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PubMed1989

[Computer-assisted determination of parameters of depth perception: studies with the 3-rod device].

Psychophysical determination of the thresholds of stereoscopic vision takes about 20 min. During this procedure, you may have the feeling that the thresholds are shifting. To verify this phenomenon, the thresholds must be determined in a period shorter than 20 min, e.g., 4-6 min. This is one of the reasons we constructed a computerized machine to detect the stereoscopic thresholds. The heart of this device is a micrometric screw driven by a stepping motor that moves the central rod of the three-rod apparatus. This motor is controlled by a microcomputer with a basic program. A special program has been designed that functions in a manner similar to that of the Octopus perimeter and detects the thresholds with in a few steps. It is thus possible to reduce the detection time for one threshold dramatically. The first results with this device are not only very precise, but also demonstrate the minute values between stereoscopic thresholds. For an observation distance of 380 mm, we were able to calculate the disparation angles down to 3 s of arc. If a number of measurements are taken, the threshold fluctuations and physiological zero position can be calculated.

Depth Perception↗
PubMed1987

Chromatic imbalance due to commonly used red-green filters reduces accuracy of stereoscopic depth perception.

This study was designed to determine the effect on stereopsis of interocular retinal chromatic and illuminance imbalance in 30 subjects with normal binocularity. A Randot 3 Circle Stereotest, viewed through polarizing glasses only, was the control condition. In each of three additional conditions, illuminance and chromatic imbalances were created by commonly used red and green filters and neutral density filters combined with the polarizing filters. The effect of each of these experimental conditions on stereopsis was determined by comparing total stereo judgement errors on the Randot Circle Stereotest for each condition to the control condition. Total average flux through the filter combinations was held constant by adjusting the luminance level of light reflected from the target. The chromatic imbalance created by the red-green filters significantly increased the number of stereo judgment errors (37%, p less than 0.05). However, illuminance imbalance (0.2 log units) of the magnitude created by the red-green filters did not significantly increase the number of errors (2.9%, p less than 0.65). Finally, the combined illuminance and chromatic imbalance created by the red-green filters significantly increased the error frequency (46%, p less than 0.05). The chromatic imbalance caused by red-green glasses significantly degrades stereopsis, whereas the illuminance imbalance caused by these filters has no significant effect on stereopsis.

Adolescent↗
PubMed2002

A pilot study. Depth perception and near stereoacuity: is it related to academic performance in young children?

PURPOSE: A study of the relationship between an overall measure of visual function at near, specifically stereoacuity, and academic performance in kindergarten through second grade was conducted. METHOD: One hundred seventeen children (mean age = 7.33 +/-0.97 years) from a middle class, suburban, elementary school participated in this masked investigation. The Randot 2 stereotest was used to measure stereoacuity at 40 cm. The relationship between stereoacuity and teachers' personal ratings of academic ability was analyzed because teachers' grades are a primary means of assessing school performance. The children's regular classroom teachers rated the children with respect to reading, mathematics, and writing ability. Children in the second grade (n = 47) were also rated on spelling ability. Only experienced teachers were included in the investigation and the validity of the teachers' rating was substantiated by significant correlations with standardized test scores. Teachers were masked to performance on the stereotest. RESULTS: Performance on the Randot was found to be "statistically significantly" (p=<0.05) and "medically-clinically significantly" related to standardized reading test scores (p=0.033) and teachers' personal ratings of reading (p<0.001), mathematics (p<0.001), writing (p<0.001) and spelling (p=0.048) ability. CONCLUSION: Good visual function at near, particularly good stereoacuity, is significantly correlated to academic performance.

Achievement↗
PubMed1999

Size-disparity correlation in human binocular depth perception.

To use the small horizontal disparities between images projected to the eyes for the recovery of three-dimensional information, our visual system must first identify which feature in one eye's image corresponds with which in the other. The earliest level of disparity processing in primates (V1) contains cells that are spatial-frequency tuned. If such cells have a disparity range that covers only a single period of their mean tuning frequency, there will always be exactly one potential match within this range. Here, this 'size-disparity' hypothesis was tested by measuring the contrast sensitivity of stereopsis as a function of disparity for single bandpass-filtered items. It was found that thresholds were low and relatively constant up to disparities an order of magnitude larger than is predicted by this constraint. Furthermore, peak sensitivity was relatively independent of spatial frequency. A control experiment showed that binocular correlation of the carrier is necessary for this task. In a third experiment, the maximum disparity that supports threshold performance was compared for an isolated bandpass item and bandpass-filtered noise. This limit was found to be five times larger for the isolated stimuli. In summary, these findings show that the initial stage of disparity detection is not limited by the size-disparity constraint. For stimuli with multiple false targets, however, processes subsequent to this stage reduce the disparity range over which the correspondence problem can be solved.

Depth Perception↗
PubMed1984

Shape and depth perception from parallel projections of three-dimensional motion.

Parallel projections of dots on the surface of a transparent sphere rotating about a vertical axis provide strong impressions of depth and spherical shape. The hypothesis was tested that these impressions are the result of three perceptual heuristics: (a) The sinusoidal projected velocity function of each dot in the horizontal dimension tends to be perceived as a rotary motion in depth; (b) the projected velocity gradient in the vertical dimension is perceived as curvature in depth; and (c) the simultaneously visible fields of dots moving in opposite directions are perceived as surfaces separated in depth. When each factor was varied independently, all three significantly affected judgments of spherical shape and depth. Similar results were obtained with cylinders. The first factor was more important for shape judgments; the second was generally more important for depth judgments. These results, together with those of earlier studies in which these factors led to similar effects for different stimuli and transformations, suggest that these are general principles applicable to the perception of structure from both rigid and nonrigid motion.

Depth Perception↗
PubMed1991

Pictorial and motion-based information for depth perception.

When computer-generated objects approached the viewpoint in midair, a large far object appeared to be nearer than a small near object and appeared to hit the viewpoint before the small object, which was specified by time-to-contact information to arrive sooner. These judgements were consistent with relative size and occurred even when motion-based information was potentially above threshold. The effects of relative size persisted with higher resolution animated films of approaching objects, were weakened by ground-intercept information, and were not as robust with laterally translating objects. Although it is often asserted that the kinds of information that have traditionally been called static depth cues are superseded by motion-based depth information, this article attempts to show that the reverse also can occur in distance perception, as has been shown in form perception.

Adult↗
PubMed1996

Interactions between self-motion and depth perception in the processing of optic flow.

Moving and acting in a 3D environment requires the perception of its 3D structure. Vision is known to play a crucial role in the control of self-motion, particularly through the changes in the retinal image subsequent to movements of the observer. Reciprocally, signals related to self-motion can also influence our visual perception of 3D space. These interactions between 3D visual perception and self-motion, as demonstrated behaviourally, are now better understood thanks to the development of computational models for processing moving images. They also bear a particular interest in the context of the recent intensive exploration of the inferior parietal lobe (IPL) by neurophysiologists. The IPL is now firmly established as one site of interaction between 3D visual perception and motor control. The parallel between behaviour and neurophysiology leads to a set of crucial, yet unanswered, questions.

Humans↗
PubMed2004

Disruption of eye movements by ethanol intoxication affects perception of depth from motion parallax.

Motion parallax, the ability to recover depth from retinal motion generated by observer translation, is important for visual depth perception. Recent work indicates that the perception of depth from motion parallax relies on the slow eye movement system. It is well known that ethanol intoxication reduces the gain of this system, and this produces the horizontal gaze nystagmus that law enforcement's field sobriety test is intended to reveal. The current study demonstrates that because of its influence on the slow eye movement system, ethanol intoxication impairs the perception of depth from motion parallax. Thresholds in a motion parallax task were significantly increased by acute ethanol intoxication, whereas thresholds for an identical test relying on binocular disparity were unaffected. Perhaps a failure of motion parallax plays a role in alcohol-related driving accidents; because of the effects of alcohol on eye movements, intoxicated drivers may have inaccurate or inadequate information for judging the relative depth of obstacles from motion parallax.

Adult↗
PubMed2006

Infants' perception of depth from cast shadows.

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocular-viewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.

Depth Perception↗
PubMed2003

Perception of depth from shading in infant chimpanzees ( Pan troglodytes).

We investigated the ability to perceive depth from shading, one of the pictorial depth cues, in three chimpanzee infants aged 4-10 months old, using a preferential reaching task commonly used to study pictorial depth perception in human infants. The chimpanzee infants reached significantly more to three-dimensional toys than to pictures thereof and more to the three-dimensional convex than to the concave. Furthermore, two of the three infants reached significantly more to the photographic convex than to the photographic concave. These infants also looked longer at the photographic convex than the concave. Our results suggest that chimpanzees perceive, at least as early as the latter half of the first year of life, pictorial depth defined by shading information. Photographic convexes contain richer information about pictorial depth (e.g., attached shadow, cast shadow, highlighted area, and global difference in brightness) than simple computer-graphic graded patterns. These cues together might facilitate the infants' perception of depth from shading.

Age Factors↗