Fig 2. Experimental setups.

(a) Experiment 1: The right hand of the participant is placed inside a box and equipped with a sensor glove. The box and the participant’s upper body are covered by a black cloth. The participant is instructed to grasp and release the ball. (b) Experiment 2: A ball device is attached to the robotic hand system. When the ball is at its zero position (maximally away from the open robotic hand), it is hidden under the visual cover. While the robotic hand is closing, the ball moves towards the palm in a circular trajectory (dashed red arrow).