Daylight and Productivity - a Possible Link to Circadian Regulation

It has been long held that daylight positively affects worker productivity. Two recent studies reinforce this belief, but the cause-and-effect relationship between daylight and productivity has not been established. Basic research in circadian photobiology suggests that light has a very important role regulating human behavior, including the sleep-wake cycle and seasonal depression. Given these findings, it was hypothesized that during winter months in northern latitudes the absence of daylight in interior spaces might have a negative impact on worker productivity during work hours. The present pilot study compared occupancy rates and types of behavior in matched samples of office workers assigned to interior or to windowed offices during the winter of 2001. Although occupancy rates were identical, workers in windowed offices spent more time on computer tasks, less time talking on the telephone and to coworkers than matched workers in interior offices. The root cause of these findings remains unknown, but the results are consistent with the hypothesis that bright light during the day improves productivity during winter months.