Disentangling task-selection failures from task-execution failures in task switching: an assessment of different paradigms.

Differentiating errors on the basis of the distinct cognitive mechanisms that may have generated them has provided neuropsychologists with useful diagnostic tools. For example, perseverative errors arising from the inability of the patient to set a new criterion for responding are considered one of the hallmarks of cognitive inflexibility. Similarly, in the task-switching paradigm it is possible to distinguish between task-confusion errors, produced by a failure in task selection, and response-confusion errors, arising when the correct task is selected, but the wrong response is given. Nonetheless, only a few studies so far have exploited the existence of different kinds of errors in multitasking situations to inform theories of cognitive flexibility. In the present study, we set out to use a variety of methodologies employed so far in the literature for disentangling errors due to task-selection failure from errors due to task-execution failure. In three experiments, we assessed the capacity of each method to produce error categories that can be mapped as clearly as possible to the cognitive mechanism(s) underlying them using multinomial processing tree modelling. Subsequently, the distinction between task- and response-confusion errors was used to test their differential impact on inhibitory mechanisms in task switching as measured by N-2 repetition costs. Our results are encouraging regarding the possibility of correctly detecting response- and task-selection failures, thus allowing us to assess their differential impact on N-2 repetition costs.

A spurious correlation between difference scores in evidence-accumulation model parameters.

Evidence-accumulation models are a useful tool for investigating the cognitive processes that give rise to behavioural data patterns in reaction times (RTs) and error rates. In their simplest form, evidence-accumulation models include three parameters: The average rate of evidence accumulation over time (drift rate) and the amount of evidence that needs to be accumulated before a response becomes selected (boundary) both characterise the response-selection process; a third parameter summarises all processes before and after the response-selection process (non-decision time). Researchers often compute experimental effects as simple difference scores between two within-subject conditions and such difference scores can also be computed on model parameters. In the present paper, we report spurious correlations between such model parameter difference scores, both in empirical data and in computer simulations. The most pronounced spurious effect is a negative correlation between boundary difference and non-decision difference, which amounts to r = - .70 or larger. In the simulations, we only observed this spurious negative correlation when either (a) there was no true difference in model parameters between simulated experimental conditions, or (b) only drift rate was manipulated between simulated experimental conditions; when a true difference existed in boundary separation, non-decision time, or all three main parameters, the correlation disappeared. We suggest that care should be taken when using evidence-accumulation model difference scores for correlational approaches because the parameter difference scores can correlate in the absence of any true inter-individual differences at the population level.

On the reliability of behavioral measures of cognitive control: retest reliability of task-inhibition effect, task-preparation effect, Stroop-like interference, and conflict adaptation effect.

This study examined the reliability (retest and split-half) of four common behavioral measures of cognitive control. In Experiment 1 (N = 96), we examined N - 2 task repetition costs as a marker of task-level inhibition, and the cue-stimulus interval (CSI) effect as a marker of time-based task preparation. In Experiment 2 (N = 48), we examined a Stroop-like face-name interference effect as a measure of distractor interference control, and the sequential congruency effect ("conflict adaptation effect") as a measure of conflict-triggered adaptation of cognitive control. In both experiments, the measures were assessed in two sessions on the same day, separated by a 10 min-long unrelated filler task. We observed substantial experimental effects with medium to large effect sizes. At the same time, split-half reliabilities were moderate, and retest reliabilities were poor, for most measures, except for the CSI effect. Retest reliability of the Stroop-like effect was improved when considering only trials preceded by congruent trials. Together, the data suggest that these cognitive control measures are well suited for assessing group-level effects of cognitive control. Yet, except for the CSI effect, these measures do not seem suitable for reliably assessing interindividual differences in the strength of cognitive control, and therefore are not suited for correlational approaches. We discuss possible reasons for the discrepancy between robustness at the group level and reliability at the level of interindividual differences.

Mood state and conflict adaptation: an update and a diffusion model analysis.

The present study investigated the affective modulation of conflict adaptation. In a first step, we conducted a direct replication of a previous study (Schuch & Pütz, 2018). Positive vs. negative mood state was induced by a success-failure manipulation (between-groups, N = 40 per group). In a subsequent task-switching experiment, the congruency sequence effect was assessed in task repetitions and task switches, measuring conflict adaptation within tasks and between tasks, respectively. We found conflict adaptation (averaged across task repetitions and task switches) to be enhanced in negative mood. We did not replicate our previous finding of enhanced conflict adaptation in task switches in positive mood. In a second step, we combined the replication data with the original data set, yielding a larger database with N = 80 per mood group. Using diffusion modeling, we explored the affective modulation of conflict adaptation in task repetitions. Conflict adaptation was reflected in drift rate, consistent with the idea that response conflict triggers an increase in processing selectivity, thereby attenuating the influence of the irrelevant stimulus dimension. Conflict adaptation was also reflected in boundary separation, suggesting that response conflict on the previous trial triggered an increase in response caution. The mood manipulation did not seem to affect processing selectivity (as captured by drift rate) but affected the setting of response caution (as captured by the boundary separation parameter), with faster and more error-prone responding in the negative than positive mood group. We discuss theoretical implications of these findings, and also briefly consider the affective modulations of other cognitive control measures.

Increased cognitive control after task conflict? Investigating the N-3 effect in task switching.

Task inhibition is considered to facilitate switching to a new task and is assumed to decay slowly over time. Hence, more persisting inhibition needs to be overcome when returning to a task after one intermediary trial (ABA task sequence) than when returning after two or more intermediary trials (CBA task sequence). Schuch and Grange (J Exp Psychol Learn Mem Cogn 41:760-767, 2015) put forward the hypothesis that there is higher task conflict in ABA than CBA sequences, leading to increased cognitive control in the subsequent trial. They provided evidence that performance is better in trials following ABA than following CBA task sequences. Here, this effect of the previous task sequence ("N-3 effect") is further investigated by varying the cue-stimulus interval (CSI), allowing for short (100 ms) or long (900 ms) preparation time for the upcoming task. If increased cognitive control after ABA involves a better preparation for the upcoming task, the N-3 effect should be larger with long than short CSI. The results clearly show that this is not the case. In Experiment 1, the N-3 effect was smaller with long than short CSI; in Experiment 2, the N-3 effect was not affected by CSI. Diffusion model analysis confirmed previous results in the literature (regarding the effect of CSI and of the ABA-CBA difference); however, the N-3 effect was not unequivocally associated with any of the diffusion model parameters. In exploratory analysis, we also tested the alternative hypothesis that the N-3 effect involves more effective task shielding, which would be reflected in reduced congruency effects in trials following ABA, relative to trials following CBA; congruency effects did not differ between these conditions. Taken together, we can rule out two potential explanations of the N-3 effect: Neither is this effect due to enhanced task preparation, nor to more effective task shielding.

Action control in task switching: do action effects modulate N - 2 repetition costs in task switching?

Ideomotor theory posits that actions are controlled by the anticipation of their effects. In line with this theoretical framework, response-contingent action effects have been shown to influence performance in choice-reaction time tasks, both in single-task and task-switching context. Using a task-switching paradigm, the present study investigated whether task-contingent action effects influenced N - 2 repetition costs in task switching. N - 2 repetition costs are thought to be related to task-switch costs, and reflect inhibitory control in task switching. It was expected that task-contingent action effects reduce between-task interference, leading to reduced N - 2 repetition costs. An experimental group (N = 24) performed eight blocks of trials with task-contingent action effects, followed by one block with non-contingent action effects; a control group (N = 24) performed nine blocks of trials with non-contingent action effects. In line with our expectations, a three-way interaction of group, block, and task sequence was obtained, indicating differential data patterns for the two groups: In error rates, the group who had received contingent action effects throughout blocks 1-8 showed larger N - 2 repetition costs in the random block 9 than in block 8, whereas the control group showed a reversed data pattern. The RT data pattern was in the same direction, although no significant three-way interaction was obtained. Taken together, we tentatively conclude that task-contingent action effects reduce task inhibition in task switching, and we outline directions for future research on the role of action effects in multitasking performance.

Explaining response-repetition effects in task switching: evidence from switching cue modality suggests episodic binding and response inhibition.

Task switching studies revealed that the usual response-repetition benefit is abolished and often reversed if the task switches. According to episodic binding accounts, performing responses strengthens task-specific bindings, leading to response-repetition benefits in task repetitions, whereas such bindings can lead to interference (i.e., costs of "unbinding") in task switches. An alternative account assumes that responses are generally inhibited after execution but that the assumed sequential carryover of response inhibition is overcompensated by positive priming of stimulus category in task repetitions (resulting in a positive net effect in response-repetition conditions). In the present study, we manipulated task-cue modality (visual vs. auditory) to introduce a variation of encoding and retrieval context, which should vary the strength of episodic bindings. Across two experiments (Experiment 1A, showing the initial evidence, and Experiment 1B, providing a successful replication), we found that the response-repetition benefit in task repetitions was substantially larger with repeated cue modality than with changed cue modality, suggesting that cue modality primes retrieval of task-specific stimulus categories and responses. However, the observed response-repetition cost in task switches remained unaffected by this contextual change. This data pattern suggests a hybrid account, assuming that response-repetition benefits are driven by episodic bindings, whereas response-repetition costs are primarily due to (non-episodic) carryover of response inhibition.

Investigating task inhibition in children versus adults: A diffusion model analysis.

One can take n-2 task repetition costs as a measure of inhibition on the level of task sets. When switching back to a Task A after only one intermediate trial (ABA task sequence), Task A is thought to still be inhibited, leading to performance costs relative to task sequences where switching back to Task A is preceded by at least two intermediary trials (CBA). The current study investigated differences in inhibitory ability between children and adults by comparing n-2 task repetition costs in children (9-11years of age, N=32) and young adults (21-30years of age, N=32). The mean reaction times and error rate differences between ABA and CBA sequences did not differ between the two age groups. However, diffusion model analysis revealed that different cognitive processes contribute to the inhibition effect in the two age groups: The adults, but not the children, showed a smaller drift rate in ABA than in CBA, suggesting that persisting task inhibition is associated with slower response selection in adults. In children, non-decision time was longer in ABA than in CBA, possibly reflecting longer task preparation in ABA than in CBA. In addition, Ex-Gaussian functions were fitted to the distributions of correct reaction times. In adults, the ABA-CBA difference was reflected in the exponential parameter of the distribution; in children, the ABA-CBA difference was found in the Gaussian mu parameter. Hence, Ex-Gaussian analysis, although noisier, was generally in line with diffusion model analysis. Taken together, the data suggest that the task inhibition effect found in mean performance is mediated by different cognitive processes in children versus adults.

Mood states influence cognitive control: the case of conflict adaptation.

Conflict adaptation can be measured by the "congruency sequence effect", denoting the reduction of congruency effects after incongruent trials (where response conflict occurs) relative to congruent trials (without response conflict). Recently, it has been reported that conflict adaptation is larger in negative mood than in positive mood (van Steenbergen et al., Psychological Science 21:1629-1634, 2010). We conducted two experiments further investigating this important finding. Two different interference paradigms were applied to measure conflict adaptation: Experiment 1 was a Flanker task, Experiment 2 was a Stroop-like task. To get as pure a measure of conflict adaptation as possible, we minimized the influence of trial-to-trial priming effects by excluding all kinds of stimulus repetitions. Mood states were induced by presenting film clips with emotional content prior to the interference task. Three mood states were manipulated between subjects: amused, anxious, and sad. Across both interference paradigms, we consistently found conflict adaptation in negative, but not in positive mood. Taken together with van Steenbergen et al. (Psychological Science 21:1629-1634, 2010) findings, the results suggest that the negative-mood-triggered increase in conflict adaptation is a general phenomenon that occurs independently of the particular mood-induction procedure and interference paradigm involved.

Reward-based modulation of task-switching performance: a diffusion model analysis.

Investigating the interface between motivation and cognitive control, we conducted two task switching experiments (N = 96 each) with reward manipulation where participants switched between three different tasks. We measured N-2 task repetition costs, which denote the performance decrement in N-2 task repetition sequences (ABA) relative to N-2 task switch sequences (CBA), and which are presumed to be a marker of inhibitory control in task switching. Participants in the reward group received performance-contingent reward in the second phase of each experiment, and in the second experiment they were additionally penalized for errors. Reward thresholds were determined individually based on participants' performance during the first phase of each experiment. Participants in the control group did not receive any reward. The reward manipulation led to faster performance in the reward group relative to the control group. Diffusion modeling revealed that the reward manipulation induced an increase in drift rate parameter, consistent with dopamine-based enhancement of attentional focus under reward. Contrary to our expectations, no robust evidence for a reward-based modulation of N-2 repetition costs was found across the two experiments. N-2 task repetition costs were small in both experiments, and possibly, a larger amount of inhibitory control is needed in order to obtain empirical evidence for a reward-related modulation thereof. However, additional analyses suggested that reward may not interact with inhibitory control on the task level at all.

Stimulus-triggered task conflict affects task-selection errors in task switching: A Bayesian multinomial processing tree modeling approach.

In the present study, we used a modeling approach for measuring task conflict in task switching, assessing the probability of selecting the correct task via multinomial processing tree (MPT) modeling. With this method, task conflict and response conflict can be independently assessed as the probability of selecting the correct task and the probability of selecting the correct response within a given task, respectively. These probabilities can be estimated on the basis of response accuracy in the different experimental conditions. In two task-switching experiments, we used bivalent stimuli and manipulated irrelevant-task difficulty by varying the saliency of the stimulus feature belonging to the irrelevant task. The more salient the task-irrelevant stimulus feature, the more salient the irrelevant task, leading to more task conflict. Consistent with this assumption, we observed that task conflict, but not response conflict, was larger when the task-irrelevant stimulus feature was made more salient. Furthermore, both task conflict and response conflict were larger when the task switched than when the task was repeated. On a methodological level, the present results demonstrate that MPT modeling is a useful approach for measuring task conflict in task switching and for dissociating it from within-task response conflict. Furthermore, the present results inform theories of task switching by showing that the task-irrelevant feature tends to activate the irrelevant task set rather than being associated with a specific response option via a direct stimulus-response route. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Local and global control adjustments to stimulus-based task conflict in task switching.

A prominent feature of cognitive control is that its deployment is regulated depending on the environmental circumstances. Control upregulation has been widely documented in response-conflict paradigms where congruency effects are reduced both following incongruent trials, and in blocks where incongruent trials are the majority. In two pre-registered task-switching experiments, we investigated whether similar flexible mechanisms are also available when dealing with stimulus-based task conflict. Building up on previous Stroop studies, task conflict was measured as the difference in performance between bivalent congruent and univalent trials, which we name the "valency effect." If cognitive control is upregulated analogously to what observed with response conflict, valency effects should be reduced following bivalent trials and in majority-bivalent blocks. Furthermore, as cognitive control upregulation has been proposed to be task specific, we assessed whether switching to a new task eliminates the expected modulations of task. The results broadly matched our predictions. First, we observed a reduction of the valency effect following bivalent trials similar to the well-known congruency sequence effect, demonstrating similar patterns of flexible control adjustment to task and response conflict. This valency sequence effect was limited to task repetitions, indicating that local control adjustments are task specific. Furthermore, task conflict was reduced in majority-bivalent blocks, similar to the proportion-congruency effect. This finding extends previous Stroop studies suggesting that control is recruited proactively when dealing with stimulus-based task. The proportion valency effect was limited to task-switch trials, leaving open the question on the precise mechanisms behind sustained control adjustments.

N-2 Repetition Costs in Task Switching: Task Inhibition or Interference Between Task Episodes?

A prominent behavioral marker of inhibition in task switching is the "N-2 repetition cost" that denotes the decrement in performance in task sequences with an N-2 task repetition (ABA), relative to task sequences without an N-2 task repetition (CBA). Recently, it has been critized that N-2 repetition costs at least partially reflect interference between task episodes, rather than persisting inhibition, raising doubts about the interpretation of N-2 repetition costs as a measure of inhibition. Here, we aim to generalize these conclusions in two ways. First, we define episodic effects in task switching with respect to the last episode of the same task, which might have occurred several trials back (e.g., in trial N-2, N-3, etc.). Second, we distinguish between episodic interference caused by task-relevant and task-irrelevant features. We present a re-analysis of previously published data, and a new pre-registered experiment, where we manipulated the degree of interference between task episodes in three levels (episodic match of both task-relevant and task-irrelevant features, episodic match of only task-relevant features, episodic mismatch of both kinds of features). We observed empirical evidence for both cognitive mechansims: Episodic interference was indicated by a main effect of episodic condition; task-level inhibition was indicated by N-2 repetition costs, and by a performance benefit with increasing task lag in an exploratory task-lag analysis. We did not observe any significant modulation of N-2 repetition costs by episodic condition, suggesting that if there was such a modulation, this effect appears to be smaller than the individual contributions of episodic interference and inhibition to task performance.

Task conflict biases decision making.

The present research explores decision making in multitasking, investigating how people make optimal decisions between tasks. Empirical evidence suggests that difficulties in task performance (i.e., response conflict within a task) can bias decision making. Here we investigate whether also conflict between task representations can tune choices away from conflict-associated tasks. Using a combined forced/free-choice task-switching design, we tested whether task conflict that arises because of proactive interference of previously activated tasks biases task choice. We compared free-choice decisions between 3 tasks after forced-choice sequences that instigated either high task conflict (task sequences of type ABA, in which persisting inhibition needs to be overcome because one switches back to a just-abandoned task) or low task conflict (task sequences of type CBA). Results of 2 experiments (N = 16; N = 32, preregistered) showed that participants were more likely to switch away from the previously performed task after high than after low task conflict. Furthermore, participants preferably selected the task that suffered least from task conflict and/or proactive interference. In addition, a third experiment (N = 32) confirmed that this bias in task selection could not be explained in terms of randomness heuristics. These results suggest a close link between decision making and performance in multitasking. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Errors in task switching: Investigating error aftereffects in a N-2 repetition cost paradigm.

Studies of switching between tasks and studies of error commission have both provided solid behavioral measures of executive control. Nonetheless, a gap remains between these strands of research. In three experiments we sought to reduce this gap by assessing the impact of task errors on N-2 repetition costs, an effect supposedly related to task-set inhibition. Based on previous literature reporting a task-switch benefit following task errors, due to incidental learning of the erroneously executed task-set, we predicted N-2 repetition costs to be decreased after task errors in Trial N-2, relative to correct responses. Furthermore, we predicted this effect to be present only when corrective control mechanisms would not have the time to build up on the post-error trial (i.e., following fast post-error trial only). This hypothesis was tested in a three-tasks paradigm using incongruent stimuli, under the assumption that errors on such trials are partly due to task confusions. Consistent with our predictions, N-2 repetition costs following N-2 errors were found to be reduced when responses in Trial N-1 were fast but were present when the N-1 response was slow. Taken together, our results suggest that task execution leads to associative strengthening of the corresponding task-set, irrespective of response accuracy, and that such automatic strengthening can be counteracted by slowly acting control mechanisms. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Interplay of morphological configuration and language switching in numerical processing and word processing.

The aim of the present study was to examine the interplay of morphological configuration switching and language switching. The morphological configuration is present in word-formation whenever a word contains more than one free morpheme. The morphological configuration is variable both within and between languages for example in two-digit number names (is the decade named first as in twenty-one or the unit named first as in seventeen) and in compound words (is the modifier or the head named first). In the present experiments, participants had to switch between morphological configurations and between languages (German, English, and Spanish). Language-switch cost was measured as the performance difference between language-switch trials and language-repetition trials. In Experiments 1 and 2, participants performed language-comprehension tasks on two-digit numbers and a language-production task on compound words in Experiment 3. All three experiments revealed an under-additive switch cost pattern in which a larger language-switch cost occurred in morphological configuration-repetition trials than in morphological configuration-switch trials. Thus, the present data indicate integration of the morphological configuration and language into one language-related schema-irrespective of the language task (comprehension vs. production) and the type of stimuli (number words vs. compound nouns). (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Attention modulates motor system activation during action observation: evidence for inhibitory rebound.

Perceiving another individual's actions activates the human motor system. We investigated whether this effect is stronger when the observed action is relevant to the observer's task. The mu rhythm (oscillatory activity in the 8- to 13-Hz band over sensorimotor cortex) was measured while participants watched videos of grasping movements. In one of two conditions, the participants had to later report how many times they had seen a certain kind of grasp. In the other condition, they viewed the identical videos but had to later report how many times they had seen a certain colour change. The colour change and the grasp always occurred simultaneously. Results show mu rhythm attenuation when watching the videos relative to baseline. This attenuation was stronger when participants later reported the grasp rather than the colour, suggesting that the motor system is more strongly activated when the observed grasping actions were relevant to the observer's task. Moreover, when the graspable object disappeared after the offset of the video, there was subsequent mu rhythm enhancement, reflecting a post-stimulus inhibitory rebound. This enhancement was again stronger when making judgments about the grasp than the colour, suggesting that the stronger activation is followed by a stronger inhibitory rebound.

Cognitive Multitasking: Inhibition in Task Switching Depends on Stimulus Complexity.

We report a series of three experiments investigating inhibition in task switching, using N-2 repetition costs as an empirical marker. The experiments were structurally identical, employing a standard experimental paradigm where participants switch between three different categorization tasks. The experiments differed with respect to the stimulus material. According to prominent theories of cognitive control, N-2 repetition costs should be observed in all three experiments. To our surprise, this is not what we observed: N-2 repetition costs did not occur in Experiment 1, where we used static pictures from a driving simulator environment showing an oncoming car, embedded in a car-driving scene. In contrast, we observed robust N-2 repetition costs in Experiment 2, where we used static pictures of faces, and in Experiment 3, where the identical car stimuli from Experiment 1 were used, but without the surrounding visual scene. These results suggest that N-2 repetition costs depend on the complexity of the stimulus material. We discuss two aspects of complexity: 1) When the relevant stimulus feature is embedded in a complex visual scene, task-irrelevant features in that scene might trigger additional task sets, and thus induce additional task switches, attenuating N-2 repetition costs among the instructed task sets. 2) The presence of distractors might lead to additional covert or overt shifts of spatial attention, which in turn might reduce the size of N-2 repetition costs. On a more general level, the results illustrate the difficulty of transferring laboratory tasks to settings that bear more similarity to everyday life situations.

Examining binding effects on task switch costs and response-repetition effects: Variations of the cue modality and stimulus modality in task switching.

Typically, response-repetition effects are obtained in task-switching experiments: In task repetitions, performance is enhanced when the response, too, repeats (response-repetition benefits), whereas in task switches, performance is impaired when the response repeats (response-repetition costs). A previous study introduced cue modality switches in a cued task-switching paradigm with visual stimuli and obtained enhanced response-repetition benefits when the cue modality repeated (Koch, Frings, & Schuch Psychological Research, 82, 570-579, 2018). In the present study, we aimed to replicate this finding with auditory stimuli (Exp. 1), and further examined whether response-repetition effects could be modulated by introducing stimulus modality switches (Exp. 2). We found clear evidence that the cue modality and stimulus modality affect task switch costs. The task switch costs were higher with a repeated cue modality or stimulus modality. However, cue modality switches or stimulus modality switches did not affect the response-repetition effects. We suggest that response-repetition effects are elicited by response-associated bindings, which are not necessarily affected by all episodic task features to the same extent. Our results are also in line with theoretical accounts that assume a hierarchical organization of task selection and response selection.

Multilingual two-digit number naming: The influence of composition rules on language switching.

The aim of this study was to examine language switching in a two-digit number naming task. In contrast to single digits, two-digit numbers have a composition rule (i.e., morphological configuration) that may differ between languages. For example, the Arabic number 21 is read with an inverted composition rule in German (unit before decade) and a non-inverted composition rule in English (decade before unit). In the present experiment, one group of German native speakers and one group of Spanish native speakers had to name two-digit numbers in German, English, or Spanish. The results demonstrate a language-switch cost, revealing better performance in language repetition than in language-switch trials. This switch cost was further modulated by repeating or switching the composition rule, since the language repetition benefit (i.e., the switch cost) was reduced in trials with composition-rule switches compared with trials with composition-rule repetitions. This finding indicates that the language in which the number word has to be produced and its composition rule are not switched independently but rather may be integrated into one language schema.