Fig. 4: Schematic presentation of the experimental setup.

The participants‘ view was constrained by an opaque cylindrical tube (shown here in translucent green in order to illustrate the inside) and by black shrouds (omitted here for clarity). The right (dominant) hand reached into the cylinder to depress the luminated starting button (red). When the starting button was extinguished and the LED ring around the switch lit up (circle near the cylinder wall), participants moved their hand towards the switch, flipped it “down”, and then returned their arm to the starting button. Before the next trial, switch position was changed by rotating the switch about the starting button, i.e., along the tube wall. a shows condition vis-tilt: tube insight was dimly lit, and participants saw a display rotated 45° with respect to their body axis. In condition vis-body, the display was aligned with their body and in condition no vis it was not visible. b shows condition vis-tilt with grip-body, and c shows condition vis-tilt with grip-tilt. Condition vis-tilt with belt is not shown. In session E (on earth), participants’ torso was supported by a box. In session P (parabolic flight), their torso was free-floating and only secured by a loose strap around the waist. At the end of each 22-s microgravity episode, an experimenter pushed participants’ bodies back towards the box for safety reasons.