Fig. 8. Learning curves for the induced polarization of the water molecule due to interaction with image charges in the metal slab, computed only for separations greater than 4.5 Å. The error is computed as a fraction of the intrinsic variability of the test set of 215 configurations. Contrary to the local model (green), a linear model (blue) can learn this self-consistent polarization, with no significant reduction of the learning rate up to 1000 training configurations.