Fig. 3

A The psychophysical curve corresponding to the inter-participant average (solid blue, 22.7%) with one inter-participant standard deviation (shaded, ± 17.0%). B Participant-specific data: the likeliest psychophysical curve for each participant (solid blue), participant responses (red circles), and the 95% credible interval of possible curves from the posterior distribution (shaded blue). C The posterior distribution for the inter-participant psychophysical curve (dashed black) vs. the posterior distributions for each participant with modeled inter-participant JND differences (blue). The inter-participant model posterior distributions show clear differences between participants and thus proved a better choice of model. D A comparison of different JND models using the Watanabe-Akaike Information Criterion (WAIC) metric. A higher WAIC score (black circle, standard deviations given by black lines) indicates a better model. The best model has a light gray dotted line through its empty circle to aid in comparison. Grey triangles indicate the difference in WAIC between that model and the top model (standard error given by grey bars). E The absolute range of reference costs aggregated across all participants. The vertical red line denotes the average net cost of walking at 1.25 m/s across different studies [61]