Thirty male and 30 female Ss indicated by means of a luminescent rod in the darkroom and by means of a metal bar with closed eyes the vertical direction of space under systematic variation of tilt from erect to the horizontal position. Deviations of apparent from true vertical had a non-linear relation to the degree of body tilt. The trend of deviations was similar for the visual and tactual experiment: With small angles of body tilt apparent vertical tended to deviate opposite to the direction of tilt; with large degrees of tilt apparent vertical tended to deviate in the direction of tilt. The latter tendency was more pronounced for visual than for tactual vertical.
The results were interpreted in keeping with sensory-tonic field theory of perception, according to which deviations of apparent vertical were due to changes in the "sensory-tonic" state of the organism. Such changes were experimentally introduced through lateral body tilt. To explain the non-linear relation between deviations of apparent vertical and the degree of body tilt, it was hypothesized that there is a dynamic interplay between a primary tendency of the organism to towards stimulation and a secondary opposing tendency serving the maintenance of constancy of spatial dimensions. The result of this interplay was interpreted by introducing the notion of biological relevance of spatial constancy of the upright position versus the reclining position for visual far-space and tactual near-space.
Zusammen/assung. 30 weibliche und 30 mi~nnliche Versuchspersonen gaben im Dunkelraum bzw. mit geschlossenen Augen bei seitlieher KSrperneigung bis in die Horizontale an, in welcher Position ihnen eine Leuchtlinie und ein Metallstab senkrecht erschienen. In nichtlinearer Abh~ngigkeit vom Grad der K6rperneigung zeigten sich dabei Abweichungen der scheinbaren yon der objektiven Vertikalen. Die Tendenz dieser Abweichung war fiir den visuellen wie ffir den taktflen Wahraehmungsbereich gleich, bei geringer K6rperneigung entgegen, bei groBer K6rperneigung in die Richtung der Neigung, wobei letztere Tendenz starker fiir die visuelle Vertikale ausgepr~gt war. Die Ergebnisse wurden auf dem Boden der sensoritonischen Wahrnehmungstheorie interpretiert, nach der sich die Ver~nderungen in der Lage der scheinbaren Vertikalen nach dem Prinzip der sensori-tonisehen Induk-