Curvature Detectors in Human Vision?

Observers were required to judge apparent straightness following exposure to curved lines. A curvature aftereffect was found when subjects had maintained steady fixation or made continuous eye movements at right angles to the chord of the arc during inspection, but no aftereffect was obtained when eye movements had been made in the direction of the chord. It is proposed that curved contours are processed in the visual system by reference to the orientation of local straight line approximations within an arc, rather than through global analysis of the extent and direction of curvature. The loss in aftereffect with eye movements in the direction of the chord is attributed to nonselective adaptation of orientation detectors.