![]() ![]() It strongly influences the perception of some fundamental properties, namely, depth, lightness and contours. The perception of an illusory surface, a subjectively perceived surface that is not given in the image, is one of the most intriguing phenomena in vision. Furthermore, the segments between junctions appear to facilitate scene classification, possibly due to their involvement in symmetry relationships with other contour segments. The spatial locations of the junctions are important, as well as their relationships with one another. ![]() These results suggest that categorizing line drawings of real-world scenes does not solely rely on junction statistics. Moreover, observers were better at classifying a scene when shown only segments between junctions, than when shown only the junctions, with the middle segments removed. Observers were better at classifying images when the contours were randomly translated (disrupting the junctions) than when the junctions were randomly shifted (partially disrupting contour information). Here, we manipulate the junctions in images, either randomly translating them, or selectively removing or maintaining them. Contour junctions and points of high curvature have been shown to be important for perceptual organization (Attneave, 1954 Biederman, 1987) and have been proposed to be influential in rapid scene classification (Walther & Shen, 2014). Photographs and line drawings of natural scenes are easily classified even when the image is only briefly visible to the observer. These findings reveal a general methodological problem that can arise using methods of adjustment and provide quantitative data that may be used to identify the neural mechanisms responsible for IC genesis and their perceived strength. We further show that these illusory contours also arise when the occluding disks are rendered transparent and exhibit similar forms of contrast dependencies. We show that the perceived strength of the illusory contours generated by these displays depends monotonically on the relative contrast of the occluding and occluded contours and that previous attempts to measure their strength with a method of adjustment appears to be contaminated by response bias. The present work sought to more precisely characterize the quantitative dependence of these 'irrational' contours on the relative contrasts in the image. These motion sequences generate illusory contours even though they play no necessary role in accounting for occlusion and disocclusion of the thin contours. One striking apparent counter-example to this view was described in Current Biology 21 (2011) 492-496, which showed that illusory contours could arise in motion displays depicting visible occluding discs occluding and disoccluding thin contours. The mechanisms responsible for generating illusory contours are thought to fulfil an adaptive role in providing estimates of missing contour fragments generated by partial camouflage. ![]() The results hence indicate that infants are able to extract spatial information from monocular regions in a binocular display. A control condition supported the hypothesis that the infants 7 months of age in the experimental condition indeed responded to the coherent illusory surface instead of simply detecting differences in the geometric arrangement of the half‐occlusions. The participants aged 7 but not 4 months preferred looking at the standard phantom stereogram. In both stereograms, the gaps moved up and down. This stereogram evokes the impression of two small separate illusory contours. Infants in the experimental condition were presented with a standard phantom stereogram displaying a phantom contour versus a non‐standard phantom stereogram, the half‐images of which were exchanged. The visual system accounts for the binocular unmatched gaps by perceiving an illusory contour. The left line in the half‐image for the right eye and the right line in the half‐image for the left eye have a gap in the middle. The present natural preference study investigated infants 4 and 7 months of age for their ability to respond to phantom contoubrs, illusory surfaces generated by half‐occlusions in a stereoscopic display consisting of a pair of parallel vertical lines. ![]()
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