Purpose. The purpose of this experiment was to evaluate the developmental differences in movement microstructure as a function of target width and movement length manipulations in children and adults. Basic procedures. Children, 6 years old (n = 20) and 9 years old (n = 20), and adults (n = 20) performed four rapid aiming tasks using the arm and hand. Index of difficulty (from the easy to difficult as estimated by Fitts’ law) was used to create four tasks levels with all participants performing 15 trials at each level. Task performance was measured by speed of movement which was subdivided into the ballistic and feedback control phases using velocity and acceleration profiles. Main findings. Results showed that participants decreased the portion of primary submovement for smaller targets and longer movements and these changes were proportional for children and adults. Conclusions. Based on their small ballistic phase of the movement, children appear to have a limited amount of the movement programmed and use feedback control for most of the movement distance and time. Adults have a substantially greater proportion of the movement time and distance in the ballistic phase leading to faster movements with fewer corrections.
Key words: age and motor performance, speed-accuracy trade-off, movement substructures, fine motor coordination, Fitts’ law