Schematic demonstrating the experimental tasks used by Ostry et al. (2010). A: participants reached toward a visual target while holding the handle of a robot that could generate velocity-dependent force fields. Visual feedback of target positions and a cursor representing hand position were provided by a computer-generated display on the mirror. A horizontal semisilvered mirror (transparent gray box) was placed just above the hand to block vision of the arm during the task. Reaching was performed before adapting to the force field (Null), in the force field (force field) and after force-field adaptation (After effect). B: parameter estimation by sequential testing (PEST) test of proprioceptive hand position sense, in which a threshold was determined indicating participants' estimates of left/right hand location with respect to the target (reference) position. C: method of constant stimuli (MOCS) test of proprioceptive hand position sense, in which a threshold was determined estimating participants' awareness of whether their right hand was closer or further from the body than their left hand, which served as a reference.