Fig. 1*B* | Effect of group on number of trials Effect of day on number of trials Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.49, df = 28.48, *p *=* *0.63
*t *=* *124, df = 3.58, *p *=* *4.88 × 10^{−4}
*t *=* *124, df = −0.47, *p *=* *0.64 |

Fig. 1*C* | Effect of group on first reach success rate Effect of day on first reach success rate Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.442, df = 25, *p *=* *0.66
*t *=* *5.55, df = 123, *p *=* *1.70 × 10^{−7}
*t* = −4.78, df = 123, *p *=* *4.98 × 10^{−6} |

Extended Data Fig. 1-1*C* | Effect of group on number of reach attempts Effect of day on number of reach attempts Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.81, df = 19, *p *=* *0.43
*t* = −4.12, df = 124, *p *=* *6.88 × 10^{−5}
*t *=* *1.37, df = 124, *p *=* *0.17 |

Extended Data Fig. 1-1*D* | Effect of day on performance outcomes, learners Effect of day on performance outcomes, non-learners | Linear mixed model | *n* = 4 | No pellet: *t* = −0.11, df = 35, *p *=* *0.91 First success: *t *=* *4.96, df = 35, *p *=* *1.83 × 10^{−5} Multiple success: *t* = −2.53, df = 35, *p *=* *0.02 Drop in box: *t *=* *0.42, df = 35, *p *=* *0.68 Pellet knock off: *t* = −4.59, df = 35, *p* =5.46 × 10^{−5} Tongue: *t *=* *0, df = 35, *p *=* *1 Trigger error: *t* = −0.52, df = 38, *p *=* *0.61 Pellet remained: *t* = −0.78, df = 38, *p *=* *0.44 Non-preferred hand: *t* = −0.87, df = 38, *p *=* *0.39 Tongue and hand: *t *=* *0, df = 38, *p *=* *1 Hand through slot: *t* = −0.78, df = 38, *p *=* *0.39 No pellet: *t* = −0.62, df = 98, *p *=* *0.54 First success: *t *=* *0.51, df = 88, *p *=* *0.61 Multiple success: *t* = −0.79, df = 89, *p *=* *0.43 Drop in box: *t *=* *0.36, df = 89, *p *=* *0.72 Pellet knock off: *t *=* *0.49, df = 89, *p *=* *0.62 Tongue: *t *=* *0, df = 98, *p *=* *1 Trigger error: *t* = −1.37, df = 98, *p *=* *0.18 Pellet remained: *t* = −0.95, df = 98, *p *=* *0.35 Non-preferred hand: *t* = −0.87, df = 98, *p *=* *0.39 Tongue and hand: *t *=* *0, df = 98, *p *=* *1 Hand through slot: *t *=* *0.01, df = 98, *p *=* *0.99 |

Fig. 2*C* | Effect of group on paw trajectory variability Effect of day on paw trajectory variability Group × day interaction | Linear mixed model | *n* = 14 | Reach: *t *=* *0.53, df = 23, *p *=* *0.60 Grasp: *t* = −0.08, df = 26, *p *=* *0.94 Reach: *t* = −1.85, df = 124, *p *=* *0.07 Grasp: *t* = −2.75, df = 124, *p *=* *6.91 × 10^{−3} Reach: *t *=* *0.37, df = 124, *p *=* *0.71 Grasp: *t *=* *1.08, df = 124, *p *=* *0.28 |

Fig. 2*D* | Negative correlation between trajectory variability and success rate, learners Negative correlation between trajectory variability and success rate, non-learners | Linear correlation | *n* = 4
*n* = 10 | Session 1: *r *=* *0.73, *p *=* *5.33 × 10^{−6} Session 2: *r* = −0.55, *p *=* *1.70 × 10^{3} Session 3: *r* = −0.03, *p *=* *0.86 Session 4: *r* = −0.68, *p *=* *4.25 × 10^{−5} Session 5: *r* = −0.53, *p *=* *2.50 × 10^{−3} Session 6: *r* = −0.82, *p *=* *2.16 × 10^{−8} Session 7: *r *=* *0.15, *p *=* *0.44 Session 8: *r* = −0.70, *p *=* *1.51 × 10^{−5} Session 9: *r *=* *0.39, *p *=* *0.03 Session 10: *r* = −0.24, *p *=* *0.20 Session 1: *r* = −0.88, *p *=* *1.78 × 10^{−10} Session 2: *r* = −0.02, *p *=* *0.91 Session 3: *r *=* *0.02, *p *=* *0.91 Session 4: *r* = −0.67, *p *=* *4.33 × 10^{−5} Session 5: *r* = −0.33, *p *=* *0.08 Session 6: *r* = −0.38, *p *=* *0.04 Session 7: *r *=* *0.67, *p *=* *4.33 × 10^{−5} Session 8: *r* = −0.42, *p *=* *0.02 Session 9: *r* = −0.07, *p *=* *0.73 Session 10: *r* = −0.83, *p *=* *1.53 × 10^{−8} |

Fig. 2*E* | Effect of group on reach duration Effect of day on reach duration Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.29, df = 21, *p *=* *0.78
*t* = −1.03, df = 124, *p *=* *0.31
*t* = −0.11, df = 124, *p *=* *0.91 |

Fig. 2*F* | Effect of group on reach velocity Effect of day on reach duration Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.16, df = 15, *p *=* *0.87
*t* = −0.07, df = 124, *p *=* *0.94
*t *=* *1.02, df = 124, *p *=* *0.31 |

Fig. 3*B* | Effect of group on reach endpoint Effect of day on reach endpoint Group × day interaction | Linear mixed model | *n* = 14 | Paw *x*: *t* =1.30, df = 18, *p *=* *0.21 Paw *y*: *t* = −0.94, df = 18, *p *=* *0.36 Paw *z*: *t* = −0.38, df = 124, *p *=* *0.71 Digit 2 ×: *t *=* *1.80, df = 17, *p *=* *0.09 Digit 2 year: *t* = −0.90, df = 19, *p *=* *0.38 Digit 2 *z*: *t* = −0.63, df = 19, *p *=* *0.53 Paw *x*: *t *=* *2.13, df = 124, *p *=* *0.04 Paw *y*: *t* = −2.45, df = 124, *p *=* *0.02 Paw *z*: *t *=* *1.73, df = 124, *p *=* *0.09 Digit 2 ×: *t *=* *3.12, df = 124, *p *=* *2.25 × 10^{3} Digit 2 year: *t* = −1.80, df = 124, *p *=* *0.07 Digit 2 *z*: *t *=* *0.99, df = 124, *p *=* *0.33 Paw *x*: *t* = −2.40, df = 124, *p *=* *0.02 Paw *y*: *t *=* *1.45, df = 124, *p *=* *0.15 Paw *z*: *t* = −1.23, df = 124, *p *=* *0.22 Digit 2 ×: *t* = −3.16, df = 124, *p *=* *1.97 × 10^{3} Digit 2 year: *t *=* *1.16, df = 124, *p *=* *0.25 Digit 2 *z*: *t* = −0.58, df = 124, *p *=* *0.57 |

Fig. 3*D* | Effect of group on endpoint variability, raw data Effect of day on endpoint variability, raw data Group × day interaction, raw data Effect of group on endpoint variability, subtracted position Effect of day on endpoint variability, subtracted position Group × day interaction, subtracted position | Linear mixed model | *n* = 14 | Hand: *t* = −0.95, df = 51, *p *=* *0.35 Digit 1: *t* = −0.71, df = 56, *p *=* *0.48 Digit 2: *t* = −0.86, df = 45, *p *=* *0.39 Digit 3: *t* = −0.42, df = 49, *p *=* *0.67 Digit 4: *t* = −0.29, df = 48, *p *=* *0.78 Hand: *t* = −2.27, df = 124, *p *=* *0.02 Digit 1: *t* = −1.97, df = 124, *p *=* *0.05 Digit 2: *t* = −2.25, df = 124, *p *=* *0.03 Digit 3: *t* = −1.85, df = 124, *p *=* *0.07 Digit 4: *t* = −1.78, df = 124, *p *=* *0.08 Hand: *t *=* *1.39, df = 124, *p *=* *0.17 Digit 1: *t *=* *1.15, df = 124, *p *=* *0.25 Digit 2: *t *=* *1.42, df = 124, *p *=* *0.16 Digit 3: *t *=* *0.90, df = 124, *p *=* *0.37 Digit 4: *t *=* *0.89, df = 124, *p *=* *0.37 Digit 1: *t *=* *0.13, df = 78, *p *=* *0.89 Digit 2: *t* = −1.61, df = 112, *p *=* *0.11 Digit 3: *t* = −0.75, df = 136, *p *=* *0.45 Digit 4: *t *=* *0.62, df = 107, *p *=* *0.54 Digit 1: *t* = −0.87, df = 124, *p *=* *0.39 Digit 2: *t* = −2.23, df = 124, *p *=* *0.03 Digit 3: *t* = −1.64, df = 136, *p *=* *0.10 Digit 4: *t* = −0.67, df = 124, *p *=* *0.51 Digit 1: *t *=* *0.64, df = 124, *p *=* *0.52 Digit 2: *t *=* *1.79, df = 124, *p *=* *0.08 Digit 3: *t *=* *1.21, df = 136, *p *=* *0.23 Digit 4: *t *=* *0.03, df = 124, *p *=* *0.98 |

Fig. 3*E* | Effect of part on % mislabeled frames Effect of day on % mislabeled frames Part × day interaction | Linear mixed model | *n* = 14 | *t* = −0.05, df = 123, *p *=* *0.96
*t *=* *0.98, df = 123, *p *=* *0.33 Hand: *t* = −0.79, df = 117, *p *=* *0.43 Digit 1: *t *=* *1.07, df = 117, *p *=* *0.29 Digit 2: *t *=* *0.91, df = 117, *p *=* *0.37 Digit 3: *t *=* *1.82, df = 117, *p *=* *0.07 Digit 4: *t *=* *2.71, df = 117, *p *=* *7.74 × 10^{−3} |

Fig. 4*A* | Effect of group on digit 2 trajectory variability Effect of day on digit 2 trajectory variability Group × day interaction | Linear mixed model | *n* = 14 | Reach: *t *=* *1.39, df = 23, *p *=* *0.18 Grasp: *t* = −0.60, df = 27, *p *=* *0.55 Reach: *t* = −1.69, df = 124, *p *=* *0.09 Grasp: *t* = −3.92, df = 124, *p *=* *1.46 × 10^{−4} Reach: *t* = −0.01, df = 124, *p *=* *0.99 Grasp: *t *=* *2.29, df = 124, *p *=* *0.02 |

Fig. 4*D* | Effect of group on aperture Effect of day on aperture Group × day interaction | Linear mixed model | *n* = 14 | *t* = −0.81, df = 15, *p *=* *0.43
*t *=* *0.97, df = 124, *p *=* *0.34
*t *=* *0.36, df = 124, *p *=* *0.72 |

Fig. 4*F* | Effect of group on aperture variance Effect of day on aperture variance Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.96, df = 22, *p *=* *0.35
*t* = −1.53, df = 124, *p *=* *0.13
*t *=* *0.90, df = 124, *p *=* *0.37 |

Fig. 4*H* | Effect of group on hand orientation Effect of day on hand orientation Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.78, df = 15, *p *=* *0.45
*t *=* *2.72, df = 124, *p *=* *7.42 × 10^{−3}
*t* = −1.54, df = 124, *p *=* *0.13 |

Fig. 4*J* | Effect of group on orientation variance Effect of day on orientation variance Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *0.80, df = 61, *p *=* *0.43
*t *=* *1.97, df = 124, *p *=* *0.05
*t* = −0.98, df = 124, *p *=* *0.33 |

Fig. 4*L* | Effect of group on digit flexion Effect of day on digit flexion Group × day interaction | Linear mixed model | *n* = 14 | *t* −0.68, df = 16, *p *=* *0.51
*t* = −1.49, df = 124, *p *=* *0.14
*t *=* *0.98, df = 124, *p *=* *0.33 |

Fig. 4*N* | Effect of group on flexion variance Effect of day on flexion variance Group × day interaction | Linear mixed model | *n* = 14 | *t* = −1.00, df = 26, *p *=* *0.33
*t *=* *1.02, df = 124, *p *=* *0.31
*t* = −0.01, df = 124, *p *=* *0.99 |

Fig. 5*B* | Effect of group on aperture Effect of day on aperture Group × day interaction | Linear mixed model | *n* = 14 | *t* = −0.53, df = 30, *p *=* *0.60
*t* = −0.17, df = 111, *p *=* *0.86
*t *=* *1.35, df = 111, *p *=* *0.18 |

Fig. 5*D* | Effect of group on orientation Effect of day on orientation Group × day interaction | Linear mixed model | *n* = 14 | *t *=* *1.11, df = 18, *p *=* *0.28
*t *=* *2.20, df = 111, *p *=* *0.03
*t* = −2.08, df = 111, *p *=* *0.04 |

Fig. 5*F* | Effect of group on flexion Effect of day on flexion Group × day interaction | Linear mixed model | *n* = 14 | *t* = −0.184, df = 19, *p *=* *0.86
*t* = −0.05, df = 111, *p *=* *0.96
*t* = −0.52, df = 111, *p *=* *0.60 |

Fig. 6*A* | Effect of outcome on reach trajectory variability Effect of day on reach trajectory variability Outcome × day interaction | Linear mixed model | *n* = 4
*n* = 10
*n* = 4
*n* = 10
*n* = 4
*n* = 10 | Learners: *t *=* *1.26, df = 72, *p *=* *0.21 Non-learners: *t *=* *4.44, df = 183, *p *=* *1.56 × 10^{−5} Learners: *t* = −1.84, df = 72, *p *=* *0.07 Non-learners: *t* = −2.01, df = 183, *p *=* *0.046 Learners: *t* = −0.46, df = 72, *p *=* *0.64 Non-learners: *t* = −1.25, df = 183, *p *=* *0.21 |

Fig. 6*B* | Effect of outcome on grasp trajectory variability Effect of day on grasp trajectory variability Outcome × day interaction | Linear mixed model | *n* = 4
*n* = 10
*n* = 4
*n* = 10
*n* = 4
*n* = 10 | Learners: *t *=* *4.77, df = 72, *p *=* *9.34 × 10^{−6} Non-learners: *t *=* *5.58, df = 183, *p *=* *8.47 × 10^{−8} Learners: *t* = −0.30, df = 72, *p *=* *0.77 Non-learners: *t* = −2.88, df = 183, *p *=* *4.42 × 10^{3} Learners: *t* = −2.23, df = 72, *p *=* *0.03 Non-learners: *t* = −1.02, df = 183, *p *=* *0.31 |

Fig. 6*C* | Effect of outcome on reach endpoint Effect of day on reach endpoint Outcome × day interaction | Linear mixed model | *n* = 4
*n* = 10
*n* = 4
*n* = 10
*n* = 4 | Learners *X*: *t* = −2.31, df = 72, *p *=* *0.02 Learners *Y*: *t* = −0.95, df = 72, *p *=* *0.35 Learners *Z*: *t *=* *3.52, df = 72, *p* =7.48 × 10^{−4} Non-learners *X*: *t* = −1.53, df = 185, *p *=* *0.13 Non-learners *Y*: *t* = −1.49, df = 185, *p *=* *0.14 Non-learners *Z*: *t *=* *4.94, df = 185, *p *=* *1.76 × 10^{−6} Learners *X*: *t *=* *0.95, df = 72, *p *=* *0.34 Learners *Y*: *t *=* *1.54, df = 72, *p *=* *0.13 Learners *Z*: *t *=* *1.31, df = 72, *p *=* *0.20 Non-learners *X*: *t* = −1.46, df = 185, *p *=* *0.15 Non-learners *Y*: *t *=* *0.59, df = 185, *p *=* *0.56 Non-learners *Z*: *t *=* *0.76, df = 185, *p *=* *0.45 Learners *X*: *t *=* *1.94, df = 72, *p *=* *0.06 Learners *Y*: *t *=* *0.23, df = 72, *p *=* *0.82 Learners *Z*: *t* = −1.86, df = 72, *p *=* *0.07 Non-learners *X*: *t* = −0.03, df = 185, *p *=* *0.97 Non-learners *Y*: *t *=* *0.77, df = 185, *p *=* *0.44 Non-learners *Z*: *t* = −1.53, df = 185, *p *=* *0.13 |

Fig. 6*D* | Effect of outcome on hand endpoint variability Effect of day on hand endpoint variability Outcome × day interaction | Linear mixed model | *n* = 4
*n* = 10
*n* = 4
*n* = 10
*n* = 4
*n* = 10 | Learners: *t *=* *2.67, df = 72, *p *=* *9.26 × 10^{−3} Non-learners: *t *=* *2.63, df = 185, *p *=* *9.34 × 10^{−3} Learners: *t* = −0.06, df = 72, *p *=* *0.96 Non-learners: *t* = −0.26, df = 185, *p *=* *0.80 Learners: *t* = −1.95, df = 72, *p *=* *0.05 Non-learners: *t* = −0.67, df = 185, *p *=* *0.50 |

Fig. 6*E* | Effect of outcome on digit 2 endpoint variability Effect of day on digit 2 endpoint variability Outcome × day interaction | Linear mixed model | *n* = 4
*n* = 10
*n* = 4
*n* = 10
*n* = 4
*n* = 10 | Learners: *t *=* *2.64, df = 72, *p *=* *0.01 Non-learners: *t *=* *2.60, df = 185, *p *=* *0.01 Learners: *t* = −0.14, df = 72, *p *=* *0.89 Non-learners: *t* = −0.22, df = 185, *p *=* *0.83 Learners: *t* = −1.92, df = 72, *p *=* *0.06 Non-learners: *t* = −0.25, df = 185, *p *=* *0.80 |