We typically observe a decrement in vigilance with time-on-task, which favors the propensity for mind-wandering, i.e., the shifting of attention from the task at hand to task-unrelated thoughts. Here, we examined participants’ mind-wandering, either intentional or unintentional, while performing vigilance tasks that tap different components of vigilance. Intentional mind-wandering is expected mainly when the arousal component is involved, whereas unintentional mind-wandering is expected mainly in tasks involving the executive component. The Psychomotor Vigilance Task (PVT) assessed the arousal component, whereas the Sustained Attention to Response task (SART) assessed the executive component of vigilance. The two types of mind-wandering were probed throughout task execution. The results showed that the overall rate of mind-wandering was higher in the PVT than in the SART. Intentional mind-wandering was higher with the PVT than with the SART, whereas unintentional mind-wandering was higher with the SART than with the PVT. Regarding mind-wandering as a function of vigilance decrement with time-on-task, unintentional mind-wandering in the PVT increased between blocks 1 and 2 and then stabilized, whereas a progressive increase was observed in the SART. Regarding intentional mind-wandering, a progressive increase was only observed in the SART. The differential patterns of intentional and unintentional mind-wandering in both tasks suggest that, intentional mind wandering occurs mainly in arousal tasks in which propensity to mind-wander has little impact on task performance. However, unintentional mind-wandering occurs mainly in executive tasks as a result of a failure of cognitive control, which promotes attentional resources to be diverted toward mind-wandering. These results are discussed in the context of the resource-control model of mind-wandering.

Background: The current study examined people’s propensity to mind wander when they perform vigilance tasks that tap different components of vigilance, namely arousal or executive. We suggest that the propensity to mind-wander may occur not only spontaneously (unintentional), but also deliberately (intentional) and that this distinction may have considerable theoretical implications. Thus, while intentional mind-wandering could arise from a lack of motivation and monotonicity of the task, unintentional mind-wandering could be driven mainly by a failure of executive control. Methods: Participants performed the Psychomotor Vigilance Task (PVT) to assess the arousal component of vigilance, and the Sustained Attention to Response task (SART) to assess the executive component of vigilance. Two types of mind wandering were probed throughout the task execution, intentional and unintentional. Results: The rates of overall mind-wandering were greater for the PVT than for the SART. Although there was greater propensity to develop unintentional than intentional mind-wandering in both tasks, propensity to intentional mind-wandering was higher with the PVT than with the SART, whereas the ratio of unintentional mind-wandering was higher with the SART than with the PVT. Finally, regarding unintentional mind wandering, in the PVT, the most pronounced increment occurred between blocks 1 and 2, and thereafter it stabilized. In the SART, a rather progressive increment was observed as the task progressed. Regarding intentional mind wandering, progressive increment was observed mainly in the SART.Conclusions: The differential patterns of intentional and unintentional mind wandering as a function of task suggest that, intentional mind wandering occurs mainly in monotonous tasks where propensity to mind wander has little impact on task performance. However, unintentional mind wandering is the result of a failure to keep control on the primary executive task and therefore attentional resources deviate to mind wander, the default mode. These results support and extend the Thompson et al.’s (2015) resource-control model.