Fig. 9.

a Posterior distributions of the mean group threshold parameters μ_a of the diffusion decision model in which separate drift rates were fit for easy and difficult decisions, and separate thresholds were fit for all different pairs of choices. Solid lines represent the 95% Bayesian credible interval, and squares represent the mean of the posterior distribution. b Posterior distribution of the mean group (in orange) and of the individual (in grey) threshold modulator parameters a_mod of the full reinforcement learning diffusion decision model