Effects of monochromatic light on time sense for short intervals

We examined the effects of monochromatic light on the time sense and the central nervous system. Nine young adult volunteers participated in this study. They were exposed to red-light and blue-light environments (illuminance was kept at 310 lx). We evaluated the time sense by time-production tests of 90 s and 180 s and measured the P300 event-related potentials during an auditory oddball task. The 90-s time intervals produced by subjects in the two monochromatic light conditions were not significantly different. However, the 180-s time interval produced in the red-light condition (163.2+/-50.4 s) was significantly (p<0.05) shorter than that in the blue-light condition (199.0+/-54.4 s). The peak latency of P300 in the red light (322.2+/-26.6 ms) was found to be significantly (p<0.05) shorter also than that in the blue light (332.6+/-20.2 ms). The feelings measured by the visual analogue scales in the two light conditions were not significantly different. These results indicate that the time sense ran faster in the red-light than in the blue-light condition. We suggest that the higher activity in the central nervous system that is accounted for by the shorter latency of P300 is related to the acceleration of the time sense.