Ultradian rhythms in stereotyped and self-injurious behavior.

Institutionalized profoundly mentally retarded persons who exhibited stereotyped motor movements, including self-injurious behavior, were observed continuously in their typical environments for periods of 8 to 14 hours on each of several days. In addition to targeting stereotyped responses, we collected data pertaining to activities, settings, other behavioral states, and social interactions. Spectral and cross-spectral analyses were conducted on data from each daily session. Power spectra indicated a marked ultradian or less than 24-hour rhythm for each subject on each day. Spectral density estimates were thought to reflect the influence of rhythmic changes in the institutional environment and, to a less degree, the influence of an endogenous rest--activity rhythm.