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Results for “Distance Perception”

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PubMed1996

Horizontal and vertical distance perception: the discorded-orientation theory.

We sought the conditions where the horizontal-vertical illusion (HVI) takes place outdoors in an open field. Longitudinal distance from a subject to a building wall was adjusted to appear equal to the vertical or horizontal distance on the wall. To examine validity of previous theories (physiology, frame, depth, and gravity theories), boundary of visual field (ellipse and circle), bodily orientation (upright and lying), and orientation of visual objects (normal, 90 degrees-tilted, and inverse) were manipulated in eight experiments. These three independent variables affected the HVI effects, but their effects were not explained by the previous theories. We therefore proposed a model on the basis of discord among the retinal, visual, and gravitational orientations. We also found that longitudinal distance was adjusted as being consistently larger than the standard distance. This result was explained by the reduction of cues to distance and the HVI effect.

Attention↗
PubMed1985

Distance perception with holographically reconstructed objects.

It has been assumed that a holographically reconstructed object is seen as though it is the actual object, including that it is seen at the distance of the actual object when it was holographed. A psychophysical experiment was carried out with seven subjects to test this assumption. The results clearly show that the perceived distances of holographically reconstructed objects are not equivalent to the perceived distances of actual objects. Thus a fundamental assumption in holography has not been supported by experimental data.

Distance Perception↗
PubMed2000

Reaching measures of monocular distance perception: forward versus side-to-side head movements and haptic feedback.

We investigated whether forward or side-to-side head movements yielded more accurate and precise monocular egocentric distance information, as shown by performance in a reaching task. Observers wore a head-mounted camera and display to isolate the optic flow generated by their head movements and had to reach to align a stylus directly under a target surface. Performance in the two head movement conditions was also tested with normal monocular vision. We tested performance in the two head movement conditions when the observers were given haptic feedback and compared performance when haptic feedback was removed. Performance was both more accurate and more precise in the forward head movement condition than in the side-to-side head movement condition. Performance in the side-to-side condition also deteriorated more after the removal of haptic feedback than did performance in the forward head movement condition. In the normal monocular condition, performance was comparable for the two head movement conditions. The implications for enucleated patients are discussed.

Distance Perception↗
PubMed2003

Distance perception for points at equiconvergence and equidistance loci.

Subjects viewed luminescent targets placed at an equidistance (ED) locus or on a comparable equiconvergence locus, the Vieth-Müller circle (VMC). In darkness, subjects moved the index finger to the apparent distance of the visible target. This was repeated at leftward eccentricities of 0 degrees (straight ahead), 15 degrees, 22.5 degrees, 30 degrees, 37.5 degrees, and 45 degrees. Contrary to theoretical expectations, apparent distance to points on the VMC did not describe an equidistance locus, but diminished significantly with increasing eccentricity, whereas ED settings increased slightly but significantly. Binocular and monocular groups performed equivalently. Veridicality of results appears to be the outcome of an accommodation-convergence conflict with a dominant role for accommodation.

Accommodation, Ocular↗
PubMed2003

Modification of depth and distance perception caused by long-term wearing of left-right reversing spectacles.

For 35 to 39 days, four observers wore continuously left-right reversing spectacles which pseudoscopically reverse the order of binocular disparity and direction of convergence. In three tests, we investigated how the visual system copes with the transformation of depth and distance information due to the reversing spectacles. In stereogram observation, after a few days of wearing the spectacles. the observers sometimes perceived a depth order which was opposite to the depth order that they had perceived in the pre-spectacle-wearing period. Monocular depth cues contributed more to depth perception in the spectacle-wearing period than they did in the pre-spectacle-wearing period. While the perceived distance significantly decreased during the spectacle-wearing period, we found no evidence of adaptive change in distance perception. The results indicate that the visual system adapts itself to the transformed situation by not only changing the processing of disparity but also by changing the relative efficiency of each cue in determining apparent depth.

Adaptation, Physiological↗
PubMed1994

How accurate is size and distance perception for very far terrestrial objects? Function and causality.

This study investigated absolute estimation of size and distance for natural and artificial objects at viewing distances of 1.1-15.3 km (Experiments 1 and 2) and 0.4-5.0 m (Experiment 3). The main results were that, regardless of distance range, size and distance estimates (S' and D') were related to objective size and distance (S and D), respectively, by a power function with an exponent of unity, but great individual differences in exponent were obtained for the far objects. The ratio S'/D' was reasonably represented by S'/D' = K theta n and S'/D' = tan(a theta +b), rather than S'/D' = tan theta, where theta is the visual angle. Partial correlations were obtained to examine whether (1) apparent size is determined by taking apparent distance into account or (2) both apparent size and apparent distance are determined directly by external stimuli. The combined data for the far objects and the data for the close objects showed that there were high correlations between S and S' and between D and D' and a low correlation between D' and S'. The data of Experiment 2 showed that both D' and S' were highly correlated with S, D, and theta, and there was a high positive correlation between D' and S'. It was suggested that the direct-perception model is valid under some situations, but the taking-into-account model is not supported in any set of data.

Distance Perception↗
PubMed2006

Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?

The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there is a trend to overconstancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer's task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, underconstancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe underconstancy, and beyond this age, with mild underconstancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly overconstancy) to underconstancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of underconstancy that occurs in larger distances, where adults presented lower levels of underconstancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception.

Adolescent↗
PubMed2002

Absolute distance perception during in-depth head movement: calibrating optic flow with extra-retinal information.

We investigated the ability of monocular human observer to scale absolute distance during sagittal head motion in the presence of pure optic flow information. Subjects were presented at eye-level computer-generated spheres (covered with randomly distributed dots) placed at several distances. We compared the condition of self-motion (SM) versus object-motion (OM) using equivalent optic flow field. When the amplitude of head movement was relatively constant, subjects estimated absolute distance rather accurately in both the SM and OM conditions. However, when the amplitude changed on a trial-to-trial basis, subjects' performance deteriorated only in the OM condition. We found that distance judgment in OM condition correlated strongly with optic flow divergence, and that non-visual cues served as important factors for scaling distances in SM condition. Absolute distance also seemed to be better scaled with sagittal head movement when compared with lateral head translation.

Adolescent↗
PubMed1998

Relative size perception at a distance is best at eye level.

Relative size judgments were collected for two objects at 30.5 m and 23.8 from the observer in order to assess how performance depends on the relationship between the size of the objects and the eye level of the observer. In three experiments in an indoor hallway and in one experiment outdoors, accuracy was higher for objects in the neighborhood of eye level. We consider these results in the light of two hypotheses. One proposes that observers localize the horizon as a reference for judging relative size, and the other proposes that observers perceive the general neighborhood of the horizon and then employ a height-in-visual-field heuristic. The finding that relative size judgments are best around the horizon implies that information that is independent of distance perception is used in perceiving size.

Analysis of Variance↗
PubMed2001

Neuronal population codes and the perception of object distance in weakly electric fish.

Weakly electric fish use an electric sense to navigate and capture prey in the dark. Objects in the surroundings of the fish produce distortions in their self-generated electric field; these distortions form a two-dimensional Gaussian-like electric image on the skin surface. To determine the distance of an object, the peak amplitude and width of its electric image must be estimated. These sensory features are encoded by a neuronal population in the early stages of the electrosensory pathway, but are not represented with classic bell-shaped neuronal tuning curves. In contrast, bell-shaped tuning curves do characterize the neuronal responses to the location of the electric image on the body surface, such that parallel two-dimensional maps of this feature are formed. In the case of such two-dimensional maps, theoretical results suggest that the width of neural tuning should have no effect on the accuracy of a population code. Here we show that although the spatial scale of the electrosensory maps does not affect the accuracy of encoding the body surface location of the electric image, maps with narrower tuning are better for estimating image width and those with wider tuning are better for estimating image amplitude. We quantitatively evaluate a two-step algorithm for distance perception involving the sequential estimation of peak amplitude and width of the electric image. This algorithm is best implemented by two neural maps with different tuning widths. These results suggest that multiple maps of sensory features may be specialized with different tuning widths, for encoding additional sensory features that are not explicitly mapped.

Algorithms↗
PubMed1991

Gender differences in apparent motion perception.

Distance disparity is a strong cue to element correspondence in apparent motion. Using a 2-AFC paradigm we have previously shown that shape similarity also plays a role. We now demonstrate a small gender difference in these effects: women are more sensitive to distance disparity, whereas men are more sensitive to differences in shape. Furthermore, in the competing presence of a shape cue, women's sensitivity to distance decreases while men's sensitivity is unaffected. These observations may be related to putative gender differences in the 'form' and 'motion-spatial relations' cortical pathways.

Adult↗
PubMed1984

Binocular cues in the perception of distance of a point source of light.

The ability to make egocentric distance estimates of a single point source of light, seen in darkness and without the cues of changing size and luminance, was investigated in sixteen observers. The attenuation required to maintain constant luminance, when the target was viewed from different distances, was shown to follow the inverse square law providing the angle subtended by the light was less than 20 s arc. Distance changes were also simulated by means of a split mirror which produced vergence cues, or by test lenses to provide accommodation cues. Over the range 0.5 to 9.2 m distance estimates were surprisingly accurate, although there was some overestimation of near and underestimation of far distances. Most observers made good judgements when only convergence cues were varied, whereas no observers made consistently good judgements when only accommodation cues were varied. The difficulties are discussed in terms of the accommodation-convergence link. When distance was simulated by changing convergence and accommodation cues, estimates were not as good as when real distance was changed. Since good estimates were made with brief target exposures, these judgements were not based on subsequent convergence or accommodation changes. It is suggested that the metric or reference against which the apparently absolute judgements were made was the efferent demand signal associated with a 'resting' position of convergence in darkness.

Accommodation, Ocular↗