Effects of extended practice in a one-finger keypressing task.

This paper addresses skilled operations underlying the initiation and execution of rapid movement sequences in a task consisting of three sequential keypresses made with one finger. It sought to provide evidence for the notion that, as a result of practice, processes required to produce a keypressing sequence become concurrent. The results of the experiment show, first, that unpacking of the third keypress in a three-keypress sequence, which is assumed to occur normally after execution of the second keypress, is shifted in time during practice so as to occur during or before actual depression of the second key. Second, no evidence was found that selection of a stimulus-dependent key occurring later in the sequence could be performed during execution of earlier, stimulus-independent keypresses. Third, the pattern of dual-task interference suggested that attention is required for preparing as well as for executing movement sequences. Dual-task interference hardly reduced with practice which was interpreted as evidence for the notion that reduction of attentional demands of keypressing with practice is used only for increasing the amount of concurrent unpacking. In conclusion, the present experiment suggests that a major reason that movement sequences are executed faster with practice is that the reduction of attentional demands of individual subprocesses is utilized to increase the amount of concurrent processing.