Prior experience of form and illusory figures: new demonstrations.
Explore the source record for details and available documents.
Depth Perception↗
SEARCH · Search PubMed
Results for “Perceptual Closure”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Surface completion complements boundary interpolation in the visual integration of partly occluded objects.
Previous research on perceptual completion has emphasized how the spatial relationships of edges influence the visual integration of the image fragments that result from partial occlusion. We report studies testing the hypothesis that the similarity of surface features also influences visual integration, complementing edge interpolation processes. Using displays that separated edge interpolation processes from surface-feature interpolation processes, we tested the hypotheses that a surface completion process integrates image fragments with similar surface features, and that surface completion is constrained by amodally interpolated and amodally extended boundaries. Both edge relatability and surface-feature similarity were manipulated in a series of paired-comparison and classification tasks. The results of these studies supported the hypotheses and were extended to surface features of colors, textures, and color gradients. Results also suggest that, under certain conditions, surface completion may interact with and influence edge interpolation.
Form Perception↗
The missing-fundamental illusion at isoluminance.
The missing-fundamental illusion describes how a square wave with its fundamental Fourier component removed appears as a square wave. This illusion is normally explained with reference to the bandpass nature of the luminance-contrast-sensitivity function, together with a 'default-to-square-wave' rule. Since the chromatic-contrast-sensitivity function is low-pass, we should not expect a missing-fundamental illusion at isoluminance. Using a simultaneous-detection-and-identification paradigm to eliminate contrast as a cue to discrimination, we nevertheless found that chromatic missing fundamentals and square waves could not be separately identified at detection threshold: just under twice the contrast required to detect the stimuli was needed to identify them. To test whether this was due to insufficiently narrow chromatic-channel bandwidths, we measured detection and identification thresholds for chromatic F and 3F sine-wave gratings. In this case identification was possible almost at detection threshold, suggesting that channel bandwidth limitations were not the critical factor. It is suggested that the weak missing-fundamental illusion observed at isoluminance probably reflects the operation of mechanisms similar to those that are responsible for the chromatic Craik-Cornsweet illusion.
Color Perception↗
Shrinkage and expansion by amodal completion: a critical review.
The whole literature on the so-called dimensional effects of amodal completion (shrinkage of a partially occluded figure and expansion of modally visible parts of the same figure) is critically reviewed. It is claimed that phenomenal shrinkage is the sum of at least two illusions independent of figure ground distinction: (1) shrinkage of spaces divided into a few parts, and (2) shrinkage of empty spaces. It is also shown that a partially occluded figure can widen, rather than shrink. It is concluded that the stratification in two phenomenally superimposed figures accompanies the shrinkage effect, but is irrelevant to its generation. Further experiments are needed in order to draw a well-grounded conclusion on the expansion effect.
Humans↗
Test of Petter's rule for perceived surface stratification.
Petter's rule applies to two-dimensional patterns formed by two overlapping surfaces that alternatively appear in front of one another. It states that the surface with the shorter contours in the region where the surfaces look superimposed has a greater probability of appearing in front of the other surface. An experiment is reported the results of which show that Petter's rule is valid for chromatically homogeneous and for uniformly dense dotted patterns, and invalid for different kinds of chromatically inhomogeneous patterns. Petter's rule has been found to be valid when the overlapping surfaces have contours with gaps. It is proposed that Petter's rule derives from the dynamics of filling-in of contour gaps.
Depth Perception↗
Configural processing at birth: evidence for perceptual organisation.
We report a series of ten experiments aimed to investigate the newborn's ability to discriminate the components of a visual pattern and to process the visual information that specifies the global configuration of a stimulus. The results reveal that: (i) newborn babies are able to distinguish individual elements of a stimulus (experiments 1A, 1B, 1C, and 1D); (ii) they can group individual elements into a holistic percept on the basis of Gestalt principles (experiments 2A and 3A); (iii) their spontaneous preferences cannot be easily modified by habituation (experiments 2B and 3B); and (iv) when horizontal stimuli are paired with vertical stimuli, they prefer the horizontal ones (experiments 4A and 4B).
Discrimination, Psychological↗
The illusory-letters phenomenon: an illustration of graphemic restoration in visual word recognition.
We present a demonstration of word perception in which stimuli containing very few letters (just 50% of their original number) are presented for unlimited durations and yet are seen unequivocally as complete words. The phenomenon suggests that recognition of words can be achieved even when perception of their component letters is prevented.
Humans↗
Surface formation and depth in monocular scene perception.
The visual perception of monocular stimuli perceived as 3-D objects has received considerable attention from researchers in human and machine vision. However, most previous research has focused on how individual 3-D objects are perceived. Here this is extended to a study of how the structure of 3-D scenes containing multiple, possibly disconnected objects and features is perceived. Da Vinci stereopsis, stereo capture, and other surface formation and interpolation phenomena in stereopsis and structure-from-motion suggest that small features having ambiguous depth may be assigned depth by interpolation with features having unambiguous depth. I investigated whether vision may use similar mechanisms to assign relative depth to multiple objects and features in sparse monocular images, such as line drawings, especially when other depth cues are absent. I propose that vision tends to organize disconnected objects and features into common surfaces to construct 3-D-scene interpretations. Interpolations that are too weak to generate a visible surface percept may still be strong enough to assign relative depth to objects within a scene. When there exists more than one possible surface interpolation in a scene, the visual system's preference for one interpolation over another seems to be influenced by a number of factors, including: (i) proximity, (ii) smoothness, (iii) a preference for roughly frontoparallel surfaces and 'ground' surfaces, (iv) attention and fixation, and (v) higher-level factors. I present a variety of demonstrations and an experiment to support this surface-formation hypothesis.
Cues↗
Perceptual continuation and depth in visual phantoms can be explained by perceptual transparency.
We try to explain perceptual continuation and depth in the visual-phantom illusion in terms of perceptual transparency. Perceptual continuation of inducing gratings across the occluder in stationary phantoms could be explained with unique transparency, a notion proposed by Anderson (1997 Perception 26 419-453). This view is consistent with a number of previous reports including that of McCourt (1994 Vision Research 34 1609-1617) who criticized the stationary phantom illusion from the viewpoint of his counterphase lightness induction or grating induction, which might involve invalid transparency. Here we confirm that the photopic phantom illusion (Kitaoka et al, 1999 Perception 28 825-834) really gives in-phase lightness induction and involves bistable transparency. It is thus suggested that perceptual continuation and depth in the visual-phantom illusion depend on perceptual transparency.
Analysis of Variance↗
Mental imagery of visual motion modifies the perception of roll-vection stimulation.
When viewing a wide-angle visual display, which rotates in the frontoparallel plane around the line of sight, observers experience an illusory shift of the direction of gravity; this shift leads to an apparent tilt of the body and displaces allocentric space coordinates. In this study, subjects adjusted an indicator to the apparent horizontal while viewing a rotating display. To determine whether top down processes could affect the illusion, the subjects were asked to visualize a rotating configuration of dots onto a blank central portion of the moving visual field. Visualizing dots and actually viewing the dots deflected the spatial judgment in very similar ways. These results demonstrate that top down processing can affect allocentric space coordinates.
Adolescent↗
Multistability of overlapped face stimuli is dependent upon orientation.
Stimuli composed of two overlapped faces, one rotated 45 degrees clockwise and the other 45 degrees counterclockwise, produce perceptual rivalry whereby both faces cannot be simultaneously perceived. We obtained subjective and quantitative measures of this rivalry effect and examined if it persists with inverted stimuli. Our results show that upright stimuli are multistable, with alternations occurring from one face to the other within 2 s. Inverted stimuli were instead perceived as ambiguous in half of the trials, indicating weaker perceptual rivalry in that condition. We suggest that overlapped faces produce perceptual rivalry because each face is readily interpreted into a Gestalt, an effect that in turn is dependent upon orientation.
Adolescent↗
Connectivity perception of partly occluded gratings in 4-month-old infants.
Four groups of eight 4-month-old infants were each habituated to one of four displays consisting of a grating of either low (0.4 cycle deg(-1) or high (1.2 cycles deg(-1) spatial frequency, whose central portion was covered up with a horizontal occluder which was either narrow (1.33 deg) or broad (4.17 deg). Posthabituation displays consisted of a complete grating of the same frequency as the habituated grating, along with a separate grating whose central portion was replaced with a black gap of the same height as the occluder in the habituation displays. All the infants, except those who were habituated to the high frequency with the broad occluder, looked longer at the separate grating than the complete grating display during posthabituation trials. Previously, we found that infants under 1 month of age perceive the grating continuation only when the occluder height is less than about 0.5 cycle of the grating; our present results show that this figure increases to about 1.6 cycles of the grating frequency in the case of 4-month-old infants. These findings indicate that those developmental changes depend on both the sufficiency of visual information available and the efficiency of the perceptual ability of infants for grasping spatial relationships.
Analysis of Variance↗
Beyond junctions: nonlocal form constraints on motion interpretation.
Because of the aperture problem, local motion measurements must be combined across space. However, not all motions should be combined. Some arise from distinct objects and should be segregated, and some are due to occlusion and should be discounted because they are spurious. Humans have little difficulty ignoring spurious motions at occlusions and correctly integrating object motion, and are evidently making use of form information to do so. There is a large body of theoretical and empirical evidence supporting the importance of form processes involving junctions in the way motion is integrated. To assess the role of more complex form analysis, we manipulated nonlocal form cues that could be varied independently of local junctions. Using variants on diamond and plaid stimuli used in previous studies, we found that manipulations distant from the junctions themselves could cause large changes in motion interpretation. Nonlocal information often overrides the integration decisions that would be expected from local cues. The mechanisms implicated appear to involve surface segmentation, amodal completion, and depth ordering.
Cues↗
Visual inter-attribute contour completion.
A new visual phenomenon, inter-attribute illusory (completed) contours, is demonstrated. Contour completions are perceived between any combination of spatially separate pairs of inducing elements (Kanizsa-like 'pacman' figures) defined either by pictorial cues (luminance contrast or offset gratings), temporal contrast (motion, second-order-motion or 'phantom' contours), or binocular-disparity contrast. In a first experiment, observers reported the perceived occurrence of contour completion for all pair combinations of inducing elements. In a second experiment they rated the perceived clarity of the completed contours. Both methods generated similar results contour completions were perceived even though the inducing elements were defined by different attributes. Ratings of inter-attribute clarity were no lower than in either of the two corresponding intra-attribute conditions and seem to be the average of these two ratings. The results provide evidence for the existence of attribute-invariant Gestalt processes, and on a mechanistic level indicate that the completion process operates on attribute-invariant contour detectors.
Contrast Sensitivity↗
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.
Adult↗
Global visual completion of quasi-regular shapes.
The topic of amodal completion has often been investigated by using partly occluded shapes that are regular. In research that has typically been done with displays such as these regular shapes, it has been shown that global aspects of a shape can determine completion. To see how robust these global influences in the completion process are, we investigated quasi-regular shapes, ie shapes with a certain overall regularity but not based on metrical identities. First, in experiment 1 participants had to complete quasi-regular shapes in a drawing task. Then, in experiment 2 the primed-matching paradigm was used. Results from both experiments provided evidence for global completions. In experiment 3 we found that multiple global completions can be primed, which, as a control experiment showed, cannot be explained by some inability of the visual system to see the difference between the different completions. These data support the notion that global influences on visual occlusion are apparent even when the partly occluded stimulus is outside the domain of regular shapes. Implications for a global approach are provided.
Humans↗
Eclipse, shape-from-shadow, and perceiving astronomic size--Earth's.
Explore the source record for details and available documents.
Earth, Planet↗
Effects of occlusion on pigeons' visual object recognition.
Casual observation suggests that pigeons and other animals can recognize occluded objects; yet laboratory research has thus far failed to show that pigeons can do so. In a series of experiments, we investigated pigeons' ability to 'name' shaded, textured stimuli by associating each with a different response. After first learning to recognize four unoccluded objects, pigeons had to recognize the objects when they were partially occluded by another surface or when they were placed on top of another surface; in each case, recognition was weak. Following training with the unoccluded stimuli and with the stimuli placed on top of the occluder, pigeons' recognition of occluded objects dramatically improved. Pigeons' improved recognition of occluded objects was not limited to the trained objects but transferred to novel objects as well. Evidently, the recognition of occluded objects requires pigeons to learn to discriminate the object from the occluder; once this discrimination is mastered, occluded objects can be better recognized.
Animals↗