Fig. 2.

Average shear and grip force profiles for each of the 4 directional conditions. The shear forces are represented by the positive traces above the line and grip force as the traces below the line for the first (CR01; dashed line) and second (FL02; solid line) monkey. Both monkeys exerted somewhat similar forces when lifting and pulling, although monkey CR01 additionally used the webbing between Digits 1 and 2 to push and press on the manipulandum, resulting in a grip force that was less than the shear force. The central polar plot represents the distribution of shear force directions on a logarithmic scale, where 1% represents ∼240 trials.