The temporal dynamics of task processing and choice in a novel multitasking paradigm.

This study investigated the temporal dynamics of task performance and voluntary task choice within a multitasking paradigm in which the task-related processing outcomes themselves determined the to-be-performed task. In the novel forced-no-go trials, the stimulus for one task required an overt response, but the stimulus for the other task was associated with a no-go response. Task performance results showed that participants often processed the no-go task's stimulus before switching to the go-task. Dual-task interference effects and switch costs indicated various forms of multitasking interference, with their underlying causes appearing to overlap, as engagement in parallel processing seemed to be limited by switch-related reconfiguration processes. Intermixing free-choice trials, where both stimuli were associated with overt responses, revealed costs associated with switching between processing modes, providing new evidence that the distinctions between free and forced task goals stem from differences in their internal representations rather than alterations in processing due to different presentations in the environment. Task choice results align with this perspective, demonstrating a preference for repeating a free- over a forced-choice task. Furthermore, these free-choice results illuminate the interplay of cognitive (task-repetition bias) and environmental constraints (first-task bias) in shaping task choices: It appears that task-specific information increases goal activations for both task goals concurrently, with participants favoring central processing of the second- over the first-presented task to optimize their behavior when shorter central processing is required (task repetition). Overall, this study offers new insights into the dynamics of task processing and choice in environments requiring the balance of multiple tasks.

Exploring behavioral adjustments of proportion congruency manipulations in an Eriksen flanker task with visual and auditory distractor modalities.

The present study investigated global behavioral adaptation effects to conflict arising from different distractor modalities. Three experiments were conducted using an Eriksen flanker paradigm with constant visual targets, but randomly varying auditory or visual distractors. In Experiment 1, the proportion of congruent to incongruent trials was varied for both distractor modalities, whereas in Experiments 2A and 2B, this proportion congruency (PC) manipulation was applied to trials with one distractor modality (inducer) to test potential behavioral transfer effects to trials with the other distractor modality (diagnostic). In all experiments, mean proportion congruency effects (PCEs) were present in trials with a PC manipulation, but there was no evidence of transfer to diagnostic trials in Experiments 2A and 2B. Distributional analyses (delta plots) provided further evidence for distractor modality-specific global behavioral adaptations by showing differences in the slope of delta plots with visual but not auditory distractors when increasing the ratio of congruent trials. Thus, it is suggested that distractor modalities constrain global behavioral adaptation effects due to the learning of modality-specific memory traces (e.g., distractor-target associations) and/or the modality-specific cognitive control processes (e.g., suppression of modality-specific distractor-based activation). Moreover, additional analyses revealed partial transfer of the congruency sequence effect across trials with different distractor modalities suggesting that distractor modality may differentially affect local and global behavioral adaptations.

Reactive and proactive control processes in voluntary task choice.

Deciding which task to perform when multiple tasks are available can be influenced by external influences in the environment. In the present study, we demonstrate that such external biases on task-choice behavior reflect reactive control adjustments instead of a failure in control to internally select a task goal. Specifically, in two experiments we delayed the onset of one of two task stimuli by a short (50 ms), medium (300 ms), or long (1,000 ms) stimulus-onset asynchrony (SOA) within blocks while also varying the relative frequencies of short versus long SOAs across blocks (i.e., short SOA frequent vs. long SOA frequent). Participants' task choices were increasingly biased towards selecting the task associated with the first stimulus with increasing SOAs. Critically, both experiments also revealed that the short-to-medium SOA bias was larger in blocks with more frequent long SOAs when participants had limited time to prepare for an upcoming trial. When time to select an upcoming task was extended in Experiment 2, this interaction was not significant, suggesting that the extent to which people rely on reactive control adjustments is additionally modulated by proactive control processes. Thus, the present findings also suggest that voluntary task choices are jointly guided by both proactive and reactive processes, which are likely to adjust the relative activation of different task goals in working memory.

Motor demands influence conflict processing in a mouse-tracking Simon task.

Previous studies have shown incorrect motor activation when making perceptual decisions under conflict, but the potential involvement of motor processes in conflict resolution is still unclear. The present study tested whether the effects of distracting information may be reduced when anticipated motor processing demands increase. Specifically, across two mouse-tracking Simon experiments, we manipulated blockwise motor demands (high vs. low) by requiring participants to move a mouse cursor to either large versus small (Experiment 1) or near versus far (Experiment 2) response boxes presented on the screen. We reasoned that participants would increase action control in blocks with high versus low motor demands and that this would reduce the distracting effect of location-based activation. The results support this hypothesis: Simon effects were reduced under high versus low motor demands and this modulation held even when controlling for time-varying fluctuations in distractor-based activation via distributional analyses (i.e., delta plots). Thus, the present findings indicate that anticipation of different motor costs can influence conflict processing. We propose that the competition between distractor-based and target-based activation is biased at premotor and/or motor stages in anticipation of motor demands, but also discuss alternative implementations of action control.

Investigating limits of task prioritization in dual-tasking: evidence from the prioritized processing and the psychological refractory period paradigms.

Dual-tasking often requires prioritizing one task over the other. For example, in the psychological refractory period (PRP) paradigm, participants are instructed to initially respond to Task 1 (T1) and only then to Task 2 (T2). Furthermore, in the prioritized processing paradigm (PP), participants are instructed to perform T2 only if T1 was a no-go trial-requiring even more prioritization. The present study investigated the limits of task prioritization. Two experiments compared performance in the PRP paradigm and the PP paradigm. To manipulate task prioritization, tasks were rewarded differently (e.g., high reward for T1, low reward for T2, and vice versa). We hypothesized (a) that performance will improve for the highly rewarded task (Experiments 1 and 2) and (b) that there are stronger reward effects for T1 in the PRP than in the PP paradigm (Experiment 2). Results showed an influence of reward on task prioritization: For T1, high reward (compared to low reward) caused a speed-up of responses that did not differ between the two paradigms. However, for T2, reward influenced response speed selectively in the PP paradigm, but not in the PRP paradigm. Based on paradigm-specific response demands, we propose that the coordination of two motor responses plays a crucial role in prioritizing tasks and might limit the flexibility of the allocation of preparatory capacity.

Beyond mean reaction times: Combining distributional analyses with processing stage manipulations in the Simon task.

We combined analyses of reaction time (RT) distributions with experimental manipulations of different processing stages (perception, decision, motor execution) in a Simon task to investigate which changes in Simon effects could be explained entirely by fading irrelevant response activation. Consistent with fading activation accounts, the Simon effect on mean RT was usually smaller for conditions with slower responses (Expts. 1-3 but not Expt. 4), and delta plot analyses revealed that it was always smaller for the slower responses within each condition. Critically, however, these analyses also revealed that some experimental manipulations produced upward or downward shifts in the RT delta plots, thus altering the Simon effect on mean RT in ways that could not be explained by fading activation. The results demonstrate the power of combining RT distributional analyses with experimental manipulations to reveal mechanisms contributing to the Simon effect that would not be revealed using only mean RT. We consider alternatives to fading activation accounts of decreasing delta plots and discuss the contribution of different cognitive stages in modulating Simon effects.

Exploring the repetition bias in voluntary task switching.

In the voluntary task-switching paradigm, participants are required to randomly select tasks. We reasoned that the consistent finding of a repetition bias (i.e., participants repeat tasks more often than expected by chance) reflects reasonable adaptive task selection behavior to balance the goal of random task selection with the goals to minimize the time and effort for task performance. We conducted two experiments in which participants were provided with variable amount of preview for the non-chosen task stimuli (i.e., potential switch stimuli). We assumed that switch stimuli would initiate some pre-processing resulting in improved performance in switch trials. Results showed that reduced switch costs due to extra-preview in advance of each trial were accompanied by more task switches. This finding is in line with the characteristics of rational adaptive behavior. However, participants were not biased to switch tasks more often than chance despite large switch benefits. We suggest that participants might avoid effortful additional control processes that modulate the effects of preview on task performance and task choice.

Trading off switch costs and stimulus availability benefits: An investigation of voluntary task-switching behavior in a predictable dynamic multitasking environment.

In the present study, we introduce a novel, self-organized task-switching paradigm that can be used to study more directly the determinants of switching. Instead of instructing participants to randomly switch between tasks, as in the classic voluntary task-switching paradigm (Arrington & Logan, 2004), we instructed participants to optimize their task performance in a voluntary task-switching environment in which the stimulus associated with the previously selected task appeared in each trial after a delay. Importantly, the stimulus onset asynchrony (SOA) increased further with each additional repetition of this task, whereas the stimulus needed for a task switch was always immediately available. We conducted two experiments with different SOA increments (i.e., Exp. 1a = 50 ms, Exp. 1b = 33 ms) to see whether this procedure would induce switching behavior, and we explored how people trade off switch costs against the increasing availability of the stimulus needed for a task repetition. We observed that participants adapted their behavior to the different task environments (i.e., SOA increments) and that participants switched tasks when the SOA in task switches approximately matched the switch costs. Moreover, correlational analyses indicated relations between individual switch costs and individual switch rates across participants. Together, these results demonstrate that participants were sensitive to the increased availability of switch stimuli in deciding whether to switch or to repeat, which in turn demonstrates flexible adaptive task selection behavior. We suggest that performance limitations in task switching interact with the task environment to influence switching behavior.

Transfer of task-probability-induced biases in parallel dual-task processing occurs in similar, but is constraint in distinct task sets.

Although humans often multitask, little is known about how the processing of concurrent tasks is managed. The present study investigated whether adjustments in parallel processing during multitasking are local (task-specific) or global (task-unspecific). In three experiments, participants performed one of three tasks: a primary task or, if this task did not require a response, one of two background tasks (i.e., prioritized processing paradigm). To manipulate the degree of parallel processing, we presented blocks consisting mainly of primary or background task trials. In Experiment 1, the frequency manipulation was distributed equally across the two background tasks. In Experiments 2 and 3, only one background task was frequency-biased (inducer task). The other background task was presented equally often in all blocks (diagnostic task) and served to test whether processing adjustments transferred. In all experiments, blocks with frequent background tasks yielded stronger interference between primary and background tasks (primary task performance) and improved background task performance. Thus, resource sharing appeared to increase with high background task probabilities even under triple task requirements. Importantly, these adjustments generalized across the background tasks when they were conceptually and visually similar (Experiment 2). Implementing more distinct background tasks limited the transfer: Adjustments were restricted to the inducer task in background task performance and only small transfer was observed in primary task performance (Experiment 3). Overall, the results indicate that the transfer of adjustments in parallel processing is unrestricted for similar, but limited for distinct tasks, suggesting that task similarity affects the generality of resource allocation in multitasking. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Perceptual target discriminability modulates the Simon effect beyond the fading of distractor-based activation: Insights from delta plots and diffusion model analyses.

The visual Simon task is widely employed to explore the underlying mechanisms of sensorimotor processing in the presence of task-relevant (targets) and task-irrelevant (distracting) location information. Critically, the Simon effect is considered as an indicator of action-related interference resulting from distractor-based activation, which fades out over time. In this study, we tested whether attenuated Simon effects with slower task processing may be fully explained by the fading of distractor-based response activation. To that end, we selectively manipulated perceptual target discriminability by varying the ratio of differently colored dots within (Experiment 1) and between blocks (Experiment 2). According to pure fading activation accounts, the negative-going delta plots of the two discriminability conditions should overlap across the entire reaction time (RT) distribution. In contrast to this prediction, the negative-going DPs for the two discriminability conditions did not overlap in either experiment. Instead, the Simon effect was either consistently smaller (Experiment 1) or larger (Experiment 2) across the entire RT distribution in the easy condition compared to the hard condition. This result pattern indicates that perceptual target discriminability affected conflict resolution beyond the mere fading of distractor-based activation. Exploratory model-based analyses suggest a stronger processing of relevant perceptual information with more discriminable targets, which may counteract the influence of distracting location information. However, as the exact effects of discriminability on conflict processing seem to depend on variation mode (trialwise vs. blockwise), the importance of global strategic effects is also highlighted. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Transfer of cognitive control adjustments within and between speakers.

Congruency effects in conflict tasks are typically larger after congruent compared to incongruent trials. This congruency sequence effect (CSE) indicates that top-down adjustments of cognitive control transfer between processing episodes, at least when controlling for bottom-up memory processes by alternating between stimulus-response (S-R) sets in confound-minimised designs. According to the control-retrieval account, cognitive control is bound to task-irrelevant context features (e.g., stimulus position or modality) and retrieved upon subsequent context feature repetitions. A confound-minimised CSE should therefore be larger when context features repeat rather than change between two trials. This study tested this prediction for a more abstract contextual stimulus feature, speaker gender. In two preregistered auditory prime-probe task experiments, participants classified colour words spoken by a female or male voice. Across both experiments, we found confound-minimised CSEs that were not reliably affected by whether the speaker gender repeated or changed. This indicates that speaker transitions have virtually no influence on the transfer of control adjustments in the absence of S-R repetitions. By contrast, when allowing for bottom-up memory processes by repeating the S-R set, CSEs were consistently larger when the speaker gender repeated compared to changed. This suggests that speaker transitions can in principle influence transfer between processing episodes. The discrepancy also held true when considering learning and test episodes separated by an intervening episode. Thus, the present findings call for a refinement of the control-retrieval account to accommodate the role of more abstract contextual stimulus features for the maintenance of memory traces in auditory conflict processing.

Proactive reward in conflict tasks: Does it only enhance general performance or also modulate conflict effects?

In the present study, we investigated the influence of performance-contingent reward prospects on task performance across three visual conflict tasks with manual responses (Experiments 1 & 2: Simon and Stroop tasks; Experiment 3: Simon and Eriksen flanker task) using block-wise (Experiment 1) and trial-wise (Experiments 2 & 3) manipulations to signal the possibility of reward. Across all experiments, task performance (in reaction time and/or error rates) generally improved in reward compared with no-reward conditions in each conflict task. However, there was, if any, little evidence that the reward manipulation modulated the size of the mean conflict effects, and there was also no evidence for conflict-specific effects of reward when controlling for time-varying fluctuations in conflict processing via distributional analyses (delta plots). Thus, the results provide no evidence for conflict-specific accounts and instead favor performance-general accounts, where reward anticipation leads to overall performance improvements without affecting conflict effects. We discuss possible implications for how proactive control might modulate the interplay between target- and distractor-processing in conflict tasks.

The impact of distractor relevance on the strength and timing of cognitive control: Evidence from delta plots and diffusion model analyses.

In the present study, we examined how the relevance of potentially distracting information modulates the interplay of target and distractor processing in conflict tasks. Specifically, we manipulated the degree to which distracting information is relevant for performing the overall task by varying the proportion of trials in which a response to the distractor(s) (Experiments 1a and 1b: location in a Simon task; Experiment 2: flankers in an Eriksen flanker task) instead of to the target was required. Across all experiments, the congruency effect on mean RT was larger with the increasing relevance of the distractor(s). Critically, the slopes of the delta plot were more strongly increasing when the distractors were potentially relevant (as opposed to completely irrelevant), suggesting that cognitive control affects the timing of suppressing distractor-based activation. In addition, delta plot and diffusion model analyses revealed that the strength of suppressing distractor processing and the efficiency of target processing were enhanced when the distractors were less relevant. Overall, the present study dissociated multiple and time-dependent adjustments of control processes (i.e., target processing enhancement plus timing and strength of distractor suppression) in environments that encourage either a more stable or more flexible processing mode. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Cognitive control in cross-modal contexts: Abstract feature transitions of task-related but not task-unrelated stimuli modulate the congruency sequence effect.

Context information can guide cognitive control, but both the extent and the underlying processes are poorly understood. Previous studies often found that the congruency sequence effect (CSE) is larger when perceptual context features (e.g., modality and format) of task-related distractors and targets repeat compared to change. However, it is unclear whether control adjustments can also be contextualized by more abstract stimulus features and/or by features of task-unrelated stimuli. The present study addressed this issue using a novel context manipulation in a confound-minimized prime-probe task. In Experiment (Exp.) 1, the modality (visual and auditory) of the distractor and target either repeated or changed. Critically, in Exp. 2, the distractor and target modality always switched, but the cross-modal intensity (brightness and loudness) could either repeat (e.g., bright → loud) or change (e.g., bright → soft). A larger CSE for context repeats (vs. changes) was observed in Exps. 1 and 2, indicating that both concrete (modality) and abstract stimulus features (cross-modal intensity) can contextualize control adjustments. Exps. 3 and 4 demonstrated that the CSE was not reliably affected when the context manipulation concerned a prior signal or a simultaneous background stimulus. Thus, task-related, but not task-unrelated, concrete and abstract stimulus features contextualize control adjustments. Moreover, distributional (delta plot) analyses of present and previous data revealed that the confound-minimized CSE and its contextual modulation reflect adjustments in the strength of cognitive control rather than in its timing. Overall, the present study provides new insights into how context information interacts with cognitive control to optimize decision making under conflict. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The influence of reward in the Simon task: Differences and similarities to the Stroop and Eriksen flanker tasks.

Previous studies have suggested that performance-contingent reward can modulate cognitive control by biasing irrelevant location-response associations in the Simon task. However, the influence of reward in the case of irrelevant words (Stroop task) or irrelevant flankers (Eriksen Flanker task) remains unclear. Across two preregistered experiments, the present study investigated the influence of reward on conflict processing with different types of distractors. Conflict effects on mean reaction time (RT) were reduced in the Simon task (Experiments 1 and 2) when incongruent versus congruent trials were rewarded, and this modulating effect of reward on conflict processing was also observed in the Eriksen flanker task (Experiment 2), but not in the Stroop task (Experiment 1). We propose that cognitive control adjustments to distractor-specific reward contingencies can be generalized across distractor types producing both perceptual-related (Flanker task) and motor-related (Simon task) conflict, but, if any, to a limited degree when distractors produce additional higher-level task conflict (Stroop task). In addition, distributional RT analyses (delta plots) revealed that rewarded distractor-response associations modulate cognitive control not only via biasing the strength (Simon and Eriksen tasks) but also the time-course of suppressing distractor processing (Eriksen task). Overall, the present study dissociated distractor-general and distractor-specific effects of reward on cognitive control.

The Role of Effector-Specific Task Representations in Voluntary Task Switching.

There has been an increasing interest in uncovering the mechanisms underpinning how people decide which task to perform at a given time. Many studies suggest that task representations are crucial in guiding such voluntary task selection behavior, which is primarily reflected in a bias to select task repetitions over task switches. However, it is not yet clear whether the task-specific motor effectors are also a crucial component of task representations when deciding to switch tasks. Across three experiments using different voluntary task switching (VTS) procedures, we show that a greater overlap in task representations with a task-to-finger mapping than task-to-hand mapping increases participants' switching behavior (Exp. 1 and Exp. 2), but not when they were instructed to randomly select tasks (Exp. 3). Thus, task-specific stimulus-response associations can change the way people mentally represent tasks and influence switching behavior, suggesting that motor effectors should be considered as a component of task representations in biasing cognitive flexibility.

A Diffusion Model Analysis of Object-Based Selective Attention in the Eriksen Flanker Task.

Selective attention might be space-, feature-, and/or object-based. Clear support for the involvement of an object-based mechanism is rather scarce, possibly because the predictions of models from these different classes often overlap. Yet, only object-based models can account for a larger congruency effect (CE) in the Eriksen flanker task when flankers are more (vs. less) strongly grouped to the target, but spacing and other response-irrelevant features of target and flankers are held constant. Exactly this was observed by Kramer and Jacobson (1991). So far, this theoretically relevant finding has not been replicated closely. We replicated the finding in two web-based experiments. Specifically, CEs were larger when flanker lines were connected to the central target line (vs. to outer neutral lines). We also successfully fitted the Diffusion Model for Conflict tasks (DMC) to the experimental data. Critically, diffusion modeling (DMC) and distributional analyses (delta functions) revealed that object membership primarily affected target processing strength rather than strength or timing of flanker processing. This challenges the prominent attentional spreading (sensory enhancement) account of object-based selective attention and motivates an alternative target attenuation account.

Electrophysiological evidence against parallel motor processing during multitasking.

We combined behavioral measures with electrophysiological measures of motor activation (i.e., lateralized readiness potentials, LRPs) to disentangle the relative contribution of premotor and motor processes to multitasking interference in the prioritized processing paradigm. Specifically, we presented stimuli of two tasks (primary and background task) in each trial, but participants were instructed to perform the background task only if the primary task required no response. As expected, task performance was substantially influenced by a task probability manipulation: Background task responses were faster, psychological refractory period effects were smaller, and interference from the second task (i.e., backward compatibility effects) was larger when there was a larger probability that this task required a response. Critically, stimulus-locked and response-locked LRP analyses indicate that these behavioral effects of parallel processing were not driven by background task motor processing (e.g., motoric response activation) taking place during primary task processing. Instead, the LRP results suggest that these effects were exclusively localized during premotor stages of processing (e.g., response selection). Thus, the present results generally provide evidence for multitasking accounts allowing parallel task processing during response selection, whereas the task-specific motor responses are activated in a serial manner. One plausible account is that multiple task information sources can be processed in parallel, with sharing of limited cognitive resources depending on task relevance, but a primary and still active task goal prevents motor activation related to the goals of other tasks in order to avoid outcome conflict.

The role of temporal order of relevant and irrelevant dimensions within conflict tasks.

Conflict tasks are commonly used to investigate control processes under situations of relevant and irrelevant sources of information. In addition to compatibility effects at a mean behavioral level, delta plot analyses of reaction time distributions reveal that the compatibility effect generally increases with time (i.e., positive delta plot slopes) across most conflict-like tasks. Critically, the underlying causes of the increasing delta plot slopes with different types of distractors are still poorly understood. The present study tested whether the relative onset of target-to-distractor processing affects the delta plot slope. Specifically, we manipulated the temporal order of relevant and irrelevant dimensions within an Eriksen flanker task (Experiment [Exp.] 1), an Arrow-Simon task (Exp. 2), and a manual Stroop task (Exp. 3a/3b). The results of the Eriksen flanker task and Arrow-Simon task revealed that the delta plots slopes were less increasing (and instead rather decreasing) when the irrelevant dimension appears first (IR condition) compared to the reversed order (RI condition)-consistent with the idea that the underlying mechanism driving the slope of the delta plot is the temporal overlap of activation between the relevant and irrelevant dimensions. In contrast, for the Stroop task, the delta plots in the RI condition were not more increasing than the ones for the IR condition. Overall, these results suggest that the temporal properties strongly influence delta plot shape, but that the temporal dynamics operating in the flanker task and the Arrow-Simon task differs from the Stroop task, at least under conditions where relevant and irrelevant information is presented sequentially. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Perceptual processing demands influence voluntary task choice.

Previous studies have suggested that people are sensitive to anticipated cognitive processing demands when deciding which task to perform, but the influence of perceptual processing demands on voluntary task choice is still unclear. The present study tested whether voluntary task choice behavior may be influenced by unpredictable task-specific perceptual processing demands. Across four experiments using different voluntary task choice procedures, we randomly varied the perceptual discriminability of stimuli (easy vs. hard color discrimination) for one of the two tasks. We reasoned that people could only reactively adjust their task choice behavior to the unpredictable discriminability manipulation if they engaged in some perceptual processing before a task goal becomes sufficiently activated to select the task for further processing. The results confirmed this hypothesis: Task performance data demonstrated the presence of perceptual (discriminability effects) and cognitive (switch costs) processing demands. Participants' choice behavior was affected by both types of processing demands (as reflected in a task repetition bias and a bias to select the color task with easy compared to hard discriminations). Thus, the present findings indicate that both perceptual and cognitive processing demands influence voluntary task choice behavior. We propose that higher-level goal activations interact at least partially with early perceptual processes to influence task choice behavior, suggesting a locus of voluntary choices during or after the perceptual stage within the information-processing stream.