Curvature extrapolation in dependence on visual stimulus orientation

Abstract

On a dark monitor screen, bright circle arcs of various length and orientation were presented. In each presentation, a test-dot was shown at some distance apart from one of the ends of the arc. A gap between the test-dot and the arc was considered as an invisible stimulus segment to be extrapolated by test subjects. They moved the test-dot with the panel keys and placed it on the trajectory of the invisible part of the circle. In experimental sessions both with asymmetric one-arc and symmetric two-arc stimuli, the subjects demonstrated periodic changes of error values of curvature extrapolation in dependence of stimulus orientation. They made the extrapolated trajectories more flat at the oblique than at vertical and horizontal orientations of the stimulus. Moreover, the error magnitudes for horizontal and vertical orientations, left and right, upward and downward positions were different. The magnitudes for various oblique positions differed as well. In general, the experimental data showed a radial non-homogeneity of the human visual field while performing the curvature extrapolation task. Keywords: anisotropy, oblique effect, extrapolation of curvature