Becoming circadian--A one-year study of the development of the sleep-wake cycle in children.

Data on three children's sleep-wake behavior during the first year of life submitted to spectral analysis reveal the presence of several frequencies in the circadian and ultradian ranges. The changes in the resulting spectra as age progresses show both an increase in overall rhythmicity, i.e., more data are explained by regular oscillations, and irregular changes in the circadian component. This circadian component shows an increase in power which appears at different ages among the individuals studied.