Circadian rhythm distinctness predicts academic performance based on large-scale learning management system data

The subjective amplitude of circadian oscillations (distinctness) is an understudied dimension of circadian rhythmicity, which describes how strongly mood and cognition fluctuate during the day. Emerging evidence suggests that distinctness may be as important as chronotype in regulating the temporal organization of key physiological processes. Previous studies have relied on questionnaires and lacked an objective measure of distinctness. Here, we propose the first objective behavioral measure of distinctness based on circular statistics. We applied this approach to 3.4 million login events from 13,894 unique university students and found a non-linear association between distinctness and academic performance: students with moderate daily rhythmicity achieved the highest performance. This relationship varied by chronotype: larks benefited from stronger rhythms, finches from moderate rhythms, and owls from weaker, more flexible rhythms. Circadian distinctness was also closely linked to social jetlag, which increased with more rigid rhythmicity across chronotypes. These findings suggest that the academic disadvantage often attributed to specific chronotypes does not stem from time preference itself, but from the overall interplay of chronotype, distinctness, and schedules that are incompatible with individual biological timings. Considering rhythm flexibility alongside chronotype may therefore improve educational design and equity.