Effective performance in dual-task (DT) situations requires coordinating the temporal order of two task streams. While prior research has shown that practice can reduce DT interference, it remains unclear which specific subprocesses of task-order coordination are trainable and how improvements generalize beyond trained stimuli. The present study investigated whether monitoring the temporal order of incoming stimuli constitutes a separable, trainable component of task-order coordination, and how its improvement contributes to broader DT training gains.

Participants completed one of four training regimens: random-order DT training, mixed single-task (ST) training selectively targeting stimulus-order monitoring, fixed-order DT training, or pure ST training. Pre- and post-tests assessed coordination costs in random-order and fixed-order DT blocks, along with transfer to tasks involving untrained stimuli.

Both experimental regimens—random-order DT and mixed ST training—produced significant reductions in coordination costs compared to control conditions, demonstrating that monitoring the stimulus order is a trainable subprocess that contributes to coordination improvements. Although frequentist analyses showed comparable training benefits within the trained context, Bayesian analyses and transfer results revealed important differences in generalization: random-order DT training yielded robust transfer to novel stimuli, whereas mixed ST training produced weaker but reliable transfer effects. This pattern suggests that while monitoring is necessary for effective coordination, broader generalization requires its integration with additional mechanisms such as updating, sequencing, and scheduling.

Together, the findings support a modular account of DT coordination in which monitoring forms a foundational component, but robust and generalizable coordination skills emerge only when monitoring is embedded within the broader coordination process.