Impact of artificial colored lights on performance in working memory task

The contemporary lifestyle obligates exposure to artificially illuminated environments often with a variation in spectral composition of light. The wavelength of light, perceived as the color, differentially stimulates the short, medium, and long wavelength cones. Through the non-image-forming pathways, light possibly affects cognitive functions including working memory. Commensurately, this warrants an evaluation of the effects of exposure to colored lights of specific wavelength, on the performance in cognitive task. A within-subject approach was planned to ascertain the impact of light in white, red, green, and blue wavelengths (corresponding to the retinal cone cells) on performance in the Forward Digit Span Task (FDST) and Backward Digit Span Task (BDST) in four randomized sessions. Each light exposure session was preceded by 15 min of dark state and performances were assessed using percent accuracy. The mean age of participants (N = 50) was 28.8 years. A statistically significant difference was found in performance in FDST (P < 0.0005) and BDST (P < 0.0005) with exposure to different colored light (specific wavelengths) when compared to white light (broad-spectrum). Performance in FDST was better than the performance in BDST in all light conditions. The results suggest that working memory performance was affected by the color of light and performance in DST was better under red light than other lights. Therefore, the color of light plays an important role in cognitive performance and ambient light color needs to be adjusted while testing cognitive functions. Red lights may enhance memory recall compared to blue and green lights.