Psychologists have always had to accept the task of commentary on folklore. In pulp fiction, a light-sleeping elderly victim is the first to sense a creeping perpetrator. A recent review of what psychologists might call “the medical demography of sleep” broadly supports the pulp-fiction account; it records that older people experience an advance in their circadian rhythms, tending to lose body temperature and become drowsy earlier in the evening and to wake earlier in the morning. Sleep scientists use measurements of changes in the electrical activity of the brain to distinguish different depths of sleep. In shallow sleep, the rhythms of brainwaves recorded through the scalp are fast and pronounced and bursts of rapid eye movements are frequent. Research on the effects of loss of sleep and drowsiness on mental competence has been mainly driven by interest in the effects of irregular sleep patterns on relatively young people – military personnel and young workers on rotating shifts.