Figure 2.

Effect of reward on motor skill learning

(A) Error. Average Error is represented across practice for the three experimental groups (gray: Group_-S, light green: Group_-SR, dark green: Group_-SRR). The gray shaded area highlights the blocks concerned by the reinforcement manipulation. The remaining blocks were performed with knowledge of performance only (i.e., in a Block_-SR setting).

(B) Skill learning. Bar plot (left) and violin plot (right, each dot = one subject) representing skill learning (quantified as the Error in Post-training blocks expressed in percentage of Pre-training blocks) in the three experimental groups. Skill learning was significantly enhanced in Group_-SRR compared to the two other groups. This result remained significant when removing the subject showing an extreme value in the Group_-SR (ANOVA: F_(2,86) = 6.44, p = 0.0025, partial η² = 0.13; post-hocs; Group-SRR vs. Group-SR: p = 0.027; Group-SRR vs. Group-S: p = 0.00064; Group-SR vs. Group-S: p = 0.21).

(C) Skill maintenance. Bar plot (left) and violin plot (right) representing skill maintenance quantified as the Error in Re-test blocks expressed in percentage of Pre-training blocks) in the three experimental groups.

(D) Success. Proportion of successful trials for each block.

(E) Force profiles. Individual force profiles of one representative subject of Group_-S (left), Group_-SR (middle) and Group_-SRR (right) in the Pre- (gray) and Post-training blocks (blue). Note the better approximation of the Target_Force and the reduced inter-trial variability at Post-training in the exemplar subject of Group_-SRR.

∗: significant difference between groups (p<0.05). #: significant difference within a group between normalized Post-training Error and a constant value of 100% (p<0.017 to account for multiple comparisons). Data are represented as mean ± SE