Two types of between-task conflict trigger respective processing adjustments within one dual-task

Sequential adjustments of task-pair control in dual-task contexts: Examining the role of repetition priming effects at the level of task-pair sets and abstract control states

In dual-task situations, two stimuli are presented in rapid succession, requiring participants to perform two tasks simultaneously. Prior studies suggested that when two tasks are performed simultaneously, information about the identity of the two tasks is represented in a joint cognitive representation, referred to as the task-pair set. This evidence comes from studies showing that switching between different task pairs results in performance costs, called task-pair switch costs (i.e., performance in task-pair switches vs. repetitions). In the present study, we focused on the adjustive characteristics of task-pair switching by investigating whether task-pair switch costs are sequentially modulated by the previous experience with a task-pair switch (vs. repetition). First, we reanalyzed the data of four published experiments and observed a reduction of task-pair switch costs after a task-pair switch trial relative to after a task-pair repetition trial. Second, we confirmed this novel finding in a new experiment. The new experiment also showed that performance in a current task-pair repetition was better after a task-pair repetition than after a task-pair switch, whereas the performance in a current task-pair switch was not modulated by the task-pair sequence in the previous trial. These findings suggest that automatic bottom-up repetition priming at the level of task-pair sets, rather than repetition priming at the level of abstract control states, contributes to the sequential adjustment of task-pair switch costs.

Prospective reward in dual task induces a bias towards action at the cost of less accurate Task 2 performance

In dual tasks, with a visual-manual choice reaction time task in Task 1 and a go/no-go task in Task 2, not responding to Task 2 can have adverse effects on Task 1 performance, as demonstrated by no-go backward crosstalk effects (no-go BCE). Here, the response inhibition required to not respond to Task 2 spills over and slows response execution in Task 1. Over three experiments, we investigated whether the prospect of reward, which is a potent cognitive control modulator, influences no-go BCE. In Experiment 1, reward for fast and accurate responses in both tasks was modulated as a within-subject factor, and in Experiments 2 and 3, as a between-subject factor. The results revealed three major insights. In all three experiments, reward led to faster Task 1 and Task 2 performance. Second, despite this speeding, the no-go BCE was not modulated by reward. Finally, the reward led to more errors in Task 2 no-go trials. These results reveal a reward-induced bias for action, suggesting better preparedness to respond and, consequently, larger commission errors in Task 2 no-go trials. The absence of a reward-based modulation of the no-go BCE indicates that the reward-induced bias for action does not necessarily translate into larger response inhibition. These findings point towards the complex interactions between reward and inhibitory control and shed light on the potentials and limitations of reward-based modulation of dual-task interference.

The affective consequences of response inhibition determine no-go-based crosstalk effects in dual tasks

Backward crosstalk effects (BCEs) are observed in dual-task studies when characteristics of Task 2 influence Task 1 performance. When Task 2 is a go/no-go task, responses in Task 1 are slower when Task 2 is a no-go as compared with a go trial. This no-go BCE has been argued to be due to response inhibition spilling over from Task 2 to Task 1. Growing evidence shows that response inhibition elicits negative affect leading to affective devaluation of associated stimuli. We tested for a functional role of the negative affective consequence of response inhibition in the no-go BCE by investigating its interaction with affective processing in Task 1. In four experiments, Task 1 was a valence categorisation task, and Task 2 a go/no-go task. In all experiments, the no-go BCE strongly depended on affective processing in Task 1. While this modulation could be attributed to an affective (mis)match between stimulus features in both tasks in Experiments 1 and 2, Experiments 3 and 4 provided evidence for an affective (mis)match between stimulus valence in Task 1 and affective consequences of Task 2 response inhibition. The results are discussed in the context of current theories of no-go BCEs in dual tasks.

Temporal aspects of two types of backward crosstalk in dual-tasks: An analysis of continuous mouse-tracking data

A common explanation for processing limitations in dual-tasking is the existence of a bottleneck during response selection, meaning that the selection of responses can only occur serially for different tasks. However, a large body of data shows that features of a (secondary) Task 2 can already influence the processing of a (primary) Task 1. Such effects are referred to as backward crosstalk effects (BCEs). In the present study, two types of such BCEs were investigated: the compatibility-based BCE, which depends on the dimensional (often spatial) overlap between task features, and a BCE based on a go/no-go task in Task 2 (no-go BCE). Joining a line of research that suggests different mechanisms for these two types of BCEs, we investigated them using a mouse-tracking setup. Time continuous analyses revealed that the compatibility-based BCE triggered a spatial activation of the Task 2 response early during Task 1 processing, whereas the no-go BCE triggered an inhibitory effect in the case of a no-go Task 2, which spills over to Task 1 execution. This occurred, however, earlier in the time course than expected. The results are discussed with regard to recent models of dual-task processing.

Modulation of the executive control network by anodal tDCS over the left dorsolateral prefrontal cortex improves task shielding in dual tasking

Task shielding is an important executive control demand in dual-task performance enabling the segregation of stimulus-response translation processes in each task to minimize between-task interference. Although neuroimaging studies have shown activity in left dorsolateral prefrontal cortex (dlPFC) during various multitasking performances, the specific role of dlPFC in task shielding, and whether non-invasive brain stimulation (NIBS) may facilitate task shielding remains unclear. We therefore applied a single-blind, crossover sham-controlled design in which 34 participants performed a dual-task experiment with either anodal transcranial direct current stimulation (atDCS, 1 mA, 20 min) or sham tDCS (1 mA, 30 s) over left dlPFC. Task shielding was assessed by the backward-crosstalk effect, indicating the extent of between-task interference in dual tasks. Between-task interference was largest at high temporal overlap between tasks, i.e., at short stimulus onset asynchrony (SOA). Most importantly, in these conditions of highest multitasking demands, atDCS compared to sham stimulation significantly reduced between-task interference in error rates. These findings extend previous neuroimaging evidence and support modulation of successful task shielding through a conventional tDCS setup with anodal electrode over the left dlPFC. Moreover, our results demonstrate that NIBS can improve shielding of the prioritized task processing, especially in conditions of highest vulnerability to between-task interference.