Visual Space Perception Research Articles

Visual Distance Estimation in Static Compared to Moving Virtual Scenes

Visual motion is used to control direction and speed of self-motion and time-to-contact with an obstacle. In earlier work, we found that human subjects can discriminate between the distances of different visually simulated self-motions in a virtual scene. Distance indication in terms of an exocentric interval adjustment task, however, revealed linear correlation between perceived and indicated distances but with a profound distance underestimation. One possible explanation for this underestimation is the perception of visual space in virtual environments. Humans perceive visual space in natural scenes as curved, and distances are increasingly underestimated with increasing distance from the observer. Such spatial compression may also exist in our virtual environment. We therefore surveyed perceived visual space in a static virtual scene. We asked observers to compare two horizontal depth intervals, similar to experiments performed in natural space. Subjects had to indicate the size of one depth interval relative to a second interval. Our observers perceived visual space in the virtual environment as compressed, similar to the perception found in natural scenes. However, the nonlinear depth function we found can not explain the observed distance underestimation of visual simulated self-motions in the same environment.

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.

Influence of the Instructions on the Performance and Establishment of Memorization Strategies in Space Judgments

Studies of visual space perception have been assuming that people have an internal representation of the physical space that surrounds them. A variety of psychophysical procedures has been used in an attempt to measure the properties of visual space. The goal of the present study was to evaluate the accuracy of the mental representation and the strategies adopted to acquire and retain visuo-spatial information of a configuration as a function of two types of instructions. Thirty-eight undergraduate and graduate students participated in the study and were distributed in perceptive and mnemonic experimental conditions. The effect of the instructions (intentional and incidental) on the representation of the distances among the objects of the scene was estimated using exponents of power function, based on the reproduction of the distances among the stimuli of the scene. The results revealed that judgments made under intentional instructions were more frequently based on strategies related to the location of the stimuli, whereas judgments originating from incidental instructions were based on strategies related to the name of the stimuli. It was observed that the intentional instruction facilitated a more accurate mental representation of the observed experimental configuration, enhancing participants' performance.

Visuospatial functions in atypical parkinsonian syndromes

Objectives: Visuospatial deficits have been occasionally reported but never systematically studied in atypical parkinsonian syndromes. The interpretation of existing studies is complicated by the possible influence of motor and frontal...

Increased inattentional blindness in severe traumatic brain injury: Evidence for reduced distractibility?

Primary objective: To examine the role of selective attention and visual perception in medicating inattentional blindness in a severe traumatic brain injured sample.Research design: Cross-sectional design with age and education matched control sample.Methods and procedures: Twenty participants with severe traumatic brain injury (n = 10) and matched controls (n = 10) completed a series of tests of focused attention (Stroop test), divided attention (Trail Making Test), visual perception (Visual Object and Space Perception Battery) and two tasks of inattentional blindness.Main outcomes and results: The group with severe TBI were significantly slower on the Stroop test and TMT and displayed significantly elevated Stroop interference and TMT ratio scores. On the inattentional blindness tasks, fewer TBI participants identified a distracting stimulus.Conclusion: The results indicate severe TBI is associated with deficits to focused and divided attention with the finding of a potentially more debilitating impairment arising from reduced distractibility following severe TBI.

P.8.a.008 The utility of structural neuroimaging in the psychiatric inpatients

Radford KA, Lincoln NB. Concurrent validity of the Stroke Drivers Screening Assessment. Arch Phys Med Rehabil 2004;85:324–8.To determine the concurrent validity of the Stroke Drivers Screening Assessment (SDSA).Comparison of the SDSA with criterion standards.Subjects’ homes in the community in the United Kingdom.Ninety-three stroke patients (age range, 22–83y) who were referred for assessment of fitness to drive or who had been driving before their stroke. Participants were assessed a median of 5 months poststroke.Not applicable.Patients were assessed on the SDSA and tests of visuospatial ability (Visual Object and Space Perception [VOSP] Battery), executive abilities (Stroop Neuropsychological Screening Test, Trail-Making Test [TMT], Cognitive Estimates Test [CET]), and visual memory (Recognition Memory Tests [RMT], Verbal Descriptions of Road Signs [VDRS]).The SDSA subtests all correlated significantly with the Stroop test (P<.001) and TMT (P<.001), which suggests that they measure executive abilities and attention. The SDSA Dot Cancellation (DC) also correlated significantly with the VDRS (P<.01). The SDSA Square Matrices (SM) test correlated significantly with the VOSP cube analysis (P≤.01) and the RMT faces subtest (P<.001), which suggests that the SM test also measures visuospatial abilities and visual memory. The SDSA Road Sign Recognition (RSR) test also correlated significantly with the VOSP cube analysis (P<.05), which suggests that the RSR test also measures visuospatial abilities. Factor analysis produced a 2-factor solution with DC time, SM compass, and RSR all loading on factor 1, together with the Stroop and TMT. This factor was interpreted as “executive abilities and attention.” The RMT faces subtest and CET loaded onto a second factor.The SDSA seems to measure predominantly attention and executive abilities, which have previously been shown to be important determinants of safety to drive. This may account for the high predictive validity of the SDSA.

비쥬얼 가이더 : 몰입형 가상세계에서의 공간지각 보조도구

몰입형 가상현실 시스템에서는 실제로 가상세계가 입체적으로 가시화된다 할지라도 현실에서와 같이 정확한 거리 및 깊이 단서가 제공되지 않기 때문에, 사용자가 가상객체들과 원활한 상호작용을 하는데 많은 불편함이 있다. 본 논문에서는 이 점을 개선하기 위하여 몰입형 가상세계에서 사용자가 효과적으로 시공간지각을 할 수 있도록 지원해 주는 Visual Guider를 제안한다. Visual Guider는 사용자가 가상객체들 간의 상대적 거리 정보를 신속하고 정확하게 파악할 수 있도록 이차원 윈도우 어플리케이션에서 활용되는 눈금자 개념을 도입하여 삼차원 가상공간상에 적용한 것이다. 본 논문에서는 제안 기법을 <TEX>$CAVE^(TM)-like$</TEX> 시스템 상에서 구현된 실험용 가상공간 상에 적용하여 사용자의 위치 이동과 가상객체의 선택 및 조작에 활용한 결과를 보인다. In immersive virtual reality system, since virtual worlds do not supply users with sufficient spatial information af real world does, the users frequently experience clumsiness and roughness while manipulating virtual objects. To overcome this problem, we propose Visual Guider in this paper as a tool for enhancing user's visual space perception in immersive virtual worlds. The Visual Guider aids users to recognize exocentric distances between different scene points and egocentric distances from the observation point to other points in the scene fast and precisely. Its concept is imported from the rectangular grids frequently used in two-dimensional windows applications. We applied the proposed technique to an experimental virtual space implemented in <TEX>$CAVE^(TM)-like$</TEX> system and tested its effectiveness while users grasp and move virtual objects.

Detailed Analyses of Ganzfeld Phenomena as Perceptual Events in Stimulus-Reductive Situations

Experiment 1 reexamined in detail conscious experiences in Ganzfeld situations with homogeneous light (red, green, or blue). Subjects were instructed to report everything, including phenomena attributed to the external world (colour, brightness, space) and those of the self (somatosensory experience, body movement, and emotion). The reports were richer in the red-light condition. Naïve subjects reported a larger variety of events than sophisticated subjects. In Experiment 2 pupillary responses were recorded while the subjects were exposed to a Ganzfeld at two different levels of illumination. Pupillary size for high illumination decreased with time and then recovered to the initial level, while for low illumination it remained constant. Subjective brightness correlated with pupillary size. Experiment 3 revealed a temporal pattern of spatial events. The findings obtained are discussed in relation to the ontogenetic process of visual space perception and emotion.

Dissociation between visual perception and visually directed action in locomotion

Evidence has suggested that differences in performance exist when comparing tasks involving visually directed locomotion to those involving visual perception of space. Such evidence indicates that systematic errors apparent in visual space perception do not influence the motoric responding associated with such visual exposure. For instance, when subjects are required to verbally match distance intervals oriented in a frontal-parallel plane to those oriented in-depth when provided with static visual cues alone, a robust foreshortening effect is observed for in-depth estimates — an effect that disappears when responding via blindfolded locomotion. Our intention was to replicate this finding using a slightly different task and to examine additional conditions in which dynamic visual information and non-visual information are concurrently available. The current experiment was conducted in a large, open, outdoor environment. Subjects were required to view a target distance oriented in-depth and match that distance, first in an in-depth plane and subsequently in a frontal-parallel plane (forming a 90 deg angle). Responding occurred in one of three ways: 1) verbally positioning a target from the original viewing position using static visual information, 2) blindfolded locomotion, 3) locomotion with vision. Results demonstrated that visually perceived estimates varied as a function of orientation, with distance estimates produced in the frontal-parallel plane resulting in a substantially smaller extent than those oriented in-depth. Such a result is in agreement with other findings demonstrating a dissociation between perception and action in locomotion. For visually directed action, a strong effect of optic flow was also found. When subjects walked without vision, a consistent undershoot of the target distance was observed, whereas when subjects walked with vision, a consistent overshoot of the target distance was observed.

Perception of Shared Visual Space: Establishing Common Ground in Real and Virtual Environments

When people have visual access to the same space, judgments of this shared visual space (shared vista) can facilitate communication and collaboration. This study establishes baseline performance on a shared vista task in real environments and draws comparisons with performance in visually immersive virtual environments. Participants indicated which parts of the scene were visible to an assistant or avatar (simulated person used in virtual environments) and which parts were occluded by a nearby building. Errors increased with increasing distance between the participant and the assistant out to 15 m, and error patterns were similar between real and virtual environments. This similarity is especially interesting given recent reports that environmental geometry is perceived differently in virtual environments than in real environments.

Testbatterie für visuelle Objekt- und Raumwahrnehmung (VOSP): Normwerte für 8- bis 12-Jährige

Diagnostics of central visual perception is a relevant branch of developmental medicine and neuropsychological diagnostic efforts of morphological or functional lesions of the brain. However, no assessment battery for testing the central-visual perception in German-speaking children exists. PROBANDS AND METHOD: In 30 children, aged 8 - 12 years, the Visual Object and Space Perception Test Battery (VOSP) was applied. The group values were documented as standard values. Instructions and aims of the tests were well comprehended by the children. The VOSP is well applicable to children. Further studies examining correlation between the VOSP and clinical data are warranted.

Visual space perception and action: Introductory remarks

Vision evolved from the vital necessity to act in a dynamic environment. Following this view it is clear that perceptual processes and action planning are much more interlocked than is evident at first sight. This is especially evident in visual space perception; actions are performed in space and are guided and controlled by objects in spatial positions. Here we shortly introduce the three research camps dealing with the relationship between space perception and action: the ecological camp, the two‐visual‐systems camp, and the constructivist camp. We show that these camps emphasize and open different theoretical and empirical perspectives, but that they can be seen to complement each other. We end with an overview of the papers in this special issue.

Perception of Visual Space at the Time of Pro- and Anti-Saccades

The localization of peri-saccadically flashed objects shows two types of errors: first, a uniform shift in saccade direction, and second, a compression of visual space around the saccade target. Whereas the uniform shift occurs when the experiment is performed in complete darkness compression occurs when additional visual references are available. Thus peri-saccadic mislocalization contains motor and visual components. To distinguish between both factors we compared peri-saccadic localization errors during pro- and anti-saccades. In the case of anti-saccades, the visual cue that elicits the saccade and the actual eye movement are in opposite directions. We asked whether peri-saccadic compression can be observed with anti-saccades, and if so, whether the compression is directed toward the visual cue or follows the actual eye movement. In blocked trials, subjects performed saccades either toward a visual cue (pro-saccade) or to the mirrored position opposite to a visual cue (anti-saccade). Peri-saccadically, we flashed a thin vertical bar at one of four possible locations. Subjects had to indicate the perceived position of the bar with a mouse pointer about 500 ms after the saccade. Experiments were performed in complete darkness and with visual references. Peri-saccadic mislocalizations occurred during anti-saccades. The mislocalizations were very similar for pro- and anti-saccades in magnitude and direction. For both, pro- and anti-saccades, mislocalizations were directed toward the actual eye movement and not the visual cue.

Concurrent validity of the stroke drivers screening assessment

Radford KA, Lincoln NB. Concurrent validity of the Stroke Drivers Screening Assessment. Arch Phys Med Rehabil 2004;85:324–8. Objective To determine the concurrent validity of the Stroke Drivers Screening Assessment (SDSA). Design Comparison of the SDSA with criterion standards. Setting Subjects’ homes in the community in the United Kingdom. Participants Ninety-three stroke patients (age range, 22–83y) who were referred for assessment of fitness to drive or who had been driving before their stroke. Participants were assessed a median of 5 months poststroke. Interventions Not applicable. Main outcome measures Patients were assessed on the SDSA and tests of visuospatial ability (Visual Object and Space Perception [VOSP] Battery), executive abilities (Stroop Neuropsychological Screening Test, Trail-Making Test [TMT], Cognitive Estimates Test [CET]), and visual memory (Recognition Memory Tests [RMT], Verbal Descriptions of Road Signs [VDRS]). Results The SDSA subtests all correlated significantly with the Stroop test ( P<.001) and TMT ( P<.001), which suggests that they measure executive abilities and attention. The SDSA Dot Cancellation (DC) also correlated significantly with the VDRS ( P<.01). The SDSA Square Matrices (SM) test correlated significantly with the VOSP cube analysis ( P≤.01) and the RMT faces subtest ( P<.001), which suggests that the SM test also measures visuospatial abilities and visual memory. The SDSA Road Sign Recognition (RSR) test also correlated significantly with the VOSP cube analysis ( P<.05), which suggests that the RSR test also measures visuospatial abilities. Factor analysis produced a 2-factor solution with DC time, SM compass, and RSR all loading on factor 1, together with the Stroop and TMT. This factor was interpreted as “executive abilities and attention.” The RMT faces subtest and CET loaded onto a second factor. Conclusions The SDSA seems to measure predominantly attention and executive abilities, which have previously been shown to be important determinants of safety to drive. This may account for the high predictive validity of the SDSA.

Influence of Age, Sex, and Education on the Visual Object and Space Perception Battery (VOSP) In a Healthy Normal Elderly Population

The assessment of visual perception and cognition forms an important part of any general cognitive evaluation. We have studied the possible influence of age, sex, and education on a normal elderly Spanish population (90 healthy subjects) in performance in visual perception tasks. To evaluate visual perception and cognition, we have used the subjects performance with The Visual Object and Space Perception Battery (VOSP). The test consists of 8 subtests: 4 measure visual object perception (Incomplete Letters, Silhouettes, Object Decision, and Progressive Silhouettes) while the other 4 measure visual space perception (Dot Counting, Position Discrimination, Number Location, and Cube Analysis). The statistical procedures employed were either simple or multiple linear regression analyses (subtests with normal distribution) and Mann–Whitney tests, followed by ANOVA with Scheffe correction (subtests without normal distribution). Age and sex were found to be significant modifying factors in the Silhouettes, Object Decision, Progressive Silhouettes, Position Discrimination, and Cube Analysis subtests. Educational level was found to be a significant predictor of function for the Silhouettes and Object Decision subtests. The results of the sample were adjusted in line with the differences observed. Our study also offers preliminary normative data for the administration of the VOSP to an elderly Spanish population. The results are discussed and compared with similar studies performed in different cultural backgrounds.

Visual Processing Impairments and Decrements in Regional Brain Activity in Alzheimer’s Disease

The relationships between intermediate visual processes, involving object and space perception, and regional brain activity using positron emission tomography and single photon emission tomography were investigated in 16 patients with Alzheimer’s disease. Significant region specific correlations were found between unfamiliar face matching and cerebral activity in the left occipito-temporal region and middle/inferior temporal regions bilaterally. Letter-word identification correlated significantly with brain activity in the angular gyri and occipital association cortices bilaterally, as well as a broad region of activation in the left hemisphere temporal, parietal and occipital lobes. Additionally, a significant correlation was found between ratings of performance of instrumental activities of daily living and brain activity in occipito-temporal and middle/inferior temporal regions. The present study demonstrates that the neuropathological distribution typically seen in Alzheimer’s disease corresponds to impairments in specific aspects of intermediate visual perceptual processing, and it is related to the daily living skills of patients with Alzheimer’s disease.

Visual space perception: phenomenology and function

This article presents a brief overview of visual space perception. It begins by noting the significance of visual space perception to broader issues in philosophy and science and observes that the appreciation of visual space perception as a scientific topic is impeded by naïve realism. The second section notes the longstanding interest in the phenomenology of visual space and focuses on one issue, the dissocation between perceived location and perceived shape in visual space. The last section discusses three conceptions of how vision controls action, with special attention to the role of visual space.

Using immersive virtual reality to study visual space perception, visual control of locomotion, and visually-based navigation

Using immersive virtual reality to study visual space perception, visual control of locomotion, and visually-based navigation

Effects of prismatic adaptation on judgements of spatial extent in peripersonal and extrapersonal space

Recent research has shown that visuomotor adaptation to a lateral displacement of the visual field induces significant perceptual aftereffects in normal observers, and in right hemisphere patients with spatial neglect [Neuroreport 11 (2000) 1899; Nature 395 (1998) 166]. These findings suggest that adaptive realignment following prism exposure induces a bias in visual space perception, even in tasks that require no visually guided motor response. Given recent neurophysiological and behavioural data suggesting independent visual representations for peripersonal and extrapersonal space, here we asked whether adaptive aftereffects extend beyond participants’ immediate reaching space to stimuli presented beyond arms’ reach (i.e. in extrapersonal space). Thirty-two participants underwent adaptive realignment to 10° left- or right-displacing wedge-prisms. Before and after adaptation participants performed a visual landmark task that required estimation of the midpoint of horizontal line stimuli. There was a significant rightward shift in visual midpoint judgements following adaptation to left-deviating prisms, which was evident in both peripersonal and extrapersonal space. Paradoxically, a significant rightward shift also occurred following adaptation to right-deviating prisms, but only in extrapersonal space. We suggest that the pattern of adaptive aftereffects observed reflects the different reference frames used by participants to perform spatial judgements in peripersonal and extrapersonal space. We also propose that an underlying hemispheric asymmetry in the processing of spatial errors during adaptation may contribute to the direction of aftereffects in both normal observers, and in patients with unilateral lesions.

Range image statistics can explain the anomalous perception of length.

A long-standing puzzle in visual perception is that the apparent extent of a spatial interval (e.g., the distance between two points or the length of a line) does not simply accord with the length of the stimulus but varies as a function of orientation in the retinal image. Here, we show that this anomaly can be explained by the statistical relationship between the length of retinal projections and the length of their real-world sources. Using a laser range scanner, we acquired a database of natural images that included the three-dimensional location of every point in the scenes. An analysis of these range images showed that the average length of a physical interval in three-dimensional space changes systematically as a function of the orientation of the corresponding interval in the projected image, the variation being in good agreement with perceived length. This evidence implies that the perception of visual space is determined by the probability distribution of the possible real-world sources of retinal images.