The level of mental effort when performing everyday activities depends on many factors, and it is constrained by the working memory capacity. Factors such as the type of work, the work schedule,...Show moreThe level of mental effort when performing everyday activities depends on many factors, and it is constrained by the working memory capacity. Factors such as the type of work, the work schedule, and special events like exams, deadlines, or holidays may cause temporary increases or decreases to the cognitive load of daily routines. Given the dominance of circadian clocks in human behaviours and cognitive output, is mental effort also consistently influenced by the time of day? This study explored the possibility that cognitive load fluctuates in a consistent temporal pattern that is close to diurnal cycles observed in human behaviour and cognition. The approach was based on the assumption that smartphones tapping data can act as a proxy for cognitive load levels in order to capture the daily dynamic changes unobtrusively and in vivo. The sample data was collected from 64 healthy individuals, with a duration period on average of 33 days. A spectral analysis on the time-series of the tapping sessions revealed the existence of a diurnal cycle of 24 h in both low and high cognitive load measures, with no significant differences in the cycles’ amplitude. This suggests that people distribute their mental effort consistently across the day with similar intensity between activities that require low and high cognitive resources. This finding was again confirmed at the individual level by a cross correlation analysis. Interestingly, the participants exhibit barely visible weekly cycles with relatively weak signals, which could be a reflection of the time of the study during coronavirus lockdown; hence the influence of weekday/weekend rhythm may be diminished. Further research should examine the time of day when cognitive load peaks and declines, as well as the individual differences. The information can be valuable for various domains that are concerned with learning, performance and health.Show less
