The development and integration of fine motor sequences in 12- to 18-month-old children: a test of the modular theory of motor skill acquisition.

According to the modular model, skill development proceeds through the development of stable units of action called subroutines. The development of these programmed units frees the child to attend to those parts of the action not yet mastered. Once consolidated they can be applied to many different contexts. Thus, complex skill sequences can be produced. The theory generates several predictions, most fundamental being an association between increasing proficiency and increasing consistency. Experiment 1 was a longitudinal study in which six 12-month-old children were observed over a period of eight months. Various manipulative tasks were used, notably the placement of rods in corresponding holes. Experiment 2 was a cross-sectional study of performance consistency in rod placement (N = 30). Results showed that consistency decreases as proficiency increases. It is concluded therefore that the programmed components of complex actions are not characterized by the invariance predicted by modular theory.