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Results for “DEPTH PERCEPTION”

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At least 163 records · Page 9Linked to original sources
PubMed2000

Vergence provides veridical depth perception from horizontal retinal image disparities.

One useful source of depth information available to the human nervous system is present in the horizontal disparities that exist between the two retinal images (stereoscopic depth). The relationship between horizontal disparity and depth varies with viewing distance so that an interpreting signal is required if disparities are to yield useful information. One potentially useful interpreting signal is available from ocular vergence. A number of studies have concluded, however, that a vergence signal does not provide veridical stereoscopic depth. All of these studies required observers to make a range of judgements under conditions of uncertainty (often using random dot stimuli) and we suggest that the lack of veridicality arose because of a contraction bias: a general tendency to bias judgements towards the centre of the range of possible responses. We re-examined the role of ocular vergence in the maintenance of stereoscopic depth constancy for real three-dimensional objects. Our results question the conclusions reached by previous studies and suggest that vergence can provide a veridical interpretation of stereoscopic depth. Our results indicate that horizontal retinal image disparities are not interpreted by a 'higher order' signal (i.e. the 'perceived distance' of the fixation point). The results of the experiment have significant implications for models of depth processing from disparity.

Adolescent↗
PubMed1973

Disparity detectors in human depth perception: evidence for directional selectivity.

Viewing a target moving in depth depresses visual sensitivity to depth when test and adapting stimuli simulate motion along closed paths with the same directions of rotation. However, for opposite directions of rotation, sensitivity is either unaffected or increased. This points to two classes of disparity detectors. Either eye's input to a single class of disparity detector consists of the physiological responses to a single direction of horizontal movement.

Adaptation, Ocular↗
PubMed2005

[The effect of location of a highlight in a shaded circle on depth perception].

Two experiments were performed to examine how the apparent depth of a shaded circle on a plane was affected by the direction and the distance of a highlight in the shaded area from the center of the circle. Fourteen undergraduates were asked to rate the concentrically shaded circle according to the apparent depth using the method of magnitude estimation. Experiment I showed that the rating was the highest in the upper-left, upper-right, and top conditions of the direction and the lowest in the bottom condition. Experiment 2 showed that the rating was the highest when the highlight was located at a third of the diameter of the circle apart from the center and the lowest when the highlight was on the edge of the circle or in the center. On the whole, the results support Ramachandran's "Assumption of Light From Above", which states that humans perceive a circle shaded bright in the top and dark in the bottom as convex due to their long experience on the earth since their birth.

Depth Perception↗
PubMed1964

BINOCULAR DEPTH PERCEPTION WITHOUT FAMILIARITY CUES.

The reported phenomena were obtained through the use of special techniques. (i) All monocular depth and familiarity cues were removed from the stimuli (through the use of randomdot stereo patterns). (ii) The statistical and topological properties of the stimuli were precisely known (since they were generated according to a specific computer program). (iii) Convergence motions of the eye and proprioceptive cues were eliminated (through the use of tachistoscopic illumination). (iv) The time of presentation was under control (through erasure of the persistent afterimages). Under these conditions stereopsis could be studied in its purest form. It was shown that depth can be perceived in the absence of monocular depth and familiarity cues and of all binocular depth cues except for disparity. These findings have important implications for some existing theories of stereopsis and open up areas for further research. Some phenomena based on stereo erasure are reported here for the first time. It has been demonstrated that the perception of ambiguous depth organizations can be influenced, even subliminally, by a preceding unambiguous stimulus. Perhaps the most interesting result is the finding that the correspondence of objects and patterns in the two retinal projections can be established without actual recognition of the objects and patterns. This pattern matching is based on some relatively simple processes of finding connected clusters formed by adjacent points of similar brightness, and the processes seem to be amenable to rigorous analysis.

Biomedical Research↗
PubMed1993

A perturbation analysis of depth perception from combinations of texture and motion cues.

We examined how depth information from two different cue types (object motion and texture gradient) is integrated into a single estimate in human vision. Two critical assumptions of a recent model of depth cue combination (termed modified weak fusion) were tested. The first assumption is that the overall depth estimate is a weighted linear combination of the estimates derived from the individual cues, after initial processing needed to bring them to a common format. The second assumption is that the weight assigned to a cue reflects the apparent reliability of that cue in a particular scene. By this account, the depth combination rule is linear and dynamic, changing in a predictable fashion in response to the particular scene and viewing conditions. A novel procedure was used to measure the weights assigned to the texture and motion cues across experimental conditions. This procedure uses a type of perturbation analysis. The results are consistent with the weighted linear combination rule. In addition, when either cue is corrupted by added noise, the weighted linear combination rule shifts in favor of the uncontaminated cue.

Cues↗
PubMed2001

The effect of videoconferencing on the depth perception of observers.

The ability of the human eye to perceive depth was measured using a specially designed instrument. Visual acuity and both monocular and binocular stereoacuity were measured when viewing the instrument directly and via a videoconferencing link. Ten subjects with an average age of 32.5 years (range 24-50) took part in the study. The group mean visual acuity using both eyes under normal test conditions was -0.04 logMAR (Snellen 6/5) compared with 0.18 logMAR (Snellen 6/10) for the video-link. The mean stereoacuity using both eyes was 37" (SD 18") under normal test conditions. When a videoconferencing link was used, the mean stereoacuity fell to 1218" (SD 1203") using one eye and to 1651" (SD 1419") using both eyes. The ability to perceive depth remotely via a video-link was significantly decreased compared with normal test conditions.

Adult↗