The role of parameter variability on retention, parameter transfer, and effector transfer.

The purpose of this study was to examine the effects of parameter variability on the learning of generalized motor programs (GMP) and movement parameterization. Participants attempted to exert a force pattern that resembled in force and time a waveform displayed on a computer monitor. The analysis suggested that relative timing (a measure of the GMP) performance remained remarkably stable across retention and transfer tests, whereby the structure of the movement remained intact, although the parameter or muscle group (effector) changed during transfer The results also indicated that variable parameter (time) practice did not enhance GMP learning but did degrade the learning parameter that was not varied (force). In addition, parameter specification was substantially less stable than the GMP, with time and force parameter performance deteriorating from the retention to transfer tests. These findings suggest that parameter specification, and not the GMP, is the primary cause of poorer performance in parameter and effector transfer.