Viewing time and stereoscopic threshold with random-dot stereograms

The effect of viewing time on the threshold for depth and form discrimination using random-dot stereograms has been investigated. For 12 subjects the relation between logarithm of threshold disparity and logarithm of viewing time was linear for both depth and form discrimination, but the threshold for form discrimination was approximately twice the threshold for depth discrimination. Stereo thresholds determined with random-dot stereograms were not significantly related to stereo thresholds measured with a Howard-Dolman apparatus.