AGE-RELATED DIFFERENCES IN MOVEMENT CONTROL - ADJUSTING SUBMOVEMENT STRUCTURE TO OPTIMIZE PERFORMANCE

In this experiment older and younger adults were compared on their abi lity to position a cursor with an electromechanical mouse. Distance of the movement, size of the target, and relative emphasis on the speed or accuracy of the movement were manipulated. The study was designed t o isolate and evaluate the effects of age-related differences in the n oise-to-force ratio, perceptual feedback efficiency, strategy differen ces, and the ability to produce force as explanations for age-related differences in movement control. This was done by using two types of m ovement tasks and by analyzing movement performance according to stage s of movement. The study showed that all four factors, when isolated, are significantly different for th two age groups. However, in the tas k component where all factors could simultaneously affect performance, the age-related difference in performance was less than the differenc e in either the measure of noise-to-force ratio or perceptual efficien cy. Analysis of the submovement structure revealed how older adults co mpensated for the greater noise and less perceptual efficiency by adju sting the velocity and number of submovements. These findings are disc ussed in light of the optimized submovement model.