EFFECTS OF CONTRAST SUBSTITUTIONS UPON MOTION DETECTION IN SPATIALLY RANDOM PATTERNS

We report the effects of contrast changes between frames in a random-square kinematogram. When the contrasts of both frames are too low to permit directional discrimination, increasing the contrast of either the first or the second frame alone makes directional discrimination possible. However, at suprathreshold contrasts for motion detection, increasing the contrast of either the first or the second frame alone makes discrimination more difficult. We conclude that motion detection is a special case of contrast discrimination, in agreement with the Reichardt model of motion detection.