Abstract
When supine subjects are at rest, the degree of bodily tilt should theoretically be communicated by the static effect of gravity upon the otolithic sensors. This experiment was carried out to determine whether visual inputs enhance or degrade this ability in male and female observers. Male and female subjects reclined in a supine position face-up and directed an experimenter to make adjustments to an inversion table to achieve a specified target angle of bodily tilt (75°, 90°or 105° from vertical). Subjects delayed their directions for 3 seconds so that their judgments would not be influenced by the acceleration of the adjustments. Prior to each trial the experimenter would adjust the table to the target angle and then offset it to provide an ascending or descending trial type. When the subjects felt they had achieved the target angle, the experimenter would record the absolute discrepancy from the target angle. Half the trials were performed with the eyes open and half were performed while blindfolded. For the 90° target angle with the blindfold, the mean discrepancy scores for men and women were about 1°, but with eyes open, discrepancy scores declined for men and increased significantly for women. For the 75°and 105° angles, discrepancy score increased for both men and women (to about 3–4°), but increased more for women than men. Discrepancy scores for women were less without, than with the blindfold at the 75° target angle. These results indicate that female subjects are more influenced by visual inputs when making judgments of bodily tilt.