THE EFFECT OF WATER IMMERSION AND BODY POSITION UPON PERCEPTION OF THE GRAVITATIONAL VERTICAL,
Abstract
The purpose of this study was to measure the accuracy, particularly the sensitivity or short-term repeatability, with which humans can use their vestibular sense to preceive the gravitational vertical, and how this ability varies with body (head) position. Equipment and procedures to reduce or eliminate nonvestibular cues were selected through iterative process of design, development, test, and evaluation. Ss were restrained upon an underwater 2-axis tilt table, and required to position themselves, via signals to Es, in one of 6 cardinal positions of the body (head) with respect to gravity. Seven Ss, in 3 immersions each, made 3 judgements per immersion at each of the 6 positions. The group responses showed some large and significant constant error, most notably a pitch-forward bias shared (unequally) by all of the medial-plane positions, exceeding 30 degrees in the nominal head-down position. A Probable Error, (PE), uninflated by constant errors, was computed for each of the 2 orthogonal directions of deviation for each of the 6 positions. The results supported the classical concept of reduced sensitivity in the head-down as compared with the head-up positions. However, PE ranged from 15 degrees to 40 degrees, indicating only a marginally useful sensitivity in any position. In addition, sensitivity at any one position was not necessarily symmetrical as to direction of deviation, and some sensitivities at intermediate values of tilt overlapped head-up or head-down sensitivities. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 18, 1967
- Accession Number
- AD0658507
Entities
People
- John G. Nelson
Organizations
- Naval Air Warfare Center Warminster