Synergy formation during motor skill acquisition.

The percentage of total variance explained by each PC in artificial agents (A) and in human participants during the test blocks (B) and the training blocks (C). Both agents and human participants need two PCs to explain >90% of the total variance in reach postures (q1, q2, q3) at the end of training. In human participants, this involves a dimensionality reduction, i.e., the amount of variance explained by PC1 goes up with training (sign-test difference beginning vs. end: p = 0.041 in test; training p = 0.263), whereas the amount of variance explained by PC3 goes down (sign test difference beginning vs. end: pA, B and C depict the across-participant median, the error bars the interquartile range.