Fig. 1: Influence of length of training of skill A on generalization to skill B during early learning.

Experiment 1 evaluated the influence of length of training of a skill A on generalization to a skill B (n = 551; see Supplementary Table 1 for demographics). a Task: Participants were randomized to practice a skill A for 1, 2, 5 or 12 trials. Rest intervals between trials were 10 s duration. Practice of skill A (4-1-3-2-4) was followed in all groups by five testing trials of skill B (2-3-1-4-2). Skill was measured as the average inter-tap interval within correct sequences (tapping speed measured in keypresses/s). b Performance of the training groups (grey: skill A; cyan: skill B; mean ± s.e.m.). Training in skill A resulted in rapid performance improvements, consistent with previous work. Specifically, participants demonstrated rapid motor skill learning primarily during micro-offline periods which reached plateau by trial 11 in the 12 trials group⁹ (Supplementary Fig. 1). c Skill at the onset of skill B (red: 1 trial; blue: 2 trials; green: 5 trials; yellow: 12 trials). Following the end of practice on skill A, performance at the onset of skill B was comparable between experimental groups. d Change in skill from the end of skill A to the onset of skill B (i.e., \({{Gen}}_{{B}_{0}-{A}_{f}}\)). All groups had significant changes in performance between the end of skill A to the onset of skill B. The group that practiced one trial of skill A was the only group that showed \({{Gen}}_{{B}_{0}-{A}_{f}}\), suggestive of a micro-offline contribution to generalization (shaded bar). *p < 0.05, where * over individual group plots indicate significant one-sample t-test within-group differences between B₀ and A_f and * between group plots indicate significant Kruskal-Wallis (pairwise comparison) between-group differences.