Multitasking boosts human muscular endurance task performance due to elevated arousal.

Multitasking is generally thought to impair performance because of the interference between tasks arising from the limited processing capacity. Contrary to this view, we show that multitasking can also facilitate performance when interference between tasks is minimal. Participants performed a handgrip muscular endurance task concurrently with a cognitive task. Performance on the endurance task was enhanced with the difficulty of the cognitive task. A similar effect was observed when monetary reward was offered for the cognitive task. These facilitation effects were associated with greater pupil dilation elicited by the cognitive task. These results suggest that a concurrent cognitive task can elevate a pupil-linked arousal state that facilitates endurance performance under the task conditions examined here, potentially by increasing the overall processing capacity. Together, these results identify a previously overlooked condition under which the arousal-related benefit of a concurrent task may outweigh its interference cost and facilitate, rather than impair, performance.