ACC inhibition reduced the influence of the state transition (common or rare) on the subsequent choice (p = 0.007, Bonferroni corrected for comparison of three predictors, stimulation-by-group interaction p = 0.029, permutation test) (Figures 6D and S5A). Stimulation did not affect how either the trial outcome (p = 0.94, uncorrected) or the transition-outcome interaction (p = 0.90, uncorrected) influenced the subsequent choice. As the transition predictor most strongly differentiates model-based and model-free strategies (Figure 2), this selective effect is consistent with disrupted model-based control. If this interpretation is correct, the effect should be stronger in those subjects that rely more on model-based strategies. This was indeed the case; the inhibition effect on the transition predictor strongly correlated across subjects with the strength of model-based influence on their choices (Figure 6E; R = −0.91, p = 0.0001), as assessed by fitting the RL model to subject’s behavior in the inhibition sessions using a single set of parameters for all trials.
