Familiar size and linear perspective as distance cues in stereoscopic depth constancy

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.

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The Familiar-Size Cue to Distance and Stereoscopic Depth Perception

Perception ◽

10.1068/p220985 ◽

1993 ◽

Vol 22 (8) ◽

pp. 985-995 ◽

Cited By ~ 20

Author(s):

John Predebon

Keyword(s):

Depth Perception ◽

Size Effects ◽

Stereoscopic Depth ◽

Familiar Size ◽

Unfamiliar Object

The role of the familiar-size cue to distance in stereoscopic depth perception was examined in two experiments. In experiment 1 subjects judged the depth of a binocularly viewed interval, the far point of which was defined by either a familiar or an unfamiliar object, and in experiment 2 subjects adjusted the depth of the interval so that its extent appeared equal to the length of a vertical reference extent positioned on the surface of the object. Although familiar size influenced depth estimates (experiment 1) it did not influence matching judgments (experiment 2). The findings are discussed with reference to the issue of the nature of the familiar-size effects on judgments of stereoscopic depth.

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Some consequences of stereoscopic depth constancy

Perception & Psychophysics ◽

10.3758/bf03199874 ◽

1979 ◽

Vol 26 (3) ◽

pp. 235-240 ◽

Cited By ~ 17

Author(s):

Hans Wallach ◽

Barbara Gillam ◽

Leonard Cardillo

Keyword(s):

Stereoscopic Depth ◽

Depth Constancy

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Depth Perception in Pandora's Box and Size Illusion: Evolution with Age

Perception ◽

10.1068/p120177 ◽

1983 ◽

Vol 12 (2) ◽

pp. 177-185 ◽

Cited By ~ 6

Author(s):

Jacques Chevrier ◽

André Delorme

Keyword(s):

Depth Perception ◽

Relative Position ◽

Linear Perspective ◽

Pictorial Stimulus ◽

Texture Gradient ◽

Familiar Size ◽

Depth Cues ◽

Pictorial Depth

The aim of the experiment was to study the evolution with age (6, 8, 11 and 14 years) of pictorial depth perception in Pandora's box and to compare it with the evolution of size illusion with the same subjects and the same pictorial backgrounds. In addition to familiar size and relative position, each pictorial stimulus contained one or more of the following depth cues: linear perspective, texture gradient, and interposition. The two kinds of measurements produced different results. Size illusions, although present, did not vary with age but increased with the number of cues. Estimates of distance in Pandora's box increased with age and varied according to the type of cue present: texture gradient seemed to be critical to the amount of depth perceived. The correlation between size adjustments and distance adjustments was significant only for the two oldest groups of subjects (11 and 14 years).

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