Visual Contours in Homogeneous Space

Shipley, Thorne

doi:10.1126/science.150.3694.348

Cited by 49 publications

(16 citation statements)

References 12 publications

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“…When it is viewed stereoscopically, the central white square appears to float forward of the background, the square itself being defined (as in the situation where the figure is viewed monocularly) by subjective contours. These subjective contours are similar to the anomalous contours described by Lawson and Gulick (1967) and by Shipley (1965); however, in this case, the contours can be seen under monocular as well as under stereoscopic viewingconditions. …”

supporting

confidence: 82%

Stereopsis and subjective contours

Simmonds

1974

Perception & Psychophysics

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Ten Ss rated perceived depth and contour clarity of figures containing binocularly disparate subjective contours. There was no tendency for stereoscopic depth cues to enhance the perceived clarity of subjective contours. Disparity cues that were incompatible with monocular depth cues reduced the depth sensation but did not affect contour clarity. Although subjective contours can be perceived stereoscopically, they are seen in less depth than real contours with the same degree of horizontal disparity.In an analysis of the conditions that give rise to the perception of subjective contours in the absence of abrupt brightness gradients, Coren (1972) has discussed the significance of both form disparity and monocular depth cues. He presents as evidence for his explanation of the phenomenon a series of illustrations and demonstrations which are consistent with the view that subjective contours appear when a two-dimensional display is interpreted by the 0 to contain surfaces or planes that are in depth relative to each other. Referring to illustrations that are similar to Fig. 1 below, Coren concludes that subjective contours appear when the 0 is able visually to reorganize a chaotic collection of complex two-dimensional elements into a simple and easily coded three-dimensional array of meaningful or symmetrical elements. He explores in particular detail the effect of two types of depth cue-shading and interposition. A major assumption made by Coren is that subjective contours arise because the area bounded by the contour is seen to lie in a different plane of depth from other parts of the figure; however, he offers little empirical evidence to support this claim. Furthermore, the effect of what is perhaps the most potent depth cue of all, horizontal disparity in binocularly presented images, does not appear to have been considered.Our observations suggest that there are two stages involved in the perception of subjective contours. The first step involves an active exploratory stage of organizing the display into an orderly, symmetrical, and meaningful pattern; this stage has been discussed in detail by Coren.The unique feature of figures that are known to generate subjective contours is that at least one of the possible structurings of the display is dependent upon the addition of contours to complete the organization of planes or areas within the figures. Once the potential for organization into a simple figure has been grasped by the 0, he enters a second stage, which involves the continued perception of a stable, orderly display. However, in order to maintain this percept, it is essential for him to add the necessary contours to his percept. It is this process of actively adding cues that are not present in the display, but which are nevertheless essential for its maintenance as a stable percept, which leads him to "see" a contour line bridging the uncompleted sections of the stimulus. It is as if the 0 holds an image of the figure in his head, which he then projects out onto the physical object that he is observin...

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supporting

confidence: 82%

Stereopsis and subjective contours

Simmonds

1974

Perception & Psychophysics

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“…Frisby and Clatworthy (1975) therefore suggested that illusory figures produced by lateral disparity may be different from monocularly induced apparent depth. The finding by Mustillo and Fox (1986) that sharp illusory contours can be observed in Kanizsa-type random-dot stereograms which are completely devoid of monocular brightness cues makes the same point (see also Shipley 1965;Julesz and Frisby 1975;Prazdny 1985). These problems are currently being investigated by psychophysicists and computational vision scientists.…”

Section: Illusory Contours As Intelligent Solutions To Perceptual Promentioning

confidence: 87%

“…Similarly, Ullman (1976), Marr (1976Marr ( , 1982, and Zucker and Cavanagh (1985) suggest that there are filling-in mechanisms in early vision which rely essentially on the processing of local cues and operate before an interpretation of the image takes place. In a natural environment, local cues for occlusion are readily available at line ends and other sharp discontinuities, eg T-junctions formed by branches (Kennedy 1988;Shipley andKellman 1990, 1992a;Kellman and Shipley 1991;Peterhans and von der Heydt 1991;Enns and Rensink 1994;Dresp, submitted).…”

Section: The Biological Significance Of Illusory Contoursmentioning

confidence: 99%

“…Several authors (eg Kellman and Loukides 1987;Sambin 1987;Shipley andKellman 1992a, 1992b) still use the term amodal completion to explain how the formation of perceptual units is achieved by a cognitive system. However, its value as an explanation for illusory contours and surfaces appears to be limited (see, for example, Purghe 1988Purghe , 1991.…”

Section: The Concept Of Gestalt Completionmentioning

confidence: 99%

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Phenomena of Illusory Form: Can We Bridge the Gap between Levels of Explanation?

Spillmann

Dresp²

1995

Perception

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Abstract. The study of illusory brightness and contour phenomena has become an important tool in modern brain research. Gestalt, cognitive, neural, and computational approaches are reviewed and their explanatory powers are discussed in the light of empirical data. Two wellknown phenomena of illusory form are dealt with, the Ehrenstein illusion and the Kanizsa triangle. It is argued that the gap between the different levels of explanation, bottom-up versus top-down, creates scientific barriers which have all too often engendered unnecessary debate about who is right and who is wrong. In this review of the literature we favour an integrative approach to the question of how illusory form is derived from stimulus configurations which provide the visual system with seemingly incomplete information. The processes that can explain the emergence of these phenomena range from local feature detection to global strategies of perceptual organisation. These processes may be similar to those that help us restore partially occluded objects in everyday vision. To understand better the Ehrenstein and Kanizsa illusions, it is proposed that different levels of analysis and explanation are not mutually exclusive, but complementary. Theories of illusory contour and form perception must, therefore, take into account the underlying neurophysiological mechanisms and their possible interactions with cognitive and attentional processes.

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“…Shipley (1965) has shown that even in blurred or out-of-focus configurations, the sharp subjective contour still accompanies the perception of the central form in depth. Lawson and Gulick (1967) extended the analysis of subjective contours seen in these patterns.…”

Section: Binocular Disparity and Subjective Contourmentioning

confidence: 99%