Hemispheric efficiency during the day: the influence of circadian preference and time-of-day on verbal and...

Cognitive performance fluctuates daily due to the interaction between circadian and homeostatic processes, which may differently activate the two hemispheres. This study investigated the effects of time-of-day, circadian typology, and the synchrony effect on semantic categorization and visuospatial processing tasks with potential hemispheric lateralization.

A sample of 113 healthy young women (20.60 ± 2.60 years) performed two divided visual field tasks (semantic categorization and vertical landmark) in morning (08:00) and early afternoon (13:00) sessions.

In the semantic task, an interaction between circadian preference and spatial position showed a progressive shift toward a right-visual-field preference from morning- to evening-types. A triple interaction (typology × word dominance × response type) revealed that for yes- responses, extreme chronotypes were faster with high-dominance items, while intermediate-types were faster with low-dominance ones. For no-responses, intermediate and evening-types favored low-dominance items, whereas morning-types showed no difference. In the landmark task, a Time-of-Day × Position interaction showed a right-visual-field advantage in the morning, which shifted to a left-visual-field advantage in the afternoon.

Overall, findings indirectly suggest daily hemispheric variations based on task demands, with the left hemisphere more active in the morning and the right in the afternoon, and a modulation of circadian preference, at least for semantic processing.