Depth perception of illusory surfaces

Vision Research, 1995

We investigated four geometric optical illusions (Zfllner, Miiller-Lyer, Ponzo and Delboeuf), plus illusory contour[border induction (Kanizsa) and depth in random-dot stereograms (Julesz). Two different display conditions were compared: equiluminance with chromaticity contrast and heteroluminance without chromaticity contrast. The main results are as follows. (1) The strength of the four geometric optical illusions is the same under both display conditions. The ZSiiner illusion reaches its maximum and levels off at a luminance contrast of about 80%; it disappears at luminance contrasts of less than 15%. (2) No illusory contours are perceived in equiluminant Kanizsa figures. The minimum luminance contrast for illusory contour induction in the Kanizsa square is on average 1.8%, for illusory border induction in the abutting grating illusion it is 5.3%. (3) Random-dot stereograms were found to induce depth equally well in both display modes. The disparity threshold for perceiving depth in isochromatic random-dot stereograms levels off at a luminance contrast of 30%. With larger disparities, depth is perceived down to about 10% contrast. The findings suggest that geometric optical illusions of paraileiness (orientation), length and size are mediated by the parvocellular system; furthermore, that stereoscopic depth is mediated both by the magnocellular and the parvocellular systems; and that illusory contours are mediated by the magnocellular system.

Vision Research, 1984

When subjects with good stereoscopic acuity are given the task of judging which of two vertical lines lies nearer, the presence of other features nearby alters the perceived depth within the test pair. In the presence of a single flanking line shown with disparity, the test line pair is seen as fronto-parallel when it has disparity in the direction which tends to align it in depth with the flanking line. The notion of "salience" is introduced. This is the summed disparity-weighted approximately inversely with distancebetween test objects and their neighbours. We make the hypothesis that objects appear at equal depths when they have equal salience. The salience hypothesis accounts for a variety of depth interaction effects between test lines and adjoining features, such as one or more other lines and a lattice of dots with a disparity gradient. Whether features other than nearest neighbours influence depth judgements depends on the individual. For five good stereo subjects, in two a single line completely masked all effects beyond the nearest neighbour, two others had partial masking, and one had none. If the visual system is interested in corners between manes in deoth and in obiects orotruding from such planes, then salience constitutes <. a useful indicator for this purpose.

Journal of Vision, 2016

Does human vision show the contrast invariance expected of an ideal stereoscopic system for computing depth from disparity? We used random-dot stereograms to investigate the luminance contrast effect on perceived depth from disparity. The perceived depth of disparity corrugations was measured by adjusting the length of a horizontal line to match the perceived depth of the corrugations at various luminance contrasts. At each contrast, the perceived depth increased with disparity up to a critical value, decreasing with further increases in disparity. Both the maximum perceived depth and the disparity modulation level where this maximum occurred changed as a sigmoid function of luminance contrast. These results show that perceived depth from disparity depends in a complex manner on the luminance contrast in the image, providing significant limitations on depth perception at low contrasts in a lawful manner but that are incompatible with existing models of cortical disparity processing.

Perception & Psychophysics, 1983

Japanese Psychological Research

Spatial and temporal conditions to perceive an illusory contour figure were examined. Six figural elements inducing an illusory figure were successively presented. Total time to present all inducers and the ratio of duration to 1S1 between inducers were systematically varied. Five subjects were required to rate the clarity of illusory contour, brightness difference and apparent depth difference on an 11 point scale. The effects of total time and the ratio of duration to ISI were significant. The results of causal analysis indicated that total time determined contour, brightness and depth. In two subjects durationfISI had an influence on brightness. Contour and depth were closely related in all subjects. Spatio-temporal integration in the visual system which is higher than in the VIS was discussed.

Vision Research, 2005

Our visual system matches images from both eyes to establish a single view and stereo depth even when they contain a certain amount of vertical disparity. This paper demonstrates a new stereo effect showing an aspect of vertical disparity processing. When oblique lines without disparity are overlaid with sparse random dots with vertical disparity, the lines look closer or farther in depth. The characteristics of this stereo illusion were experimentally investigated. The results showed that the sign of the perceived depth of the oblique lines depended on the combination of the line orientation and the vertical disparity sign, and that the amount of perceived depth became larger as the line orientation became more horizontal. The depth illusion robustly existed even under conditions that ruled out eye movements (i.e., vertical vergence and cyclovergence) by local-parallel or brief presentations of the stereo figures. This phenomenon suggests that the visual system locally measures vertical disparity and is not simply tolerating a small amount of vertical disparity. Stereo capture of vertical disparity and horizontal matching after vertical image shifts were proposed as possible explanations for the depth illusion.

Journal of Vision, 2018

Binocular disparity signals can provide high acuity information about the positions of points, surfaces, and objects in three-dimensional space. For some stimulus configurations, however, perceived depth is known to be affected by surface organization. Here we examine the effects of surface continuity and discontinuity on such surface organization biases. Participants were presented with a series of random dot surfaces, each with a cumulative Gaussian form in depth. Surfaces varied in the steepness of disparity gradients, via manipulation of the standard deviation of the Gaussian, and/or the presence of differing forms of surface discontinuity. By varying the relative disparity between surface edges, we measured the points of subjective equality, where surfaces of differing steepness and/or discontinuity were perceptually indistinguishable. We compare our results to a model that considers sensitivity to different frequencies of disparity modulation. Across a series of experiments, the observed patterns of change in points of subjective equality suggest that perceived depth is determined by the integration of measures of relative disparity, with a bias toward sharp changes in disparity. Such disparities increase perceived depth when they are in the same direction as the overall disparity. Conversely, perceived depth is reduced by the presence of sharp disparity changes that oppose the sign of the overall depth change.

Vision Research, 1991

Increment thresholds were measured on either side of one of the illusory contours of a white-on-black Kanizsa square and on the illusory contour itself. The data show that thresholds are elevated when measured on either side of the illusory border. These elevations diminish with increasing distance of the target spot from the white elements which induce the illusory figure. The most striking result, however, is that threshold elevations are considerably lower or even absent when the target is located on the illusory contour itself. At an equivalent position in a control figure where no illusory contour is visible, such a threshold decrease does not occur. The present observations add empirical support to low-level explanations of illusory contour perception.

Vision Research, 2003

Here, we show a new illusion of depth induced by psychophysical adaptation to dynamic random-dot stereograms (RDS) that are interocularly anticorrelated (i.e., in which the images for the two eyes have reversed contrast polarity with each other). After prolonged viewing of anticorrelated RDS, the presentation of uncorrelated RDS (i.e., in which two images are mutually independent random-dot patterns) produces the sensation of depth, although both anticorrelated and uncorrelated RDSs are perceptually rivalrous with no consistent depth by themselves. Contrary to other aftereffects demonstrated in a number of visual dimensions, including motion, orientation, and disparity, this illusion results from unconscious adaptation; observers are not aware of what they are being adapted to during the process of adaptation. We further demonstrate that this illusion can be predicted from the simulated responses of disparity-selective neurons based on a local filtering model. Model simulations indicate that the inspection of anticorrelated RDS causes the adaptation of all disparity detectors except one sensitive to its disparity; therefore, those selectively unadapted detectors show relatively strong activation in response to the subsequent presentation of uncorrelated RDS and produce depth perception.

Science in China Series C, 2003

Investigation on illusory contours is important for understanding the mechanisms underlying the object recognition of human visual system. Numerous researches have shown that illusory contours formed in motion and stereopsis are generated by the unmatched features. Here we conduct three psychophysical experiments to test if Kanizsa illusory contours are also caused by unmatched information. Different types of motion (including horizontal translation, radial expanding and shrinking) are utilized in the experiments. The results show that no matter under what kind of motion, when figures or background move separately illusory contours are perceived stronger, and there is no significant difference between the perceived strength in these two types of motion. However, no such enhancement of perceived strength is found when figures and background move together. It is found that the strengthened unmatched features generate the enhancement effect of illusory contour perception in motion. Thus the results suggest that the process of unmatched information in visual system is a critical step in the formation of illusory contours.