Figure 4. Adaptation paths are bent toward the learned structure (continued). *A*, Across-trial adaptation of late movement hand positions: the same data as presented in Figure 3*B*, but flipped to the first quadrant and averaged over directions (group averages). Ellipses show SEM (*N* = 96 for each ellipse), with color (dark to light) showing trial number (1–5) during a probing block. The difference between groups is significant for every trial (*p* < 10^{−10}). The dashed lines show trajectories corresponding to the exponential fits, with small dots on the dashed line showing the positions on trials 1–5, according to the fit. The inset shows learning speeds for both groups with light (dark) bars corresponding to azimuth (elevation) learning speeds. Learning speed is defined as amount of error (from 0 to 1) corrected on each subsequent trial. The asterisks show statistical significance (for details, see Materials and Methods), with three asterisks meaning *p* < 0.001. *B*, The same as *A*, but for initial movement directions (200 ms after movement onset). For trials 2–5, difference between groups is significant with *p* < 0.001. Two asterisks in the inset mean *p* < 0.01. *C*, The same as *B*, but for initial directions of backward movements. Here, the data were flipped to the third quadrant only for convenience, to show that these are backward movements. Difference between groups is significant for each trial with *p* < 10^{−5}. *D*, Movement trajectories during the first trial, averaged over directions. The black ticks show the time point when the difference between groups becomes significant with *p* < 0.05. *E*, For every subject, we computed the degree of bending, calculated as a normalized area between late movement adaptation path and the straight diagonal path. These values are shown for six subjects in the vertical and six subjects in the horizontal group. The horizontal lines show mean value for each group (printed nearby in respective colors) together with SEM. *F*, Scheme of statistical testing for differences between groups, used in *A–D*. The data were first projected on a line perpendicular to the perturbation, and then Mann–Whitney–Wilcoxon rank sum test was performed. This way, we were only assessing the difference in bending of adaptation paths, and not in the learning speed.