ABSTRACT
Before discussing directly the interaction between behavior and circadian rhythms, I need to summarize briefly the general principles of human circadian rhythms in the next three sections because without knowing some specific properties of the human rhythmic system, it is hard to understand the problems of the behavioral aspects of circadian rhythmicity. Section 2 discusses those properties mainly concerned with the combined action of internal and external influences and the possibility of rhythm disorders. In Section 3, sleep as a peculiar part of general behavior is considered because the interaction between internal and external components of temporal control is especially obvious in the structure of sleep. After an excursion into the biological meaning of this interaction, Section 4 discusses the mechanisms of temporal control that are based essentially on behavioral components in humans, in contrast to the synchronization of animal rhythms. Only after treating these varied details is the ground prepared to deal with the actual topic of this chapter, the interaction between behavior and circadian rhythmicity. This interaction has two opposite aspects: (1) the circadian variations manifested by behavior in addition to those observed in physiological variables; and (2) the ways in which behavior affects circadian rhythmicity even of physiological variables. Both aspects are treated separately in the final two sections of this chapter.
