Task-set reconfiguration suspends perceptual processing: Evidence from semantic priming during the attentional blink.

When two visual targets, Target 1 (T1) and Target 2 (T2), are presented among a rapid sequence of distractors, processing of T1 produces an attentional blink. Typically, processing of T2 is markedly impaired, except when T1 and T2 are adjacent (Lag 1 sparing). However, if a shift of task set-a change in task requirements from T1 to T2-occurs, this sparing is reduced substantially. With a semantic priming technique, in which T1 could be either related or unrelated to T2, the priming of T2 by T1 diminished markedly at Lag 1, when the transition between T1 and T2 involved a switch in either location (Experiments 1 and 2) or task (Experiment 3), but remained unaffected at other lags. These results suggest that perceptual processing of T2 cannot be carried out in parallel with task-set reconfiguration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does Task-Set Reconfiguration Create Cognitive Slack?

C. Oriet and P. Jolicoeur (see record 2003-08747-016) reported 2 experiments in which the perceptual contrast of stimuli was manipulated in a task-switching paradigm. They failed to observe an interaction in the reaction time data between task switching, perceptual contrast, and response-stimulus interval. Using the locus of slack logic, they concluded from these results that early perceptual processing of stimuli awaits the completion of a task-set reconfiguration stage, rather than proceeding in parallel with it. Here, an assumption necessary for this argument is questioned, and it is shown that an existing computational model of task switching, without successive stages for task-set reconfiguration and perceptual processing, produces a similar pattern of data. Thus, C. Oriet and P. Jolicoeur's data are compatible with models in which early perceptual processing and task-set reconfiguration take place in parallel. (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)     

Stimulus-based priming of task choice during voluntary task switching.

Two voluntary task-switching experiments probed the influence of previous exposures to stimuli and categorizations of these stimuli on task choice during subsequent exposures to the same stimuli. Subjects performed origin and size judgments under standard voluntary task-switching instructions to perform the tasks equally often in a random order. Both when subjects voluntarily selected the task on the first exposure (Experiment 1) and when the experimenter manipulated the task on the first exposure (Experiment 2), subjects chose to perform the same task on subsequent exposures significantly more often than would be expected on the basis of the instructions to perform tasks in a random order. Presentation of a previously encountered stimulus may result in the retrieval of a stimulus–task binding or event file that biases task selection as well as task readiness. The pattern of data across the 2 experiments suggests that stimulus-based priming influences task choice through both retrieval of episodes within the context of the experiment and semantic memory mechanisms. (PsycINFO Database Record (c) 2010 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)     

The target of task switching.

Task switching involves processing target stimuli in accordance with a frequently changing series of tasks. An outstanding issue is whether this processing is tailored to the perceptual or categorical representation of targets. To address this issue, the authors compared switch costs in responding to targets that were perceptually distinct (words and images) but associated with the same categories (colors and shapes). In four experiments that varied the degree to which words and images were mixed together, no differences in switch costs were observed. These results support the idea that categorical target representations are central to task switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Still clever after all these years: Searching for the homunculus in explicitly cued task switching.

Many researchers interpret switch costs in the explicit task-cuing procedure as reflecting endogenous task-set reconfiguration. G. D. Logan and C. Bundesen (2003; see record 2003-05350-006) challenged this interpretation empirically and theoretically. They argued that many experiments confounded cue encoding benefits with switch costs and they showed that unconfounded switch costs could be vanishingly small. They proposed a theory in which subjects use a single task set in the explicit task-cuing procedure and switch costs reflect cue encoding benefits, not reconfiguration. S. Monsell and G. A. Mizon (2006; see record 2006-08586-001) responded to these challenges, describing conditions under which substantial switch costs could be observed in the explicit task-cuing procedure and providing a theoretical account of performance in which reconfiguration occurred in G. D. Logan and C. Bundesen's experiments. This article is a response to S. Monsell and G. A. Mizon's challenge that highlights empirical problems with their evidence and reports an experiment that challenges critical assumptions of their theoretical account. (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)     

Context-sensitive adjustments of cognitive control: Conflict-adaptation effects are modulated by processing demands of the ongoing task.

Dynamic adjustments of cognitive control in response to interference from irrelevant stimulus attributes have repeatedly been shown. The purpose of the current research was to investigate how these control adjustments are modulated by the processing demands of a primary task. To this end, the authors combined a primary task (a number comparison task: classifying digits as smaller or larger than 5) with a Simon task. Control adjustments were observed in the form of typical sequential modulations of the Simon effect. In addition, the authors found sequential modulations of the numerical distance effect and an interaction of both effects. Results suggest that not only response conflict due to interference from task-irrelevant features but also processing demands of task-relevant features determine the level of control adjustment in the subsequent trial. (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)     

Distinguishing between the partial-mapping preparation hypothesis and the failure-to-engage hypothesis of residual switch costs.

Lien, Ruthruff, Remington, & Johnston (2005) reported residual switch cost differences between stimulus–response (S–R) pairs and proposed the partial-mapping preparation (PMP) hypothesis, which states that advance preparation will typically be limited to a subset of S–R pairs because of structural capacity limitations, to account for these differences. Alternatively, the failure-to-engage (FTE) hypothesis does not allow for differences in probability of advance preparation between S–R pairs within a set; it accounts for residual switch cost differences by assuming that benefits of advance preparation may differ between S–R pairs. Three Experiments were designed to test between these hypotheses. No capacity limitations of the type assumed by the PMP hypothesis were found for many participants in Experiment 1. In Experiments 2 and 3, no evidence was found for the dependency of residual switch cost differences between S–R pairs on response-stimulus interval that is predicted by the PMP hypothesis. Mixture-model analysis of reaction times distributions in Experiment 3 provided strong support for the FTE hypothesis over the PMP hypothesis. Simulation studies with a computational implementation of the FTE hypothesis showed that it is able to account in great detail for the results of the present study. Together, these results provide strong evidence against the PMP hypothesis and support the FTE hypothesis that advance preparation probabilistically fails or succeeds at the level of the task set. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How to correct a task error: Task-switch effects following different types of error correction.

It has been proposed that switch costs in task switching reflect the strengthening of task-related associations and that strengthening is triggered by response execution. The present study tested the hypothesis that only task-related responses are able to trigger strengthening. Effects of task strengthening caused by error corrections were considered. Recent findings suggest that errors lead to erroneous task strengthening, which, however, can be reversed by immediate error correction (Steinhauser & Hübner, 2006). In three experiments, the present study examined whether this effect is also obtained when task responses and correction responses share the same response categories but are assigned to different hands or different response modalities (manual vs. vocal). Results indicated that only corrections with the same hand but not corrections with the alternative hand or a different response modality can reverse erroneous task strengthening. These results suggest that only the execution of task-related responses triggers task strengthening, whereas the activation of task-related response categories is not sufficient. (PsycINFO Database Record (c) 2010 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)     

Executive control of cognitive processes in task switching.

In 4 experiments, participants alternated between different tasks or performed the same task repeatedly. The tasks for 2 of the experiments required responding to geometric objects in terms of alternative classification rules, and the tasks for the other 2 experiments required solving arithmetic problems in terms of alternative numerical operations. Performance was measured as a function of whether the tasks were familiar or unfamiliar, the rules were simple or complex, and visual cues were present or absent about which tasks should be performed. Task alternation yielded switching-time costs that increased with rule complexity but decreased with task cuing. These factor effects were additive, supporting a model of executive control that has goal-shifting and rule-activation stages for task switching. It appears that rule activation takes more time for switching from familiar to unfamiliar tasks than for switching in the opposite direction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dot pattern expectancy task: Reliability and replication of deficits in schizophrenia.

The dot pattern expectancy (DPX) task was created to efficiently assess context-processing deficits in patients with schizophrenia. Three studies investigated the characteristics of the DPX relevant for clinical applications. To answer questions regarding the psychometric properties of the task, performance on this task was studied in 2 healthy samples. Acceptable reliability and internal consistency and retest reliability were found for most measures of context processing, but not for a difficulty control condition. These characteristics were also found in a suggested brief version (DPXbrf), which may be more practical for clinical purposes. In a 3rd study, schizophrenia patients showed a specific deficit in context processing, replicating previous findings. Findings of these studies indicated some promise for use of this task in measuring context processing and also identified characteristics of this task that need to be strengthened to increase reliability, feasibility, and single-subject interpretability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control Over the Time Course of Cognition in the Tempo-Naming Task.

Five experiments are reported in which standard naming and tempo-naming tasks were used to investigate mechanisms of control over the time course of lexical processing. The time course of processing was manipulated by asking participants to time their responses with an audiovisual metronome. As the tempo of the metronome increased, results showed that (a) the rate of lexical errors increased, whereas the rate of regularization errors remained constant; (b) onset errors increased at a faster rate than body errors; (c) stimulus effects weakened on latencies, whereas they strengthened on durations and errors; and (d) naming durations decreased more slowly when stimuli were presented prior to the response cue. These results constitute evidence that time pressure in the tempo-naming task caused a compression in the time course of lexical processing. Compression is discussed in terms of threshold mechanisms and rate mechanisms of control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)