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.

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.

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.

Role of Brightness Contrast and Brightness Contrast-Reversal in Illusory Contour Formation

1981 ◽  
Vol 52 (2) ◽  
pp. 415-424 ◽  
Author(s):  
Willard L. Brigner ◽  
Joseph T. Hammond
Keyword(s):  
Pupil Size ◽  
Illusory Contour ◽  
Brightness Contrast ◽  
Artificial Pupil

The effects of artificial pupil size and the effects of a power lens upon the relative prominence of illusory contour were evaluated. The perception of illusory contour was facilitated by conditions associated with increased retinal blur and brightness averaging. This was true whether the blur and averaging were achieved using a large artificial pupil or a power lens. The effects of power lens and the effects of artificial pupil size upon the occurrence of brightness contrast and brightness contrast-reversal (or assimilation) were also investigated. Brightness contrast was changed to brightness contrast-reversal by using either a power lens or a large artificial pupil. The occurrence of vivid illusory contour under conditions found conducive to brightness contrast-reversal was interpreted as evidence that contrast-reversal was more crucial in illusory contour formation than brightness contrast.

How a Brain Sees: Neural Mechanisms

2021 ◽  
pp. 122-183
Author(s):  
Stephen Grossberg
Keyword(s):  
Illusory Contour ◽  
Local Contrast ◽  
Simple Complex ◽  
3D Vision ◽  
Color Spreading ◽  
Surface Filling ◽  
Contour Strength ◽  
Neon Color Spreading ◽  
Glass Patterns ◽  
Boundary Completion

Multiple paradoxical visual percepts are explained using boundary completion and surface filling-in properties, including discounting the illuminant; brightness constancy, contrast, and assimilation; the Craik-O’Brien-Cornsweet Effect; and Glass patterns. Boundaries act as both generators and barriers to filling-in using specific cooperative and competitive interactions. Oriented local contrast detectors, like cortical simple cells, create uncertainties that are resolved using networks of simple, complex, and hypercomplex cells, leading to unexpected insights such as why Roman typeface letter fonts use serifs. Further uncertainties are resolved by interactions with bipole grouping cells. These simple-complex-hypercomplex-bipole networks form a double filter and grouping network that provides unified explanations of texture segregation, hyperacuity, and illusory contour strength. Discounting the illuminant suppresses illumination contaminants so that feature contours can hierarchically induce surface filling-in. These three hierarchical resolutions of uncertainty explain neon color spreading. Why groupings do not penetrate occluding objects is explained, as are percepts of DaVinci stereopsis, the Koffka-Benussi and Kanizsa-Minguzzi rings, and pictures of graffiti artists and Mooney faces. The property of analog coherence is achieved by laminar neocortical circuits. Variations of a shared canonical laminar circuit have explained data about vision, speech, and cognition. The FACADE theory of 3D vision and figure-ground separation explains much more data than a Bayesian model can. The same cortical process that assures consistency of boundary and surface percepts, despite their complementary laws, also explains how figure-ground separation is triggered. It is also explained how cortical areas V2 and V4 regulate seeing and recognition without forcing all occluders to look transparent.

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.

scholarly journals Shape Processing Area LO and Illusory Contours

Perception ◽  
10.1068/p6388 ◽  
2009 ◽  
Vol 38 (8) ◽  
pp. 1260-1263 ◽  
Author(s):  
Lee H de-Wit ◽  
Robert W Kentridge ◽  
A David Milner
Keyword(s):  
Visual Cortex ◽  
Functional Mri ◽  
Primary Visual Cortex ◽  
Visual Illusions ◽  
Visual Area ◽  
Illusory Contours ◽  
Feedback Effects ◽  
Shape Representations ◽  
Shape Processing

Recent functional MRI has demonstrated that illusory contours can activate the primary visual cortex. Our investigation sought to demonstrate whether this correlation reflects computations performed in the primary visual cortex or feedback effects from shape processing area LO. We explored this in a patient who has a bilateral lesion to LO, but a functionally spared V1. Our data indicate that illusory contours are unable to influence behaviour without visual area LO. Whilst we would not claim that our data provide evidence for the ‘cognitive’ nature of illusory contours, they certainly suggest that illusory contours are dependent upon the computations involved in extracting shape representations in LO. Our data highlight the importance of neuropsychological research in interpreting the role of feedforward and feedback effects in the generation of visual illusions.

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