Using metamers to explore motion perception.
We examined conditions under which two quite different types of random-dot cinematograms were perceptually matched. In one stimulus type, directions of motion were defined by a uniform distribution; in the other, directions were drawn from a discrete set of just a few, widely separated directions. Cinematograms whose range of uniformly distributed directions lay between 180 and 270 deg could be matched by cinematograms containing just 6-10 discrete directions. The number of discrete directions required for a match was a nonmonotonic function of the range of directions present in the other cinematogram. The results are consistent with a line-element model in which the outputs of 12 direction-selective mechanisms, each with a half-amplitude half-bandwidth of 30 deg, are combined nonlinearly to produce the percept of motion.
Williams
D
D
Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208.
Tweten
S
S
Sekuler
R
R
D006801:Humans; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011594:Psychometrics