Abstract

Visual processing of curvature was investigated by measuring increment thresholds for curvatures from 0.3 to 25 deg⁻¹. Discrimination of simple curve contours was compared with thresholds for both bandpass and low-pass filtered stimuli. Surprisingly, the higher spatial frequency, orientation selective mechanisms dominate curvature processing, even at low curvatures where lower spatial frequency masks come into play. Our data suggest two different types of curvature mechanism. A simple modification of Wilson's model is in good quantitative agreement with these data. A further modification is required, however, to explain curvature discrimination of Vernier edges created by offsetting the two halves of a grating. In this case, end-stopping must be made explicit using relatively small masks with broad orientation tuning.

© 1987 Optical Society of America