Figure 1.

Schematic representation of the experimental set up from the subject's point of view (upper panel) and from above (lower panel). Subjects placed their right hand on a starting switch (purple) and the left hand on a response button (green). The target object was a cylinder, located 35 cm from the starting point. On its upper side were two colored dots indicating the location of the fingers (red for the thumb and yellow for the index); the line between these two dots constituted the opposition axis, which could be of three orientations: −22°, 0° and +22°. On the left an arrow indicated the height to which the object should be lifted.