How Does Binocular Disparity Affect the Impressions in Viewing Stereograms?

We examined how the size of binocular disparity affects the impressions in different dimensions, as well as apparent depth, in viewing line-contoured stereograms, random dot stereogram, and stereoscopic pictures of naturalistic scenes. We used a semantic differential method with the scales that are related to the different dimensions of impression; evaluation, activity, and potency. The stereograms of naturalistic scenes were selected to give observers strong or weak impressions in different impression dimensions. We prepared the two-depth-layer condition and six-depth-layer condition for those stereograms. The size of binocular disparity between the nearest and farthest layers ranged from 0 to about 70 min of arc. Apparent depth magnitude increased with the increment of disparity size for those stereograms while the increment for the six depth-layer condition was larger than that for the two depth-layer conditions. Regardless of the type of stereograms, for the six depth-layer condition, the rating for the evaluation increased with the size of disparity although, for the two-depth-layer condition, it did not increase at the large disparity size. In addition, the rating for the activity increased with disparity size for both the two depth-layer condition and six depth-layer conditions if the stereogram induced some active impression by itself. These results indicate that the effects of binocular disparity size on apparent depth magnitude and impressions in viewing stereoscopic pictures depend upon the depth structure that is specified by binocular disparity, rather than what the stereogram representationally depicts