Figure 2. Modular Graph Learning Effects. (A) Mean reaction times (RTs) as a function of trial number for stage 1 of Experiment 1, among participants exposed to the modular graph. The red line indicates the mean for cross-cluster trials, and the black line indicates the mean for all other trials, each binned in sets of 30 trials (n=30 subjects). (B) Mean reaction times on correct trials for the modular graph. An increase in reaction time across cluster boundaries can be seen, here visualized by yellower colors in the matrix elements that sit between the larger blocks. (C) Mean reaction times collapsed across the symmetric structure of the modular graph. All three clusters were structurally identical and starting position was randomized between subjects, so we combine reaction times across the three clusters into one ‘canonical’ cluster for visualization purposes only. The mean increase in reaction time between clusters is more apparent, here visualized by yellower colors on the edges that connect the top cluster with the two bottom clusters. (D) Relationship between surprisal effect on stage 1 (random walk) and surprisal effect on stage 2 (Hamiltonian walk) for each subject of Experiment 2. Subjects that displayed a strong surprisal effect in stage 1 likewise do so when the walk structure is changed (n=59). surprisal effect was significantly reduced and not significant in the Hamiltonian walk, with an estimated increase in RT of 7.16 ms (Supplementary Table 3; linear mixed effects model; t ( 58 ) = 0 . 69 , p = 0 . 49, 95% confidence interval: -13.17 to 27.49). However, a subject’s coefficient for cross-cluster surprisal in the random walk was significantly correlated with that in the 8/29 0 1000 1200 1400 0 500 1000 1500 Trial Mean  RT (ms) Cross−Cluster Edge FALSE TRUE A Pearson's  ρ  = 0.8 p < 0.001 −100 0 100 200 300 400 −100 0 100 200 300 400 Surprisal Effect in Stage 1 (ms) Surprisal Effect in Stage 2 (ms) D n=30 1 3 5 7 9 11 13 15 1 3 5 7 9 11 13 15 Node Pr e vious Node 1050 1150 RT (ms) B n=162 n=59 C 5 1 5 1 4 2 3