Adaptation of the visual vertical during prolonged body tilt varies with susceptibility to motion sickness

Judgments of the visual vertical, made without a visual reference frame-work, from a tilted-body position, result in systematic constant errors (Aubert effects). Pitblado and Mirabile (1977) showed that these errors vary with motion-sickness susceptibility, persons of intermediate susceptibility showing the greatest error. Recent exploratory work suggested patterns of progressive intra-session change in Aubert effects which might further differentiate groups of differing susceptibility. The raw data for Pitblado and Mirabile's 1977 study were reanalyzed for possible progressive change. This new analysis showed significant progressive reductions in Aubert effects for groups originally high and low, but a nearly significant increase in the intermediate group. New implications concerning group differences in vestibular function are discussed.