Effects of Monochromatic Light on Different Time Perception

Abstract

Time is a fundamental dimension of life. Previous studies reported that time perception is affected by several physiological and psychological factors (age, gender, time of day, flickering stimulus, etc). Light exerts visual and non-visual effects with respect to biological rhythms. However, it has not been confirmed that perception of the passage of time could be affected by the light environment. In this study, we investigated the physiological and psychological responses when subjects were exposed to different monochromatic light environments (there were four conditions of light intensity that varied by illuminance and irradiance). We evaluated the time sense by time tests of 180 s and 600 s. The results showed that the time sense runs significantly faster in a red light condition than in any other monochromatic light condition (green, blue Ⅰ and blue Ⅱ which is approximate half irradiance compared with blue Ⅰ ) in a 180-s time production task. However, in the 600-s estimation time task, the time sense tended to be significantly faster in the red light condition than in the blue Ⅰ or blue Ⅱ light conditions, and in the green light condition the time sense ran significantly faster than in the blue Ⅰ light condition. There was no significant difference in color factor in P300 which is one of evoked potential components measured with electroencephalography (EEG), however, a significant trend was found in amplitudes of P300, which showed that the cognitive level tended to be high in the blue Ⅱ light condition. The EEG alpha wave amplitude significantly increased in the green light condition compared to the amplitude in the blue Ⅰ light condition. The results of SDPTG which is an index of autonomic nervous system measured with photoplethysmography (PPG), in which there was a significant trend to be faster in the blue Ⅰ light condition than in the green or blue Ⅱ light conditions, showed that blue light might have a sympathomimetic effect. There was no significant difference in color factor in the subjective assessments, except the subjects felt more eyestrain in the blue Ⅱ than in the red light condition. These results indicate that the perception of the passage of time ran faster in the red-light than in the other light conditions. We suggest that red light has an active effect in a short time interval through the visual processing pathway and decays with time. The blue light seems to have a sustained effect on the central nervous system, but people may not be responsive to a short time interval exposure to blue light.