Fig. 1.

Schematic of the task flow and feedback shifts for the x-axis movements. A: passive tasks. Subjects are moved to the start position. A blue dot appears on the screen for 3 s to show the actual index fingertip position. Their arm is then passively moved along the x-axis in the rightward direction. During this movement, subjects are shown shifted feedback of their fingertip position (white dot) for 600 ms. Active tasks: Subjects are first passively moved to the start position. Then they must hold their fingertip in the start position for 3 s, during which a blue dot appears on the screen to show the actual fingertip position. The blue dot then disappears, cueing subjects to actively move their arm along the x-axis (the movement is constrained to the x-axis using a force channel). During their movement, shifted feedback of their fingertip position (white dot) appears for 600 ms. They continue their movement until they hit the unseen end target and are stopped by the robot. In both tasks, judgments about the position of the shifted feedback relative to the fingertip are reported after movement completion. B: schematic of the feedback shifts used in the temporal inline task (shown for the x-axis movements): During the rightward movement, the white visual dot is shifted early or late in time compared with the actual index fingertip trajectory. C: schematic of the feedback shifts used in the spatial orthogonal task (shown for the x-axis movements): During the rightward movement, the white visual dot is shifted either up or down from the actual index fingertip position.