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 ◽  
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.

Illusory-Contour Formation Affected by Luminance Contrast Polarity

Perception ◽  
1998 ◽  
Vol 27 (3) ◽  
pp. 313-335 ◽  
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.

Amodal Completion and the Perception of Depth without Binocular Correspondence

Perception ◽  
10.1068/p3305 ◽  
2002 ◽  
Vol 31 (9) ◽  
pp. 1037-1045 ◽  
Author(s):  
Benoit A Bacon ◽  
Pascal Mamassian
Keyword(s):  
Amodal Completion ◽  
Correspondence Problem ◽  
Illusory Contours ◽  
Binocular Matching ◽  
Partially Occluded ◽  
Global Surface

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.

Insect perception of illusory contours

1992 ◽  
Vol 337 (1279) ◽  
pp. 59-64 ◽  
Keyword(s):  
Human Visual System ◽  
Illusory Contour ◽  
Optic Lobe ◽  
Insect Vision ◽  
Local Contrast ◽  
Fault Line ◽  
Illusory Contours ◽  
Striped Pattern ◽  
Processing Power ◽  
As If

The human visual system sees an illusory contour where there is a fault line across a regular striped pattern. We demonstrate that bees respond as if they see the same illusory contour. There is also a type of neuron in the lobula of the dragonfly optic lobe which responds directionally to motion of the illusory contour as if to an edge or line. Apparently insects have a mechanism that sees illusory contours and therefore assists in the demarcation of edges and objects at places where local contrast falls to zero at an edge, or where one textured object partially obscures another. These results suggest that insect vision, although spatially crude and low in processing power, sees separate objects by similar mechanisms to our own.

An Illusory Contour Can Facilitate Visually Induced Self-Motion Perception

2018 ◽  
Vol 31 (8) ◽  
pp. 715-727
Author(s):  
Shinji Nakamura ◽  
Shin’ya Takahashi
Keyword(s):  
Motion Perception ◽  
Illusory Contour ◽  
Uniform Motion ◽  
Horizontal Line ◽  
Illusory Contours ◽  
End Points ◽  
Line Segments ◽  
Illusory Perception ◽  
Vertically Aligned ◽  
Self Motion

Abstract Uniform motion of a visual stimulus induces an illusory perception of the observer’s self-body moving in the opposite direction (vection). The present study investigated whether vertical illusory contours can affect horizontal translational vection using abutting-line stimulus. The stimulus consisted of a number of horizontal line segments that moved horizontally at a constant speed. A group of vertically aligned segments created a ‘striped column’, while line segments in adjoining columns were shifted vertically to make a slight gap between them. In the illusory contour condition, the end points of the segments within the column were horizontally aligned to generate vertical illusory contours. In the condition with no illusory contour, these end points were not aligned within the column so that the illusory contour was not perceived. In the current study, 11 participants performed this experiment, and it was shown that stronger vection was induced in the illusory contour condition than in the condition with no illusory contour. The results of the current experiment provide novel evidence suggesting that non-luminance-defined visual features have a facilitative effect on visual self-motion perception.

Parallelism and the Perception of Illusory Contours

Perception ◽  
1993 ◽  
Vol 22 (5) ◽  
pp. 589-595 ◽  
Author(s):  
Marc K Albert
Keyword(s):  
Illusory Contour ◽  
Illusory Contours ◽  
Gestalt Principles ◽  
Contour Strength

The role of symmetry in the perception of illusory contours has been a subject of controversy ever since Kanizsa proposed his theory of illusory contours based on Gestalt principles. Today it is widely agreed that illusory contours do not necessarily occur more readily with inducers that can be ‘amodally’ completed to symmetrical objects than with inducers that cannot. But the question of whether symmetrical inducers produce weaker illusory contours than do unsymmetrical ones is still controversial. A novel determinant of illusory contour strength, parallelism, is proposed. Experiments are reported which indicate that illusory contours induced by ‘blobs’ which have boundaries that are nearby and parallel to the illusory contour are weaker than illusory contours induced by blobs that do not have this property. It is suggested that the display that has been most widely used by researchers to support their claims for a weakening of illusory contours with symmetrical inducers is weak primarily because of parallelism.

Cue-dependent deficits in grating orientation discrimination after V4 lesions in macaques

1996 ◽  
Vol 13 (3) ◽  
pp. 529-538 ◽  
Author(s):  
Peter De Weerd ◽  
Robert Desimone ◽  
Leslie G. Ungerleider
Keyword(s):  
Visual Field ◽  
Normal Control ◽  
Illusory Contour ◽  
Visual Area ◽  
Orientation Discrimination ◽  
Fixation Target ◽  
Illusory Contours ◽  
Pattern Vision ◽  
Area V4

AbstractTo examine the role of visual area V4 in pattern vision, we tested two monkeys with lesions of V4 on tasks that required them to discriminate the orientation of contours defined by several different cues. The cues used to separate the contours from their background included luminance, color, motion, and texture, as well as phase-shifted abutting gratings that created an “illusory” contour. The monkeys were trained to maintain fixation on a fixation target while discriminating extrafoveal stimuli, which were located in either a normal control quadrant of the visual field or in a quadrant affected by a lesion of area V4 in one hemisphere. Comparing performance in the two quadrants, we found significant deficits for contours defined by texture and for the illusory contour, but smaller or no deficits for motion-, color-, and luminance-defined contours. The data suggest a specific role of V4 in the perception of illusory contours and contours defined by texture.

The Multiple Determination of Illusory Contours: 2. An Empirical Investigation

Perception ◽  
1983 ◽  
Vol 12 (3) ◽  
pp. 293-303 ◽  
Author(s):  
Diane F Halpern ◽  
Billie Salzman ◽  
Wayne Harrison ◽  
Keith Widaman
Keyword(s):  
Illusory Contour ◽  
Factor Model ◽  
Illusory Contours ◽  
Contour Perception ◽  
Confirmatory Factor ◽  
Linear Effects ◽  
Explained Variance ◽  
Taxonomic Approach ◽  
Contour Strength

Judgments of contour strength or saliency for twenty-four illusory-contour configurations were subjected to a confirmatory factor analysis. A four-factor model that posited the involvement of simultaneous contrast, linear effects (assimilation and dissimilation), depth/completion cues, and feature analyzers accounted for a substantial proportion of the variance in judgments of illusory-contour strength. The hierarchical addition of a fifth factor, diffuse illusory contours, significantly improved the overall fit of the model, but added little to the proportion of explained variance. The taxonomic approach adopted provides support for a multiprocess model of illusory-contour perception.

Improbable Illusory Contours

2017 ◽  
Author(s):  
Barton L. Anderson
Keyword(s):  
Perceptual Organization ◽  
Adaptive Response ◽  
Illusory Contour ◽  
Visual Illusion ◽  
Missing Information ◽  
Illusory Contours ◽  
New Class ◽  
Testing Ground ◽  
Rational Inference

Illusory contours are one of the most widely studied kinds of visual illusion. Illusory contours are often understood as an adaptive response to filling-in missing information created from conditions of camouflage. This chapter describes a new class of very vivid illusory contours that appear impossible to understand as forms of rational inference. It presents a set of illusory contours that emerge in conditions for which there is no missing information or need for their synthesis. It argues that such contours provide a valuable testing ground for both specific theories of illusory contour formation, and general theories of perceptual organization. Videos made specifically for this chapter help illustrate the concepts discussed.

Illusory Contours in Line Patterns with Apparent Depth Due to Either Perspective or Overlay

Perception ◽  
1983 ◽  
Vol 12 (4) ◽  
pp. 485-490 ◽  
Author(s):  
Ross H Day ◽  
Richard T Kasperczyk
Keyword(s):  
Illusory Contour ◽  
Apparent Depth ◽  
Illusory Contours ◽  
Line Patterns

An illusory contour along a partially delineated border in the form of an apparent ‘outside’ corner due to perspective was as strong as one along a similarly delineated border in the form of an edge due to overlay. An illusory contour along a border in the form of an apparent ‘inside’ corner, due probably to both perspective and overlay, was stronger than either. These outcomes suggest that apparent stratification from overlay is not necessary for the occurrence of illusory contours. They also accord with the view that apparent depth due to overlay or to perspective is equally effective in rendering partially delineated borders more prominent and, in consequence, the illusory contours that form along them stronger.

The Determinants of Illusory-Contour Perception

Perception ◽  
1981 ◽  
Vol 10 (2) ◽  
pp. 199-213 ◽  
Author(s):  
Diane F Halpern
Keyword(s):  
Illusory Contour ◽  
Experimental Results ◽  
Brightness Contrast ◽  
Apparent Depth ◽  
Primary Role ◽  
Illusory Contours ◽  
Contour Perception

The term ‘illusory contours' refers to contours perceived where none physically exist. Three hypotheses that have been successful in their ability to account for this phenomenon invoke: (i) apparent depth; (ii) brightness contrast; and (iii) use of figural cues. An experiment has been designed to determine the extent to which each hypothesis accounts for the overall variation in subjects' responses to illusory contours when all three hypotheses are considered simultaneously. Experimental results suggest that different processes may assume a primary role in the perception of illusory contours depending upon the type of inducing area and the configuration. The results highlight the multifaceted nature of the processes involved, and indicate that no single theory can explain the perception of illusory contours.

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