(A) Schematic of a single trial of the Ready-Set-Go task. The animal has to estimate a sample interval, ts, between Ready and Set (estimation epoch), and produce a matching interval, tp, after Set with a delayed response (Go) via a saccade or a movement of the joystick (production epoch). (B) Reward as a function of relative error (tp-ts)/ts. (C) ‘Short’ and ‘Long’ prior distributions of ts. (D) Eight randomly interleaved trial types (see Methods): 2 prior conditions (Short and Long) × 2 effectors (Eye and Hand) × 2 target directions (Left and Right). (E) Behavior. Top: A representative session for monkey H showing tp pooled across effectors and target directions (small dots: individual trials; large open circles: average tp per ts; solid lines: Bayesian model; diagonal: unity line). The horizontal location of dots was jittered to facilitate visualization. Right: Histograms of tp for the overlapping ts (horizontal dashed line) for the two prior conditions (orange: Short; blue:Long; triangles: averages). Top-left inset: Average error (i.e., bias) for each ts (circles: data; solid lines: Bayesian model). Bottom-right inset: histogram of regression slopes relating tp to ts across sessions (red: Short; blue: Long; triangles: averages). Bottom: The same as top for Monkey G.