Amodal Completion and the Perception of Depth without Binocular Correspondence

Half-occlusions and illusory contours have recently been used to show that depth can be perceived in the absence of binocular correspondence and that there is more to stereopsis than solving the correspondence problem. In the present study we show a new way for depth to be assigned in the absence of binocular correspondence, namely amodal completion. Although an occluder removed all possibility of direct binocular matching, subjects consistently assigned the correct depth (convexity or concavity) to partially occluded ‘folded cards’ stimuli. Our results highlight the importance of more global, surface-based processes in stereopsis.

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Illusory-Contour Formation Affected by Luminance Contrast Polarity

Perception ◽

10.1068/p270313 ◽

1998 ◽

Vol 27 (3) ◽

pp. 313-335 ◽

Cited By ~ 23

Author(s):

Zijiang J He ◽

Teng Leng Ooi

Keyword(s):

Illusory Contour ◽

Necker Cube ◽

Spatial Separation ◽

Luminance Contrast ◽

Amodal Completion ◽

Illusory Contours ◽

Contrast Polarity ◽

Spatial Alignment ◽

Occluded Objects ◽

Partially Occluded

We report a new type of illusory contour (Illusory-O) whose formation is contingent upon the contrast polarity of its juxtaposed inducing elements being similar, ie both elements must either be positive or negative in contrast sign. To test the hypothesis that this contingency is primarily dictated by factors that determine amodal surface completion (occlusion) between the inducing elements we conducted a series of experiments employing known spatial properties of the amodal completion mechanism, to show that spatial conditions unfavorable to occlusion lead to a concurrent weakening of the Illusory-O formation. For instance, we found that when the juxtaposed inducing elements (solid rectangles) were spatially misaligned, or when their spatial separation increased, our observers rated the perception of the Illusory-O as reduced. We also showed that, in addition to using solid-form inducing elements, the Illusory-O can be induced by line terminals, as long as these lines respect the requirements of the amodal completion mechanism such as similar contrast polarity and spatial alignment. Then we demonstrated that the role of the amodal completion mechanism is not limited to our particular arrangement of inducing elements by showing that the formation of the illusory Necker cube also relies on similar contrast polarity. Finally, to explain why some illusory contours like the Illusory-O are dependent on contrast polarity while others (eg Kanizsa square) are not, we propose that the key rests upon the visual system's presumption of occlusion. That is, in forming the illusory contour, if the visual system infers that it is a byproduct of the inducing elements being occluded, then having inducing elements of similar contrast polarity becomes a prerequisite. This assumption can be traced to the occurrence in the real world where partially occluded objects usually have visible parts (on both ends) with similar contrast polarity. Along this line of thinking, we suggest a plausible neural circuitry that may be implemented to form both contrast polarity sensitive and insensitive types of illusory contours.

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Amodal completion as a basis for illusory contours

Perception & Psychophysics ◽

10.3758/bf03205882 ◽

1983 ◽

Vol 33 (4) ◽

pp. 355-364 ◽

Cited By ~ 30

Author(s):

R. H. Day ◽

R. T. Kasperczyk

Keyword(s):

Amodal Completion ◽

Illusory Contours

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Amodal Completion versus Induced Inhomogeneities in the Organization of Illusory Figures

Perception ◽

10.1068/p210627 ◽

1992 ◽

Vol 21 (5) ◽

pp. 627-636 ◽

Cited By ~ 2

Author(s):

Marco Davi ◽

Baingio Pinna ◽

Marco Sambin

Keyword(s):

Phenomenological Model ◽

Control Experiment ◽

Amodal Completion ◽

Brightness Contrast ◽

Primary Factor ◽

Paired Comparisons ◽

Illusory Figure ◽

Illusory Contours ◽

Energetic Model ◽

Method Of Paired Comparisons

An analysis is presented of a phenomenological model of illusory contours. The model is based on amodal completion as the primary factor giving rise to the illusory figure. In the experiment, conducted by the method of paired comparisons, the same parameter was manipulated in two series of equivalent configurations. The first series yielded examples of amodal completion, the second examples of illusory figures. Three groups of subjects evaluated the magnitude of completion, the brightness contrast of the illusory figure, and the contour clarity of the illusory figure. A control experiment was conducted, which demonstrated that in these configurations amodal completion and amodal continuation behave in the same way. Line displacement did not influence the brightness or the contour clarity of the illusory figures, though it influenced the magnitude of amodal completion. These results are in agreement with the energetic model developed by Sambin.

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Illusory Volumes from Conformation

Perception ◽

10.1068/p270977 ◽

1998 ◽

Vol 27 (8) ◽

pp. 977-992 ◽

Cited By ~ 25

Author(s):

Peter Ulric Tse

Keyword(s):

Visual System ◽

Surface Curvature ◽

Local Surface ◽

Supporting Surface ◽

Illusory Contours ◽

Flat Surfaces ◽

Contour Surface ◽

Inferential Processing ◽

Global Surface

The purpose of this paper is to offer demonstrations of ‘illusory volumes’ in the spirit of the illusory flat surfaces described by Kanizsa. These demonstrations of illusory volumes exploit a new cue to the recovery of surface curvature from ambiguous images: conformation. In assuming conformation, the visual system assumes that the surface of a volume conforms to the curvature of its neighboring, underlying, or supporting surface, in the absence of image cues to the contrary. Demonstrations that exploit the assumption of conformation provide several insights into the nature of the inferential processing that underlies contour, surface, and volume formation. In particular, these demonstrations imply that the visual system does not calculate local surface curvature, illusory contours, or occlusion relationships before it analyzes global surface relationships.

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How Configurations of Binocular Disparity Determine Whether Stereoscopic Slant or Stereoscopic Occlusion is Seen

Perception ◽

10.1068/p5274 ◽

2005 ◽

Vol 34 (9) ◽

pp. 1083-1094 ◽

Cited By ~ 4

Author(s):

Philip M Grove ◽

Jessica M Byrne ◽

Barbara J Gillam

Keyword(s):

Illusory Contour ◽

Binocular Disparity ◽

Constant Width ◽

Illusory Contours ◽

Partially Occluded ◽

Determining Factor ◽

Vertical Size

A partially occluded contour and a slanted contour may generate identical binocular horizontal disparities. We investigated conditions promoting an occlusion resolution indicated by an illusory contour in depth along the aligned ends of horizontally disparate line sets. For a set of identical oblique lines with a constant width added to one eye's view, strength, depth, and stability of the illusory contour were poor, whereas for oblique lines of alternating orientations the illusory contours were strong, indicating a reliance on vertical size disparities rather than vertical positional disparities in generating perceived occlusion. For horizontal lines, occlusion was seen when the lines were of different lengths and absolute width disparity was invariant across the set. In all line configurations, when the additional length was on the wrong eye to be attributed to differential occlusion, lines appeared slanted consistent with their individual horizontal disparities. This rules out monocular illusory contours as the determining factor.

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Illusory Contour Perception and Amodal Boundary Completion: Evidence of a Dissociation Following Callosotomy

Journal of Cognitive Neuroscience ◽

10.1162/089892999563535 ◽

1999 ◽

Vol 11 (4) ◽

pp. 459-466 ◽

Cited By ~ 38

Author(s):

Paul M. Corballis and Robert Fendrich ◽

Robert M. Shapley ◽

Michael S. Gazzaniga

Keyword(s):

Right Hemisphere ◽

Fundamental Problem ◽

Neural Mechanisms ◽

Amodal Completion ◽

Form Perception ◽

Illusory Contours ◽

Contour Perception ◽

Visual Processes ◽

The Right ◽

Boundary Completion

A fundamental problem in form perception is how the visual system can link together spatially separated contour fragments to form the percept of a unitary shape. Illusory contours and amodal completion are two phenomena that demonstrate this linking process. In the present study we investigate these phenomena in the divided hemispheres of two callosotomy (“split-brain”) patients. The data suggest that dissociable neural mechanisms are responsible for the generation of illusory contours and amodal completion. Although both cerebral hemispheres appear to be equally capable of perceiving illusory contours, amodal completion is more readily utilized by the right hemisphere. These results suggest that illusory contours may be attributable to low-level visual processes common to both hemispheres, whereas amodal completion reflects a higher-level, lateralized process.

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The Role of Amodal Completion in Shape Formation: Some New Shape Phenomena

Perception ◽

10.1068/p7331 ◽

2012 ◽

Vol 41 (11) ◽

pp. 1336-1354 ◽

Cited By ~ 4

Author(s):

Baingio Pinna

Keyword(s):

Stimulus Pattern ◽

Past Experience ◽

Amodal Completion ◽

Main Role ◽

Gestalt Principles ◽

Shape Formation ◽

Partially Occluded ◽

New Phenomena ◽

Shape Deformations

Amodal completion occurs when a portion of an object is hidden as a result of its occlusion behind another object. Under these conditions, the object perceived as occluded is seen as a unitary shape, whose boundary contours amodally complete behind the overlapping modal object. Kanizsa (1972, Studia Psychologica 14 208–210) and his collaborators demonstrated some effects related to the amodal completion: shrinkage of the whole figure partially occluded; expansion of the modally visible portions of the same figure; shape deformations against the Gestalt principles of regularity, simplicity, symmetry, and past experience; global increasing of colour quantity of the partially occluded figure. The aim of this work is to demonstrate that the amodal completion is not a necessary factor in inducing the previous effects. This was accomplished through phenomenological experiments whose stimuli were crucial instances (counterexamples) disproving the amodal completion hypothesis and proving the role played by the directional symmetry of the element components of each stimulus pattern. Some new phenomena demonstrated the main role of the directional shape organisation, considered as a principle of shape formation.

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Neuroimaging Findings on Amodal Completion: A Review

i-Perception ◽

10.1177/2041669519840047 ◽

2019 ◽

Vol 10 (2) ◽

pp. 204166951984004 ◽

Cited By ~ 4

Author(s):

Jordy Thielen ◽

Sander E. Bosch ◽

Tessa M. van Leeuwen ◽

Marcel A. J. van Gerven ◽

Rob van Lier

Keyword(s):

Computational Models ◽

Amodal Completion ◽

Lateral Occipital Complex ◽

Low Level ◽

Face Area ◽

Perceptual Completion ◽

Visual Areas ◽

High Level ◽

Partially Occluded ◽

Retinal Information

Amodal completion is the phenomenon of perceiving completed objects even though physically they are partially occluded. In this review, we provide an extensive overview of the results obtained from a variety of neuroimaging studies on the neural correlates of amodal completion. We discuss whether low-level and high-level cortical areas are implicated in amodal completion; provide an overview of how amodal completion unfolds over time while dissociating feedforward, recurrent, and feedback processes; and discuss how amodal completion is represented at the neuronal level. The involvement of low-level visual areas such as V1 and V2 is not yet clear, while several high-level structures such as the lateral occipital complex and fusiform face area seem invariant to occlusion of objects and faces, respectively, and several motor areas seem to code for object permanence. The variety of results on the timing of amodal completion hints to a mixture of feedforward, recurrent, and feedback processes. We discuss whether the invisible parts of the occluded object are represented as if they were visible, contrary to a high-level representation. While plenty of questions on amodal completion remain, this review presents an overview of the neuroimaging findings reported to date, summarizes several insights from computational models, and connects research of other perceptual completion processes such as modal completion. In all, it is suggested that amodal completion is the solution to deal with various types of incomplete retinal information, and highly depends on stimulus complexity and saliency, and therefore also give rise to a variety of observed neural patterns.

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