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.

BackgroundDecrements in performance and the propensity for increased mind-wandering (i.e., task-unrelated thoughts) across time-on-task are two pervasive phenomena observed when people perform vigilance tasks. In the present study, we asked whether processes that lead to vigilance decrement and processes that foster the propensity for mind-wandering (MW) can be dissociated or whether they share a common mechanism. In one experiment, we introduced two critical manipulations: increasing task demands and applying anodal high-definition transcranial direct current stimulation (HD-tDCS) to the left dorsolateral prefrontal cortex.MethodSeventy-eight participants were randomly assigned to one of four groups resulting from the factorial combination of task demand (low, high) and stimulation (anodal, sham). Participants completed the sustained attention to response task (SART), which included thought probes on intentional and unintentional MW. In addition, we investigated the crucial role of alpha oscillations in a novel approach. By assessing pre-post resting EEG, we explored whether participants’ variability in baseline alpha power predicted performance in MW and vigilance decrement related to tDCS or task demands, respectively, and whether such variability was a stable characteristic of participants.ResultsOur results showed a double dissociation, such that task demands exclusively affected vigilance decrement, while anodal tDCS exclusively affected the rate of MW. Furthermore, the slope of the vigilance decrement function and MW rate (overall, intentional and unintentional) did not correlate. Critically, resting state alpha-band activity predicted tDCS-related gains in unintentional MW alone, but not in vigilance decrement, and remained stable after participants completed the task.ConclusionThese results show that when a sustained attention task involving executive vigilance, such as the SART, is designed to elicit both vigilance decrement effects and MW, the processes leading to vigilance decrement should be differentiated from those responsible for MW, a claim that is supported by the double dissociation observed here and the lack of correlation between the measures chosen to assess both phenomena. Furthermore, the results provide the first evidence of how individual differences in alpha power at baseline may be of crucial importance in predicting the effects of tDCS on MW propensity.

Background Decrements in performance and the propensity for increased mind-wandering (i.e., task-unrelated thoughts) across time-on-task are two pervasive phenomena observed when people perform vigilance tasks. Whether vigilance decrement and mind-wandering (MW) are independent phenomena is still an open question. In the present study, we addressed such a contention by introducing two critical manipulations: increasing task demands and applying anodal high-definition transcranial direct current stimulation (HD-tDCS) over the left dorsolateral prefrontal cortex. Method Seventy-eight participants were randomly assigned to one of the four groups resulting from the factorial combination of task demand (low, high) and stimulation (anodal, sham). Participants completed the sustained attention to response task (SART), which included thought probes about intentional and unintentional MW. Moreover, we investigated the crucial role of alpha oscillations in a novel approach. By evaluating prepost resting EEG, we explored whether participant variability in the alpha power baseline predicted performance in MW and vigilance decrement related to tDCS or task demands, respectively, and whether such variability was a stable characteristic of participants. Results Our results showed that task demands exclusively affected vigilance decrement, while anodal tDCS exclusively affected the rate of MW. Critically, alpha-band activity at rest predicted tDCS-related gains in unintentional MW but not vigilance decrement and remained stable after participants completed the task. Conclusions These results suggest that vigilance decrement and MW are two independent phenomena. Additionally, the results provide the first evidence of how individual differences in alpha power at baseline may be of crucial importance in predicting the effects of tDCS on MW propensity.

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.