The subjective vertical under "dry" and "wet" conditions at clockwise and counterclockwise changed positions and the effect of a parallel-lined background field.

Abstract

The dependence of the subjective vertical (SV, the angle β between a subjective vertical line and body median plane) on the gravity vertical (body tilt position, angle α) and on the ‘optical vertical’ (i.e., a field of parallel lines seen as background to the line to be adjusted) was investigated. The SV was measured under ‘dry’ and ‘wet’ conditions at different degrees of body tilt attained in either clockwise (CW) or counterclockwise (CCW) progression.