Our model comprised three parameters: the SDs of the Gaussian distributions of motor noise (σ_m) and exploration following rewarded (σ_{e, rewarded}) and unrewarded (σ_{e, unrewarded}) trials. To examine the relative importance of each model parameter, we compared the full model to two reduced models: one where exploration variability does not depend on reward history (two-parameter model: σ_m and σ_e) and one that does not include motor noise (one-parameter model: σ_e). Model comparisons using BIC show the three-parameter model best fit the data from experiments 1 and 2, and the two-parameter model best fit data from the group with cerebellar damage. For each experiment, we show the difference in BIC relative to the best model (i.e., the one with 0).