Daytime intermittent bright light effects on processing of laterally exposed stimuli, mood, and light perception

Little is known about intermittent bright light (IBL) exposure during the daytime on oscillations in human performance and mood. The aims of this study were to determine whether the applied regime of IBL can differentially influence the daily oscillations of processing of laterally exposed stimuli, as well as the daily course of alertness and affective state, and the participants' perception of light conditions. A counter-balanced, within-subject study design was applied. Performance and mood of 20 student volunteers were measured every 30 min starting at 08:00 h and ending at 20:30 h in IBL and ordinary room light (ORL) conditions. Near to statistical significance, effects of the IBL regime on performance (i.e., main effect on speed of verbal logical task, and interactive effect of light conditions and measurement time on daily oscillations in speed of processing of spatial tasks) and mood (i.e., interactive effect of bright light and measurement time on global vigor assessment) were found. An assessment of IBL conditions as significantly less comfortable and natural and more glaring when compared to ORL conditions draws attention to the importance of participants' perception of the light, which may affect the application of bright light in real life situations.