1. Tracking instrumentation for measuring human motor control comprising: digital computer means; monitor means for displaying graphics in response to said computer means; load cell means for converting a force exerted by one or more muscles into a corresponding proportional electrical signal; analog-to-digital convertor means for periodically sampling and converting said electrical signal into a series of digital words, each word representing a force amplitude value at a given moment; software means operable in said computer for: (a) causing said computer means to generate a predetermined pattern on said monitor; (b) receiving said words in real time from said convertor means and scaling said represented force amplitude values according to a predetermined scaling factor for display on said monitor; and (c) plotting scaled values on said monitor superimposed on said pattern, said values being plotted according to the moment acquired so that the user may adjust said force in an attempt to track said pattern as said plotted values sweep across said monitor; said software means further including means for recording said words and for analyzing the deviation of the corresponding scaled values to determine a normalized accuracy indication value quantifying tracking performance, said analyzing means including means for: (a) calculating a first root mean square difference between said pattern and said values representing force amplitude; (b) calculating a second root mean square difference between said pattern and a baseline, said baseline corresponding to a zero level from said load cell means; and (c) calculating said normalized accuracy indication values as a function of the ratio between said first root mean square difference and said second root means square difference.