Task-switching Costs Research Articles

The Effects of Foreknowledge and Task-Set Shifting as Mirrored in Cue- and Target-Locked Event-Related Potentials

The present study examined the use of foreknowledge in a task-cueing protocol while manipulating sensory updating and executive control in both, informatively and non-informatively pre-cued trials. Foreknowledge, sensory updating (cue switch effects) and task-switching were orthogonally manipulated in order to address the question of whether, and to which extent, the sensory processing of cue changes can partly or totally explain the final task switch costs. Participants responded faster when they could prepare for the upcoming task and if no task-set updating was necessary. Sensory cue switches influenced cue-locked ERPs only when they contained conceptual information about the upcoming task: frontal P2 amplitudes were modulated by task-relevant cue changes, mid-parietal P3 amplitudes by the anticipatory updating of stimulus-response mappings, and P3 peak latencies were modulated by task switching. Task preparation was advantageous for efficient stimulus-response re-mapping at target-onset as mirrored in target N2 amplitudes. However, N2 peak latencies indicate that this process is faster for all repeat trials. The results provide evidence to support a very fast detection of task-relevance in sensory (cue) changes and argue against the view of task repetition benefits as secondary to purely perceptual repetition priming. Advanced preparation may have a stronger influence on behavioral performance and target-locked brain activity than the local effect of repeating or switching the task-set in the current trial.

Covert judgements are sufficient to trigger subsequent task-switching costs

This research examines whether we have a tendency to repeat mental processes leading to decisions or judgements that are not accompanied by overt behaviours. We adapted the task-switching paradigm so that on selected trials task processing would be terminated prior to response execution. Switch costs were present subsequent to trials where task processing was terminated either at the stage of response selection or at the earlier stage of making a covert judgement (a mental decision) about the target stimulus. These costs were residual, as they occurred despite long preparation intervals, and they did not result from cue-switching or feature-repetition effects. We conclude that the same type of control mechanism may be recruited to select between potential alternative tasks whenever a stimulus needs to be processed in a task-specific way, regardless of whether or not an overt response is required.

Task-switching costs promote the evolution of division of labor and shifts in individuality.

From microbes to humans, the success of many organisms is achieved by dividing tasks among specialized group members. The evolution of such division of labor strategies is an important aspect of the major transitions in evolution. As such, identifying specific evolutionary pressures that give rise to group-level division of labor has become a topic of major interest among biologists. To overcome the challenges associated with studying this topic in natural systems, we use actively evolving populations of digital organisms, which provide a unique perspective on the de novo evolution of division of labor in an open-ended system. We provide experimental results that address a fundamental question regarding these selective pressures: Does the ability to improve group efficiency through the reduction of task-switching costs promote the evolution of division of labor? Our results demonstrate that as task-switching costs rise, groups increasingly evolve division of labor strategies. We analyze the mechanisms by which organisms coordinate their roles and discover strategies with striking biological parallels, including communication, spatial patterning, and task-partitioning behaviors. In many cases, under high task-switching costs, individuals cease to be able to perform tasks in isolation, instead requiring the context of other group members. The simultaneous loss of functionality at a lower level and emergence of new functionality at a higher level indicates that task-switching costs may drive both the evolution of division of labor and also the loss of lower-level autonomy, which are both key components of major transitions in evolution.

Processing of representations in declarative and procedural working memory

The article investigates the relation between declarative and procedural working memory (WM; Oberauer, 2009). Two experiments test the assumption that representations in the two subsystems are selected for processing in analogous ways. Participants carried out a series of decisions on memorized lists of digits. For each decision, they had to select declarative and procedural representations. Regarding declarative representations, participants selected a memory set and a digit within this set as the input to each decision. With respect to the procedural representations, they selected a task set to be applied to the selected digit and a response within that task set. We independently manipulated the number of lists and the number of tasks to be switched among (one, two, or three; Experiment 1) and preparation time for a list switch (Experiment 2). For three effects commonly observed in task-switch studies, analogues in declarative WM were found: list-switch costs, mixing costs, and residual switch costs. List- and task-switch costs were underadditive, suggesting that declarative and procedural representations are selected separately and in parallel. The findings support the hypothesis of two analogous WM subsystems.

Investigating task and modality switching costs using bimodal stimuli

Investigations of concurrent task and modality switching effects have to date been studied under conditions of uni-modal stimulus presentation. As such, it is difficult to directly compare resultant task and modality switching effects, as the stimuli afford both tasks on each trial, but only one modality. The current study investigated task and modality switching using bi-modal stimulus presentation under various cue conditions: task and modality (double cue), either task or modality (single cue) or no cue. Participants responded to either the identity or the position of an audio–visual stimulus. Switching effects were defined as staying within a modality/task (repetition) or switching into a modality/task (change) from trial n − 1 to trial n, with analysis performed on trial n data. While task and modality switching costs were sub-additive across all conditions replicating previous data, modality switching effects were dependent on the modality being attended, and task switching effects were dependent on the task being performed. Specifically, visual responding and position responding revealed significant costs associated with modality and task switching, while auditory responding and identity responding revealed significant gains associated with modality and task switching. The effects interacted further, revealing that costs and gains associated with task and modality switching varying with the specific combination of modality and task type. The current study reconciles previous data by suggesting that efficiently processed modality/task information benefits from repetition while less efficiently processed information benefits from change due to less interference of preferred processing across consecutive trials.

The interplay between learnt representations and asymmetries in task-switch costs.

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Decomposing task-switching costs with the diffusion model.

In four experiments, task-switching processes were investigated with variants of the alternating runs paradigm and the explicit cueing paradigm. The classical diffusion model for binary decisions (Ratcliff, 1978) was used to dissociate different components of task-switching costs. Findings can be reconciled with the view that task-switching processes take place in successive phases as postulated by multiple-components models of task switching (e.g., Mayr & Kliegl, 2003; Ruthruff, Remington, & Johnston, 2001). At an earlier phase, task-set reconfiguration (Rogers & Monsell, 1995) or cue-encoding (Schneider & Logan, 2005) takes place, at a later phase, the response is selected in accord with constraints set in the first phase. Inertia effects (Allport, Styles, & Hsieh, 1994; Allport & Wylie, 2000) were shown to affect this later stage. Additionally, findings support the notion that response caution contributes to both global as well as to local switching costs when task switches are predictable.

Can task-switching training enhance executive control functioning in children with attention deficit/-hyperactivity disorder?

The key cognitive impairments of children with attention deficit/-hyperactivity disorder (ADHD) include executive control functions such as inhibitory control, task-switching, and working memory (WM). In this training study we examined whether task-switching training leads to improvements in these functions. Twenty children with combined type ADHD and stable methylphenidate medication performed a single-task and a task-switching training in a crossover training design. The children were randomly assigned to one of two groups. One group started with the single-task training and then performed the task-switching training and the other group vice versa. The effectiveness of the task-switching training was measured as performance improvements (relative to the single-task training) on a structurally similar but new switching task and on other executive control tasks measuring inhibitory control and verbal WM as well as on fluid intelligence (reasoning). The children in both groups showed improvements in task-switching, that is, a reduction of switching costs, but not in performing the single-tasks across four training sessions. Moreover, the task-switching training lead to selective enhancements in task-switching performance, that is, the reduction of task-switching costs was found to be larger after task-switching than after single-task training. Similar selective improvements were observed for inhibitory control and verbal WM, but not for reasoning. Results of this study suggest that task-switching training is an effective cognitive intervention that helps to enhance executive control functioning in children with ADHD.

Minimal Age-Related Deficits in Task Switching, Inhibition, and Oculomotor Control

Background/Study Context: We are often required to carry out complex tasks in changing, context-dependent ways. This task switching requires the rapid realignment of attention to task constraints and may be age sensitive. Methods: Three experiments, two in which eye movements were recorded, were conducted to assess age-related differences in task switching and inhibitory control. Observers carried out a Same-Different task and Go-No Go task in single and mixed blocks of trials. Results: Other than Experiment 1, although switch costs were observed, they were not larger for older adults compared to younger adults. Furthermore, eye movement and false alarm data demonstrated little evidence of age-related decline in inhibitory and oculomotor control. Conclusions: A major implication is that, at least when two tasks involve different stimuli and unique responses, older adults are no more likely than younger adults to show task-switching costs or inhibition deficit.

The multiple-weighting-systems hypothesis: Theory and empirical support

Observers respond faster when the task-relevant perceptual dimension repeats across consecutive trials (e.g., color-color) relative to when it changes (orientation-color)-the phenomenon termed the dimension repetition effect (DRE). Similarly, when two (or more) different tasks are made to vary randomly across trials, observers are faster when the task repeats, relative to task changes-the phenomenon termed task-switch cost (TSC). Hitherto, the DRE and TSC effects have been discussed independently of each other. Critically, either effect was explained by assuming a single mechanism giving rise to DREs or TSCs. Here, we elaborate strong conceptual similarities between the DRE and TSC effects; we introduce the concept of criterion-specific intertrial sequence effects, with DREs and TSCs being different manifestations of criterion-specific effects. Second, we review available evidence suggesting that none of the single mechanism explanations can readily account for all the findings in the literature. Third, we elaborate on the multiple-weighting-systems (or MWS) hypothesis, a recently proposed account that postulates the existence of several, independent mechanisms sensitive to intertrial sequences. Finally, we test predictions derived from the MWS hypothesis in two novel experiments and discuss the results from both the single- and multiple-mechanism perspectives.

Adjustments of task-set control processes: Effect of task switch frequency on task-mixing and task-switching costs

The present study tested the hypothesis that task-switch frequency triggers adjustments of task-set control processes. A mixed-task condition where task switches are frequent should promote flexibility—thus improving task-switch performance—whereas a condition where task repetitions are more expected should favour stability—thus improving task-repeat performance. In two experiments, participants performed single-task and mixed-task blocks. In mixed-task blocks, tasks varied randomly on a trial-by-trial basis. For half of the mixed-task blocks, the frequency with which the task changed was 25%, for the other half, it was 50%. Overall, depending on the task-switch frequency, performance on both task-repeat and task-switch trials was modified. Switch cost was reduced and task-repeat performance was altered by the increase in switch probability. This study demonstrates context-sensitive adjustments of task-set control processes. These results further support the view that mixing cost reflects sustained and endogenous components of cognitive control.

Cost of Mental Set Reconfiguration between Digits and their Photisms in Synaesthesia

In this study we present an experiment investigating the reconfiguration process elicited by the task switching paradigm in synaesthesia. We study the time course of the operations involved in the activation of photisms. In the experimental Group, four digit-color synaesthetes alternated between an odd-even task and a color task (to indicate the photism elicited by each digit). In both tasks, the target stimuli were numbers between 1 and 9 written in white. One of the control groups ran the same tasks but this time with colored numbers (Naive Control Group). The results of these studies showed the expected pattern for the control group in the case of regular shift: a significant task switch cost with an abrupt offset and a cost reduction in long RSI. However for the experimental group, we found switch cost asymmetry in the short RSI and non-significant cost in the long RSI. A second control group performed exactly the same tasks as the experimental group (with white numbers as targets and a second imaginary color task) -Trained Control Group-. We found no cost for this second control group. This means that the cost of mental set reconfiguration between numbers (inducers) and their photisms (concurrent sensations) occurs, that there is a specific cost asymmetry (from photisms to inducers) and that this cost cannot be explained by associative learning. The results are discussed in terms of exogenous and endogenous components of mental set reconfiguration.

In Defense of Media Multitasking: No Increase in Task-Switch or Dual-Task Costs

In Defense of Media Multitasking: No Increase in Task-Switch or Dual-Task Costs

Reducing task switch cost with action video games

Reducing task switch cost with action video games

Does the Macaque Monkey Provide a Good Model for Studying Human Executive Control? A Comparative Behavioral Study of Task Switching

The ability to swiftly and smoothly switch from one task set to another is central to intelligent behavior, because it allows an organism to flexibly adapt to ever changing environmental conditions and internal needs. For this reason, researchers interested in executive control processes have often relied on task-switching paradigms as powerful tools to uncover the underlying cognitive and brain architecture. In order to gather fundamental information at the single-cell level, it would be greatly helpful to demonstrate that non-human primates, especially the macaque monkey, share with us similar behavioral manifestations of task-switching and therefore, in all likelihood, similar underlying brain mechanisms. Unfortunately, prior attempts have provided negative results (e.g., Stoet & Snyder, 2003b), in that it was reported that macaques do not show the typical signature of task-switching operations at the behavioral level, represented by switch costs. If confirmed, this would indicate that the macaque cannot be used as a model approach to explore human executive control mechanisms by means of task-switching paradigms. We have therefore decided to re-explore this issue, by conducting a comparative experiment on a group of human participants and two macaque monkeys, whereby we measured and compared performance costs linked to task switching and resistance to interference across the two species. Contrary to what previously reported, we found that both species display robust task switching costs, thus supporting the claim that macaque monkeys provide an exquisitely suitable model to study the brain mechanisms responsible for maintaining and switching task sets.

Good Language-Switchers are Good Task-Switchers: Evidence from Spanish–English and Mandarin–English Bilinguals

Bilingual advantages in executive control tasks are well documented, but it is not yet clear what degree or type of bilingualism leads to these advantages. To investigate this issue, we compared the performance of two bilingual groups and monolingual speakers in task-switching and language-switching paradigms. Spanish-English bilinguals, who reported switching between languages frequently in daily life, exhibited smaller task-switching costs than monolinguals after controlling for between-group differences in speed and parent education level. By contrast, Mandarin-English bilinguals, who reported switching languages less frequently than Spanish-English bilinguals, did not exhibit a task-switching advantage relative to monolinguals. Comparing the two bilingual groups in language-switching, Spanish-English bilinguals exhibited smaller costs than Mandarin-English bilinguals, even after matching for fluency in the non-dominant language. These results demonstrate an explicit link between language-switching and bilingual advantages in task-switching, while also illustrating some limitations on bilingual advantages.

Evidence of reduced selective attention in schizotypal personality disorder

It has been shown that high-schizotypy and schizophrenic participants demonstrate increased task-switching costs, although high-schizotypy participants present this pattern only in incongruent trials (Cimino & Haywood, 2008). In this study, we aim to explore whether this results from difficulties in selective attention or task control. A total of 18 participants with high levels of psychometrically defined schizotypy and 16 participants with low scores were tested in two different versions of a task-switching paradigm. Participants were asked to switch between attending to the color or the shape of bidimensional objects following a previous cue. Two versions of the task were investigated, one involving only switches in the perceptual dimension to attend (color or shape) and another also switching the response set. High-schizotypy subjects consistently showed increased switch costs in incongruent trials for both versions of the tasks, demonstrating a deficit in the selection of the perceptual dimension instead of the selection of the response rules.

Complementary perspectives on cognitive control.

Complementary perspectives on cognitive control.

Regulated and Unregulated Forms of Cortisol Reactivity: A Dual Vulnerability Model

To test in a laboratory setting the hypothesis that the most problematic daily outcomes should be particular to individuals displaying higher cortisol reactivity and deficits in executive functioning as assessed in a task-switching paradigm. Thirty-eight volunteers completed a comprehensive assessment protocol. Individual differences in cortisol reactivity were quantified in an initial laboratory session involving a social stress speech task. Subsequently, individual differences in task-switching costs in a cognitive paradigm were assessed in a second session. Participants then reported on four problematic outcomes-error reactivity; worry; core aspects of negative emotionality; and aggression behavior frequency-for 15 consecutive days. Levels of cortisol reactivity did not predict task-switching costs. Instead, and as hypothesized, individual differences in cortisol reactivity and task-switching costs interacted to predict the problematic daily outcomes. The highest levels of such problematic outcomes were particular to high cortisol reactors also exhibiting greater task-switching costs. The findings support the dual vulnerability model proposed and are discussed from temperamental, health risk, and daily outcome perspectives. These findings indicate that cortisol is a risk factor, particularly when combined with deficiencies in task-switching.

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.