Effective task-order coordination (TOC) is crucial for managing bottleneck processing in dual-task (DT) situations. Prior research has identified increased TOC costs – reflected in reaction time differences – when comparing variable to fixed task orders of component tasks. Our previous work demonstrated that practicing two temporally overlapping tasks with variable task order can reduce these costs. In the present study, we investigate the mechanisms underlying this improvement, focusing on the role of working memory (WM) in TOC acquisition and application.
Participants practiced two visual-manual tasks presented in variable order under one of three conditions: (1) training with a concurrent high WM load, (2) training without additional task, or (3) training without additional task but testing under high WM load. TOC performance was assessed via Task-Order Scheduling (TOS) costs, comparing reaction times in random-order versus fixed-order blocks during pre- and post-training sessions.
In the post-training session without WM load, participants who trained without concurrent load exhibited reduced TOS costs, replicating earlier findings. However, participants who trained with additional WM load showed no such improvement in TOS. Furthermore, in the post-training test with additional WM load, none of the groups demonstrated reduced TOS costs, regardless of prior training success.
These findings highlight the critical role of WM resources in both acquiring and applying optimized TOC strategies. Specifically, WM appears necessary for effective learning of TOC during training and for the application of these skills under cognitive load.