Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Depth Perception”

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.

At least 1,369 records · Page 76Linked to original sources
PubMed1985

Perception of Glass pattern structure with stereopsis.

Stereograms are presented which demonstrate that the perceptual salience of structure in Glass patterns may be destroyed or created by the introduction of stereoscopic depth effects. Novel three-dimensional pattern structures can also be produced. Proposals concerning the nature of the primal sketch are evaluated in the light of these findings, and it is concluded that the findings are consistent with the view that depth derived from disparity information is explicitly represented in the primal sketch.

Depth Perception↗
PubMed1992

On the variety of percepts associated with dichoptic viewing of dissimilar monocular stimuli.

Upon dichoptic viewing of dissimilar patterns, several distinct perceptual states may be experienced over time. One state is exclusive monocular dominance, wherein the view of only one eye is seen in its entirety for some period of time. Another state is characterized by a mosaic-like college consisting of portions of the view of each eye. Two other states involve simultaneous perception of both monocular images in their entirety. In one of these states, the two monocular stimuli appear to be superimposed without depth (a phenomenon we shall term 'superimposition'). In the other state, the two monocular stimuli appear to be located at different depth planes (which we shall term 'transparency'). This paper documents the stimulus conditions favoring these various perceptual states. Exclusive monocular dominance occurs most often when the two eyes view dissimilar patterns with the same spatial-frequency content, particularly when both patterns consist of low spatial frequencies. Superimposition also occurs most often when the two eyes view the same spatial frequencies, but predominantly when those spatial frequencies are high. Transparency is favored when the spatial-frequency difference between the eyes is great, particularly when the view of one eye consists of high spatial-frequency information.

Depth Perception↗
PubMed1993

Maternal perceptions of pneumonia and pneumonia signs in Pakistani children.

Fifty mothers of children attending a hospital outpatient clinic with non-severe pneumonia (fast breathing but no chest indrawing) were interviewed in depth. Maternal perceptions and practices with clinical significance were documented. Results showed that most mothers initially tried "heat-producing" home remedies designed to counter the "coldness" of the disease, allowed only 2 days for any particular allopathic medicine to work, and did not go to the same practitioner twice. When mothers were asked what had alarmed them enough to come to the hospital, the symptoms named most frequently were persistent severe cough and high fever, inability to sleep and excessive crying. Fast breathing was spontaneously mentioned by only a few, although when questioned, 32/50 said that they had noticed it. The mothers who had prior experience with child pneumonia were more likely to notice fast breathing and also came to the hospital earlier than those who were inexperienced. Relatively higher levels of maternal education and income were suggestively associated with bringing a female child rather than a male child for pneumonia treatment. Fewer than half of the mothers knew where air goes when a person breathes in and where the lungs are located. Most held treatment preferences at odds with the protocols proposed for the national ARI program currently being initiated in Pakistan, e.g. they said that a doctor should use a stethoscope, should prescribe suspensions rather than tablets and should give injections. This study provides baseline data on attitudes and behaviors that can either be built on in that program or addressed through public education campaigns.

Attitude to Health↗
PubMed1996

Configural processing in the perception of apparent biological motion.

In classic demonstrations of apparent motion, observers typically report seeing motion along the shortest possible path between 2 sequentially presented objects. However, when realistic photographs of a human body are sequentially presented at slow temporal rates, observers report paths of apparent motion that are consistent with the movement limitations of the human body even when those paths are not the shortest possible. The current set of experiments examined those aspects of the human form that lead to the perception of biomechanically consistent paths of motion. The authors' findings suggest that the perception of apparent biological motion extends to human movements that involve inanimate objects. The authors also report that observers can perceive apparent motion of nonbiological objects in a manner similar to apparent motion of human bodies. However, a global hierarchy of orientation and position cues resembling the human form is required for the perception of these paths.

Adult↗
PubMed1990

The importance of velocity gradients in the perception of three-dimensional rigidity.

Sequential presentation of a number of random-dot patterns which when super-imposed yield an expanding flow field leads to the perception of a coherent motion towards the observer. The motion vectors in this type of flow field all radiate from the origin. This percept of a global coherent expanding flow results only when the local speeds (magnitude of the local motion vectors) are zero at the centre and increase linearly towards the periphery. If all the dots radiate outwards but have the same speed, a clear percept of three-dimensional nonrigidity arises.

Acceleration↗
PubMed1986

Tradeoffs between stereopsis and proximity luminance covariance as determinants of perceived 3D structure.

A 2D polar projection of a 3D wire cube (Necker cube) in clockwise rotation can be perceived either veridically as a clockwise-rotating cube (rigid percept) or as a counterclockwise-rotating rubbery, truncated pyramid (nonrigid percept). The 3D percept is influenced by various cues: linear perspective, stereo disparity, and proximity-luminance covariance (PLC, the intensification of edges in proportion to their proximity to the observer). Perspective, by itself or in combination, is a very weak cue whereas PLC is a powerful cue [Schwartz and Sperling (1983) Bull. Psychon. Soc. 21, 456-458]. Here we determined psychometric functions for perceptual resolution in static displays and dynamic rotating displays (with and without a static preview) as determined by stereopsis and PLC in isolation and with both cues jointly, possibly in conflict. Stereopsis was the dominant cue in static displays and in most dynamic displays. When a static display preceded a dynamic display, it strongly influenced the subsequent dynamic percept. Perceptual resolution in all conditions was accurately described by a winner-take-all model in which the strength of evidence for each percept from different cues is simply algebraically added.

Depth Perception↗
PubMed1991

The cyclopean ternus display and the perception of element versus group movement.

This study investigated the perception of bistable stroboscopic motion (Ternus display) with cyclopean stimuli created from retinal disparity embedded in dynamic random-element stereograms, the responses to which arise at binocular-integration levels of the visual system. To provide comparison data, observers were also tested with luminance-domain stimuli matched as closely as possible to their cyclopean counterparts. The results showed that the perception of element vs group movement was similar for both stimulus domains: element movement predominated at short interstimulus intervals (ISIs) while group movement predominated at long ISIs, and there was a tendency for a greater percentage of group movement to occur with a longer frame duration. These results cast suspicion on the interpretation of bistable motion that assumes element movement is a signature of a lower-level, short-range motion system whereas group movement is a signature of a higher-level, long-range system; both percepts are engendered at binocular-integration levels of vision.

Depth Perception↗
PubMed2004

A laminar cortical model for 3D perception of slanted and curved surfaces and of 2D images: development, attention, and bistability.

A model of laminar visual cortical dynamics proposes how 3D boundary and surface representations arise from viewing slanted and curved 3D objects and 2D images. The 3D boundary representations emerge from non-classical receptive field interactions within intracortical and intercortical feedback circuits. Such non-classical interactions within cortical areas V1 and V2 contextually disambiguate classical receptive field responses to ambiguous visual cues using cells that are sensitive to colinear contours, angles, and disparity gradients. Remarkably, these cell types can all be explained as variants of a unified perceptual grouping circuit whose most familiar example is a 2D colinear bipole cell. Model simulations show how this circuit can develop cell selectivity to colinear contours and angles, how slanted surfaces can activate 3D boundary representations that are sensitive to angles and disparity gradients, how 3D filling-in occurs across slanted surfaces, how a 2D Necker cube image can be represented in 3D, and how bistable 3D Necker cube percepts occur. The model also explains data about slant aftereffects and 3D neon color spreading. It shows how chemical transmitters that habituate, or depress, in an activity-dependent way can help to control development and also to trigger bistable 3D percepts and slant aftereffects. Attention can influence which of these percepts is perceived by propagating selectively along object boundaries.

Attention↗
PubMed1999

More thoughts on perceiving and grasping the Müller-Lyer illusion.

It has been suggested that the insensitivity of the visuomotor system to various visual illusions is based on mechanisms in the so-called 'dorsal stream' of primate extrastriate cortex, which may depend upon binocular cues for their functions. The present study investigated the effects of binocular and monocular viewing on perception of and action to Müller-Lyer figures. Fourteen participants were required to match and grasp the shaft of a Müller-Lyer display under both viewing conditions. In the matching condition, participants were required to show the perceived extent of the central shaft of one of the two Müller-Lyer figures, using the extent of the gap between their finger and thumb. In the grasping task, participants were required to quickly and accurately reach out and grasp the central shaft of the specified Müller-Lyer figure. First, there was a striking effect of the illusion on the matching performance under both viewing conditions. However, the maximum grip aperture remained unaffected by the illusion figures. These results add to the theory of distinct modes of visual processing for perception and action. However, we did not find that grasping performance was affected by the illusion under monocular conditions. It is plausible that monocular depth cues distinct from those responsible for the illusion can successfully drive accurate grasping. Additional concerns regarding claims of action system resistance to the perceptual distortions of various illusions are discussed.

Adult↗
PubMed1994

Two metric solutions to three-dimensional reconstruction for an eye in pure rotations.

A problem in space perception concerns how a mobile observer acquires information about the structure of objects. Earlier research derived the optic-flow equations for an eye undergoing pure rotations. It was suggested that, by utilizing three points and two views, one can recover the distance of points and the motion parameters. The radius of the eyeball was the metric unit. Yet the common view regards this problem as indeterminate. We derived a unique solution in the discrete case, which required three points and two views. However, when we observed a single bright point, a substantial amount of visual stability existed. We therefore derived a solution in the differential approach for a single point, which is based on a distinction that we made between mathematical and visual points. Both solutions were checked with a computer simulation and were found to be accurate, supporting the space perception in navigation (SPIN) theory.

Computer Simulation↗
PubMed1995

The perception of surface orientation from multiple sources of optical information.

An orientation matching task was used to evaluate observers' sensitivity to local surface orientation at designated probe points on randomly shaped 3-D objects that were optically defined by texture, lambertian shading, or specular highlights. These surfaces could be stationary or in motion, and they could be viewed either monocularly or stereoscopically, in all possible combinations. It was found that the deformations of shading and/or highlights (either over time or between the two eyes' views) produced levels of performance similar to those obtained for the optical deformations of textured surfaces. These findings suggest that the human visual system utilizes a much richer array of optical information to support its perception of shape than is typically appreciated.

Attention↗
PubMed2000

Subjective organization and the visibility of illusory contours.

The effects of the differential organization of a Necker cube on the perceived salience of an embedded illusory triangle were examined. Overall figural salience was greater when the triangle appeared to be localized on the front rather than the back cube face. Illusory contour salience also increased with increasing inducing area contrast and was greater when the figure was oriented on cardinal as compared to oblique coordinates. However, the latter effects were independent of perceived location within the cube. The finding that subjective organizational and structural factors influenced the perceived salience of the illusory figure but did not interact is consistent with van Tuijl and Leeuwenberg's (1982) suggestion that top-down and bottom-up determinants can operate independently in illusory contour perception.

Adolescent↗
PubMed1995

Vergence eye movement control and multivalent perception of autostereograms.

We introduce a dynamical model for automatic vergence eye movement control. In connection with our dynamical system of binocular model neurons that solves the correspondence problem of stereo-vision, we present a complete model for stereo-vision. Our automatic vergence eye movement control adjusts an image segment, which is of momentary interest to the observer. The adjustment is done in such a way that we only need to define a disparity search range of minimal extension. Recently, a new method of encoding (3D) three-dimensional information in 2D pictures was designed in the form of computer-generated patterns of colored dots. At first glimpse, these so-called autostereograms appear as structured but meaningless patterns. After a certain period of observation, a 3D pattern emerges suddenly in an impressive way. Applying our algorithm to autostereograms, we find a fully satisfactory agreement with the multivalent perception experienced by humans. As in nature, in our model the phase transition between the initial state and the 3D perception state takes place in a very short time. Our algorithm is very robust against noise, and there is no need to interpolate a sparse depth map.

Algorithms↗
PubMed1999

Measuring perceived 3D shape at multiple spatial scales.

We present and test a novel multiscale representation of perceived 3D surface orientation: the orientation path. Using a multiscale probe, we measure perceived surface orientation at multiple spatial scales; linking the measurements for a given surface location yields that location's orientation path. The multiscale data obtained show that observers consistently see different surface orientations at different spatial scales. We demonstrate that such multiscale data can reveal multiscale differences between observers' percepts of a stimulus and the stimulus geometry. We also demonstrate the use of the orientation path in evaluating the multiscale effects of adding a depth cue to a 3D display.

Computer Graphics↗
PubMed1989

Ordinal structure in the visual perception and cognition of smoothly curved surfaces.

In theoretical analyses of visual form perception, it is often assumed that the 3-dimensional structures of smoothly curved surfaces are perceptually represented as point-by-point mappings of metric depth and/or orientation relative to the observer. This article describes an alternative theory in which it is argued that our visual knowledge of smoothly curved surfaces can also be defined in terms of local, nonmetric order relations. A fundamental prediction of this analysis is that relative depth judgments between any two surface regions should be dramatically influenced by monotonicity of depth change (or lack of it) along the intervening portions of the surface through which they are separated. This prediction is confirmed in a series of experiments using surfaces depicted with either shading or texture. Additional experiments are reported, moreover, that demonstrate that smooth occlusion contours are a primary source of information about the ordinal structure of a surface and that the depth extrema in between contours can be optically specified by differences in luminance at the points of occlusion.

Cognition↗