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PubMed2000

The role of good form in young Infants' perception of partly occluded objects.

Young infants have been reported to perceive the unity of a center-occluded object when the visible ends of the object undergo common motion, but not on the basis of stationary information (e.g., P. J. Kellman & E. S. Spelke, 1983). We investigated the possibility that 4-month-old infants will attend to and utilize the global configuration (i.e., the "good form") of a partly occluded, moving object to perceive its unity and coherence behind the occluder. In the first experiment, infants viewed a partly occluded circle or cross that translated laterally. Infants who habituated in the minimum number of trials ("fast habituators") showed a reliable posthabituation preference for a broken object over a complete object, indicating perception of unity in the habituation display. Slow habituators exhibited no posthabituation preference. In the second experiment, infants were presented with small ring and cross displays, and the infants looked longer at the broken object. There were no reliable differences in performance between fast and slow habituators. A control group demonstrated no reliable posthabituation preference. In three additional conditions, infants viewed either a partly occluded half ring or a display in which two rod parts were either relatable and nonaligned or nonrelatable. The results indicated that curvature per se provided information in support of completion, in addition to global configuration and motion. Implications for theories of infants' visual development are discussed.

Case-Control Studies↗
PubMed1996

A dotted line assimilates in visibility to a solid line.

This study tested the theory that a context-produced increase in visibility of a target is due to its assimilation in visibility to the context. A context + target and a context are discriminated better than are a target and background. This occurs for two different context + targets in which the context is a solid line and the target is a dotted line. But it does not occur when solid lines replace these dotted lines. The dotted lines are much less visible than the solid lines. Therefore, the dotted lines increase in similarity in visibility to the solid lines, which is assimilation, but for visibility, rather than for a typical part. Assimilation does not occur between perceptually equal parts. Consequently, the reason why the two context + targets with only solid lines do not result in increases in visibility may be that these lines are sufficiently equal in visibility that assimilation in visibility is precluded. So, the theory is supported. This theory is consistent with evidence that one group (phenomenal whole) is associated with both assimilation and an increase in visibility. Accordingly, a stimulus with a relatively large distance between its solid and dotted lines is apprehended as a relatively weak group, and does not result in an increase in visibility.

Adult↗
PubMed1992

A critical discussion of Kellman and Shipley's (1991) theory of occlusion phenomena.

Kellman and Shipley (1991) recently advanced a new theory to explain the perception of partly occluded objects and illusory figures. The theory is a formalization of the Gestalt law of good continuation. In this paper we describe their account of occlusion when the contour of the occluder is completely specified by a display. Next, we outline some critical objections and present a number of counterexamples. Finally, we compare their theory with Wouterlood and Boselie's (in this issue) model of occlusion phenomena, which might also be considered as a formalization of the law of good continuation.

Form Perception↗
PubMed1994

Auditory-visual spatial interaction and modularity

The results of dealing with the conditions for pairing visual and auditory data coming from spatially separate locations argue for cognitive impenetrability and computational autonomy, the pairing rules being the Gestalt principles of common fate and proximity. Other data provide evidence for pairing with several properties of modular functioning. Arguments for domain specificity are inferred from comparison with audio-visual speech. Suggestion of innate specification can be found in developmental data indicating that the grouping of visual and auditory signals is supported very early in life by the same principles that operate in adults. Support for a specific neural architecture comes from neurophysiological studies of the bimodal (auditory-visual) neurons of the cat superior colliculus. Auditory-visual pairing thus seems to present the four main properties of the Fodorian module.

Adaptation, Physiological↗
PubMed2003

Filling-in phenomenon in patients with age-related macular degeneration: differences regarding uni- or bilaterality of central scotoma.

PURPOSE: The purpose of this study was to explore the presence of the filling-in phenomenon in patients with uni- or bilateral central scotoma (CS) resulting from natural history or laser photocoagulation of choroidal neovascularization in age-related macular degeneration (AMD). METHODS: Sixteen consecutive patients with unilateral CS and 14 patients with bilateral CS were assessed (44 eyes) with a scanning laser ophthalmoscope (SLO). Scotoma was delineated by scotometry with a point (1 degree x1 degree) moving radially from the periphery to the center of the lesion. In addition, patients underwent a line test, consisting of a horizontal line moving vertically and a vertical line moving horizontally, from the periphery to the center. The lines were longer than the macular lesion and were projected onto the retina. Patients were asked to indicate when the lines seemed interrupted. The perceptual filling-in phenomenon was considered to be present when limits of the perceived scotoma, determined by the line test, were smaller than those assessed by scotometry. In patients with bilateral CS, the results were analyzed to distinguish the less or more severely affected eye. RESULTS: In all eyes, the limits of the scotoma obtained with the scotometry test corresponded to the anatomic edges of the macular lesion. In patients with bilateral CS, the filling-in phenomenon was observed in 12 out of 14 (85%) less severely affected eyes, but only in one (7%) of their more severely affected eyes. In patients with unilateral CS, the phenomenon was observed in only one out of 16 (6%) eyes. CONCLUSION: These results suggest that the filling-in phenomenon mostly occurs in patients with bilateral central scotoma, and almost always in their less affected eye. Thus, it did usually not occur in an eye if the fellow eye was better.

Aged↗
PubMed2005

Collinearity, curvature interpolation, and the power of perceptual integration.

In three experiments, participants determined the orientation of a global triangle formed by three Gabor patches of a target spatial frequency in a field of distracters. The orientation of the target patches and their proximity were varied between conditions. When all the target patches had the same orientation this facilitated the response compared to random orientations. This effect occurred only when the patches were in close proximity. When the orientations of the target patches were different but aligned to the global triangle, facilitation occurred regardless of proximity. These contrasting types of facilitation were attributed to different early perceptual integration mechanisms that enable the perception of holistic structure.

Adolescent↗
PubMed2006

Identification of partially presented meaningless patterns: effect of completeness and distinctiveness.

The role of parts versus that of wholes in a visual perception has been debated for a century as two opposite approaches, namely, an analytic and holistic. In two psychophysical experiments we investigated whether the stimulus completeness or distinctiveness is essential for identification of the partially presented patterns under brief presentation conditions. For this purpose, a special class of stimuli was constructed in such a way that the patterns could be divided into informative and redundant parts. The first experiment clearly demonstrated the importance of the redundant part for effective pattern identification for the majority of subjects. The second experiment revealed the direct dependence of identification accuracy of the patterns on their completeness (2, 3, 4, 5, or 6 elements). Familiarisation of subjects with the test stimuli influenced the strength of this dependence.

Adult↗
PubMed2006

Gestalt perception and local-global processing in high-functioning autism.

This study examined gestalt perception in high-functioning autism (HFA) and its relation to tasks indicative of local visual processing. Data on of gestalt perception, visual illusions (VI), hierarchical letters (HL), Block Design (BD) and the Embedded Figures Test (EFT) were collected in adult males with HFA, schizophrenia, depression and normative controls. Individuals with HFA processed gestalt stimuli less in accord with gestalt laws, particularly regarding the principle of similarity. Gestalt processing correlated positively with global processing of the HL. EFT and BD performance correlated negatively with VI susceptibility in HFA. All clinical groups succumbed less to VI than the normative sample. Results suggest decreased gestalt perception in HFA, being associated with a more general local visual processing bias.

Adult↗
PubMed1991

Priming contour-deleted images: evidence for intermediate representations in visual object recognition.

The speed and accuracy of perceptual recognition of a briefly presented picture of an object is facilitated by its prior presentation. Picture priming tasks were used to assess whether the facilitation is a function of the repetition of: (a) the object's image features (viz., vertices and edges), (b) the object model (e.g., that it is a grand piano), or (c) a representation intermediate between (a) and (b) consisting of convex or singly concave components of the object, roughly corresponding to the object's parts. Subjects viewed pictures with half their contour removed by deleting either (a) every other image feature from each part, or (b) half the components. On a second (primed) block of trials, subjects saw: (a) the identical image that they viewed on the first block, (b) the complement which had the missing contours, or (c) a same name-different exemplar of the object class (e.g., a grand piano when an upright piano had been shown on the first block). With deletion of features, speed and accuracy of naming identical and complementary images were equivalent, indicating that none of the priming could be attributed to the features actually present in the image. Performance with both types of image enjoyed an advantage over that with the different exemplars, establishing that the priming was visual rather than verbal or conceptual. With deletion of the components, performance with identical images was much better than that with their complements. The latter were equivalent to the different exemplars, indicating that all the visual priming of an image of an object is through the activation of a representation of its components in specified relations. In terms of a recent neural net implementation of object recognition (Hummel & Biederman, in press), the results suggest that the locus of object priming may be at changes in the weight matrix for a geon assembly layer, where units have self-organized to represent combinations of convex or singly concave components (or geons) and their attributes (e.g., aspect ratio, orientation, and relations with other geons such as TOP-OF). The results of these experiments provide evidence for the psychological reality of intermediate representations in real-time visual object recognition.

Adult↗