Behavioral surprise of human participants compared to simulated surprise.

Example of an image sequence. Each image is presented for 1s followed by a 1s grey screen. Subjects are informed to focus on one specific image (e.g. ‘pen’) and the transition from there to the following image. B Sequence 1 is deterministic and used to familiarize the subject with the task. Sequence 2 has stochastic transitions so that each given image can be followed by one of K = 2 other images, with equal probability p = 0.5. C Participants observe the image sequence while attempting to predict the image following the pen and report their feeling of surprise continuously by moving a ‘Surprise slider’. Participants are randomly assigned to two different groups, with and without change points. D Scaled normalized surprise reported by the 65 participants in group 1 (blue line: mean; shaded blue: variance) as a function of time (Methods), overlaid with appropriately scaled surprise in 60 simulations with SpikeSuM (green line: mean; shaded green: variance) using the same sequence as in the experiments with change point after 150 image presentations. E Same as D, but for the sequence without change-points. F Differences in the experimental data of participants are significant (t-test) in D between the 50 steps before and 50 steps after the change point (blue bars in F); not significant in E between the 50 steps before and 50 steps after step 150 in the absence of change point; and significant for the time steps 150–200 between D and E (blue vs. red bar in F). The symbol *** indicates p < 10⁻⁵, and ‘ns’ not significant.