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PubMed2005

Do panic-agoraphobics overestimate distances?

Twenty-five subjects suffering from Panic Disorder with agoraphobia (PDA) and 25 normal controls (NC) were asked to estimate distances of familiar places of their town and non-distance stimuli. PDA subjects also completed the Mobility Inventory for Agoraphobia (MIA). Subjects with PDA significantly overestimated distances as compared to NC, whereas no significant difference was found on estimates of non-distance stimuli. Within the PDA group, significant correlations were found between distance estimates and subsets of MIA concerning the ways of moving through the environment. Although with caution, given the small sample size and the preliminary character of this study, the results could be interpreted as consistent with a cognitive dysfunction associated with PDA, probably at the level of representational mechanisms of the extrapersonal space.

Adult↗
PubMed2006

Comparing distances in mental images constructed from visual experience or verbal descriptions: the impact of survey versus route perspective.

Mental images constructed after visual examination of a spatial configuration or after processing a verbal description of that configuration have been shown to share similar properties, in particular the capacity to preserve metric information contained in the configuration represented. In the present study, we investigated the properties of mental images constructed under learning conditions resulting from the combination of a visual or a verbal mode of acquisition and a survey or route perspective. Participants memorized a virtual environment (a garden containing six objects) under one of four learning conditions: (a) viewing a map of the garden (visual-survey); (b) viewing a video presentation of a journey along the path around the garden (visual-route); (c) listening to a verbal description of the map of the garden (verbal-survey); and (d) listening to a verbal description of the journey around the garden (verbal-route). The participants were then invited to compare the distances separating objects in the garden mentally. Experiment 1, where the pairs of distances to be compared had a common starting point, revealed that the frequency of correct responses was higher, and response times were shorter when participants had learned about the environment visually rather than by a verbal description. The conditions involving a survey perspective resulted in a higher frequency of correct responses and shorter response times than those involving a route perspective. Lastly, a symbolic distance effect was obtained in the first three conditions, in that the greater the difference between the two distances being compared, the higher the frequency of correct responses, and the shorter the response times. Experiment 2, where the pairs of distances had different starting points, replicated these results, although longer response times revealed that the comparison process was more costly. Taken together, these findings support the view that mental spatial representations derived from different sources and adopting different perspectives contain genuine metric properties, except when the verbal modality and the route perspective are combined during learning.

Adolescent↗
PubMed2005

The Distance Learning Courses in Occupational Medicine--20 years and onwards.

BACKGROUND: The first Distance Learning Course in Occupational Medicine was set up in 1984 at the Department of Occupational Health, University of Manchester. AIMS: This paper describes the progress of that course and developments within distance learning education in occupational health at The University of Manchester over the subsequent 20 years. It also looks at the future objectives and modes of teaching of occupational health at Manchester via distance learning. METHODS: Analysis has been undertaken of student demographics and matching between original forecasts and actual outcomes. RESULTS: Original forecasts of student uptake have been surpassed. There are indications of increases in the number of female and part-time students, and a corresponding decline in the number of general practitioners enrolling on the Advanced course. Response to developing circumstances has resulted in the Distance Learning Unit setting up additional courses. CONCLUSIONS: The farsightedness of those who predicted the need for academic training in occupational health by distance learning has been proved correct. Further evolution is essential to maintain and improve the value and success of the courses.

Education, Distance↗
PubMed1995

The temporal-distance effect in subjects with dementia of the Alzheimer type.

The efficacy of temporal-distance processing for spatial locations was evaluated in college students, elderly controls, and subjects with mild and moderate dementia of the Alzheimer type (DAT). The elderly controls showed a slightly lower level of performance than college students, but both elderly controls and college students displayed a temporal-distance effect. The mild DAT subjects performed the task accurately only at the greatest temporal distances. The moderate DAT subjects performed at chance levels for all distances. Because similar changes in the temporal-distance function have been described for humans and animals with small hippocampal or prefrontal cortex damage, there might be important hippocampal or prefrontal cortex involvement or both in early stages of Alzheimer disease.

Adult↗
PubMed1990

Distance heterophoria and tonic vergence.

It has previously been suggested that the difference between tonic vergence (TV) and distance heterophoria may relate either to proximally induced vergence or accommodative divergence. To identify which of these components was responsible for this difference, the present study compared TV and distance heterophoria in a population of 20 subjects. However, distance heterophoria was now assessed with open-loop accommodation. No significant difference was observed between these two measures. This suggests that the previously observed variations between TV and distance heterophoria (with accommodation closed-loop) were produced by accommodative divergence. However, in a subgroup of 7 subjects, measurements of TV were more convergent (greater than 2 delta) than the distance heterophoria. In these subjects, proximally induced vergence may have accounted for the difference in response.

Accommodation, Ocular↗
PubMed1993

Effects of target distance and pupil size on letter contrast sensitivity with simultaneous vision bifocal contact lenses.

Using simulated presbyopia we measured the effects of target vergence and pupil size on letter contrast sensitivity while subjects wore accurately centered simultaneous vision bifocal contact lenses. These experiments examined the increase in depth of focus provided by two bifocal contact lenses, and the effects of pupil size on near and distance vision. Monocular contrast sensitivity was assessed with three different designs of soft contact lenses. First, as a single vision control, we measured contrast sensitivity with a Bausch & Lomb, Optima 38 lens corrected for distance. We then measured contrast sensitivity with an Allergan Optical, Hydron Echelon, which is a diffractive simultaneous bifocal and a CIBA Vision, Spectrum, which is a concentric design, center-near, two-zone simultaneous vision bifocal. In general both bifocal contact lenses improved contrast sensitivity at near but decreased contrast sensitivity at distance (when compared to the single vision lens). With a fixed 3.5-mm artificial pupil, the Echelon lens had two clear peaks of sensitivity, one at distance (0.00 D) and one at near (-2.00 D), but the Spectrum lens had no clear peaks. Performance of the Spectrum lens depended on its center zone size. Near (-2.00 D) and distance (0.00 D) contrast sensitivity was measured with pupil sizes that ranged from 1 to 6 mm. The results showed that visual performance with a diffractive lens was almost independent of pupil diameter up to 3 to 4 mm but, as predicted, performance with the two-zone lens depended critically on pupil size.

Contact Lenses, Hydrophilic↗
PubMed1999

Distance education programs for advanced practice nurses: questions to ask.

This article reviews the use of distance learning in nursing education and to summarize key questions that must be addressed by programs or students considering advanced practice nursing education using distance technology. An acute care nurse practitioner program using distance learning strategies is provided as an example to illustrate delivery of a clinically based curriculum. Examples of questions to be addressed in evaluating a distance education program include: How much of the course or graduate nursing program is available on-line? What are the specific informational technologies used? How does communication occur between graduate students and faculty? How are clinical requirements of a course managed? Are there any requirements for time to be spent directly on campus? Is it necessary for the student to have a computer and Internet provider? Knowledge of the available technology and components of distance education can enhance the ability of the advanced practice nurse to evaluate better and choose educational program offerings.

Curriculum↗
PubMed2000

Cognitive distance of stairways: a multi-stairway investigation.

The present study had two major purposes. First it sought to determine to what extent in an earlier study of distance estimation in stairways (Hanyu & Itsukushima, 1995) would generalize to other types of stairway. Second, it sought to examine which hypothesis, information storage or effort, better explain the earlier results, in which people overestimated distance and traversed time estimates. We obtained four distance and time measures: distance estimate, traversal time estimate, mental walking time and actual traversal time. To measure information, we had participants rate each stairway for complexity (simple-complex) and effort (effortless-effortful) before and after the distance and time measurement tasks. The results revealed that the earlier findings (Hanyu & Itsukushima, 1995) did not fully generalize. The results also did not support either the information storage or the effort hypothesis.

Adult↗
PubMed1993

A Müller-Lyer-type illusion of egocentric distance with 3D convex and concave objects.

An illusion of egocentric distance with concave and convex objects at a distance of 135 cm is reported. When the centre of a concave object was viewed with both eyes its surface appeared nearer than the centre of the surface of a convex object at the same distance. The distortion was about two per cent of the viewing distance with right-angle objects and about five per cent with hemicylindrical objects. The distortion was slightly reduced when size cues for distance were attached to the surfaces of the objects, absent with monocular viewing, greater with convex than with concave objects, and occurred with the generally convex surface of a model human face. Possible explanations of the findings are discussed.

Defense Mechanisms↗
PubMed2005

Invariance of evoked-potential echo-responses to target strength and distance in an echolocating false killer whale.

Brain auditory evoked potentials (AEPs) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from -22 to -40 dB; the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB. The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown their intensity dependence on target strength. It is supposed that the constancy of echo-related AEP results from variation of hearing sensitivity depending on the target strength and release of echo-related responses from masking by transmitted pulses depending on the distance.

Animals↗
PubMed2002

Motor scaling by viewing distance of early visual motion signals during smooth pursuit.

The geometry of gaze stabilization during head translation requires eye movements to scale proportionally to the inverse of target distance. Such a scaling has indeed been demonstrated to exist for the translational vestibuloocular reflex (TVOR), as well as optic flow-selective translational visuomotor reflexes (e.g., ocular following, OFR). The similarities in this scaling by a neural estimate of target distance for both the TVOR and the OFR have been interpreted to suggest that the two reflexes share common premotor processing. Because the neural substrates of OFR are partly shared by those for the generation of pursuit eye movements, we wanted to know if the site of gain modulation for TVOR and OFR is also part of a major pathway for pursuit. Thus, in the present studies, we investigated in rhesus monkeys whether initial eye velocity and acceleration during the open-loop portion of step ramp pursuit scales with target distance. Specifically, with visual motion identical on the retina during tracking at different distances (12, 24, and 60 cm), we compared the first 80 ms of horizontal pursuit. We report that initial eye velocity and acceleration exhibits either no or a very small dependence on vergence angle that is at least an order of magnitude less than the corresponding dependence of the TVOR and OFR. The results suggest that the neural substrates for motor scaling by target distance remain largely distinct from the main pathway for pursuit.

Acceleration↗
PubMed2000

Detecting binocular 3D motion in static 3D noise: no effect of viewing distance.

Relative binocular disparity cannot tell us the absolute 3D shape of an object, nor the 3D trajectory of its motion, unless the visual system has independent access to how far away the object is at any moment. Indeed, as the viewing distance is changed, the same disparate retinal motions will correspond to very different real 3D trajectories. In this paper we were interested in whether binocular 3D motion detection is affected by viewing distance. A visual search task was used, in which the observer is asked to detect a target dot, moving in 3D, amidst 3D stationary distractor dots. We found that distance does not affect detection performance. Motion-in-depth is consistently harder to detect than the equivalent lateral motion, for all viewing distances. For a constant retinal motion with both lateral and motion-in-depth components, detection performance is constant despite variations in viewing distance that produce large changes in the direction of the 3D trajectory. We conclude that binocular 3D motion detection relies on retinal, not absolute, visual signals.

Distance Perception↗
PubMed2004

Long-term retention of knowledge after a distance course in medical informatics at Charles University Prague.

BACKGROUND: Distance education is instructional delivery that does not constrain the student to be physically present in the same location as the instructor. The electronic distance learning called e-learning has evolved with the development of computer technologies and electronic communication. PURPOSE: Before setting the distance way of teaching as a standard part of medical schools' curricula, the impact of number of factors on the effectiveness of this way of teaching should be considered. METHODS: A group of 38 students went through a distance course of medical informatics. The course consisted of 10 lessons. At the end of the course the students sat for a final test that contained 60 multiple-choice test questions. There was always one correct answer. Time limit for test completion was 60 minutes. After 12 months, 31 students from the original group sat for the same test. The topics of the course were not repeated in the meantime. The students were not aware that their knowledge would be tested after 1 year. RESULTS: The average retention of knowledge expressed as a percentage of the students' performance in the first test was 66.8%. The knowledge retention correlated significantly with the statement "I liked the online course more than the classroom course" and positively with the number of hours spent with the computer weekly. CONCLUSIONS: Retention of knowledge after the electronic distance course after 12 months is close to 67%. Other results indicate that we can expect better retention of knowledge from independent, responsible, and positively motivated students who can easily operate information technologies.

Computer-Assisted Instruction↗
PubMed1979

The Mandelbaum effect: evidence for an accommodative bias toward intermediate viewing distances.

Previous research has shown that ocular accommodation tends to correspond to an intermediate distance, the dark focus, in the absence of effective stimulation. The present experiments measured accommodative responses in the presence of two adequate, monocular stimuli superimposed optically at different distances. In Experiment I, observers attempted to maintain a matrix of letters in clear focus as a superimposed mesh screen was varied in distance. In experiment II, observers were instructed to focus the "easier" of two similar grating patterns that were presented over a range of distances with a constant separation of two diopters. The results of both experiments showed an accomodative response bias toward target distances near the observers' dark focus of accommodation. The implications of these findings for the theoretical resting state of accomodation and for practical problems of visual performance are discussed.

Accommodation, Ocular↗
PubMed2001

Distance perception of vehicle rear lights in fog.

Perceptual difficulty is one of the main explanations given for the behavioral modifications and high accident rate associated with driving in fog. The present study investigates how fog and the characteristics of vehicle rear lights affect distance perception. Two experiments in a fog chamber (meteorological visibility range of 5-15 m) were run under conditions simulating nighttime fog. The participants gave verbal estimates of the distance (8-28 m) of vehicles simulated by rear-light arrangements. The results revealed an average increase of 60% in the perceived distance of vehicles in fog as compared with normal visibility conditions. Distance overestimation was particularly pronounced when the vehicle had only 1 fog light instead of 2 and when the lights were close together. No effect of light height was observed. These results suggest that the perception of vehicle distance in nighttime fog could be significantly improved by the presence of 2 lights with maximal spacing. Actual or potential applications of this research include vehicle rear light design.

Accidents, Traffic↗
PubMed1999

The art of descrying distance.

How naive can one experiment be? Imagine asking observers to judge distance -- yes, literally asking them. And in asking them, no visual evoked potentials were measured, and changes in blood flow to the occipital cortex were ignored. But serendipity occurs even to the well-prepared: One's best thought for a new experiment can prove to be one's first unbiased, uncomplicated thought.Here's a cursory review of the events: A number of observers were asked to judge distances between marked posts in a field at night. They made their judgments with the help of night vision goggles (NVG). At first the observers underestimated the distances on average. Then an experimenter began to correct the observers after each judgment. The observers' judgments of distance became accurate. On average, the observers began to estimate those distances accurately. Is this and incredible story or a difficult one?

Aerospace Medicine↗
PubMed1973

Visual acuity in the pigeon. II. Effects of target distance and retinal lesions.

Visual acuity thresholds for grating targets were determined for three pigeons at target distances ranging from 13 to 73 cm. These measurements were made both while the birds were wearing goggles restricting vision to the frontal field of view and when vision was unrestricted. Using a slightly different method, performance was also compared for target distances of 6 and 13 cm while the goggles were in place. For a second group of three pigeons, acuity data were obtained before and after laser lesions of the retina's foveal region. The findings suggested that acuity was relatively poor for targets at the intermediate distances and that it improved as distance both increased and decreased from these intermediate values. The acuity improvement with increasing distance did not occur, however, when the birds were wearing frontal goggles. The data appear to be consistent with Catania's 1964 suggestion that the pigeon has separate frontal and lateral visual systems that differ in their refractive characteristics. Foveal lesions did not appear to affect acuity for distant targets, and it was concluded that, while the fovea serves the lateral field of view, its presence is not necessary to the static acuity characteristics of this system.

Animals↗
PubMed1999

Driver distance from the steering wheel: perception and objective measurement.

OBJECTIVES: This study assessed the accuracy of driver perceptions of the distance between the driver's nose and the steering wheel of the vehicle as a factor in considering driver disconnection of an airbag contained in the steering wheel for preventing injury to the driver in an accident. METHODS: A cross-sectional survey of 1000 drivers was done to obtain perceived and objective measurements of the distance between the driver's nose and the steering wheel of the vehicle. RESULTS: Of 234 drivers who believed that they sat within 12 inches of the steering wheel, only 8 (3%) actually did so, whereas of 658 drivers who did not believe that they sat within 12 inches of the wheel, 14 (2%) did so. Shorter drivers were more likely than taller ones to both underestimate and overestimate their seating distance. CONCLUSIONS: Considerable misperception of drivers' distance from the wheel indicates that drivers should objectively measure this distance.

Adolescent↗