Cold LED lighting affects visual but not acoustic vigilance

Previous studies demonstrated that both light intensity and spectral composition of light impact on brain functioning and regulate circadian rhythms. Further, several studies have shown that light exposure, especially blue light (about 460 nm), has positive effects on alertness, vigilance, mood, also increasing mental performance and work productivity. Unfortunately, results have not been always consistent. This study investigated the effect of different lighting conditions on attention with an experiment examining the impact of correlated colour temperature (CCT) on visual and acoustic vigilance. The performance of forty participants (20 men), aged from 20 to 35 years, was investigated under warm (3000 K) or cold (6800) white LED lighting conditions: under these conditions they executed a cross-modal vigilance task and filled in the Karolinska Sleepiness Scale (KSS) and the Global Vigor and Affect (GVA) scale. Results showed a positive effect of cold light on visual vigilance and absence of effects on acoustic vigilance. Specifically, a significant effect of the cold lighting condition was found in the visual response times (RT): participants in the experimental group when executing the task with 6800 K LED maintained the same visual vigilance level and did not experience the natural vigilance decrement, as occurred to the control group under 3000 K LED Furthermore, no effects were observed on sleepiness and vigour-mood self-assessments. A hypothesis of the possible reason for this modality-specific effect could rely on different neural bases involved in visual versus auditory signals.