A mechanism underlying improved dual-task performance after practice: Reviewing evidence for the memory hypothesis.

Extensive practice can significantly reduce dual-task costs (i.e., impaired performance under dual-task conditions compared with single-task conditions) and, thus, improve dual-task performance.

Practice effects on dual-task order coordination and its sequential adjustment.

When the performance of two tasks overlaps in time, performance impairments in one or both tasks are common. Various theoretical explanations for how component tasks are controlled in dual-task situations have been advanced. However, less attention has been paid to the issue of how two temporally overlapping tasks are appropriately coordinated in terms of their order.

Cognitive control and meta-control in dual-task coordination.

When two tasks are presented simultaneously or in close succession, such as in the overlapping task paradigm of the psychological refractory period, dual-task performance on those tasks is usually impaired compared with separate single-task performance. Numerous theories explain these emerging dual-task costs in terms of the existence of capacity limitations in the constituent component tasks. The current paper proposes active dual-task coordination processes that work on the scheduling of these capacity-limited processes.

Trial-to-trial modulation of task-order switch costs survive long inter-trial intervals.

Background: Dual-tasking procedures often involve the successive presentation of two different stimuli, requiring participants to execute two tasks in a particular order. Performance in both tasks suffers if the order of the tasks is reversed (i.e.

Enhancement of task-switching performance with transcranial direct current stimulation over the right lateral prefrontal cortex.

Switching between two or more tasks is a key component in our modern world. Task switching, however, requires time-consuming executive control processes and thus produces performance costs when compared to task repetitions. While executive control during task switching has been associated with activation in the lateral prefrontal cortex (lPFC), only few studies so far have investigated the causal relation between lPFC activation and task-switching performance by modulating lPFC activation.

Endogenous control of task-order preparation in variable dual tasks.

Dual-task performance typically leads to performance impairments in comparison to single tasks (i.e., dual-task costs).

The dual-task practice advantage: Empirical evidence and cognitive mechanisms.

Practice of two simultaneous component tasks in dual-task situations leads to an improvement in dual-task performance. The present paper reviews empirical evidence for this practice-related improvement and discusses its underlying cognitive mechanisms. In particular, the robustness of the phenomenon of dual-task practice advantage (DTPA) is evaluated.

Processing order in dual-task situations: The "first-come, first-served" principle and the impact of task order instructions.

When two overlapping tasks are processed, they hit a bottleneck at a central processing stage that prevents simultaneous processing of the two tasks. Thus far, however, the factors determining the processing order of the tasks at the bottleneck are unknown. The present study was designed to (re)investigate whether the arrival times of the two tasks at the central bottleneck are a key determinant of the processing order (cf.

Modulation of dual-task control with right prefrontal transcranial direct current stimulation (tDCS).

Executive functioning of two simultaneous component tasks in dual-task situations is primarily associated with activation of the lateral prefrontal cortex (PFC), as demonstrated in functional imaging studies. However, the precise role of the lateral PFC and the causal relation between this area's activity and executive functioning in dual tasks has exclusively been demonstrated for the left lateral PFC so far. To investigate this relation for the right lateral PFC, we used anodal transcranial direct current stimulation (atDCS; 1 mA, 20 min) in contrast to sham stimulation (1 mA, 30 s) in Experiment 1 (N = 30) as well as cathodal transcranial direct current stimulation (ctDCS; 1 mA, 20 min) in contrast to sham stimulation (1 mA, 30 s) in Experiment 2 (N = 25) over the right inferior frontal junction under conditions of random task order in dual tasks; random dual tasks require decisions on task order and thus high demands on executive functioning.