The proposed study examines normal and insomniac sleep patterns in the elderly from a novel perspective to shed light on mechanisms of disturbed sleep. The central hypothesis is that many elderly desire an amount of sleep that exceeds bodily need. This discrepancy motivates frustrating awake time in bed, i.e., an insomnia-appearing sleep pattern, but does not produce daytime sleepiness, the presumed result of insomnia. Therefore, daytime sleepiness emerges as a crucial dependent variable in verifying the presence of insomnia. This study will conduct a 4-point (early morning, noon, dinner time, and bedtime) pupillometric assessment of 60 elderly subjects characterized by normal sleep, medicated insomnia, or unmedicated insomnia. The extant literature recommends pupillometry as the sole physiological marker of daytime sleepiness, though methodological weaknesses, prevent firm conclusion. Nightime sleep pattern, against which daytime sleepiness will be matched, will be monitored objectively, in the natural environment with a response-demand device. The purposes of this study are to (a) assess the validity of pupillometry as a sleepiness index on a geriatric sample by tracking the natural course of sleepiness during the day, (b) assess the effects of nighttime sleep pattern on daytime sleepiness, and (c) identify an insomniac subset presenting with poor sleep, but no excessive daytime sleepiness. This last group, termed insomnoid, reflects individuals desiring more sleep than they physiologically need, a problem hypothesized to be most common in the elderly. Successful demonstrations that some elderly insomniacs have satisfied bodily sleep need, despite the persistence of a distrubed sleep pattern, raise conflicts with traditional conceptualizations of insomnia and with medical and psychological treatments that aim at helping people sleep longer. The treatment implications of this line of research recommend sleep education in place of treatments bearing higher cost and higher risk of negative side- effects.