Difference of Shape Constancy in Upper and Lower Visual Fields

Abstract

Functions of human vision have been developed to adapt to ecological restrictions. Especially, the position in early vision is neurophysiologically different between objects in the upper visual field (UVF) and in the lower visual field (LVF). In recent years, we have studied the relationship between shape constancy and eye movement. In this study, we investigate differences of shape constancy in the UVF and in the LVF.

We performed psychophysical experiments using three types of boards (circle, square and lozenge: square turned 45 deg.) as comparison stimuli and graphic patterns on a CRT as standard stimuli. The perspective shape was displayed on the CRT as if it was inclined at angles of 10, 25, 35, 45, 55, 65 and 80 deg, respectively. Subjects were asked to actually make the shape equal to the pattern on the CRT.

The results of the test determined by the difference between two mean values show a difference at a significance level of 2.5% between the UVF and the LVF. Subjects exhibited the tendency to look at the upper end of the stimulus in case of the UVF but not in the case of the LVF.