Does exposure to artificial light in the morning reduce reaction time variability during cognitive control...

Being alert and attentive is essential for cognitive control processing, as it facilitates the detection of conflicting stimuli that require resolution. Exposure to daytime artificial light increases alertness; however, the effects on conflict resolution, referred to as cognitive control, remain poorly understood, especially since previous studies have focused solely on averaged inter-individual measures such as mean reaction time. Intra-individual (within-person) reaction time variability (RTV) provides a moment-to-moment averaged measure that conveys information about the consistency of attentional focus throughout the process of detecting and resolving stimuli conflicts. This crossover study of healthy participants (N = 39, M_age = 21.7, SD_age = 2.6, 62% female) explored the acute effects of a 2 h morning exposure to "blue" short-wavelength light (1442 lx_m-EDI), "red" long-wavelength light (3.8 lx_m-EDI), and short-wavelength-enriched bright white light (1156 lx_m-EDI, ~ 8000 K), against a control condition of white dim light (<10 lx_m-EDI), on cognitive control measured with a flanker task. Compared to white dim light, "blue" light contributed to lower RTV during the processing of cognitive conflicts, but the effect was small and non-robust. Exposure to artificial light did not affect averaged inter-individual measures. Our preliminary findings suggest that "blue" light has the potential to stabilize attentional fluctuations during cognitive conflict processing; however, this potential should be further investigated in studies with larger samples.