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Results for “Perceptual Distortion”

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At least 289 records · Page 16Linked to original sources
PubMed1999

A distortion of perceived space in patients with right-hemisphere lesions and visual hemineglect.

In twelve patients with left visuospatial hemineglect following acute right hemisphere cerebrovascular accident (CVA), and in twelve normal controls, we used a matching task to investigate judgement of the length of lines. Their task was to choose which of three lines of different length matched a separate single line. On each trial, the lines were all vertical or all horizontal. The set of three lines was presented either to the left or the right of the single line. When the lines were vertical, the choices made both by normal subjects and patients were nearly always correct. However, when the lines were horizontal and the set of comparison lines was on the left, patients mostly selected a line that was longer than the sample on the right, and never chose shorter lines, suggesting that the length of horizontal lines on the left was underestimated. When the set of three lines was on the right, patients chose the correct line more often, but made errors in both directions, i.e. longer or shorter, although shorter lines were chosen more often than longer lines. The rare errors made by normal subjects were in the same directions as those observed in the patients. The results provide further evidence for a non-Euclidean distortion of perceptual space in patients with left sided visuospatial neglect, and suggest that this distortion could be a gross exaggeration of normal performance or a product of diminished spatial attention, or both.

Aged↗
PubMed1994

Body-image perception in pre- and postadolescent females.

The purpose of this study was to examine both perceived and ideal body-image to establish if the process of adolescence was a contributory factor. A distorting mirror and silhouette pictures were used to examine the image in two groups of 59 pre- and 41 postadolescent girls. The girls' perception of themselves was reasonably accurate yet both groups had a significantly slimmer mean ideal image, irrespective of adolescent status. The differences between the two groups were nonsignificant whether using the distorting mirror or the pictures. The only difference to be observed was when using a body-satisfaction scale. The postadolescents were significantly less satisfied about their nonhead body parts. Scores from the mirror and the pictures question the assumption that body-image dissatisfaction is a postadolescent phenomenon. This should be a cause for concern as eating disorders, which appear to be linked to body-image, are being observed in younger children. The comparability between scores for the pictures and the distorting mirror opens the possibility of home-based therapy in the treatment of perceptual and eating disorders.

Adolescent↗
PubMed2004

The visual perception of 3D shape.

A fundamental problem for the visual perception of 3D shape is that patterns of optical stimulation are inherently ambiguous. Recent mathematical analyses have shown, however, that these ambiguities can be highly constrained, so that many aspects of 3D structure are uniquely specified even though others might be underdetermined. Empirical results with human observers reveal a similar pattern of performance. Judgments about 3D shape are often systematically distorted relative to the actual structure of an observed scene, but these distortions are typically constrained to a limited class of transformations. These findings suggest that the perceptual representation of 3D shape involves a relatively abstract data structure that is based primarily on qualitative properties that can be reliably determined from visual information.

Depth Perception↗
PubMed1976

The construct validity of aniseikonic lens measures of anxiety.

The construct validity of aniseikonic lens measures of anxiety as a personality trait and of anxiety toward objects was examined in an experimental setting. No evidence of convergent construct validity was found for aniseikonic measures of anxiety as a personality trait. The validity of such measures as indices of anxiety toward objects was also questioned. The findings suggested that familiarity with the object viewed, rather than anxiety, may be the underlying dimension tapped by such measures of ability to perceive aniseikonic distortion.

Adolescent↗
PubMed1994

Perceptual compensation for speaker differences and for spectral-envelope distortion.

This study asks whether perceptual mechanisms that compensate for the spectral-envelope distortion of transmission channels also contribute to compensation for speaker differences. Subjects identified test words that were played after a carrier sentence. In some conditions the carriers were synthesized with F1 in low- and high-frequency ranges and in others they were distorted by filters whose frequency response is the spectral envelope of one vowel minus the spectral envelope of another. The filter /I/ minus /epsilon/ and its inverse were used. Test words were drawn from an /Itch/ to /epsilon tch/ continuum. Carriers filtered by /I/ minus /epsilon/ and its inverse give a phoneme boundary difference, indicating compensation for spectral envelope distortion. A phoneme boundary difference also occurs between carriers with F1 in low and high ranges, indicating compensation for speaker differences. Neither of these effects is reduced by playing the carrier backwards, even though a measurement of the perceived naturalness of carriers is sharply reduced by this manipulation. Analysis of carriers synthesized with low and high F1 showed that they have different long-term spectra, and subsequent experiments used time-stationary filters to alter this characteristic. The results showed that the long-term spectra of the carriers govern their influence on the identity of subsequent test sounds. However, measurements of perceptual confusions among the carriers and of perceived talker-differences between carriers revealed that other, time-varying factors are more important for voice identification.

Humans↗
PubMed2006

The distortion of spatial relationships between local elements in hierarchical patterns decreases the global advantage effect.

The present study examined the influence of perceptual organization on the processing of global and local information in hierarchical patterns. In two experiments, we examined whether disturbing the spatial relationships between local elements by introducing between-element distance and size heterogeneity affected global processing dominance. The effects on global processing dominance of undistorted compound stimuli with equidistant and homogeneous local elements were compared with those of compound stimuli which presented between-element distance heterogeneity (Experiment 1) or heterogeneity in size (Experiment 2). The results showed that the global advantage effect decreased similarly under conditions of between-element distance and size heterogeneity that disturbed the spatial relationships between local elements. The results provide new evidence on the role of perceptual organization in hierarchical patterns processing.

Adult↗
PubMed1991

Two-dimensional spatial distortions in human strabismic amblyopia.

Two-dimensional space perception was measured in the central visual field of amblyopic subjects under special consideration of spatial distortions and spatial uncertainty. The subjects had to construct circles with different radii around a given fixation point. Subjects with deep strabismic amblyopia were showed to exhibit considerable distortion in the amblyopic eye. Each subject exhibited an individual distortion pattern. The dominant eye showed distortions similar to those seen in normal observers. Subjects with mild strabismic amblyopia, strabismic alternators and anisometropic amblyopes did not exhibit any significant spatial distortions. Data from dichoptic localization experiments indicate that anomalous retinal correspondence might contribute to monocular spatial distortions.

Adult↗