People differ in their optimal time of day to perform a cognitive task: Morning people (“larks”) perform better in the morning compared to the evening, and the reversed is true for evening people (“owls”). This synchrony effect has been observed for executive functions, such as inhibitory control. For example, participants performing the Sustained Attention to Response Task (SART) make more commission errors at their non-optimal time of day. Because mind-wandering (MW) has been related to the executive system, we here investigated a synchrony effect in the frequency of MW. After determining the participants’ chronotype (n = 130), they completed an online version of the SART twice, once in the morning and once in the evening. MW was subjectively measured using a probe-caught method. Results showed that “larks” mind-wandered more often in the evening than the morning session. In contrast, “owls” showed the opposite profile. Objective markers for MW (i.e., accuracy and reaction time coefficient of variance) confirmed these results. Furthermore, in line with earlier suggestions, the frequency of MW was also directly related to the number of hours slept the night before the experiment, and an overall higher frequency of MW was observed for evening chronotypes. The results of this study provide clear evidence for the relation between sleep-related factors and MW, and raises the importance of accounting for chronotype differences when scheduling work and academic activities.

People differ in their optimal time of day to perform a cognitive task: Morning people (“larks”) perform better in the morning compared to the evening, and the reversed is true for evening people (“owls”). This synchrony effect has been observed for executive functions, such as inhibitory control. Participants performing the Sustained Attention to Response Task (SART) make more commission errors at their non-optimal time of day. Because mind-wandering (MW) has been related to the executive system, we here investigated a synchrony effect in the frequency of MW. After determining the participants’ chronotype (n = 130), they completed an online version of the SART twice, once in the morning and once in the evening. MW was subjectively measured using a probe-caught method. Results showed that “larks” mind-wandered more often in the evening than the morning session. In contrast, “owls” showed the opposite profile. Objective markers for MW (i.e., accuracy and reaction time coefficient of variance) confirmed these results. Furthermore, in line with earlier suggestions, the frequency of MW was also directly related to the number of hours slept the night before the experiment, and an overall higher frequency of MW was observed for evening chronotypes. The results of this study provide clear evidence for the relation between sleep-related factors and MW, and raises the importance of accounting for chronotype differences when scheduling work and academic activities.