Figure 1.

Three random-dot stereograms (RDSs) with different binocular correlations. (A) Correlated RDSs. Binocular fusion of the left and right half-images with parallel (uncrossed) viewing produces a sensation of a central square floating from background. (B) Anticorrelated RDSs. The luminance contrasts are reversed for all the dots in the central square of the right half-image. Reversed, correct, or no depth is perceived, depending on stimulus configuration. (C) Half-matched RDSs. Half of the dots in the central square of the right half-image have reversed contrasts. Correct depth can be perceived, since half of the dots carry the same disparity signals as in the correlated RDSs.