Spontaneous fluctuation in rate of body rocking: a methodological note

Descriptive data are presented on the natural occurrence of stereotyped body rocking in three institutionalised, mentally retarded children. Both ward and test situation observations suggest that there is spontaneous fluctuation in rate of body rocking. These findings raise a serious methodological problem pertinent to the evaluation of experimental data on stereotyped behaviour: rate change attributed to experimental manipulation may in fact only be an instance of spontaneous fluctuation.