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It is well-known that alcohol impairs behavioral control and motor response inhibition, but it has remained rather unclear whether it also impairs cognitive inhibition. As automatized behavior is less vulnerable towards the detrimental effects of alcohol than cognitive control processes, potential cognitive inhibition deficits might however improve with training. We investigated the effect of an acute, binge-like alcohol intoxication in a balanced within-subjects design, asking n=32 healthy young males to perform a backward inhibition paradigm once sober and once while intoxicated (~1.1 ‰). To identify the underlying neurophysiological mechanisms, we analyzed stimulus- and response selection-related processes in neurophysiological data after Residue Iteration Decomposition (RIDE). Alcohol generally impaired behavioral task performance (accuracy and response times) during task switching. This was associated with impaired attentional processing of the task-relevant cue (reflected by reduced P1 and N1 amplitudes), which likely resulted in a larger need for reactive control at the later stage of response selection and control (reflected by increased fronto-central theta power). Without prior practice (~30 minutes), the intoxicated participants further struggled to overcome the cognitive inhibition of a previously relevant task set (reflected by a larger backward inhibition effect). This was linked to reduced posterior theta power, which reflects alcohol-induced impairments in working memory capacity and task set-relevant memory retrieval. As individuals with ~30 min task practice did not show the same alcohol-related deficit, it may be deduced that (partial) task set automatization via stimulus-response associations may help to reduce the detrimental effects of alcohol on cognitive inhibition during task switching.

Perseverative cognition (PC), that is, the continuous cognitive representation of uncontrollable threats, is known to dampen executive control processes in experimental paradigms. Similarly, PC has been shown to impair sleep and to be implicated in the exacerbation of insomnia, which may in turn contribute to the disruption of executive functions. The interactions between PC and insomnia in influencing executive functions, however, have never been tested to date. In the present study, we explored whether insomnia symptoms may moderate the associations between PC and disrupted executive functions, with the hypothesis to find a stronger relationship between these variables at increasing levels of insomnia. Fifty participants completed measures of trait PC and insomnia severity in the previous month and also completed a computerized task-switching paradigm assessing backward inhibition, switch cost, and accuracy. Prior to the task switching, participants completed a measure of state rumination in order to control for the effects of state PC on cognitive performance. Results show that trait PC was significantly correlated with higher insomnia symptoms and state rumination and marginally correlated with lower backward inhibition and longer switch cost. Moreover, insomnia severity moderated the relationship between trait PC and backward inhibition after controlling for the effects of state rumination; that is, the relationship between PC and inhibitory deficits was stronger in those with higher versus lower levels of insomnia symptoms. Findings suggest the need to better elucidate the associations between PC, insomnia, and executive functioning in clinical samples and longitudinal designs.

Ignoring or withholding a response from a stimulus causes it to become affectively devalued. Leading accounts posit that this is due to negative affect elicited by neurocognitive inhibition when it is applied to resolve conflict from distracting or otherwise inappropriate stimulus/response representations. Other research, however, suggests that stimulus/response conflict may itself elicit negative affect and devalue stimuli, raising questions about whether effects previously attributed to inhibition may instead reflect the emotional impact of conflict, per se. To address this, we measured affective ratings of art-like patterns that previously appeared on critical trials of a task-switching paradigm (ABA vs. CBA task sequences) known for its capacity to distinguish behavioural effects of inhibition and conflict. Stimuli from the ABA-sequence experimental condition showing behavioural evidence of backward inhibition (n-2 repetition costs) received more negative ratings than those from the CBA-sequence control condition. This stimulus-devaluation effect was not impacted by the level of conflict associated with high uncertainty or low uncertainty about upcoming task order. Moreover, the response-time index of inhibition was larger on ABA trials in which the associated stimuli later received negative ratings than on trials preceding relatively positive ratings. Inhibition therefore appears to have negative affective consequences that exceed any emotional impact of conflict, with fluctuations in inhibition linked to subsequent stimulus evaluations.

Previous studies have found that inhibiting a task set plays an important role in task switching. However, the impact of stimulus–response (S–R) complexity on this inhibition processing has not been explored. In this study, we applied the backward inhibition paradigm (switching between tasks A, B, and C, presented in sets of three) in order to investigate inhibition performance under different S–R complexities caused by corresponding S–R mappings. The results showed that the difficult condition resulted in a greater switch cost than the moderate and easy conditions. Furthermore, we found a significant n−2 repetition cost under the easy S–R complexity that was reversed under the difficult S–R complexity. To verify stability of the reversed n−2 repetition cost in the difficult condition, we recruited another independent sample to conduct an additional experiment with the difficult condition. These results replicated the reversed n−2 repetition cost. These findings suggest that S–R complexity affects task-set inhibition in task switching because the effect of the task-set inhibition was insignificant when the S–R complexity increased; it was only significant under the easy condition. This result was caused by the different cognitive resource assignments.

Recent studies using an induction task paradigm indicated that unconscious automatic processes underlying masked semantic priming are susceptible to cognitive control influences. In this paradigm, participants first perform different induction tasks (semantic decision vs. perceptual decision), which serve to activate a corresponding task set. Thereafter, the masked prime and the target for the lexical decision task is presented. Previously, perceptual and semantic induction tasks were presented in separate blocks, and the response to the induction task was given immediately after the inducing stimulus. The present study, therefore, tested two possible boundary conditions, flexibility of cognitive control and completeness of task set execution, for the emergence of task set effects on masked semantic priming. In the first experiment, perceptual and semantic induction tasks were presented in a randomized fashion, to assess whether task set influences on masked semantic priming can occur on a trial-by-trial basis. The other two experiments tested whether task set effects on masked priming survive, when the response to the induction task is delayed. The present study yielded the same pattern of results irrespective of the variations in the induction task paradigm: When the masked prime was shortly presented after the induction task, masked semantic priming was larger subsequent to the semantic than subsequent to the perceptual induction task. The present study shows that task sets can configure unconscious processing streams rapidly on a trial-by-trial basis and demonstrates the generalizability of cognitive control effects on masked semantic priming across variations of the induction task paradigm.

Task inhibition (also known as backward inhibition) is an hypothesised form of cognitive inhibition evident in multi-task situations, with the role of facilitating switching between multiple, competing tasks. This article presents a novel cognitive computational model of a backward inhibition mechanism. By combining aspects of previous cognitive models in task switching and conflict monitoring, the model instantiates the theoretical proposal that backward inhibition is the direct result of conflict between multiple task representations. In a first simulation, we demonstrate that the model produces two effects widely observed in the empirical literature, specifically, reaction time costs for both (n-1) task switches and n-2 task repeats. Through a systematic search of parameter space, we demonstrate that these effects are a general property of the model's theoretical content, and not specific parameter settings. We further demonstrate that the model captures previously reported empirical effects of inter-trial interval on n-2 switch costs. A final simulation extends the paradigm of switching between tasks of asymmetric difficulty to three tasks, and generates novel predictions for n-2 repetition costs. Specifically, the model predicts that n-2 repetition costs associated with hard-easy-hard alternations are greater than for easy-hard-easy alternations. Finally, we report two behavioural experiments testing this hypothesis, with results consistent with the model predictions.

Sequential cognitive flexibility is a major requirement for goal-directed behavior. Recent findings show that inhibitory control processes are crucial for sequential cognitive flexibility. These processes are indicated by the ‘backward inhibition (BI) effect’ which emerges when a mental representation that has recently been suppressed in favour of another task has to be re-activated. Alterations in the catecholaminergic neural transmission including the norepinephrine (NE) system have been shown to modulate inhibitory processes. However, a possible role of the NE system in sequential cognitive flexibility is elusive. The present study examines the relevance of the NE system for sequential cognitive flexibility by integrating pupil diameter data and electrophysiological (EEG) data applying signal decomposition techniques and source localization. We show that the BI effects modulated amplitudes in the P1/N1 time window, as well as in the N2 time window. Correlating this data with the pupil diameter data only revealed substantial correlations in the P1/N1 time window. Moreover, it is shown that regions in the right inferior frontal gyrus are activated during modulations in the P1 time window, in which correlations with the pupil diameter data were also evident. The results are interpreted that sequential cognitive flexibility modulates early inhibitory gating processes (P1) which are related to the suppression of task-irrelevant information in inferior frontal regions. These processes are likely modulated by the NE system.

Prior research has suggested that impairments of switching abilities are associated with depression as well as rumination. Backward inhibition (BI) refers to the ability to inhibit the processing of previously relevant information and is demonstrated to be one of the key mechanisms underlying switching abilities. However, the association between BI in internal switching and depression/rumination remains uninvestigated. To examine this association, a modified Internal Shifting Task (IST) was administered to a sample of dysphoric and healthy control undergraduates. Results showed that depressive symptoms were not associated with difficulties in switching among subjects held in working memory, while trait ruminators performed poorly in switching internally. Surprisingly, no association between BI in internal switching and rumination/depressive symptoms was found. These findings indicate that rumination is characterized by poor performance in internal switching, but this deficit is not associated with BI.

The cholinergic system is one of the most important neurotransmitter systems, but knowledge about the relevance of the cholinergic muscarinergic receptor system for cognitive functions is still scarce. Evidence suggests that the cholinergic muscarinic 2 receptor (CHRM2) plays an important role in the processing of cueing/prior information that help to increase the efficacy of lower-level attentional processes. In the current study, we investigated whether this is also the case for higher-level cognitive flexibility mechanisms. To this end, we tested N = 210 healthy adults with a backward inhibition task, in which prior information needs to be used to guide cognitive flexibility mechanisms. Testing different polymorphisms of the CHRM2 gene, we found that variation in this gene play a role in cognitive flexibility. It could be demonstrated that rs8191992 TT genotype carriers are better able to suppress no longer relevant information and to use prior information for cognitive flexibility, compared to A allele carriers. We further found that rs2350780 GG genotype carriers performed worse than A allele carriers. The results broaden the relevance of the CHRM2 system for cognitive functions beyond attentional selection processes. Corroborating recent theories on the relevance of the cholinergic system for cognitive processes, these results suggest that CHRM2 is important to process of “prior information” needed to inform subsequent cognitive operations. Considering the importance of prior information for adaptive behavioral control, it is possible that CHRM2 also modulates other instances of higher-level cognitive processes as long as these require the processing of “prior information.”

Background and objectives The aim of the present study was to investigate the effects of a partial sleep deprivation night on executive functions in participants reporting chronic insomnia and good sleepers using a Task Switching paradigm. Methods Sixteen participants reporting symptoms of chronic insomnia and sixteen good sleepers were tested after a night of habitual sleep and after a night of partial sleep deprivation (5 h of sleep allowed). The Switch Cost (SC) and the Backward Inhibition (BI) were computed as measures of switching attention and response inhibition, respectively. Results We observed a marginally significant interaction Night × Group on SC (F(1,29) = 4.06, p = 0.053), η2 = 0.123. Fisher's least significant difference (LSD) post-hoc revealed a smaller SC after the sleep deprived night relative to the habitual night for the good sleepers (p = 0.027; M = 192.23 ± 201.81 vs M = 98.99 ± 141.16). Differently, participants with insomnia did not show any change after the two nights. Limitations Several limitations must be acknowledged including the use of a convenient sample of university students and the use of a single task of cognitive performance. Conclusions We found that SC was smaller in the good sleepers after a night of partial sleep deprivation compared to a habitual night, indicating a better switching performance. The insomnia group showed no differences in performance after the two experimental nights. Several factors may account for these results, including increased levels of arousal and cognitive effort during task execution.

Performing an act of self-regulation such as making decisions has been suggested to deplete a common limited resource, which impairs all subsequent self-regulatory actions (ego depletion theory). It has however remained unclear whether self-referred decisions truly impair behavioral control even in seemingly unrelated cognitive domains, and which neurophysiological mechanisms are affected by these potential depletion effects. In the current study, we therefore used an inter-individual design to compare two kinds of depletion, namely a self-referred choice-based depletion and a categorization-based switching depletion, to a non-depleted control group. We used a backward inhibition (BI) paradigm to assess the effects of depletion on task switching and associated inhibition processes. It was combined with EEG and source localization techniques to assess both behavioral and neurophysiological depletion effects. The results challenge the ego depletion theory in its current form: Opposing the theory's prediction of a general limited resource, which should have yielded comparable effects in both depletion groups, or maybe even a larger depletion in the self-referred choice group, there were stronger performance impairments following a task domain-specific depletion (i.e., the switching-based depletion) than following a depletion based on self-referred choices. This suggests at least partly separate and independent resources for various cognitive control processes rather than just one joint resource for all self-regulation activities. The implications are crucial to consider for people making frequent far-reaching decisions e.g., in law or economy.

Background and Objectives: The present study examines backward inhibition and non-inhibitory switching performance among depressed and healthy participants in a modified mixed antisaccade task. Specifically, sad and neutral faces were incorporated in the design to examine executive control difficulties associated with brooding trait. Methods: Thirty-nine participants took part in the study, including 19 depressed patients and 20 healthy control subjects. Participants completed a diagnostic interview and self-report questionnaires, including the Beck Depression Inventory and Ruminative Response Scale-Brooding Subscale. They were then instructed to complete prosaccade and antisaccade trials in the pure and mixed blocks whereby eye gazes were tracked to assess inhibition and switching efficiency. Results: For the switching effects, a significant group x brooding x task type interaction was found as hypothesized when multilevel modeling analysis was employed. Switching deficits associated with brooding was found to be greatest when sad faces were presented to depressed group. No significant results in backward inhibition or error rates were observed. Conclusions: The patterns observed suggest that as opposed to backward inhibition, set shifting difficulty associated with brooding trait may be modulated by negative mood and cognition. In future research, emotional faces other than sad faces may be used to further explore if the observations could be generalized to other affective conditions.

Recently, effects of reward incentives on interference-induced cognitive adjustments have drawn much attention. It has been demonstrated that reward can reduce or eliminate switch costs which occurred when alternating between different tasks. However, it still remains a question how reward affects inhibitory processes underlying task switching. The present study examined this issue by combining a task-switching paradigm with performance-contingent reward. Results showed that the inhibitory processes were modulated by reward, with n-2 repetition costs incremented after reward delivery. Data suggest that reward-triggered reduction or elimination of switch costs may reflect enhancing inhibitory processes which are motivated by reward signals and targeted at the irrelevant task set. These findings shed new light on the role of reward in cognitive control.

The role of cue processing has become a controversial topic in research on cognitive control using task-switching procedures. Some authors suggested a priming account to explain switch costs as a form of encoding benefit when the cue from the previous trial is repeated and hence challenged theories that attribute task-switch costs to task-set (re)configuration. A rich body of empirical evidence has evolved that indeed shows that cue-encoding repetition priming is an important component in task switching. However, these studies also demonstrate that there are usually substantial “true” task-switch costs. Here, we review this behavioral, electrophysiological, and brain imaging evidence. Moreover, we describe alternative approaches to the explicit task-cuing procedure, such as the usage of transition cues or the task-span procedure. In addition, we address issues related to the type of cue, such as cue transparency. We also discuss methodological and theoretical implications and argue that the explicit task-cuing procedure is suitable to address issues of cognitive control and task-set switching.

The n-2 repetition cost seen in task switching is the effect of slower response times performing a recently completed task (e.g. an ABA sequence) compared to performing a task that was not recently completed (e.g. a CBA sequence). This cost is thought to reflect cognitive inhibition of task representations and has been well replicated (Koch, Gade, Schuch, & Philipp, 2010). As such, the n-2 repetition cost has started to be used as a measure of individual differences in inhibitory control (e.g. Whitmer & Banich, 2007); however, the reliability of this measure has not been investigated in a systematic manner. The current study addressed this important issue. Seventy-two participants performed three task switching paradigms; participants were also assessed on rumination traits and processing speed-measures of individual differences potentially modulating the n-2 repetition cost. We found significant n-2 repetition costs for each paradigm. However, split-half reliability tests revealed that this cost was not reliable at the individual-difference level. Neither rumination tendencies nor processing speed predicted this cost. We conclude that the n-2 repetition cost is not reliable as a measure of individual differences in inhibitory control.

The concept of inhibition plays a major role in cognitive psychology. In the present article, we review the evidence for the inhibition of task sets. In the first part, we critically discuss empirical findings of task inhibition from studies that applied variants of the task-switching methodology and argue that most of these findings— such as switch cost asymmetries—are ambiguous. In the second part, we focus on n-22 task-repetition costs, which currently constitute the most convincing evidence for inhibition of task sets. n-22 repetition costs refer to the performance impairment in sequences of the ABA type relative to CBA, which can be interpreted in terms of persisting inhibition of previously abandoned tasks. The available evidence suggests that inhibition is primarily triggered by conflict at selection of stimulus attributes and at the response level. Author Note

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.

Task-switching has proved to be a fruitful paradigm for studying cognitive control mechanisms. Interestingly, this avenue of study has revealed that subjects are, to some degree, able to bring about a change in task-set prior to the performance of that task (provided that they are given advance warning of the upcoming task, for instance in the form of a cue). Event-related potentials (ERPs) have proved to be a good way of measuring these rapid anticipatory control processes. To explore these processes further, the current study examined the relationship between the availability of spatial information and cue-locked task-switching ERP effects. Two groups of subjects were compared: one group could separate the task-sets on the basis of the targets’ colour (the ‘colour’ group), the second on the basis of the targets’ location (the ‘spatial’ group). The performance of both groups benefited to the same extent from advance cueing of task-transitions (switches or repeats), yet the ERP data revealed cue-locked (but not target-locked) differences between the two groups. The most striking of these differences was the absence of both a late positivity over posterior scalp and a late negativity over frontal scalp when the spatial group switched between tasks. Thus, it seems unlikely that these effects index stimulus-response ‘reconfiguration’ per se – as the mappings were identical for both groups of subjects – but rather that these taskswitching processes are sensitive to how the mappings are represented.

Performance after a shifting of task is supported by the inhibition of the executed task, as revealed by slower reaction times (RTs) on alternating compared to nonalternating task sequences (ABA vs CBA). In the present study we investigated the role of stimulus processing in the establishment of task inhibition during task switching, irrespective of the response selection process. Comparing performance on AbA and CbA task sequences within a procedure in which the b-task only involved stimulus encoding processes for later comparison but response selection did not occur, we found slower RTs on AbA compared to CbA task sequences. This revealed that inhibition of the executed task can be triggered at the stimulus processing stage of the new task. In accordance, inhibition only emerged when interference between tasks occurred at the stimulus level, due to stimuli having features relevant for both the executed and the upcoming task.

A feature of human cognition is the ability to monitor and adjust one's own behavior under changing circumstances. A dynamic balance between controlled and rapid responding is needed to adapt to a fluctuating environment. We suggest that cognitive control may include, among other things, two distinct processes. Incongruent stimuli may drive top-down facilitation of task-relevant responses to bias performance toward exploitation vs. exploration. Task or response switches may generally slow responses to bias toward accuracy vs. speed and exploration vs. exploitation. Behavioral results from a task switching study demonstrate these two distinct processes as revealed by higher-order sequential effects. A computational model implements the two conflict-control mechanisms, which allow it to capture many complex and novel sequential effects. Lesion studies with the model demonstrate that the model is unable to capture these effects without the conflict-control loops and show how each monitoring component modulates cognitive control. The results suggest numerous testable predictions regarding the neural substrates of cognitive control.

The aim of the present study was to examine the contribution of overlapping response sets to the occurrence of task inhibition, measured as n-2 task repetition cost. We had subjects switch among four tasks. Three tasks overlapped on both stimulus set and response set. A fourth, neutral, univalent task never overlapped on the stimulus set but, across three experiments, varied in terms of the degree of overlap in the response set. We found that overlap in response set affects task inhibition. We suggest that response set overlap increases the competition among tasks and, thus, triggers task inhibition to resolve this competition.

The present study used a go/no-go signal delay (GSD) to explore the role of response-related processes in task switching. A go/no-go signal was presented at either 100 ms or 1,500 ms after the stimulus. Participants were encouraged to use the GSD for response selection and preparation. The data indicate that the opportunity to select and prepare a response (i.e., long GSD) resulted in a substantial reduction of task-shift costs (Experiment 1) and n-2 task-repetition costs (i.e., backward inhibition; Experiment 2) in the current trial. These results suggest that interference from the preceding trial can be resolved during response selection and preparation. Furthermore, the shift costs and the n-2 repetition costs after no-go trials with long GSD (i.e., response selection but no execution) were markedly smaller than after go trials. These findings suggest that the interference that gives rise to shift costs and n-2 repetition costs is related not solely to response selection but also to response execution. Thus, the present study demonstrates dissociable contributions of response selection and response execution to interference effects in task switching.

Effective task switching is supported by the inhibition of the just executed task, so that potential interference from previously executed tasks is adaptively counteracted. This inhibitory mechanism, named Backward Inhibition (BI), has been inferred from the finding that switching back to a recently executed task (A-B-A task sequence) is harder than switching back to a less recently executed task (C-B-A task sequence). Despite the fact that BI effects do impact performance on everyday life activities, up to now it is still not clear whether the BI represents an amodal and material-independent process or whether it interacts with the task material. To address this issue, a group of individuals with Williams syndrome (WS) characterized by specific difficulties in maintaining and processing visuo-spatial, but not verbal, information, and a mental age- and gender-matched group of typically developing (TD) children were subjected to three task-switching experiments requiring verbal or visuo-spatial material to be processed. Results showed that individuals with WS exhibited a normal BI effect during verbal task-switching, but a clear deficit during visuo-spatial task-switching. Overall, our findings demonstrating that the BI is a material-specific process have important implications for theoretical models of cognitive control and its architecture.

Three experiments were conducted to examine the backward inhibition effect in attention switching within verbal working memory. Experiment one showed significant backward inhibition effect in a "tri-count task". Experiment two suggested that the effect was not due to a perceptual inhibition on the previously presented figure. Experiment three excluded the sequential expectancy explanation for this inhibition effect. Our results suggest that attention switching between working memory items is accompanied by inhibition of the previously attended working memory item. The findings are discussed in respect to the account of the executive function.

Abstract. Task inhibition was explored in two experiments that employed a paradigm in which participants switched among three tasks. Two tasks required manual choice responses based on numerical judgment (parity or magnitude), whereas a third task required an unconditional double-press of both response keys. Both experiments showed that switching to a just-abandoned task (n-2 task repetition) generally leads to a performance cost relative to switching to another task. Specifically, this task inhibition effect also occurred for the double-press task, suggesting inhibition of response mode. Prolonging the task-cuing interval showed that advance task preparation reduced only inhibition of the double-press task but not of the choice tasks (Experiment 1). Prolonging the response-cue interval led to a decrease of the inhibition effect in all tasks (Experiment 2), suggesting a time-based release of task inhibition. Together, the experiments support the notion of a response-related component of task inhibition.

Endogenously initiated transitions between tasks are associated with inhibition of the attentional set for the task preceding the transition, as demonstrated by slowed reactions to a task most recently switched away from (U. Mayr & S. W. Keele, 2000). Using an altered methodological approach, the authors found that this backward inhibition counteracts perseverative tendencies when switching to a new task in that it selectively reduces interference exerted by the preceding task set. The reduction of interference was dependent on endogenous preparation for the new task and did not occur for unpredictable task switches or for task switches that were precued without information about the identity of the new task.

Does the explicit task-cuing procedure require an endogenous a act of control? In 5 experiments, cues indicating which task to perform preceded targets by several stimulus onset asynchronies (SOAs). Two models were developed to account for changes in reaction time (RT) with SOA. Model 1 assumed an endogenous act of task switching for cue alterations but not for cue repetitions. Model 2 assumed no such act. In Experiments 1 and 2, the cue was masked or not masked. Masking interacted underadditively with repetition and alternation, consistent with Model 2 but not Model 1. In Experiments 3 and 4, 2 cues were used for each task. RT was slower for task repetition than for cue repetition and about the same as RT for task alternation, consistent with Model 2 but not Model 1. The results suggest that the explicit task-cuing procedure does not require an endogenous act of control.

Recently, we have shown that the consideration of joy, without the actual experience of the emotion, impaired performance on the antisaccade task (Katzir, Eyal, Meiran, & Kessler, 2010). We interpreted this finding as indicating inhibitory control failure. However, impaired antisaccade performance may result from either the weakening of inhibitory control, the potentiation of the competing automatic response, or both. In the current research we used a task switching paradigm, which allowed us to assess cognitive control more directly, using Backward Inhibition, Competitor Rule Suppression, and Competitor Rule Priming as cognitive-control indices as well as assessing the Task Rule Congruency Effect (TRCE) which, like the antisaccade, is influenced by both control and automaticity. We found that considering joy compared to pride did not influence any of the cognitive control indices but increased the TRCE. We interpret this finding as evidence that joy consideration leads to increased reliance on automatic tendencies, such as short-term desires.

Switching between two tasks afforded by the same stimuli results in slower reactions and more errors on the first stimulus after the task changes. This "switch cost" is reduced, but not usually eliminated, by the opportunity to prepare for a task switch. While there is agreement that this preparation effect indexes a control process performed before the stimulus, the "residual" cost has been attributed to several sources: to a control process essential for task-set reconfiguration that can be carried out only after the stimulus onset, to probabilistic failure to engage in preparation prior to the stimulus, and to two kinds of priming from previous trials: positive priming of the now-irrelevant task set and inhibition of the now-relevant task-set. The main evidence for the carry-over of inhibition is the observation that it is easier to switch from the stronger to the weaker of a pair of tasks afforded by the stimulus than vice versa. We survey available data on interactions between task switching and three manipulations of relative task strength: pre-experimental experience, stimulus-response compatibility, and intra-experimental practice. We conclude that it is far from universally true that it is easier to switch to the weaker task. Either inhibition of the stronger task-set is a strategy used only in the special case of extreme inequality in strength, or its consequences for later performance may be masked by slower post-stimulus control operations for more complex tasks. Inhibitory priming may also be stimulus specific.

This article describes a quantitative model, which suggests what the underlying mechanisms of cognitive control in a particular task-switching paradigm are, with relevance to task-switching performance in general. It is suggested that participants dynamically control response accuracy by selective attention, in the particular paradigm being used, by controlling stimulus representation. They are less efficient in dynamically controlling response representation. The model fits reasonably well the pattern of reaction time results concerning task switching, congruency, cue-target interval and response-repetition in a mixed task condition, as well as the differences between mixed task and pure task conditions.

This individual differences study examined the separability of three often postulated executive functions-mental set shifting ("Shifting"), information updating and monitoring ("Updating"), and inhibition of prepotent responses ("Inhibition")-and their roles in complex "frontal lobe" or "executive" tasks. One hundred thirty-seven college students performed a set of relatively simple experimental tasks that are considered to predominantly tap each target executive function as well as a set of frequently used executive tasks: the Wisconsin Card Sorting Test (WCST), Tower of Hanoi (TOH), random number generation (RNG), operation span, and dual tasking. Confirmatory factor analysis indicated that the three target executive functions are moderately correlated with one another, but are clearly separable. Moreover, structural equation modeling suggested that the three functions contribute differentially to performance on complex executive tasks. Specifically, WCST performance was related most strongly to Shifting, TOH to Inhibition, RNG to Inhibition and Updating, and operation span to Updating. Dual task performance was not related to any of the three target functions. These results suggest that it is important to recognize both the unity and diversity of executive functions and that latent variable analysis is a useful approach to studying the organization and roles of executive functions.

Executive processes necessary for flexibly switching between different tasks were studied using a set switching paradigm that requires participants to rapidly switch between different tasks across consecutive trials. Switch cost reflects poorer performance for task- switch trials than for consecutive same-task trials. Significant switch cost was observed even with considerable preparation time before a task- switch, an effect known as residual switch cost. This study tested the hypothesis that one process underlying residual switch cost is inhibition of the previous task-set. We 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 (Mayr & Keele, in press). 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. Executive control processes that underlie voluntary direction of cognitive resources to some specific goal are not well understood. Much is known about how our minds work to do specific tasks such as process language (e.g., Pinker, 1994), arithmetic (e.g., Ashcraft, 1992), music (e.g., Schmuckler, 1997; Steinke, Cuddy, & Holden, 1997), or to control motor movements such as throwing to a target (e.g., Castiello, 1996; MacKenzie & Marteniuk, 1985). But how we effect decisions to use our minds to process language instead of music at a particular moment is still largely a mystery. Executive processes theoretically function to select and coordinate the operation of multiple processes for any given task, including relevant perception, memory, and motor control processes. Until recently, most of what we knew about executive control was learned by studying those who can no longer use these processes efficiently, especially those with brain damage to frontal cortices (Damasio, 1994; Pollux, Wester, & De Haan, 1995; Robertson, Manly, Andrade, Baddeley, & Yiend, 1997; Shallice, 1988; Spatt & Goldenberg, 1993). One reason for the apparent neglect of executive control in the cognitive literature is the difficulty of designing methods to isolate executive control processes. In any task, the behaviour that is emitted is always a combination of the task-specific processes and executive control processes (Allport, Styles, & Hsieh, 1994; Rogers & Monsell, 1995), making behavioural measurement of executive control difficult. Recently, however, two methods have been developed to study executive processing. Baddeley and his colleagues use dual task paradigms to determine which cognitive skills involve executive processes (Baddeley, 1996; Baddeley, Emslie, Kolodny, & Duncan, 1998; Baddeley & Wilson, 1988), and hypothesize that executive control is needed for tasks that require frequent switches between retrieval plans (e.g., category fluency and random number generation). A second method, set switching, directly examines switching between tasks (Allport et al., 1994; Meiran, 1996; Rogers & Monsell, 1995). In a set-switching study, participants perform two or more different tasks within a series of trials, and performance on trials that involve switching between tasks is compared to that for trials without a switch. For example, Allport et al. (1994) had participants switch between naming the ink colour and reading the word for Stroop colour-word stimuli. Set- switching studies indicate a robust cost for switching tasks, presumably reflecting the time necessary for executive control processes to operate. However, switch cost is not observed if the to-be-performed tasks are uniquely cued by stimulus type within the experimental context. …

OBJECTIVE Developmental Topographical Disorientation (DTD) is a selective difficulty in way-finding showed by individuals with normal intellectual ability. We aimed to clarify whether getting lost even in familiar contexts could be because of a variety of developmental deficits that may affect the acquisition of one or more navigational competencies. METHOD Two DTD individuals were submitted to neuropsychological assessment and MRI exam, to verify the absence of further cognitive deficits and brain abnormalities; navigational and visuospatial tasks, and Radial Arm Maze (RAM) paradigms to assess spatial competencies; and switching paradigms to assess backward inhibition processes in spatial- and no-spatial contexts. DTD performances were compared with those of controls matched for gender, age, and education. RESULTS DTD participants were not able to retrace a previously showed route, but they could recognize previously seen landmarks. They performed RAM paradigms without significant differences from controls and adopted complex navigational strategies as the cognitive mapping. It is interesting that DTD participants exhibited a peculiar alteration of Backward Inhibition, a mechanism that allows flexibly adapting to continuously changing environments. CONCLUSIONS These findings demonstrate that getting lost for DTD participants did not imply the lack of basic navigational strategies and was not related to visuospatial or spatial memory deficits. We discuss the hypothesis that Backward Inhibition might play a role in updating environment representation during navigation.

Participants performed choice reaction time (RT) tasks on 2-dimensional stimuli such that each task was based on 1 stimulus dimension. A cue preceded the target stimulus and instructed the participant about which (randomly selected) task to perform. Shifting between tasks was associated with an RT cost, which was larger when the (randomly varying) cue-target interval was short as opposed to when it was long. Cue-target interval was not confounded with the remoteness from the previous trial. Hence, it affected the task-shift cost through preparation rather than by allowing carryover effects to dissipate. Similar results were obtained for 2 location tasks and for the object-based tasks (color and shape discrimination). They indicate a time-effort consuming process that operates after a task shift, precedes task execution, and presumably reflects the advance reconfiguration of processing mode.

The role of inhibition in the task-switching process has received increased empirical and theoretical attention in the literature on cognitive control. Many accounts have suggested that inhibition occurs when a conflict must be resolved-for example, when a target stimulus contains features of more than one task. In the two experiments reported here, we used variants of backward inhibition, or N - 2 repetition, designs to examine (1) whether inhibition occurs in the absence of conflict at the stimulus or response level, (2) when in the task-switching process such inhibition may occur, and (3) the potential consequences of inhibition. In Experiment 1, we demonstrate that neither stimulus- nor response-level conflict is necessary for inhibition to occur, while the results of Experiment 2 suggest that inhibition may be associated with a reduction of proactive interference (PI) from a previously performed task. Evidence of inhibition and the reduction of PI both occurred at the task-set level. However, inhibition of specific stimulus values can also occur, but this is clearly separable from task-set inhibition. Both experiments also provided evidence that task-set inhibition can be applied at the time of the new task cue, as opposed to at the onset of the target or at the response stage of the trial. Taken together, the results from these experiments provide insight into when and where in the task-switching process inhibition may occur, as well as into the potential functional benefits that inhibition of task sets may provide.

Previous studies have demonstrated that individuals with major depressive disorder have difficulties switching attention from one task set to another. In the current study we examined whether ruminative thinking drives the switching deficits of depressed individuals. A secondary, more exploratory, goal of this study was to examine whether state rumination would impair depressed individuals’ ability to activate a new task set, to inhibit a no longer relevant task set, or both. Participants underwent either a rumination induction or a distraction induction and then completed a backward inhibition task that measures general switching abilities and the ability to inhibit previous task sets. Although depression was not related to switching ability as a main effect, depressed individuals who were induced to ruminate exhibited poorer switching ability than did both depressed and control individuals who were distracted from ruminating and control participants who were induced to ruminate. These findings suggest that depressed individuals are characterized by switching deficits only if they are ruminating. Moreover, the finding that state rumination did not affect participants’ ability to inhibit previous task sets suggests that state rumination primarily impairs noninhibitory task-switching processes. It is interesting that the opposite pattern of results was obtained for trait rumination, which was related to inhibitory deficits during switching, but not to generally poorer switching. Thus, state and trait rumination may be associated with dissociable cognitive deficits.

The adjustment of behavior to changing goals and environmental constraints requires the flexible switching between different task sets. Cognitive flexibility is an endophenotype of executive functioning and is highly heritable, as indicated by twin studies. Individual differences in global flexibility as assessed by reaction-time measurement in a task-switching paradigm were recently related to a single nucleotide polymorphism in the vicinity of the dopamine d2 receptor gene DRD2. In the present study, we assessed whether the DRD2 gene is related to backward inhibition, a control mechanism that contributes to cognitive flexibility by reducing proactive interference by no longer relevant task sets. We found that carriers of the DRD2 A1+ variant who have a lower striatal dopamine d2 receptor density than A1– carriers show a larger backward inhibition effect. This is in line with previous results demonstrating increased behavioral flexibility in carriers of this genetic variant. The discussion relates the present finding to those of previous studies assessing the neurogenetic foundations of inhibitory control.

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.

According to classical theories, automatic processes are autonomous and independent of higher level cognitive influence. In contrast, the authors propose that automatic processing depends on attentional sensitization of task-congruent processing pathways. In 3 experiments, the authors tested this hypothesis with a modified masked semantic priming paradigm during a lexical decision task by measuring event-related potentials (ERPs): Before masked prime presentation, participants attended an induction task either to semantic or perceptual stimulus features designed to activate a semantic or perceptual task set, respectively. Semantic priming effects on the N400 ERP component, an electrophysiological index of semantic processing, were obtained when a semantic task set was induced immediately before subliminal prime presentation, whereas a previously induced perceptual task set attenuated N400 priming. Across experiments, comparable results were obtained regardless of the difficulty level and the verbal or nonverbal nature of the induction tasks. In line with the proposed attentional sensitization model, unconscious semantic processing is enhanced by a semantic and attenuated by a perceptual task set. Hence, automatic processing of unconscious stimuli is susceptible to top-down control for optimizing goal-related information processing.

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.

Task switching requires maintaining readiness to execute any task of a given set of tasks. However, when tasks switch, the readiness to execute the now-irrelevant task generates interference, as seen in the task rule incongruence effect. Overcoming such interference requires fine-tuned inhibition that impairs task readiness only minimally. In an experiment involving 2 object classification tasks and 2 location classification tasks, the authors show that irrelevant task rules that generate response conflicts are inhibited. This competitor rule suppression (CRS) is seen in response slowing in subsequent trials, when the competing rules become relevant. CRS is shown to operate on specific rules without affecting similar rules. CRS and backward inhibition, which is another inhibitory phenomenon, produced additive effects on reaction time, suggesting their mutual independence. Implications for current formal theories of task switching as well as for conflict monitoring theories are discussed.

When one is sequentially switching among three tasks, performance is impaired when tasks alternate (ABA) relative to when one is switching between all three tasks (CBA), an effect known as backward inhibition (BI). BI is not observed when component tasks are uniquely located in space, however (Arbuthnott, 2005). In this study, the locations of task precues and target stimuli were manipulated independently to determine whether this elimination of BI is related to distinct cue location or to distinct target location. Results clearly indicated that BI is eliminated with distinct cue localization independent of the location of target stimuli. This indicates that BI, which reflects suppression of task-set representations, can be influenced by cue characteristics that are associated with task representations.

Backward inhibition (BI) refers to a reaction time cost incurred when returning to a recently abandoned task compared to returning to a task not recently performed. The effect has been proposed to reflect an inhibitory mechanism that aids transition from one task to another. The question arises as to precisely what aspects of a task may be inhibited and when the process takes place. Recent work has suggested a crucial role for response-related components of the task, which occur late in the typical trial structure (cue-target-response). In contrast to this suggestion, the authors present evidence that the way in which the task is cued can also modulate BI. Specifically, they find that the less transparent the cue-target relationship, the greater the level of BI. This also demonstrates that BI can be triggered at early stages of the trial structure, specifically during task preparation and prior to response processes. The authors conclude that BI is not tied to any particular component of the task structure but arises from whatever component generates the greatest intertrial conflict.

Lag 2 repetition costs are a performance cost observed when participants return to a task after just one intervening trial of a different task, compared to returning after a longer interval (AB A vs. CB A sequences, where A, B, C are tasks). This effect is known as backward inhibition (BI) and is thought to reflect the need to overcome inhibition applied specifically to Task “A” during disengagement at trial n – 1. Druey and Hübner (2007) have suggested that employment of such a specific inhibitory mechanism relies upon the cue and the target of the task overlapping temporally. We provide evidence across three experiments (including a direct replication attempt) that this is not the case, and that the presence of task-specific BI relies to some extent on the need to translate the cue–target relationship into working memory. Additionally, we provide evidence that faster responses in no overlap conditions are driven by low-level perceptual differences between target displays across overlap conditions. We conclude that BI is an effective sequential control mechanism, employed equally in cases of temporally overlapping and temporally separated cues and targets.

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. Keywords: task switching, inhibition, priming, task difficulty Asymmetric switch cost is observed when switching between tasks varying in difficulty. Counterintuitively, the difference between repeat and switch trials is greater when switching to the easier task. For instance, using Stroop colour-word stimuli, switch cost is greater when switching from colour naming to word naming than vice versa (Allport, Styles, & Hsieh, 1994). This has proved to be a robust effect, observed with various combinations of tasks, such as dominant-secondary language for bilinguals (Campbell, 2005; Meuter & Allport, 1999), and in various populations, including children (Davidson, Amso, Anderson, & Diamond, 2006; Ellefson, Shapiro, & Chater, 2006). In the original report of this effect, Allport et al. (1994) proposed a task-set inertia explanation. Specifically, performance on a trial would result in both positive priming of the relevant task and negative priming of the irrelevant task. Greater inhibition (negative priming) of the easier task would be necessary when performing the more difficult task because of interference from the easier task set (reading), which would be more readily activated by the ambiguous colour-word stimuli. Then, when switching from the difficult task to the easy task, the easy task set would be suppressed. At the same time, positive priming of the difficult task would be larger to enable correct performance of this task on the previous trial despite the interference from the easy task. Thus, in combination, switches to the easy task are more effortful because the easy set is more inhibited (negative priming) and the difficult task provides more competition (positive priming). When a previous trial (trial N - \) involved the easy task, both less negative priming (inhibition of the difficult task set) and positive priming (activation of the easy task set) would be needed, and thus a switch to the more difficult task results in less switch cost. This account thus posits greater suppression of the easy task and greater activation of the difficult task on consecutive trials as the combined source of asymmetric switch cost. This pattern of asymmetric switch cost is not, however, observed in all contexts. For instance, Monsell, Yeung, and Azuma (2000) reported no asymmetric switch cost when degraded Stroop stimuli were used. Similarly, Yeung and Monsell (2003) observed reversed switch cost asymmetry (i.e., greater cost to switch to the more difficult task) when between-task interference was reduced either by delaying onset of the competing stimulus feature or by using separate response modalities for the two tasks (e.g., manual and verbal responses). They explained this pattern of findings by using a mathematical model incorporating processes of priming, control, and baseline task strength. Specifically, their model attributes switch costs to the relative activation of the competing task sets, with more similar activation resulting in greater switch costs. …

Alternating tasks in a sequence of task switches results in impaired performance, relative to switches across three different tasks, an effect known as backward inhibition. Despite the robustness of this effect across task and response variations, backward inhibition is not observed when tasks are uniquely located at different points in space (Arbuthnott, 2005). Three hypotheses about the source of this anomaly were tested. Experiment 1 indicated that perceptually distinct task features other than location did not eliminate backward inhibition. Experiment 2 indicated that when switches across task and location were manipulated independently (i.e., all tasks appeared at all locations), backward inhibition was observed for task switches even when consecutive trials appeared at different spatial locations, ruling out eye movement as the source of the difference. The third experiment indicated that when component tasks involved judgments of spatial location, backward inhibition was observed across unique task—location switches. These results indicate that sequential inhibition is a very flexible mechanism that is sensitive to the amount of interference from previous tasks.