Processing modes and parallel processors in producing familiar keying sequences.

Recent theorizing indicates that the acquisition of movement sequence skill involves the development of several independent sequence representations at the same time. To examine this for the discrete sequence production task, participants in Experiment 1 produced a highly practiced sequence of six key presses in two conditions that allowed little preparation so that interkey intervals were slowed. Analyses of the distributions of moderately slowed interkey intervals indicated that this slowing was caused by the occasional use of two slower processing modes, that probably rely on independent sequence representations, and by reduced parallel processing in the fastest processing mode. Experiment 2 addressed the role of intention for the fast production of familiar keying sequences. It showed that the participants, who were not aware they were executing familiar sequences in a somewhat different task, had no benefits of prior practice. This suggests that the mechanisms underlying sequencing skills are not automatically activated by mere execution of familiar sequences, and that some form of top-down, intentional control remains necessary.