Task-order control in dual-tasks: Only marginal interactions between conflict at lower levels and higher processes of task organization.

When simultaneously performing two tasks that share response properties, interference can occur. Besides general performance decrements, performance in the first task is worse when the second task requires a spatially incompatible response, known as the backward crosstalk effect (BCE). The size of this BCE, similar to congruency effects in conflict tasks, is subject to a sequential modulation, with a smaller BCE after incompatible compared to compatible trials. In the present study, we focus on a potential bidirectional interaction between crosstalk (and its resolution) at a lower level of task performance and higher-order processes of task organization. Two questions were of particular interest: First, do participants switch task order more frequently after a conflict-prone incompatible trial than after a compatible trial? Second, does changing task order influence the efficiency of conflict resolution, as indexed by the size of the sequential modulation of the BCE. Across four experiments, we only found marginal evidence for an influence of lower-level conflict on higher-order processes of task organization, with only one experiment revealing a tendency to repeat task order following conflict. Our results thus suggest practical independence between conflict and task-order control. When separating processes of task selection and task performance, the sequential modulation was generally diminished, suggesting that conflict resolution in dual-tasks can be disrupted by a deliberate decision about task order, or, alternatively, by a longer inter-trial interval. Finally, the study found a strong bias towards repeating the same task order across trials, suggesting that task-order sets not only impact task performance but also guide task selection.

Separating facilitation and interference in backward crosstalk.

When two speeded tasks have spatially overlapping responses, preactivated Task 2 (T2) response information influences Task 1 (T1) response selection, a phenomenon known as the backward crosstalk effect (BCE). Current models of the BCE implicitly assume that T2 response information is equally present in trials requiring compatible or incompatible responses, such that T1 performance improves when T2 requires a compatible response and deteriorates when T2 requires an incompatible response. Thus, T2 response information should have a facilitatory and an interfering effect on T1. Interestingly, this hypothesis has never been tested, and the present study (conducted between 2021 and 2023) attempts to fill this gap by using neutral trials in which T2 responses did not spatially overlap with those in T1. The results suggest that the BCE (in T1) reflects both facilitation and interference effects of comparable magnitude, thus corroborating current conceptualizations of the BCE. We also observed an unexpected pattern of effects for T2, with only an interference effect, but no facilitation effect. Additional experiments led us to conclude that the T2 result was sensitive to the specific task characteristics. Conclusions about how the crosstalk transfers from T1 to T2 when switching tasks are therefore not possible. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

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).

Response activation and activation-transmission in response-based backward crosstalk: Analyses and simulations with an extended diffusion model.

In dual-task experiments, overlapping response characteristics of two subsequently performed tasks may not only affect performance in Task 2 but also in Task 1. This phenomenon is often explained through activated Task 2 response information influencing Task 1 response selection, which then possibly propagates again into Task 2. So far, however, only little is known about (a) the time course of this Task 2 response activation and (b) possible transmission/propagation mechanisms. The present study addressed both issues by testing 10 plausible drift-diffusion models with 5 data sets from dual-task experiments. To this end, we first examined if the temporal course of the response activation is linearly increasing or pulse like. The pulse-like model turned out to be superior, but the corresponding dynamics of the response activation often described a monotonically increasing function that reached its peak late during Task 1 processing. By extending the pulse-like model with an additional diffusion process, we then examined whether and how the Task 2 response information could affect subsequent Task 2 response selection. Concerning the transmission mechanisms, none of the assumed models proved to be entirely satisfactory. However, additional simulations suggest that Task 2 response activation-transmission does not occur at all. Instead, a model in which Task 2 started with a trace of the previous Task 1 response (i.e., irrespective of the preexisting Task 2 activation) turned out to be the most promising account. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The role of task-relevant and task-irrelevant information in congruency sequence effects: Applying the diffusion model for conflict tasks.

In conflict tasks, such as the Simon, Eriksen flanker, or Stroop task, the congruency effect is often reduced after an incongruent compared to a congruent trial: the congruency sequence effect (CSE). It was suggested that the CSE may reflect increased processing of task-relevant information and/or suppression of task-irrelevant information after experiencing an incongruent relative to a congruent trial. In the present study, we contribute to this discussion by applying the Diffusion Model for Conflict tasks (DMC) framework in the context of CSEs to flanker and Simon tasks. We argue that DMC independently models the task-relevant and task-irrelevant information and thus is a first good candidate for disentangling their unique contributions. As a first approach, we fitted DMC conjointly or separately to previously congruent or incongruent trials, using four empirical flanker and two Simon data sets. For the flanker task, we fitted the classical DMC version. For the Simon task, we fitted a generalized DMC version which allows the task-irrelevant information to undershoot when swinging back to zero. After considering the model fits, we present a second approach, where we implemented a cognitive control mechanism to simulate the influence of increased processing of task-relevant information or increased suppression of task-irrelevant information. Both approaches demonstrate that the suppression of task-irrelevant information is essential to create the typical CSE pattern. Increased processing of task-relevant information, however, could rarely describe the CSE accurately.

A tutorial on using the paired t test for power calculations in repeated measures ANOVA with interactions.

The a priori calculation of statistical power has become common practice in behavioral and social sciences to calculate the necessary sample size for detecting an expected effect size with a certain probability (i.e., power). In multi-factorial repeated measures ANOVA, these calculations can sometimes be cumbersome, especially for higher-order interactions. For designs that only involve factors with two levels each, the paired t test can be used for power calculations, but some pitfalls need to be avoided. In this tutorial, we provide practical advice on how to express main and interaction effects in repeated measures ANOVA as single difference variables. In particular, we demonstrate how to calculate the effect size Cohen's d of this difference variable either based on means, variances, and covariances of conditions or by transforming [Formula: see text] or [Formula: see text] from the ANOVA framework into d. With the effect size correctly specified, we then show how to use the t test for sample size considerations by means of an empirical example. The relevant R code is provided in an online repository for all example calculations covered in this article.

Serial and parallel processing in multitasking: Concepts and the impact of interindividual differences on task and stage levels.

In multitasking research, a central question revolves around whether humans can process tasks in parallel. What "in parallel" refers to, however, differs between research perspectives and experimental approaches. From a task-level perspective, parallel processing can be conceived as to whether complete tasks are processed in an overlapping manner and how this impacts task performance. In contrast, a large body of literature solely focuses on the central stage of response-selection and whether it can run in parallel with other processing stages, an approach we refer to as the stage-level perspective. Importantly, although each perspective addresses related topics and highlights interindividual differences, they evolved through independent lines of research. In 2 experiments, we have taken a first step to investigate if individuals' tendencies for an overlapping versus serial processing mode on the task level are related to vulnerabilities for task interference on the stage level. Individual preferences for either task processing mode were assessed in the task switching with preview (TSWP) paradigm. Individuals' vulnerability for task interference was assessed with the backward crosstalk effect (BCE) in a classical dual task. Our results suggest that individuals who prefer overlapping relative to serial task processing at the task level are less vulnerable to task interference during response selection, indicated by a smaller BCE. This difference, however, only emerged in the second experiment with an increased sample size and with task-stimuli that facilitate a bottom-up separation of tasks in the dual-task. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

S1-R2 and R1-R2 Backward Crosstalk Both Affect the Central Processing Stage.

A frequent observation in dual-task experiments is that performance in Task 1 is influenced by conceptual or spatial overlap with features of Task 2. Such compatibility-based backward crosstalk effects (BCEs) can occur when overlap exists between the responses of two tasks-the R1-R2 BCE-or between the stimulus in Task 1 and the response in Task 2-the S1-R2 BCE. The present study investigated whether the S1-R2 BCE has a perceptual locus, and by implication, whether the two BCEs have a common processing locus or different ones. To this end, we applied the additive factors logic and manipulated the duration of the Task 1 perceptual stage. The results argue against a perceptual locus for both BCEs. As a possible explanation, we suggest that the R1-R2 BCE and the S1-R2 BCE have their locus within a capacity-limited central stage, but that they arise from different processes within this stage. The R1-R2 BCE influences Task 1 response selection, whereas the S1-R2 BCE influences Task 1 stimulus classification. A plausible though post-hoc model is presented within the Discussion.