Time-series analysis of stereotyped movements: relationship of body-rocking to cardiac activity.

The pathological stereotypies frequently observed among severely mentally retarded and autistic persons are highly rhythmical in nature. Most attempts to quantify such behavior, however, have not analyzed stereotypy in terms of its cyclical properties. In the present paper we have detailed a method for electronically transducing stereotyped body-rocking and analyzing its frequency and amplitude characteristics with a standard polygraph and microprocessor. The relationship between stereotyped body-rocking and cardiac activity was also described using time-series analysis. The method described should provide a sensitive index of various experimental manipulations and treatment effects.