LIGHT, SOCIAL ZEITGEBERS, AND THE SLEEP-WAKE CYCLE IN THE ENTRAINMENTOF HUMAN CIRCADIAN-RHYTHMS

The availability of sufficient zeitgebers is essential for entrainment of circadian rhythms. Bright light is an important human zeitgeber. H owever, social cues acting through the sleep-wake cycle may also be im portant in the entrainment of human rhythms. Current research suggests that humans receive inadequate and sporadic exposure to bright light. Social cues, although less powerful, may be an important form of entr ainment for contemporary humans, and also serve to augment the effects of available bright light. Both light and social zeitgebers should be investigated for their roles in the genesis, prevention, and treatmen t of alterations in health. (C) 1994 John Wiley & Sons, Inc.