Is mind wandering reflected in microsaccade dynamics?

Mind wandering is a state in which our mental processes are directed towards task-unrelated thoughts. This phenomenon has been shown to underlie attentional lapses and represents a common experience in everyday life. Previous studies have found an association between mind wandering and eye-related indices. In the present study, we addressed for the first time whether the rate of microsaccades-miniaturised saccades that we spontaneously produce during prolonged fixation-is sensitive to the occurrence of mind wandering. Participants performed the Sustained Attention to Response Task, a go/no-go task highly vulnerable to mind wandering. The analyses focused on possible differences in microsaccade rate emerging from the comparison of time intervals preceding commission errors and time intervals preceding correct target withholds, under the assumption that a commission error would reflect a mind wandering episode. The results showed that microsaccadic rate was consistently reduced in time windows preceding a target trial in which participants produced a commission error as compared to when they correctly inhibited the tendency to manually respond. Cluster-based analyses established that this pattern was robust. Because microsaccades are known to occur involuntarily and a reduction in their frequency has been associated with higher mental effort, the present findings provide new insights as regards the relevance of mind wandering and lend support to the idea that during mind wandering our mind is far from being idle and is absorbed and committed to effortful activities instead.