Over 20% of the population exhibits incomplete stereopsis whereby binocular cues for distance are not fully utilized. Such individuals are said to be stereoanomalous. By examining the similarities and differences between such normal and anomalous observers we may deduce the nature of the mechanisms that underly stereoscopic depth perception. Our first objective is to continue to explore the nature of the confusions made by the anomalous individuals. These confusions appear dependent upon the character of the uncorrelated binocular or monocular information present in the display. A second objective is to relate the types of stereoanomalies of Ogle's types of fixation disparity, and to the extent of deviation in strabismus. These psychophysical studies will be conducted with a strong bias toward interpretations base upon possible neurophysiological correlates. To strengthen such interpretive correlations, a parallel program in neuroanatomy will be conducted examining the structure of the visual pathways in cats with congenital and induced squint. Our preliminary studies have already shown that the pathways in a non-Siamese crosseyed cat are abnormal. A third objective is to reinforce this finding following selective breeding of more such animals. A fourth objective is to induce squint artificially in the cat by a particular disruption of the visual pathway suggested by a joint anatomical-psychophysical model for stereopsis.