Abstract

Previous studies on the phenomenon of disparity averaging have used random-dot stereograms or line stimuli, leaving open the question of whether disparity averaging occurs across spatial scales as well as within them. We have examined this question by performing a series of depth-matching experiments using stimuli composed of the sum of two cosine gratings of different frequency and retinal disparity. When the frequencies of the cosines are separated by 3.5 octaves or less, perceived depth is close to the average disparity of the components. Similar results are obtained when the relative orientation of the components is less than 30°. Beyond these limits in spatial frequency and orientation, averaging no longer occurs, and the components are perceived transparently in depth. Perceived depth is also contrast-dependent. As the relative contrast of the gratings is varied, perceived depth varies smoothly in the direction of the higher contrast component. These results demonstrate that disparity averaging does occur across spatial scales and that disparity-selective mechanisms are tuned for both spatial frequency and orientation.

© 1990 Optical Society of America