Full Bayesian observer. (A) Two stimuli (filled circles) touch the fingertip in rapid succession. The observer is uncertain as to stimulus location (vertical arrows: ±2 σs for clarity) and time of occurrence (horizontal arrows: ±1 σt ), and considers slow movement most probable a priori (inset slopes: ±1 σv). (B) Actual (filled circles, solid line) and perceived (open circles, dashed line) trajectories. Perception underestimates ISD (l' = 0.64 cm <l = 1 cm; vertical bars) and overestimates IST (t' = 40 ms>t = 26 ms; horizontal bars). (C) Perceived IST on finger dilates as ISD increases from 0–20 mm (solid line; kappa effect). The basic observer, by contrast, perceives IST veridically (dotted line). (D) Time dilation of full observer on forearm for 0–20 cm ISD (solid line). Perception on finger (C) is reproduced for comparison (dashed line). All panels: IST, 26 ms; σt, 5 ms; σs (finger), 1 mm; σs (forearm), 1 cm; σv, 4.7 cm/s.