We sought neural correlates of the prediction errors from both models. For this, we derived an RPE from the SARSA learner for session 2 and an SPE from the FORWARD learner for both sessions and included them as parametric modulators at the second decision state and the final outcome state in the single subject analyses (see Experimental Procedures). The voxel-wise parameter estimate (beta) for these regressors indicates how strongly a particular brain area covaries with these model-derived prediction errors. These beta images were included in a repeated measures ANOVA at the second level testing for the effect of each error signal across the group (see Experimental Procedures).
