↵^aThe first three columns show the parameter estimates across all participants and trials within each stimulation group (anodal, cathodal, or sham) in the baseline condition. Columns 4 to 6 show the change in the parameter estimates under tDCS relative to baseline for each stimulation condition. Parameters β and ϕ were allowed to vary individually across participants and were fit in a hierarchical manner (see Materials and Methods). For these parameters, the table reports the means (± standard deviations) of the median values of each subject's posterior distribution. The remaining parameters were fit across the population; for these parameters, the table reports the medians of the population posterior distribution.