Selectivities of Human Visual Mechanisms for Direction of Movement and Contour Orientation*

Abstract

The luminance threshold for horizontal contours which move upward is raised by prior exposure of any of wide range of different directions of movement. The threshold for a stationary grating of horizontal bars is raised only by prior exposure of similarly oriented bars. It is also found that sensitivity to changes in orientation of a stationary grating is greater than sensitivity to changes in the direction in which a grating moves. It is proposed that the interactions between pre-exposed adapting stimuli and the stimuli for which thresholds are determined reflect the orientation and direction selectivities of the underlying mechanisms.