Issues in the selection and use of mechanical transducers to directly measure motor activity in clinical settings.

The application of instrumentation in the social sciences to measure human behavior lags far behind medical practice and the physical sciences. According to Rugh and Schwitzgebel (1977), this primitive state of development and lack of technological sophistication is related to the prevailing belief that many variables of interest to psychologists are not subject to direct measurement. We identified five varieties of maladaptive behaviors commonly displayed by mentally retarded persons which can be measured directly by means of mechanical transducers: hyperactivity, hypoactivity, inadequate postural control, disorders of the sleep/wake cycle, and stereotyped movements. The operating characteristics of several types of motion sensors were described and issues related to the selection and use of these mechanical transducers in clinical settings were considered. Finally, various meanings of the terms reliability and validity were discussed as they pertain to the clinical application of these mechanical measurements of motor activity.