In dual-task (DT) situations, effective task-order coordination (TOC) is vital for scheduling bottleneck-processing of component tasks, as evidenced by recent observations indicating increased TOC costs in DT situations when comparing variable to fixed orders of component tasks. Our prior work showcased improvements in these processes through the practice of two temporally overlapping tasks with variable presentation orders. This study delves into the underlying mechanisms, specifically exploring the role of working memory (WM) in these enhancements.
Participants practiced the same two visual-manual component tasks with variable order within three distinct groups. They either trained the two tasks with an additional high WM load task, an additional low WM load task, or without any extra task. Pre- and post-training sessions compared TOC costs across these groups, considering situations with unchanged and untrained stimuli to assess stimulus-unspecific training-related improvements.
Results indicate enhanced TOC (i.e., reduced TOC costs) for participants who trained without an additional task, consistent with prior findings. Conversely, participants faced with an additional task taxing WM capacity failed to achieve improved TOC. Notably, the low WM load group demonstrated enhanced performance, highlighting that the mere addition of a task did not drive this outcome.
These findings align with the Efficient Task Instantiation (ETI) model, suggesting that practicing the flexible adaptation of processing orders for two component tasks in DT scenarios can lead to efficient, conjoint instantiation of both potential task orders in working memory. This higher-order, stimulus-unspecific instantiation facilitates effective task-order scheduling, independent of the specific stimuli presented.