An Investigation of Visual Orientation Constancy Using Orientation-Specific Properties of Acuity and Adaptation

Abstract

Recent neurophysiological studies have suggested that orientation constancy might be achieved by the action of a compensatory signal from the vestibular system operating at the level of the visual cortex. Two experiments were carried out in an attempt to find psychophysical evidence for such a system. In the first the variation of visual acuity with stimulus orientation was measured as the subject's head was tilted through 45°, and in the second the orientation specific adaptation to gratings of Blakemore and Campbell (1969) was similarly studied. The results showed that both visual discriminations were dependent upon the retinal properties of the stimulus only; in other words no effect of phenomenal orientation could be detected.