Modularity and hierarchical organization of action programs in human acquisition of graphic skills.

If motor or action programs become modules with practice their defining features (e.g. relative timing) should remain relatively invariant in new tasks. To test this hypothesis 24 adults practiced a graphic skill over 100 trials and were transferred to a more complex task enclosing the practiced figure. The data acquired by a digital tablet resulted in total movement and total pause times to draw the figure indicating skill acquisition and variability measures of relative timing and pause time and sequencing referring to features that identify a module. Being transferred to a more complex task did not lead to significant increases in the time to perform the criterion figure embedded in the new pattern. Modularity was evidenced by the stability of relative timing and sequencing shown in the performance of the criterion figure. Hence, it might be that action programs become modules that are then hierarchically organized to form more complex skills.