Vertical disparity, egocentric distance and stereoscopic depth constancy: a new interpretation

There has long been a problem concerning the presence in the visual cortex of binocularly activated cells that are selective for vertical stimulus disparities because it is generally believed that only horizontal disparities contribute to stereoscopic depth perception. The accepted view is that stereoscopic depth estimates are only relative to the fixation point and that independent information from an extraretinal source is needed to scale for absolute or egocentric distance. Recently, however, theoretical computations have shown that egocentric distance can be estimated directly from vertical disparities without recourse to extraretinal sources. There has been little impetus to follow up these computations with experimental observations, because the vertical disparities that normally occur between the images in the two eyes have always been regarded as being too small to be of significance for visual perception and because experiments have consistently shown that our conscious appreciation of egocentric distance is rather crude and unreliable. Nevertheless, the veridicality of stereoscopic depth constancy indicates that accurate distance information is available to the visual system and that the information about egocentric distance and horizontal disparity are processed together so as to continually recalibrate the horizontal disparity values for different absolute distances. Computations show that the recalibration can be based directly on vertical disparities without the need for any intervening estimates of absolute distance. This may partly explain the relative crudity of our conscious appreciation of egocentric distance. From published data it has been possible to calculate the magnitude of the vertical disparities that the human visual system must be able to discriminate in order for depth constancy to have the observed level of veridicality. From published data on the induced effect it has also been possible to calculate the threshold values for the detection of vertical disparities by the visual system. These threshold values are smaller than those needed to provide for the recalibration of the horizontal disparities in the interests of veridical depth constancy. An outline is given of the known properties of the binocularly activated cells in the striate cortex that are able to discriminate and assess the vertical disparities. Experiments are proposed that should validate, or otherwise, the concepts put forward in this paper.

[1]  M Ritter,et al.  Perception of depth: Processing of simple positional disparity as a function of viewing distance , 1979, Perception & psychophysics.

[2]  S Yamane,et al.  Stereoscopic mechanisms: binocular responses of the striate cells of cats to moving light and dark bars , 1986, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[3]  H. Wallach,et al.  The constancy of stereoscopic depth. , 1963, The American journal of psychology.

[4]  K. N. Ogle.  INDUCED SIZE EFFECT: III. A STUDY OF THE PHENOMENON AS INFLUENCED BY HORIZONTAL DISPARITY OF THE FUSION CONTOURS , 1939 .

[5]  E. Ludvigh,et al.  IS OCULAR PROPRIOCEPTIVE SENSE CONCERNED IN VISION , 1936 .

[6]  K N OGLE,et al.  Stereopsis and vertical disparity. , 1955, A.M.A. archives of ophthalmology.

[7]  M. Sanders.  Handbook of Sensory Physiology , 1975 .

[8]  T. Whiteside,et al.  Binocular Cues in the Perception of Distance of a Point Source of Light , 1984, Perception.

[9]  J M Foley,et al.  Binocular distance perception: egocentric distance tasks. , 1985, Journal of experimental psychology. Human perception and performance.

[10]  C. Blakemore,et al.  The neural mechanism of binocular depth discrimination , 1967, The Journal of physiology.

[11]  H. C. Longuet-Higgins,et al.  A computer algorithm for reconstructing a scene from two projections , 1981, Nature.

[12]  J Mayhew,et al.  The Interpretation of Stereo-Disparity Information: The Computation of Surface Orientation and Depth , 1982, Perception.

[13]  Kenneth N. Ogle,et al.  INDUCED SIZE EFFECT: I. A NEW PHENOMENON IN BINOCULAR SPACE PERCEPTION ASSOCIATED WITH THE RELATIVE SIZES OF THE IMAGES OF THE TWO EYES , 1938 .

[14]  I. Ohzawa,et al.  The binocular organization of simple cells in the cat's visual cortex. , 1986, Journal of neurophysiology.

[15]  J M Loomis,et al.  Agreement between indirect measures of perceived distance , 1985, Perception & psychophysics.

[16]  Kenneth N. Ogle,et al.  INDUCED SIZE EFFECT WITH THE EYES IN ASYMMETRIC CONVERGENCE , 1940 .

[17]  P. O. Bishop,et al.  Neural mechanisms of binocular vision , 1986, Vision Research.

[18]  W. Epstein.  Stability and constancy in visual perception : mechanisms and processes , 1977 .

[19]  K. N. Ogle.  Researches in binocular vision. , 1950 .

[20]  H. C. Longuet-Higgins.  The Role of the Vertical Dimension in Stereoscopic Vision , 1982, Perception.

[21]  Walter C. Gogel,et al.  The Perception of a Depth Interval with Binocular Disparity Cues , 1960 .

[22]  Kenneth N. Ogle,et al.  INDUCED SIZE EFFECT: II. AN EXPERIMENTAL STUDY OF THE PHENOMENON WITH RESTRICTED FUSION STIMULI , 1939 .

[23]  P. O. Bishop,et al.  Binocular simple cells for local stereopsis: Comparison of receptive field organizations for the two eyes , 1984, Vision Research.

[24]  P. O. Bishop.  Neurophysiology of Binocular Single Vision and Stereopsis , 1973 .

[25]  Andrew C. Sleigh,et al.  Physical and Biological Processing of Images , 1983 .

[26]  B. Gillam,et al.  The induced effect, vertical disparity, and stereoscopic theory , 1983, Perception & psychophysics.

[27]  R. W. Rodieck.  Central nervous system: afferent mechanisms. , 1971, Annual review of physiology.

[28]  P. O. Bishop.  NEURAL MECHANISMS FOR BINOCULAR DEPTH DISCRIMINATION , 1981 .

[29]  Edward Jackson.  Corresponding Retinal Points, the Horopter and Size and Shape of Ocular Images. , 1933 .

[30]  J. E. W. Mayhew,et al.  A computational model of binocular depth perception , 1982, Nature.

[31]  M. Ritter,et al.  Effect of disparity and viewing distance on perceived depth , 1977 .

[32]  P. O. Bishop,et al.  End-stopped cells and binocular depth discrimination in the striate cortex of cats , 1986, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[33]  H C Longuet-Higgins.  Appendix to Paper by John Mayhew Entitled: “The Interpretation of Stereo-Disparity Information: The Computation of Surface Orientation and Depth” , 1982, Perception.