Figure 1.

Schematic illustration of the stimuli and setup used for experiments 1 and 2. a, Stimuli were Lego pieces assembled to create ∼10 different novel 3D objects. b, The setup required participants gaze at the fixation point (fp) while performing the tasks at two possible object locations: near and far from the hand (white dotted circles). The white star represents the fixation point, which was located midway between the two objects. c, d, For both experiments, the setup is illustrated from the point of view of the participants. The starting positions of the hand are highlighted by black dotted rectangles. In experiment 1, only one starting position was used (c). In experiment 2, two starting positions were used (c, d). At trial onset, participants were asked to perform one of the following tasks: (1) looking (left column): passively viewing the objects; (2) touching (middle column): touching the object with the knuckles; or (3) grasping (right column): using a precision grip (with the index finger and the thumb) to grasp and lift the object. Actions performed at the location furthest from the starting position required arm transport. The hand down starting position (c) involved a rotation of the elbow to extend (abduct) the arm while keeping the palm down (pronated). The hand up starting position (d) involved a rotation of the elbow to flex (adduct) the arm while keeping the palm down (pronated). Grasping at the near locations required hand displacement but no arm transport. Overall there were six actions: Gf, grasping the far object; Tf, touching the far object; Lf, passive viewing of the far object; Gn, grasping the near object; Tn, touching the near object; Ln, passive viewing of the near object.