Developmental Differences in Stereoscopic Discrimination: Is perceptual grouping responsible for depth discrimination deficits in adults?

A. Solski; D. Giaschi; L. Wilcox

doi:10.1167/10.7.367

Convex Grouping Impedes Detection of Stereoscopic Depth

Perception ◽

10.1068/v970142 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 242-242

Author(s):

Z Liu

Keyword(s):

Perceptual Grouping ◽

Image Plane ◽

Stereoscopic Depth ◽

Relative Depth ◽

Objective Method ◽

Good Continuation ◽

Depth Discrimination ◽

Ground Segmentation ◽

Planar Regions ◽

Oval Shape

When two image regions are separated by an occluder, the strength of their perceptual grouping behind the occluder depends in part on the possible smoothness of the hidden contour completions (ie, Gestalt ‘good continuation’). We consider if grouping strength also depends on whether the contour completion is convex or concave. We hypothesised that the stronger the grouping between two such regions, the harder it is to resolve their relative stereoscopic depth; and employed accordingly an objective method of relative depth discrimination. The stimulus was in stereo. A horizontal bar in the centre of the image occluded two pairs of planar regions parallel with the image plane. One pair assumed a convex (oval) shape behind the occluder, the other pair a concave (hourglass) shape. The regions in one pair had a slight depth difference. The task was to detect which pair was not coplanar. The convex grouping impeded detection of stereoscopic relative depth (73% vs 86%, F1,10=8.66, p < 0.02). This held even when the convex completion boundaries were less smooth than the concave ones, a result opposite to predictions by Gestalt ‘good continuation’. In a control experiment, the stimulus was viewed with the ‘occluder’ in the background, so grouping was no longer possible. No difference between the two pairs was found. Our results suggest that convexity, known to play a role in figure/ground segmentation, is also significant in perceptual grouping, and can even win out over ‘good continuation’. We also propose an objective method of depth discrimination to study perceptual grouping in general.

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Low-light-level three-dimensional video microscope with long working distance objective lenses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168864 ◽

1994 ◽

Vol 52 ◽

pp. 226-227

Author(s):

W. Lin ◽

J. Gregorio ◽

T.J. Holmes ◽

D. H. Szarowski ◽

J.N. Turner

Keyword(s):

Three Dimensional ◽

Light Level ◽

Stereo Pair ◽

Light Illumination ◽

Initial Image ◽

Low Light ◽

Image Recording ◽

Depth Discrimination ◽

Video Microscope ◽

Working Distance

A low-light level video microscope with long working distance objective lenses has been built as part of our integrated three-dimensional (3-D) light microscopy workstation (Fig. 1). It allows the observation of living specimens under sufficiently low light illumination that no significant photobleaching or alternation of specimen physiology is produced. The improved image quality, depth discrimination and 3-D reconstruction provides a versatile intermediate resolution system that replaces the commonly used dissection microscope for initial image recording and positioning of microelectrodes for neurobiology. A 3-D image is displayed on-line to guide the execution of complex experiments. An image composed of 40 optical sections requires 7 minutes to process and display a stereo pair.The low-light level video microscope utilizes long working distance objective lenses from Mitutoyo (10X, 0.28NA, 37 mm working distance; 20X, 0.42NA, 20 mm working distance; 50X, 0.42NA, 20 mm working distance). They provide enough working distance to allow the placement of microelectrodes in the specimen.

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Recent Developments in the Assessment and Diagnosis of Child Psychopathology

European Journal of Psychological Assessment ◽

10.1027/1015-5759.11.3.203 ◽

1995 ◽

Vol 11 (3) ◽

pp. 203-212 ◽

Cited By ~ 3

Author(s):

Frank C. Verhulst

Keyword(s):

Problem Behaviors ◽

Child Psychopathology ◽

Developmental Differences ◽

Multiple Informants ◽

Cultural Research ◽

Assessment Approach ◽

Multicultural Knowledge ◽

Recent Developments ◽

Basic Characteristics ◽

Assessment And Diagnosis

In this article, recent developments in the assessment and diagnosis of child psychopathology are discussed with an emphasis on standardized methodologies that provide data that can be scored on empirically derived groupings of problems that tend to co-occur. Assessment methodologies are highlighted that especially take account of the following three basic characteristics of child psychopathology: (1) the quantitative nature of child psychopathology; (2) the role of developmental differences in the occurrence of problem behaviors, and (3) the need for multiple informants. Cross-cultural research is needed to test the applicability of assessment procedures across different settings as well as the generalizability of taxonomic constructs. Assessments of children in different cultures can be compared or pooled to arrive at a multicultural knowledge base which may be much stronger than knowledge based on only one culture. It is essential to avoid assuming that data from any single source reveal the significance of particular problems. Instead, comprehensive assessment of psychopathology requires coordination of multisource data using a multiaxial assessment approach.

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