Combined Effects of Ambient Light and Color on Cognitive Performance and Sleepiness in a Simulated Working Environment

Abstract

This study investigated the combined effect of correlated color temperature and wall color on subjective sleepiness and cognitive performance in a simulated workplace. Six combined conditions were designed by partitioning a room into three booths with the same dimensions in three colors of blue, red, and white and two cool and warm light: color temperatures of 6000 and 3000°K (Red × 3000, Red × 6000, Blue × 3000, Blue × 6000, White × 3000, and White × 6000) during the day. Thirty-three healthy males aged 21–35 were recruited. They were asked to conduct cognitive tests in three workload levels and finally estimate the subjective sleepiness level. The findings indicated that cool light had a more significant effect on reducing sleepiness when compared to warm light, particularly in white and blue colors. However, this effect was not observed in the case of red color. The rate of sleepiness was higher in the cool light and red color compared to warm light. The blue color slightly decreased sleepiness compared to the white and red colors. The mean correct responses of the cognitive tests in cool light and white color were more than in other conditions. Moreover, the effect of blue and red were higher in the correct response percentages, compared to white in warm and cool light. There were no significant differences in reaction time between two different lights in all colors. However, reaction time was better in blue than in two other colors. To conclude, designing a work environment with a combination of cool light and blue-colored walls may improve employee alertness and performance.