Fig. 2.

Experimental protocol. a In each trial, participants were required to make a reaching movement: move a cursor from a start position (white circle) toward a target (green circle). During null-field trials, no force-field was presented. In force channel trials, participants’ movement was constrained to straight trajectory by using virtual walls. In force-field trials, a velocity-dependent force was applied, perpendicular to movement direction from start to target. Here, we had three conditions: (1) g = 0 – control group (yellow) with only force-field, (2) g = 100 – force-field with skin-stretch in the same direction (blue), and (3) g = − 100 – force-field in one direction and skin-stretch in the opposite direction (red). b The experiment was divided into three sessions: Baseline (green bar), Adaptation (yellow/blue/red bar), and Washout (green bar). During the Baseline and Washout sessions, null-field trials were presented. During the Adaptation session, we presented force-field trials with and without augmented tactile information. Throughout the experiment, in randomly selected trial we applied force channel trials (white bar, see Methods for details)