Many motor skills are learned with the help of instructions. In the context of complex motor sequences, instructions often break down the movement into chunks that can then be practiced in isolation. Thus, instructions shape an initial cognitive representation of the skill, which in turn guides practice. Are there ways of breaking up a motor sequence that are better than others? If participants are instructed in a way that hinders performance, how much practice does it take to overcome the influence of the instruction? To answer these questions, we used a paradigm in which participants were asked to perform finger sequences as fast and accurately as possible on a keyboard-like device. In the initial phases of training, participants had to explicitly remember and practice two- or three-digit chunks. These chunks were then combined to form seven 11-digit sequences that participants practiced for the remainder of the study. Each sequence was broken up into chunks in a way such that the instruction was either aligned or misaligned with the basic execution-level constraints. We found that misaligned chunk instruction led to an initial performance deficit compared with the aligned chunk instruction. Overall, instructions still influenced the temporal pattern of performance after 10 days of subsequent training, with shorter interpress intervals within a chunk compared with between chunks. However, for the misaligned instructed sequences, this temporal pattern was altered more rapidly, such that participants could overcome the induced performance deficit in the last week. At the end of training, participants found idiosyncratic, but interindividually stable, ways of performing each sequence.NEW & NOTEWORTHY Instructions often break down motor sequences into smaller parts, such that they can be more easily remembered. Here, we show that different ways of breaking down a finger sequence can subsequently lead to better or worse performance. The initial instruction still influenced the temporal performance pattern after 10 days of practice. The results demonstrate that the initial cognitive representation of a motor skill strongly influences how a skill is learned and performed.
Keywords: chunking; habits; instructions; motor learning; motor skill.