A) A posterior distribution of group mean drift rate was calculated using HDDM, and indicates the rate of evidence accumulation over 8 different coherences. The most likely group means are plotted; error bars indicate the posterior standard deviation. With higher coherence, higher drift rates were observed for both high doubt (orange color, N = 10) and low (black color, N = 36) subjects. However, at higher levels of coherence, high doubt subjects exhibited even faster drift rates and reaction times than low doubt subjects (q<0.01 for 70% coherence). B) No significant differences in the posterior distribution of HDDM threshold were observed between high and low doubt subjects.