Figure 1. Experimental setup.

Panel A shows a top view of the experimental setup. In this figure, the subject is shown performing the matching task using the left hand (“Test” hand) to reproduce the vertical distance (d_y) between the thumb and index finger pad of the right hand (“Reference” hand) (see text for more details). Note that the table top (gray) prevented the subjects from seeing their forearms and hands but is shown as transparent for graphical purposes only. Forearms and wrists were strapped to the table to prevent movements within and across trials while the handles were anchored to the table. Panel B shows a frontal view of one of the two handles used for the study (“a” denotes force/torque sensors). Panel C shows the frontal view of the handle with the three d_ys of the reference hand used for the study. Note that d_y is defined as positive or negative when the thumb pad is higher or lower than the index finger pad, respectively.