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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources

PubMed1984

A counterexample to the rigidity assumption in the visual perception of structure from motion.

It has been proposed that the human visual system prefers perceptions of objects that are rigid or undergo minimum form change. A counterexample is presented in which a rigid two-dimensional figure rotating in the frontal plane is perceived as a distorting three-dimensional shape. It is argued that this perception results from the stimulation of automatic processes for perceiving size change, and that these processes are not subject to a general rigidity assumption.

Depth Perception↗

PubMed1994

Stereoscopic perception with brief exposures.

In this report we describe the results of an experiment in which we demonstrated that a powerful and compelling stereoscopic experience is elicited with very brief (< 1 msec) stimulus durations. The observers were highly successful in recognizing briefly flashed, stereoscopic, random-dot surfaces in the absence of monocular contours. The results are shown to be closely related to the range of depths for any stimulus form; however, the recognition thresholds were nonmonotonic as a function of disparity. Previous investigators have disagreed about the existence of a temporal threshold for stereopsis. We believe that prior findings suggesting that stereopsis cannot occur at short exposure durations are probably due to inadequate control of fixation disparity. Therefore, there is poor dichoptic image registration when a stereoscopic stimulus is presented. The present results also raise difficulties for any theory of stereopsis that requires eye movements.

Adult↗

PubMed2001

Effect of geometric field of view on stereoscopic spatial judgments.

Within a stereoscopic display the field of view (FOV) was held constant at 13.86 degrees while the geometric field of view (GFOV) was varied across four levels: 0 degrees (parallel), 13.86 degrees (veridical), 50 degrees and 100 degrees. Participants performed a distance-matching task where they adjusted the distance of a standard track from the centre of the display to match the distance of a target track from the same point. The results indicated that while the least error occurred in the veridical GFOV condition, small variations of GFOV away from the veridical have little effect. Large differences between FOV and GFOV (36 degrees and 86 degrees) increased errors markedly. A trend toward better performance in the veridical GFOV condition relative to the parallel GFOV condition suggests that the use of linear perspective information in a stereoscopic display may facilitate more accurate spatial perception. Actual or potential applications of this work include stereoscopic display design in aviation and non-aviation settings.

Adult↗

PubMed2001

Veridicality of three-dimensional shape perception predicted from amplitude spectra of natural textures.

We show that the amplitude spectrum of a texture pattern, regardless of its phase spectrum, can be used to predict whether the pattern will convey the veridical three-dimensional (3-D) shape of the surface on which it lies. Patterns from the Brodatz collection of natural textures were overlaid on a flat surface that was then corrugated in depth and projected in perspective. Perceived ordinal shapes, reconstructed from a series of local relative depth judgments, showed that only about a third of the patterns conveyed veridical shape. The phase structure of each pattern was then randomized. Simulated concavities and convexities were presented for both the Brodatz and the phase-randomized patterns in a global shape identification task. The concordance between the shapes perceived from the Brodatz patterns and their phase-randomized versions was 80-88%, showing that the capacity for a pattern to correctly convey concavities and convexities is independent of phase information and that the amplitude spectrum contains all the information required to determine whether a pattern will convey veridical 3-D shape. A measure of the discrete oriented energy centered on the axis of maximum curvature was successful in identifying textures that convey veridical shape.

Contrast Sensitivity↗

PubMed1981

Volume discrimination learning in golden hamsters: effects of the structure of complex rearing cages.

Golden hamsters (Mesocricetus auratus) were reared from birth to adulthood in a spatially diversified situation (EG); their performances were compared with those of other hamsters housed in standard laboratory cages (SG). The task was to discriminate between 2 cubic volumes of different sizes followed by various test situations designed to define the respective parts played by the 3 spatial dimensions during perception. The results show that surfaces of volumes were mainly taken into account by EG subjects whereas width, alone, was used by the SG animals.

Animals↗

PubMed1997

Spatial properties of shear disparity processing.

We investigated whether vertical-shear disparity was extracted from the whole visual field or from a more local area and how global estimates of vertical disparity are derived. We also investigated the role of cyclovergence in processing shear disparity. Random-dot stereoscopic displays in various configurations were presented with horizontal-shear disparity, vertical-shear disparity or same-sign horizontal- and vertical-shear (rotation) disparity. Vertical-shear disparity introduced into only the right half of a 60 deg-wide display produced perceived inclination of the whole display when the center of shear was on the fovea, but did not produce inclination, either of the whole display or of a local area when the centre of shear was in an eccentric retinal position. A display containing dots with vertical-shear disparity mixed with dots with zero-disparity produced one inclined surface. Horizontal-shear disparity always produced inclination confined to the local area of disparity. Rotation disparity produced no inclination when introduced into the whole display, but when introduced with zero-disparity dots. It produced an inclined plane distinct from the plane defined by the zero-disparity dots. These results could be attributed to cyclovergence, which we therefore eliminated in our last experiment. We conclude that the perception of surface inclination is based on the difference between local horizontal-shear disparity and global vertical-shear disparity averaged over the whole visual field.

Depth Perception↗

PubMed1996

The visual perception of three-dimensional length.

A set of 4 experiments evaluated observers' sensitivity to three-dimensional (3-D) length, using both discrimination and adjustment paradigms with computer-generated optical patterns and real objects viewed directly in a natural environment. Although observers were highly sensitive to small differences in two-dimensional length for line segments presented in the frontoparallel plane, their discrimination thresholds increased by an order of magnitude when the line segments were presented at random orientations in 3-D space. There were also large failures of constancy, such that the perception of 3-D length varied systematically with viewing distance, even under full-cue conditions.

Computer-Aided Design↗

PubMed1981

[Visual acuity and binocular function in cases of bilateral pseudophakia (author's transl)].

Of 37 patients with bilateral pseudopakia, 33 had a visual acuity of at least 0.3 in the better eye and 26 at least 0.3 in the eye with poorer vision. Ten out of 17 patients achieved stereopsis of 100 angle-seconds and better. Normal perception of space-body relationships is rapidly regained after operation and patients are spared the trouble of getting accustomed to cataract lenses. Useful binocular function can be achieved.

Aged↗

PubMed1986

Multiple 3-D interpretations in a classic stereokinetic effect.

It is known that a flat ellipse rotating in the frontoparallel plane sooner or later appears as a rigid circular disc tilting in 3-D space. An experiment is reported in which prolonged exposure to the same flat pattern produces a second previously unnoticed 3-D percept: an elongated egg slanted in 3-D space, which points towards the observer and the end parts of which describe a circular trajectory in the frontal plane. It is shown that the achievement of this alternative percept is not affected by the particular shape of the ellipse, although the time needed to reach it increases with an ellipse with a 2:3 axis ratio.

Depth Perception↗

PubMed2005

Perceptual grouping in pigeons.

Animal studies reveal that many species perceive partially occluded objects in the same way as do humans. Pigeons have been a notable exception. We re-investigated this anomaly of pigeon perception using a different approach from previous studies. With our method, we show that pigeons perceive occluded objects in the same manner as do other species. In addition, we report that pigeons can recognize perceptually transparent surfaces when the effect is induced by the same perceptual mechanisms as occlusion. These results give behavioral evidence that the perception of both occlusion and transparency is a common visual function shared by pigeons and humans, despite the structural differences between their visual systems.

Animals↗

PubMed2006

The perceived motion of a stereokinetic stimulus.

An ellipse rotating in the image plane can produce several different percepts. The two-dimensional (2D) percepts are either a rotating rigid ellipse or a constantly deforming non-rigid ellipse. The 3D percept is a rotating rigid circular disk that is tilted relative to the image plane. Stimuli that generate 3D percepts based on purely 2D rotational motion are known as stereokinetic stimuli. We examined the 3D percepts generated by the rotating ellipse stimulus. In theory, the motion of the 3D percept cannot be reliably inferred based on the 2D stimulus. When we quantitatively estimated observers' perceived motion, however, we found that the perceived motion was nearly identical across observers. These results suggest that all observers had similar 3D percepts. We assumed that given the 2D rotating ellipse stimulus the visual system generates a rigid 3D percept that is as slow and smooth as possible. The percepts predicted by these assumptions closely matched the experimental data. These findings suggest that perceptual ambiguity in stereokinetic stimuli is resolved using slow and smooth motion assumptions.

Depth Perception↗

PubMed1984

Detection of three-dimensional structure in moving optical patterns.

Three experiments examined parameters affecting human observers' ability to detect the global three-dimensional (3D) organization of a random-dot display corresponding to the polar projection of a rotating sphere. Results indicate that the detection of 3D structure is critically dependent on the detectability of motion, is disrupted by increased redundant information specifying the two-dimensional location of points in the display, and undergoes a rapidly increasing resistance to the disruptive effects of noise with increasing numbers of frames. These results, in conjunction with earlier findings, are inconsistent with existing theories concerning the perception of three-dimensionality in moving displays, in that they indicate a high degree of visual sensitivity to stimulus organizations with unique topological representations.

Attention↗

PubMed1991

Unity and variety in visual form.

Some stimuli are perceived as unitary patterns, and others as dual or plural patterns. Such 'unity-and-variety' phenomena are explained by various process approaches of perception, such as the global precedence hypothesis, the preattentive orientation detection assumption, and the recognition-by-components model. However, these three approaches, which will be discussed in this paper, each explain a different subset of these phenomena. It will be argued that not only these three subsets but also other unity-and-variety phenomena can be explained from just one point of view by adopting the descriptive minimum principle. This principle states that the preferred interpretation of a pattern is reflected by the simplest of all possible representations of that pattern. The highest hierarchical level in the simplest pattern-representation will be called the 'superstructure' of the pattern. The superstructure of a pattern neither refers necessarily to the largest or global pattern component, nor is assessed necessarily in a primary stage in the perception process. Yet, it will be argued that the superstructure is decisive in determining whether a shape is perceived either as unitary or as dual.

Attention↗

PubMed2006

Dynamics of the influence of segmentation cues on orientation perception.

Contextual effects abound in vision. The tilt illusion (TI) is an example-a tilted surrounding annulus causes a vertical central pattern to appear rotated away from the surround. We investigate the dynamics of this effect by presenting components of the stimulus asynchronously. At equal contrast, the largest illusion occurs when centre and surround are presented simultaneously. We vary the spatial gap between centre and surround, the relative contrast and depth and find that these segmentation cues result in a reduced TI upon simultaneous presentation, but not all other times. This reveals the dynamics of orientation and other segmentation cue interactions.

Contrast Sensitivity↗

PubMed1991

The visual perception of smoothly curved surfaces from minimal apparent motion sequences.

A series of four experiments was designed to investigate the minimal amounts of information required to perceive the structure of a smoothly curved surface from its pattern of projected motion. In Experiments 1 and 2, observers estimated the amplitudes of sinusoidally corrugated surfaces relative to their periods. Observers' judgments varied linearly with the depicted surface amplitudes, but the amount of perceived relative depth was systematically overestimated by approximately 30%. The observers' amplitude judgments were also influenced to a lesser extent by the amount of rotary displacement of a surface at each frame transition, and by increasing the length of the apparent motion sequences from two to eight frames. The latter effect of sequence length was quite small, however, accounting for less than 3% of the variance in the observers' judgments. Experiments 3 and 4 examined observers' discrimination thresholds for sinusoidally corrugated surfaces of variable amplitude and for ellipsoid surfaces of variable eccentricity. The results revealed that observers could reliably detect differences of surface structure as small as 5%. The length of the apparent motion sequences had no detectable effect on these tasks, although there were significant effects of angular displacement and surface orientation. These results are considered with respect to the analysis of affine structure from motion proposed by Todd and Bressan (1990).

Attention↗

PubMed1998

Comparative study of two-dimensional and three-dimensional vision systems for minimally invasive surgery.

BACKGROUND: The aim of this comparative study was to gain subjective and objective data to determine for which operative tasks three-dimensional (3-D) vision systems are superior to two-dimensional (2-D) systems and to demonstrate any advantages or disadvantages of 3-D systems. METHODS: A model with five standardized tasks including sewing and knotting was developed to objectively measure performance times and to count technical faults. In our training center for minimally invasive surgery, surgeons involved in basic and advanced laparoscopic courses trained using both 2-D and 3-D vision systems. They subsequently completed analog scale questionnaires to record a subjective impression of comparative ease of operation tasks under 2-D and 3-D vision and to identify perceived deficiencies in the 3-D system. RESULTS: Compared to 2-D vision, the objective performance time was significantly shorter and significantly less mistakes were made using 3-D vision. All operative tasks were subjectively judged significantly easier under 3-D vision. CONCLUSIONS: Users with a normal capability for spatial perception can perform standard tasks more quickly and safely using 3-D vision, and a greater benefit is apparent for more complicated surgical maneuvers.

Depth Perception↗

PubMed2004

Effects of spatial arrangement of visual stimulus on inverted self-motion perception induced by the foreground motion: examination of OKN-suppression hypothesis.

Our previous study revealed that a slowly moving foreground, which is presented in front of a fast-moving orthogonal background, can induce self-motion perception in the same direction as its motion (inverted vection; Vis. Res. 40 (2000) 2915). The present study shows that inverted vection becomes stronger in the conditions where the foreground stimulus is presented in the central area of observer's visual field and the observer's eyes converge on the same depth plane. These stimulus conditions are consistent with the one where the foreground can induce observer's optokinetic nystagmus more effectively, and therefore, the results of this study support our hypothesis in that mis-registered eye-movement information caused by the suppression of optokinetic nystagmus induced by the foreground motion is a critical factor in perceiving inverted vection.

Adult↗

PubMed2002

The role of the cyclopean eye in vision: sometimes inappropriate, always irrelevant.

During binocular fixation, the eyes usually point in different directions, and yet, each object is judged to lie in a single direction. It is commonly believed that a particular location in the head serves as the origin for such directional judgments. This location is known as the cyclopean eye. We argue here that observers can judge visually perceived directions from angular information alone, and do not require positional information supplied by a cyclopean eye. We show that experimental findings reported as evidence for the cyclopean concept can also be explained solely by angular information without the need for a cyclopean eye. Recent findings concerning binocular shape perception and the cyclopean illusion demonstrate that binocular perception is incompatible with vision from a single vantage point. The concept of the cyclopean eye is sometimes inappropriate and always irrelevant as far as vision is concerned.

Depth Perception↗