Specificity versus variability: effects of practice conditions on the use of afferent information for manual aiming.

Although proponents of the motor schema theory hold that a decrease in the reliance on afferent information will occur with practice in consort with the development of motor programs, supporters of the specificity of practice by hypothesis suggest that a performer's reliance on the available sources of afferent information during acquisition increases with the amount of practice. To reconcile these competing positions, four groups of 9 participants aimed to targets under either a constant or a variable practice schedule, with or without vision of the effector. After modest (15 trials) and moderate (150 trials) practice, participants were tested in both their own and in the alternate vision condition. Results indicate that the utilization of online kinesthetic information was enhanced through practice regardless of the availability of vision during acquisition. This was especially true for the groups practicing under a variable practice schedule