The Suppression of Monocularly Perceivable Symmetry During Binocular Fusion

Symmetries that we can perceive with one eye can be made to disappear during binocular fusion--that is, a symmetrical pattern in one of a pair of stereoscopic images may not be seen when we view the pair stereoscopically. This phenomenon should not be confused vrith the classically-known binocular rivalry in which the left and right images cannot be fused and one of the images is alternately suppressed. The type of suppression phenomenon reported here is obtained for computer-generated random-dot patterns in which locally each picture element can be fused in a stable way. The binocularly suppressed symmetry can be one-, two-, and four-fold, and the experiments give some insight into the processes underlying the perception of symmetry. In addition to symmetries, it becomes possible to scramble text by exhibiting it stereoscopically. I. BINOCULAR F U S I O N , RIVALRY, AND A T H I R D POSSIBILITY Recently, the author added a third possibility of perceptual response to the class of stereoscopic images traditionally consisting of binocular fusion and binocular rivalry. 1 In these computer-generated stereoscopic images the local and global properties are juxtaposed such that locally each picture element can be stereoscopically fused, causing the monocularly apparent global symmetry to disappear in the fused percept. In the demonstration of Ref. 1, the left stereoscopic image consisted of randomly selected black and white dots with bilateral (one-fold) symmetry across the center horizontal axis.