Task-order representations in dual tasks: Separate or integrated with component task sets?

Abstract

In situations requiring the execution of two tasks at around the same time, we need to decide which of the tasks should be executed first. Previous research has revealed several factors that affect the outcome of such response order control processes, including bottom-up factors (e.g., the temporal order of the stimuli associated with the two tasks) and top-down factors (e.g., instructions). In addition, it has been shown that tasks associated with certain response modalities are preferably executed first (e.g., temporal prioritisation of tasks involving oculomotor responses). In this study, we focused on a situation in which task order has to be unpredictably switched from trial to trial and asked whether task-order representations are coded separately or integrated with the component task sets (i.e., in a task-specific manner). Across three experiments, we combined two tasks known to differ in prioritisation, namely an oculomotor and a manual (or pedal) task. The results indicated robust task-order switch costs (i.e., longer RTs when task order was switched vs. repeated). Importantly, the data demonstrate that it is possible to show an asymmetry of task-order switch costs: While these costs were of similar size for both task orders in one particular experimental setting with specific spatial task characteristics, two experiments consistently indicated that it was easier for participants to switch to their prioritised task order (i.e., to execute the dominant oculomotor task first). This suggests that in a situation requiring frequent task-order switches (indicated by unpredictable changes in stimulus order), task order is represented in an integrated, task-specific manner, bound to characteristics (here, associated effector systems) of the component tasks.

Controlling response order without relying on stimulus order – Evidence for flexible representations of task order

“…First, the finding of significant task-order switch costs only for the second component task was unexpected given that in typical task-order control studies using sequential task stimuli both component tasks are usually affected by a task-order switch (Luria & Meiran, 2003Strobach et al, 2021) and potential reasons will be discussed in the General Discussion. Second, and more importantly, the previous study by Huestegge et al (2021) on representations of differentially preferred task orders with sequential stimuli found significant order switch cost asymmetries that went in the same direction for both component tasks (i.e., order switch costs were smaller for switches to the oculomotor-manual vs. the manualoculomotor task order). This pattern was taken as indication for task-order representations that are integrated with component task information (e.g., "oculomotor-manual" vs. "manualoculomotor").…”

“…However, regarding the content of task-order representations in the present setting, representations of task order that are integrated with component task features would be reflected in asymmetries in taskorder switch costs for transitioning to a preferred versus a non-preferred task order (e.g., orderswitch costs should be smaller for the oculomotor-manual task order than for the manualoculomotor task order). Such an asymmetry should be in the same direction for both component tasks (oculomotor task and manual task) based on previous findings of integrated task-order representations (Huestegge et al, 2021). In contrast, generic task-order representations that do not contain any information about component-task features should rather lead to symmetric taskorder switch costs in both the preferred and the non-preferred task order.…”

“…Thereby, potential asymmetries of task-order switch costs might have been masked in this study as they were potentially attenuated in Experiment 2 of our study (c.f. discussion of Experiment 1 in Huestegge et al, 2021). Furthermore, in the current study, the notion of generic task-order representations obtained in Experiment 1 has a different meaning than in the study by Kübler and colleagues (2022a) in that it refers to completely generic representations of task-order (i.e., "0-1" vs. "1-0", potentially even "repeat order" vs. "switch order") instead of task-order representations containing "only" no information of the exact types of component task being ordered (i.e., in the Kübler et al study, a representation such as "visual task first" would already count as "generic", even though the visual nature of the task could be part of the representation).…”

“…Such task order coordination costs are likely associated with the need to maintain readiness for and to coordinate two (or more) task orders in working memory (Los, 1996) and not with the process of reconfiguring task order per se (Luria & Meiran, 2003). Additionally, however, in mixed-order blocks, performance in both component tasks is usually worse in task-order switches (relative to the previous trial) compared with task-order repetitions (Huestegge et al, 2021;Kübler et al, 2018;Luria & Meiran, 2003Szameitat et al, 2006). These task-order switch costs are typically taken as evidence for the costly reconfiguration of explicit task-order representations within a task-order set (Kübler et al, 2022a;Szameitat et al, 2006) and the fact that both component tasks are usually affected by an order switch supports the notion that this reconfiguration happens before the first component task is being processed (Luria & Meiran, 2003.…”

Element-level features in conjoint episodes in dual-tasking

“…They obtained substantial costs when the task order changed from one trial to the next. Meanwhile, several findings support this observation (Huestegge et al, 2021 ; Kübler et al, 2018 , 2021 ; Sigman & Dehaene, 2006 ; Stelzel et al, 2008 ; Strobach et al, 2018 , 2021 ).…”