VISUAL DISTURBANCE, HEAD TILT AND AUBERT EFFECT

Subjective-vertical adjustment errors made in combined disturbance sit uations (observers tilted in front of a tilted frame) are systematical ly greater than in single disturbance situations. This study shows tha t adjustment errors are triggered by the addition of two simple effect s, a visual effect and a postural effect. In the first experiment, 39 women were asked to adjust a rod to their subjective vertical under th ree conditions: frame tilted alone (RFT), head tilted alone (RHT), fra me and head tilted simultaneously (RHFT). The results showed that 1) h ead and frame effects occur without interference in the RHFT condition ; 2) it is possible to extract the head and frame effects from the RHF T condition by computing the main effects; 3) the RHFT head effect and the RHFT frame effect correlate with the RHT head effect and the RFT frame effect respectively; 4) these head and frame effects are never c orrelated. The second experiment allowed us to confirm and extend our first results to the rest of the population (30 girls, 34 boys, and 32 men).