Temporal changes in attentional resources consumed by mind-wandering that precede awareness: An ERP study.

A relationship between the awareness of mind-wandering (MW) and the disruption of MW because of external stimuli has previously been reported. Attention often fluctuates without external stimuli and such disruptions can spontaneously precede awareness of MW. To elucidate whether changes in attentional resources used by MW exist, we used event-related potentials (ERPs), focusing on the P300 (P3) ERP component as an index of attention to a task. Participants performed a simple task, in which they pressed a key in synchrony with continually presented tones. Moreover, they were asked to stop the response whenever they became aware of their MW. We analyzed the P3 induced by the tones before self-reports of MW using a state-space model that was used for analysis to detect changes over time. The results revealed that the mean amplitude of P3 increased significantly from the third to the second tone before the self-reports; no other clear increasing or decreasing tendencies were observed. We concluded that the attentional resources allocated to the main task returned, suggesting that such awareness requires a decrease in resources to task-unrelated thoughts. These findings highlight a transitional state related to awareness between the MW state and self-reports. Therefore, the state immediately before self-reports should not be defined as merely an MW state when using the self-caught method.