The wandering mind oscillates: EEG alpha power is enhanced during moments of mind-wandering

Compton, Rebecca J.; Gearinger, Dylan; Wild, Hannah · 2019 · Crossref

DOI: 10.3758/s13415-019-00745-9

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Summary

This study investigates the neural correlates of mind-wandering, specifically testing whether episodes of task-unrelated thought are associated with increased EEG alpha power (8–12 Hz oscillations). While functional MRI has linked mind-wandering to the default mode network, its poor temporal resolution limits the ability to track momentary cognitive fluctuations. EEG offers superior temporal precision, and prior research suggests alpha waves index internally directed cognition. However, previous EEG studies yielded conflicting results, likely due to methodological differences in task design and mind-wandering detection. This research aimed to resolve these inconsistencies by using a within-subjects experience-sampling design during a demanding external task. Sixty-two undergraduate participants completed a six-choice Stroop task consisting of 864 trials while EEG was recorded. The task required identifying font colors while ignoring word meanings, with trials divided into congruent, incongruent, and neutral conditions. Interspersed throughout the task were 24 random experience-sampling probes asking participants to report if they were on-task, mind-wandering, or engaged in both states just prior to the probe. To ensure robust statistical power, the analysis focused on a subsample of 50 participants who provided at least five responses for both on-task and mind-wandering (including "both") categories. EEG data were segmented into epochs preceding the probes, and alpha power was extracted and compared between on-task and mind-wandering conditions. The results demonstrated that EEG alpha power was significantly higher in the 5-second window preceding probes where participants reported mind-wandering compared to those reporting on-task cognition. This effect was robust across different epoch lengths (2, 5, and 10 seconds) and persisted even when analyzing data from 5 to 10 seconds before the probe. The alpha differentiation was most pronounced at posterior scalp sites. Although performance accuracy and reaction times were slightly worse preceding mind-wandering reports, these behavioral differences were not statistically significant. Notably, participants whose alpha power best distinguished mind-wandering from on-task states were those whose performance was least disrupted by mind-wandering, suggesting alpha power may detect internal cognitive shifts that overt performance measures miss. These findings provide strong evidence that enhanced alpha oscillations serve as a reliable neural index of mind-wandering during externally directed tasks. The study supports the hypothesis that alpha power reflects inward-directed attention, complementing prior findings that mind-wandering involves reduced external attention. The results suggest that EEG alpha power can detect momentary fluctuations in mind-wandering even when task performance remains stable, offering a valuable tool for studying the dynamics of spontaneous thought. Future research should explore the causal relationship between alpha rhythms and mind-wandering and examine how these neural signatures interact with other physiological markers, such as pupil dilation.

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Topics

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• mind wandering
• neuro workload indices