost that occurs when an individual returns to a task after 1 (vs. more than 1) intervening trial, and it may reflect the inhibition of task-set components during switching. In 3 experiments, we support the theory that inhibition can target cue-based preparatory stages of a task. Participants performed a cued target-localization task that had been previously shown to produce BI. In Experiment 1, reassignment of arbitrary cue-target pairings midway through the experiment doubled the size of BI, though cue, target, and response sets remained unchanged. In Experiment 2, we controlled for effects of order of conditions or simple change of cue meaning. In Experiment 3, we demonstrated that the effect depends on re-pairing members of the same cue and target sets. The results are attributed to heightened conflict (and hence greater inhibition) during cue-target translation when a previously learned cue-target mapping is remapped. (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)     

Changes in executive control across the life span: Examination of task-switching performance.

A study was conducted to examine changes in executive control processes over the life span. More specifically, changes in processes responsible for preparation and interference control that underlie the ability to flexibly alternate between two different tasks were examined. Individuals (N?=?152) ranging in age from 7 to 82 years participated in the study. A U-shaped function was obtained for switch costs (i.e., the time required to switch between tasks compared with a repeated-task baseline), with larger costs found for young children and older adults. Switch costs were reduced with practice, particularly for children. All age groups benefited from increased preparation time, with larger benefits observed for children and older adults. Adults benefited to a greater extent than children when the interval between the response to one task and the cue indicating which task to perform next was lengthened, which suggested faster decay of interference from the old task set for adults than for children. A series of hierarchical analyses indicated that the age-related variance in task-switching performance is independent, at least in part, from the age-related variance in other cognitive processes such as perceptual speed and working memory. The results are discussed in terms of the development and decline of executive control processes across the life span. (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)     

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)     

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. (PsycINFO Database Record (c) 2010 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)     

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)     

Can Practice Overcome Age-Related Differences in the Psychological Refractory Period Effect?

Can dual-task practice remove age-related differences in the psychological refractory period (PRP) effect? To answer this question, younger and older individuals practiced 7 blocks of a PRP design, in which Task 1 (T1) required a vocal response to an auditory stimulus and Task 2 (T2) required a manual response to a visual stimulus (Experiment 1). The results showed that practice did not reduce, but rather increased, age-related differences in PRP interference. Using the trained individuals, the introduction of a less complex new T1 (Experiment 2) or a less complex new T2 (Experiment 3) with the task previously practiced reduced the PRP interference but only in older adults. The authors propose that older adults suffer from a large task-switch cost that is more sensitive to task complexity than to the amount of practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is there semantic interference in delayed naming?

The semantic interference effect in the picture–word interference task is interpreted as an index of lexical competition in prominent speech production models. Janssen, Schirm, Mahon, and Caramazza (2008) challenged this interpretation on the basis of experiments with a novel version of this task, which introduced a task-switching component. Participants either named the picture or read the word, depending on the word's color. Janssen et al. reported semantic interference in picture naming, regardless of whether the word appeared simultaneously with the picture (immediate naming) or 1,000 ms after the picture (delayed naming). Because picture name retrieval is completed in less than 1,000 ms, the finding in delayed naming was taken as evidence against the lexical competition account. In 3 sets of experiments conducted in German and English, we tested for semantic effects in Janssen et al.'s task-switching version and in the standard picture–word interference task. Using identical materials, we obtained sizeable interference effects in the standard task (Experiments 2, 4, and 6) but no effects in the task-switching version (Experiments 1, 3, and 5). When the word reading trials of the task-switching version were replaced with no-go trials (Experiment 7), semantic interference reemerged in immediate naming but was still absent in delayed naming. The experiments question the reliability of Janssen et al.'s critical finding and suggest that theoretical inferences about the origin of semantic effects in the standard picture–word interference task based on results from the task-switching version used by Janssen et al. are difficult to draw. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Task switching: Interplay of reconfiguration and interference control.

The task-switching paradigm is being increasingly used as a tool for studying cognitive control and task coordination. Different procedural variations have been developed. They have in common that a comparison is made between transitions in which the previous task is repeated and transitions that involve a change toward another task. In general, a performance switch cost is observed such that switching to a new task results in a slower and more error-prone execution of the task. The present article reviews the theoretical explanations of the switch cost and the findings collected in support of those explanations. Resolution and protection from interference by previous events explain part of the switching cost, but processes related to task setting and task preparation also play a prominent role, as testified by faster execution and lower switch costs when the preparation time is longer. The authors discuss the evidence in favor of each of these sets of accounts and raise a number of questions that situate task switching in a broader context of cognitive control processes. The role of several aspects of the task set, including task variations, task-set overlap, and task-set structure, is addressed, as is the role of knowledge about probability of task changes and about the structure of task sequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating cue-related and task-related processes in task inhibition: Evidence from using a 2:1 cue-to-task mapping.

Performance of task sequences is assumed to rely on activation and inhibition of tasks. An empirical marker of task inhibition is the so-called n - 2 repetition cost, which is assessed by comparing performance in trial n - 2 task repetitions (i.e., ABA) with that in n - 2 task switches (i.e., CBA). Current theoretical accounts assume that inhibition acts on the level of task representations (i.e., task sets). However, another potential target of task inhibition could be the representation of the task cue. To decide between these two alternatives, the authors used a 2:1 cue-to-task mapping design. They found significant n - 2 task repetition costs both with n - 2 cue repetitions and n - 2 cue switches. These costs were about equal (Experiment 1), and this data pattern was found for both short and long cuing intervals (Experiment 2). Together, the data suggest that task inhibition acts on task sets and not on cue representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sticky Rules: Integration Between Abstract Rules and Specific Actions.

The authors manipulated repetitions and/or changes of abstract response rules and the specific stimulus- response (S-R) associations used under these rules. Experiments 1 and 2, assessing trial-to-trial priming effects, showed that repetition of complete S-R couplings produced only benefits when the rule also repeated (i.e., rule-S-R conjunctions) but costs when identical S-R couplings repeated while rules changed. In Experiments 3 and 4, the authors manipulated amount of experience with specific rule-S-R conjunctions and demonstrated integration between rules and S-R couplings in terms of cumulative practice effects. However, unlike short-term priming effects, cumulative practice supported generalization of experience with specific S-R couplings across rule boundaries (Experiment 4). Results are discussed in terms of constraints on models of hierarchical control and in terms of qualitatively different ways in which people profit from very recent experiences (i.e., all-or-none access to working memory representations) versus cumulative experience (i.e., similarity-based retrieval from long-term memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Voluntary Task Switching: Chasing the Elusive Homunculus.

In the voluntary task switching procedure, subjects choose the task to perform on a series of bivalent stimuli, requiring top-down control of task switching. Experiments 1-3 contrasted voluntary task switching and explicit task cuing. Choice behavior showed small, inconsistent effects of external stimulus characteristics, supporting the assumption of top-down control of task choice. Switch costs were smaller when subjects chose to switch tasks than when instructed by an external cue. Experiments 4-6 separated choice costs from switch costs. These findings support models of task switching that incorporate top-down processes in accounts of switch costs. The degree to which task switching procedures capture top-down versus bottom-up processes may depend on the extent of environmental support provided by the procedure. (PsycINFO Database Record (c) 2011 APA, all rights reserved)