Non-Visual Perception of the Postural Vertical. I. Sagittal Plane,
DEFENCE RESEARCH MEDICAL LABS TORONTO (ONTARIO)
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The three experiments reported here were tests of the effects of four variables upon the perception of the postural upright following body tilt in a forward or backward direction. The four variables studied were 1 the degree of initial tilt, i.e., the degree to which the subject was tilted before being moved toward the vertical, 2 the time held at initial tilt, 3 the direction of initial tilt, and 4 the angular velocity of return. The fourth variable investigated in the present experiments, velocity of return, had not been evaluated before, nor had any one of the other three variables been studied systematically in the sagittal plane. Immediately bearing on the present report are certain studies dealing with the non-visual perception of the upright, most of which were conducted using lateral tilt. Briefly these reveal that a the error of judgment of the upright is directly determined by the degree of initial tilt, increasing as an underestimation of the upright as the magnitude of initial tilt increases. b the error of judgment, either as an underestimation or an over-estimation of the vertical, does not differ significantly for the two directions of initial tilt within any one plane. c the error of underestimation of the vertical increases as the time held at the initial tilt increases.
- Anatomy and Physiology