a. Comparison of four different methods for computing individual Just-Noticeable-Difference (JND), estimated on the behavior-only group, indicating no difference between the approaches (see Methods for the different approaches; F2,46 = 0.7, p = 0.5, Bayes-Factor > 1.5) which validates the use of staircase JND to normalize the results (n=18). b. Comparison between JND before and after main paradigm. Left plot demonstrates no difference between different measures of JND after main paradigm, whereas right plot demonstrates that perceptual threshold did not change (after minus before) due to main paradigm and was identical across different images (n=47 for first three violins, n=22 for last two violins). The two sets of left violins measure JND when the two consecutive images were overlaid with the same number (positive or negative), to control for value and visual differences. The middle (PE0) and right set of violins (PE+/PE-) measure JND when the two consecutive images are either [0 0],[0 +4],[0–2], correspondingly. Therefore, although we denote it as PE here for clarity, there is no real prediction-error because the outcome is fully predicted within the block. Before the paradigm numbers did not have any meaning (that is did not provide reward/loss), while at the end they did (like in the main paradigm). Overall, the different conditions show that perceptual thresholds did not change: before to after the main paradigm, with or w/o real outcome, and with outcome that is predicted (that is no PE). Error bars represent SEM.