Stereotyped behavior in developmentally delayed or autistic populations. Rhythmic or nonrhythmic?

Stereotypies are high-frequency, highly repetitive, nonfunctional behaviors that are also often characterized as rhythmic. Rhythmicity suggests that the behavior is periodic, occurring at fixed intervals. Few studies, however, have rigorously demonstrated periodicity in stereotypy. This study examined various topographies of stereotypy in 9 participants and used spectral methods to detect existence of periodicties. Two general patterns emerged in the spectral analysis. Participants who engaged in stereotypic rocking showed peaks in their power spectra; participants who engaged in other topographies of stereotypy did not show peaks. Thus, it appears that although some stereotypies--notably, rocking--have a periodic component, rhythmicity does not appear to be a characteristic of stereotypy in general.