omission of reward. This abs(RPE) signal correlated with a number of brain regions including an IPS locus anterior to where we found SPE correlates at p < 0.001 uncorrected (Figure S3). However, a direct comparison between SPE and abs(RPE) revealed a region of both posterior IPS that was significantly better explained by the SPE than by the abs(RPE) signal at p < 0.05 corrected, as well as a region of lateral PFC that showed a difference at p < 0.001 uncorrected (Figure S4). We also tested whether the conjunction of SPE and abs(RPE) showed a significant effect in our target region, in order to assess whether these signals were even partially overlapping. No voxel survived the conjunction contrast, even at an uncorrected threshold. Taken together, these findings suggest that the SPE signal we observe in parietal cortex and lateral PFC is unlikely to reflect a non-specific arousal or attentional signal.
