DISPARITY AVERAGING ACROSS SPATIAL SCALES

To determine whether disparity averaging occurs across spatial scales, a series of depth matching experiments was performed using stimuli co mposed of the sum of two cosine gratings of different spatial frequenc y and retinal disparity. Although there were large individual differen ces in the data, averaging was observed when the relative frequency of the cosines were separated by 3.5 octaves or less and when the relati ve orientation was less than 30 deg. Beyond these limits, averaging ne ver occurred and the stimulus components were perceived transparently in depth. Furthermore, as the relative contrast of the gratings was va ried, perceived depth varied smoothly in the direction of the higher c ontrast component. This dependence on contrast can be accounted for by a multi-channel model in which separate disparity estimates are gener ated on each spatial scale and then combined to determine the overall perceived depth of the stimulus.