"Spatial Orientation and Motor Skills: How to Flip Switches Down in Weightlessness?"

"The circular instrument panel that subjects will see into the cylindrical mask consists of one switch surrounded by a luminous ring (left part of the figure below). The switch can be flipped into any direction within the full 360° range. The switch provides no visual cues about down, but the experimenter can add such cues by means of visually polarized labelling displayed on a circular black screen at the center of the panel (right part the figure below)."