Circadian timing of sleepiness in man and woman

Men and women living contentedly in long-term isolation from the usual time-of-day cues have revealed surprising new regularities about the timing of human sleep/wake alternations. Contemporary effort to ferret out and articulate these regularities in quantitative terms lead to a diversity of mathematical models. If these eventually acquire predictive competence then we may expect practical improvements of therapy for insomnia, jet lag, and some kinds of psychiatric depression.