Abstract: Depth-discrimination was studied with a Haward-Dalman apparatus under 3 conditions: 1) both the body and the test object tilted to 0°, 45°, 90°, 135°, 180° correspondingly; 2) S seated in an upright position but the test object tilted to 22°, 45°, 65°, 90°; 3) the test object in upright position but S tilted to 45°, 90°, 135°, 180°. The results indicated that: in condition 1, the error of depth-discrimination at 0° position was significantly less than that at the other four positions, however, the differences among the errors at these four positions were not significant statistically; in condition 2, errors increased with the amount of tilt of the test object; in condition 3, the greatest error took place at 90°. No significant difference was found between the errors at the similar positions (45°, 90°) in the latter two conditions. The results of these experiments do not seem to be consistent with the sensory-tonic field theory.

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