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 1,513 records · Page 84Linked to original sources
PubMed1987

Perceptual "blankout" of monocular homogeneous fields (Ganzfelder) is prevented with binocular viewing.

The loss of visual perception or "blankout" which occurs when a homogeneous field (Ganzfeld) is presented monocularly is prevented when the same field is viewed binocularly. Thus, blankout cannot be retinal; and contours or transients in time and space are unnecessary for the continuous maintenance of visual perception. Experiments are reported in which blankout ensues only if the two eyes receive luminance disparities ca 0.75 log I. Furthermore, blankout is only marginally affected by stimulus intensity, nor is it dependent on stimulus hue. However, equally luminant but disparate hues presented to the two eyes produce perceptions reminiscent of blankout, with the darkness of blankout replaced with that of color. It is hypothesized that the underlying mechanisms have a commonality in the phenomena of blankout and binocular rivalry but several noncongruent features require explanation.

Depth Perception↗
PubMed1995

Binocular perception of slant about oblique axes relative to a visual frame of reference.

From the literature it is known that the processing of disparity for slant is different in the presence and in the absence of a visual frame of reference. The experimental finding that vertical disparity is not processed for slant perception in the presence of a visual reference is elaborated. This theoretical analysis results in a reduction of the three basic first-order transformations between the retinal half images (divergence, rotation, and deformation) to only two basic orthogonal transformations. The first of these, horizontal scale, results in slant perception about the vertical axis, whereas the second, horizontal shear, results in slant perception about the horizontal axis. These transformations are based primarily on horizontal disparity. It is shown experimentally that in the presence of a frame of reference the amount of vertical transformation that is added to the two basic transformations (horizontal scale and shear) of a random-dot stimulus is indeed irrelevant for slant perception. It is suggested that, in the presence of a visual reference, slant perception about oblique axes is based solely on linear combinations of the horizontal-scale and horizontal-shear transformations. Subjects are able to reproduce slants about oblique axes experimentally merely by combining horizontal scale and shear.

Adult↗
PubMed2003

Shadows in the brain.

The aims of the present study were to investigate whether the processing of an object shadow occurs implicitly, that is without conscious awareness, and where physically within the human brain shadows are processed. Here we present neurological evidence, obtained from studies of brain-injured patients with visual neglect, that shadows are implicitly processed and that this processing may take place within the temporal lobe. Neglect patients with lesions that do not involve the right temporal lobe were still able to process shadows to optimize object shape perception. In contrast, shadow processing was not found to be as efficient in neglect patients with lesions that involve the right temporal lobe.

Aged↗
PubMed1991

Perceptual rivalry between illusory and real contours.

The interactions between illusory and real contours have been investigated under monocular, binocular and dichoptic conditions. Results show that under all three presentation conditions, periodic alterations, generally called rivalry, occur during the perception of cognitive (or illusory) triangles, while earlier research had failed to find such rivalry (Bradley and Dumais 1975). With line triangles, rivalry is experienced only under dichoptic conditions. A model is proposed to account for the observed phenomena.

Computer Simulation↗
PubMed2000

What limits the contribution of second-order motion to the perception of surface shape?

Both motion and stereopsis can be derived from contrast as well as luminance defined stimuli. It is currently assumed that these two different sources of information about objects feed into one common stage. Thus it would not be expected that their role in visual perception would be different. Here we show that although motion can be carried by contrast-defined elements, such motion is not used to define three-dimensional (3D) surfaces. A similar effect has been reported in stereopsis; although such contrast-defined elements can give signed disparity signals they nevertheless do not contribute to the percept of shape. We show that the reason for this lies in the inability of the second order signals to cohere or bind across space/spatial scales rather than a characteristic of the elementary motion signals per se.

Contrast Sensitivity↗
PubMed2006

[The influence of information about drawing technique on impression of paintings: in the case of inaccurate perspective].

Some paintings by renowned artists were drawn in inaccurate perspective, but the psychological effects of such technique on impression of paintings were not clarified. This study investigated the influence of information about inaccurate perspective on impression of paintings. Three famous paintings drawn in inaccurate perspective were used as stimuli. In two experiments, participants were asked to answer the impression of paintings using two kinds of rating scales, information rate scale (IRS) and semantic differential (SD) scale. When watching paintings, half of participants were given information about inaccurate perspective, and the other half were not. The impressions were compared between two groups. Results showed that information about inaccurate perspective increased "novelty" impression of paintings that consisted of mainly IRS items. We discussed the relationship between perception of inaccurate perspective and impression of paintings. Furthermore, we confirmed that it is efficient to separate impression of paintings into informational impression measured by IRS and semantic impression measured by SD scale in empirical study of paintings.

Adolescent↗
PubMed1992

Perceived direction of moving two-dimensional patterns depends on duration, contrast and eccentricity.

Type II two-dimensional motion is produced by superimposing two one-dimensional drifting cosine gratings with velocity vectors lying on the same side of the intersection-of-constraints (IOC) resultant. When type II patterns were constructed with components having the same spatial frequency and contrast, perceived direction was found to be biased toward the vector sum direction at short durations and approached the direction predicted by IOC only after some time lag. This time lag was contrast dependent. At 5% contrast, the perceived direction after 1 sec of presentation remained biased by more than 20 degrees. Direction perception was also measured at 15 degrees eccentricity. At this eccentricity the perceived direction of type II patterns was grossly biased away from the IOC prediction in the direction of the component vectors by an average of 25 degrees.

Contrast Sensitivity↗
PubMed1962

The visual space sense.

At the conclusion of this discussion it is important to keep in mind the influences of all the complex processes involved in visual spatial localization, among which stereopsis is only one. The various factors and cues for this spatial localization interact with, complement, reinforce, and perhaps even inhibit one another, depending upon the varying visual surroundings of the moment and upon the physiologic perfection of the visual apparatus. In one's daily work probably no single factor or group of factors dominates at all times. "Any one who knows how pliable our spatial visual perceptions are under the influence of various conditions of observation and under the influence of past experience, taken into account consciously or unconsciously, should not be surprised at the multiplicity of results of observations on different objects and with different observers" (see 18).

Cues↗
PubMed1997

Poor stereopsis can support size constancy in albinism.

PURPOSE: The size of a retinal image is inversely related to the distance to the object that generates the image. Normal subjects therefore exhibit size constancy, in which the perceived size of an image is scaled according to its perceived distance. Albinos usually have such poor binocular vision that they perform very poorly on clinical tests for stereopsis. To investigate the functional consequences of this poor stereopsis, we investigated whether stereopsis in these subjects could support size constancy. METHODS: The stereothresholds of 10 albinos and 12 normal control subjects were measured. The presence of absence of size constancy was investigated by having subjects equate the subjective size of stereoscopically presented images whose image disparity indicated that they were at different distances. RESULTS: Laboratory results indicated that eight albinos (including five whose clinical tests indicated a lack of stereopsis) had measurable stereopsis of several thousand are seconds or better. Of these, four also exhibited size constancy. CONCLUSIONS: Albinos who do not demonstrate stereopsis on clinical tests can have stereoscopic perception that commonly used clinical tests do not detect. Moreover, some of these patients even use this poor stereopsis in judging the size of stereoscopically presented images.

Adolescent↗
PubMed1996

Effects of changing viewing conditions on the perceived structure of smoothly curved surfaces.

Observers' perceptions of a male and a female torso were investigated using monocular and stereoscopic images under varying conditions of illumination. Observers judged the shapes of these torsos by adjusting a gauge figure to estimate the local slant and tilt at numerous probe points arranged in a lattice over the torso's surface. The results revealed that the judged surfaces in the monocular and stereoscopic conditions were related by an affine stretching transformation in depth that accounted for approximately 95% of the between-condition variance. There was also a strong affine component between the judgments obtained for the different illumination directions, although a further analysis of the residuals indicated that changing the direction of illumination influenced perceived structure in a piecewise manner.

Contrast Sensitivity↗
PubMed1991

Systematic distortions of shape from stereopsis.

The effectiveness of disparity information in defining 3-D shape was investigated by means of judgements of the shape of cylindrical continuous curved surfaces presented as random dot stereograms. At a close viewing distance, truly circular cylinders appeared elongated; at an intermediate distance, perception was close to veridical; and, at a far distance, cylinders appeared flattened. Indirect measures of scaling distance were calculated from these data. The results strongly suggest that the observed shape distortions are a consequence of scaling horizontal disparities with an incorrect measure of egocentric distance.

Depth Perception↗
PubMed2005

Stereopsis from a performance perspective.

PURPOSE: A patient can demonstrate a poor stereoscopic test or task performance for reasons inherent within the test/task itself for reasons dependent on normal physiology common to all human subjects, and also for reasons that are outside of normal physiology and are unique or idiosyncratic to a particular person's visual system. This article reviews the literature for the first two reasons, but emphasizes the pathophysiology involved in the idiosyncratic and abnormal reasons. RESULTS: Using control systems analysis, it is shown that deficits in stereoscopic performance can be explained by reference to the quantitative aspect of stereoscopic threshold and qualitative aspects such as speed of response, reliability-robustness, and strength of percept. The relationship between fixation disparity and stereopsis is seen to be central to this explanation. CONCLUSIONS: Proceeding from diagnosis to treatment, control systems analysis offers physiologically based explanations for the corrective procedures necessary to ameliorate abnormal conditions. Several topics for applied research in stereopsis are suggested.

Depth Perception↗
PubMed1981

Information for the spatial factor in Korte's 3rd Law of apparent motion.

The experiments reported here show that Korte's space-time invariance equation governing perception of apparent motion is limited to situations in which metric or apparent separation of targets define but a single interval of space. Variation in interstimulus intervals and metric separation of targets did not influence the perception of apparent motion when the background array was structured to depict apparently equal intervals of space. These results provide a test of Koffka's and more recently Gibson's view that higher order properties of intervals of space specify the spatial factor in apparent movement.

Adult↗
PubMed1990

Visual-touch perceptual equivalence for shape information in children and adults.

Although there has been substantial developmental research which has compared shape information processing performance under visual and touch conditions, there has been little work that bears on the shape attributes that are routinely employed, or on the similarity between shape attributes employed by adults and those employed by children. The present research was carried out to investigate the visual-touch perceptual equivalence of young children, using multidimensional scaling techniques, and to compare the visual and touch perceptual structures of this age group with those of adults. The results provide evidence for adult-like perceptions of shape among 6-year-olds, in terms of both the patterns of interstimulus similarities and the shape attributes attended to by children using each modality. In addition, it was found that children have somewhat more visual-touch perceptual equivalence than adults do.

Attention↗
PubMed1999

To reverse or not to reverse: when is an ambiguous figure not ambiguous?

The role of bottom-up processes in our perception of reversible figures was examined. In Experiment 1 the overlapping squares figure and nonsense reversible figures were used. The effects of adapting subjects for differing durations to an unambiguous version of the figure before presentation of the traditional reversible figure were determined under conditions of varying precision of fixation. In Experiment 2 the research was expanded to other examples of reversible figures. In both experiments, results with two dependent measures (the subject's first percept and the number of reversals reported) were generally consistent with the interpretation of bottom-up processes underlying the adaptation effects. However, the crucial role of stimulus and procedural variables and the differential sensitivity of the two dependent measures was demonstrated.

Adult↗
PubMed1998

Interaction of stereo vision and optic flow processing revealed by an illusory stimulus.

The influence of stereoscopic vision on the perception of optic flow fields was investigated in experiments based on a recently described illusion. In this illusion, subjects perceive a shift of the center of an expanding optic flow field when it is transparently superimposed by a unidirectional motion pattern. This illusory shift can be explained by the visual system taking the presented flow pattern as a certain self-motion flow field. Here we examined the dependence of the illusory transformation on differences in depth between the two superimposed motion patterns. Presenting them with different relative binocular disparities, we found a strong variation in the magnitude of the illusory shift. Especially when translation was in front of expansion, a highly significant decrease of the illusory shift occurred, down to 25% of its magnitude at zero disparity. These findings confirm the assumption that the motion pattern is interpreted as a self-motion flow field. In a further experiment we presented monocular depth cues by changing dot size and dot density. This caused a reduction of the illusory shift which is distinctly smaller than under stereoscopic presentation. We conclude that the illusory optic flow transformation is modified by depth information, especially by binocular disparity. The findings are linked to the phenomenon of induced motion and are related to neurophysiology.

Adult↗
PubMed1985

Perception of structure from motion: is projective correspondence of moving elements a necessary condition?

A fundamental assumption of almost all existing computational analyses of the perception of structure from motion is that moving elements on the retina projectively correspond to identifiable moving points in three-dimensional space. The present investigation was designed to determine the psychological validity of this assumption in several different contexts. The results demonstrate that the ability of human observers to perceive structure from motion is much more general than would be reasonable to expect on the basis of existing theory. Observers can experience a compelling kinetic depth effect even when the pattern of optical motion is contaminated by large amounts of visual noise (e.g., where the signal to noise ratio is less than 0.15). Moreover, the optical deformations of shading, texture, or self-occluding contours, which would be treated as noise by existing computational models, are analyzed by human observers as perceptually salient sources of information about an object's three-dimensional form. These results suggest that the modular analyses of visual information that currently dominate the literature will have to be modified if they are to account for the high level of generality exhibited by human observers.

Attention↗
PubMed2000

Different effects of nabilone and cannabidiol on binocular depth inversion in Man.

The physiological and pathophysiological roles of the central nervous endogenous cannabinoid system are not completely understood, but still represent a challenge in basic neurobiological, cognitive, and psychiatric research. The system has been implicated in the pathogenesis of schizophrenia. Binocular depth inversion, an illusion of visual perception, provides a model of impaired perception during psychotic states. Using this model the effects of nabilone, a psychoactive synthetic 9-trans-ketocannabinoid, and of cannabidiol, the main natural component of herbal cannabis, and a combined application of both substances on binocular depth inversion and behavioural states were investigated in nine healthy male volunteers. The time course of the effects of both substances on binocular depth inversion was analysed after oral administration using three different groups of natural stimuli. A significant impairment of binocular depth perception was found when nabilone was administered, but combined application with cannabidiol revealed somewhat reduced effects on binocular depth inversion. The influence of psychoactive cannabinoids on this perceptual model and the role of the endogenous cannabinoid system in visual information processing are discussed.

Adult↗