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PubMed2006

The association between psychological distance and construal level: evidence from an implicit association test.

According to construal level theory (N. Liberman, Y. Trope, & E. Stephan, in press; Y. Trope & N. Liberman, 2003), people use a more abstract, high construal level when judging, perceiving, and predicting more psychologically distal targets, and they judge more abstract targets as being more psychologically distal. The present research demonstrated that associations between more distance and higher level of construal also exist on a pure conceptual level. Eight experiments used the Implicit Association Test (IAT; A. G. Greenwald, D. E. McGhee, & J. L. K. Schwartz, 1998) to demonstrate an association between words related to construal level (low vs. high) and words related to four dimensions of distance (proximal vs. distal): temporal distance, spatial distance, social distance, and hypotheticality. In addition to demonstrating an association between level of construal and psychological distance, these findings also corroborate the assumption that all 4 dimensions of psychological distance are related to level of construal in a similar way and support the notion that they all are forms of psychological distance.

Concept Formation↗
PubMed2005

Social distance towards people with mental illness amongst Nigerian university students.

BACKGROUND: It had been claimed that stigma and social distance are less severe in African countries, although not enough research had been done to confirm this. Most of the studies had focussed on the general community, and specific population groups had been neglected. AIMS: The aims of this study are to examine the level of social distance of students in a Nigerian university towards people with mental illness and to assess the possible socio-demographic variables involved. This is to enable the development of appropriate mental health educational and stigma-reducing programmes. METHODS: A modified version of Bogardus Social Distance Scale was used to assess the desire for social distance towards people with mental illness amongst 1,668 students of a Nigerian federal university. Socio-demographic details were also obtained. RESULTS: The social distances increased with the level of intimacy required in the relationship and were higher than those from the western culture, with 65.1% of the respondents categorised as having high social distance towards the mentally ill people. The predictors of high social distance towards the mentally ill include female gender [odds ratio (OR) 2.09, 95% confidence interval (CI) 1.69-2.60], studying a non-medical course (OR 4.65, 95% CI 3.01-7.19) and not having a family member with mental illness (OR 6.73, 95% CI 4.34-10.44). CONCLUSION: Social distance towards the mentally ill is higher amongst Nigerian university students than expected. This challenges the notion that stigma and negative attitude towards the mentally ill are less severe in Africa than in western cultures. There are needs for intensive public awareness, effective stigma-reducing educational programmes and more research in this area.

Adult↗
PubMed2005

Kinesthetic memory in distance reproduction task: importance of initial hand position information.

The role of the initial hand position in planning and implementation of a goal-directed movement is a matter of debate. We designed a non-visually guided repetitive reaching movement task to investigate the role of proprioceptive information of the initial or end hand position in implementation of kinesthetic memory. The experimental design consisted four experiments. Each experiment consisted two phases: the training phase and the test phase. In the training phase the subjects were asked to learn and memorize the distance between start and end points by moving their hands ten times between them. In the test phase, the end point was removed, and starting from the same initial position, the subjects were asked to reproduce the memorized distance. In all experiments, varied conditions called "mask phase" preceded the test phase: a 5-s delay in experiment 1, shifting both initial and end points while keeping the distance constant in experiment 2, shifting only the end point, while keeping the initial point constant in experiment 3 and shifting only the initial point and keeping the end point constant in experiment 4. In comparison to experiment 1 (which was considered as the control group), no significant error in distance reproduction occurred in experiment 3, while experiments 2 and 4 showed significant error. These findings mean that although the distance information was available during the mask phase of experiment 2, subjects could not efficiently use this information to reproduce the distance. The other two experiments suggest that this error was caused by changing the initial hand position and not the end point. We conclude that in a kinesthetic-guided distance reproduction task, the initial hand position is more important for implementation of distance memory rather than the end point.

Adult↗
PubMed2004

Categorical and metric distance information in mental representations derived from route and survey descriptions.

Descriptions with a route perspective take the addressee into the environment and give information on the position of objects relative to the changing position of the addressee. In contrast, descriptions with a survey perspective adopt a bird's-eye view and describe objects with respect to one another. The objective of the present study was to determine whether the perspective of a spatial description influences the extent to which categorical and metric distance is represented. We studied the characteristics of the representations that were constructed from route or survey descriptions with a recognition/priming task and a bird-flight distance comparison task. Spatial priming and symbolic distance effects were present after participants had studied a verbal description. The spatial priming effect indicated that objects in the environment were spatially organized according to some kind of distance (i.e., categorical or metric) in the representation of the listener. Furthermore, this organization was not dependent on whether the objects in a given prime-target relation were explicitly mentioned in the same sentence, or instead had to be inferred from the text. The presence of symbolic distance effects indicated that larger differences in metric distance were easier to compare than smaller differences, which is an effect that is also expected if actual metric distances on a visual map have to be compared. Therefore, further evidence was provided that people are able to create map-like spatial representations of verbal descriptions. We replicated previous findings that route and survey descriptions result in representations from which categorical spatial information is equally available. This study is the first to find evidence that a mental representation, which contains some analog spatial detail (i.e., metric distance), can be constructed from a description with a route perspective. Importantly, it should be noted that a relative advantage for survey descriptions over route descriptions did exist, suggesting that survey descriptions lead to spatial representations with a more fine-grained localization of the objects than route descriptions.

Adult↗
PubMed2002

Virtual-reality techniques resolve the visual cues used by fruit flies to evaluate object distances.

Insects can estimate distance or time-to-contact of surrounding objects from locomotion-induced changes in their retinal position and/or size. Freely walking fruit flies (Drosophila melanogaster) use the received mixture of different distance cues to select the nearest objects for subsequent visits. Conventional methods of behavioral analysis fail to elucidate the underlying data extraction. Here we demonstrate first comprehensive solutions of this problem by substituting virtual for real objects; a tracker-controlled 360 degrees panorama converts a fruit fly's changing coordinates into object illusions that require the perception of specific cues to appear at preselected distances up to infinity. An application reveals the following: (1) en-route sampling of retinal-image changes accounts for distance discrimination within a surprising range of at least 8-80 body lengths (20-200 mm). Stereopsis and peering are not involved. (2) Distance from image translation in the expected direction (motion parallax) outweighs distance from image expansion, which accounts for impact-avoiding flight reactions to looming objects. (3) The ability to discriminate distances is robust to artificially delayed updating of image translation. Fruit flies appear to interrelate self-motion and its visual feedback within a surprisingly long time window of about 2 s. The comparative distance inspection practiced in the small fruit fly deserves utilization in self-moving robots.

Animals↗
PubMed2006

An empirical test of formal equivalence between Emmert's law and the size-distance invariance hypothesis.

Emmert's law and the size-distance invariance hypothesis have been said to be formally equivalent, provided that Emmert's law means that the perceived size of an afterimage is proportional to the perceived distance of the projected surface of the afterimage. However, there have been very few studies that have attempted to verify this formal equivalence empirically. We measured both the perceived size and distance of afterimages and real objects with the same proximal size. Nineteen participants projected afterimages of 1 deg in visual angle on the wall located at distances of 1 to 23 meters from the participants. They also observed real objects, disc-shaped and made from a sheet of Styrofoam board, with the same proximal size as that of the afterimages, which were located at the same physical distances as those of the wall on which the afterimages were projected. Each participant reproduced the apparent sizes of the afterimages and real objects using the reproduction method and estimated the apparent distances using the magnitude estimation method. When the mean apparent sizes of the afterimages and real objects, represented as a function of apparent distance, were fitted to a linear function, the slopes for the afterimages and real objects did not differ significantly. These results are interpreted as evidence for the formal equivalence of Emmert's law and the size-distance invariance hypothesis.

Adolescent↗
PubMed2003

Searching by rules: pigeons' (Columba livia) landmark-based search according to constant bearing or constant distance.

Pigeons (Columba livia) searched for a goal location defined by a constant relative spatial relationship to 2 landmark. For one group, landmark-to-goal bearings remained constant while distance varied. For another group landmark-to-goal distances remained constant while direction varied. Birds were trained with 4 interlandmark distances and then tested with 5 novel interlandmark distances. Overall error magnitude was similar across groups and was large than previously reported for Clark's nutcrackers (Nucifraga columbiana). During training, error magnitude increased with interlandmark distance for constant-bearing but not constant-distance birds. Both groups searched less accurately along the parallel to landmarks than along the perpendicular axis. Error magnitude increased with novel extrapolated interlandmark distances but not with novel interpolated distances. Results suggest modest geometric rule learning by pigeons.

Animals↗
PubMed1999

Do monocular time-to-collision estimates necessarily involve perceived distance?

Motivated by the debate between indirect and direct theories of perception, a large number of researchers have attempted to determine whether judgments of time to collision are based on the ratio of perceived distance to perceived speed or on the ratio theta/(d theta/dt), i.e. tau. Despite the considerable research effort devoted to this question there seems to be no clear resolution. We used a staircase tracking procedure to estimate errors in estimating time to collision for a simulated approaching object. To investigate the role of perceived distance in the judgment of time to collision, we asked observers to alternate between two viewing distances (100 and 500 cm). For the 500 cm viewing distance, we magnified the visual display by a factor of five so that the retinal images [and the values of theta/(d theta/dt) through time] were identical for the two viewing distances. All visual cues to distance were available. There were no significant differences between estimates of time to collision made at the two viewing distances. We conclude that our observers ignored perceived distance when estimating time to collision and based their responses on theta/(d theta/dt). We concur with recent proposals that, in the future, time-to-collision research should move away from the either/or analysis of different information sources that has dominated previous studies towards investigations of how different information sources are integrated.

Adult↗
PubMed1999

Distance, lighting, and parental beliefs: understanding near work in epidemiologic studies of myopia.

PURPOSE: To develop measures and indices of factors (distance of eye from object, posture, and lighting) that may modify a possible effect of near work activity on myopia. METHODS: The duration of near work, the distance of an object from eye, lighting conditions, and other sociodemographic characteristics were asked in an interview. Both distance and lighting information from the questionnaire were compared with more precise measurements. RESULTS: Diopter hours were quantified as the duration of near work multiplied by the reciprocal of the distance which the activity was performed. The intraclass correlation coefficient of the reliability of distance information for each type of near work activity ranged from 0.43 to 0.91. Home light meter readings were significantly higher for children who were reading under both room and reading light, and the distances from the questionnaire were comparable to the measured distances. CONCLUSIONS: Measures of posture, distance, and lighting factors have been developed to study the possible effect modifiers of the effects of near work on myopia.

Accommodation, Ocular↗
PubMed2002

The proximity-fixation-disparity curve and the preferred viewing distance at a visual display as an indicator of near vision fatigue.

PURPOSE: This laboratory study investigates the relation between measures of fixation disparity (FD) (and other optometric measures) and near vision fatigue at a computer workstation. METHODS: Young adult subjects with normal binocular vision performed three blocks of a visual task of 30 min each. In Block A, the viewing distance was 100 cm, as a reference without near vision. In Block B, the viewing distance of 50 cm induced a defined near vision load. In Block C, subjects were free to choose a comfortable viewing distance. This preferred viewing distance was used as an indicator of near vision fatigue because subjects adopting longer viewing distances in Block C had more near vision fatigue at 50 cm in Block B. RESULTS: Subjects with preferred viewing distances longer than average (63 cm) had steeper slopes of FD as a function of viewing distance (100-30 cm), as shown by discriminant analyses. CONCLUSIONS: Thus, this steep proximity-FD curve indicates a weak disparity vergence system that may cause near vision fatigue. This may explain why some young adults prefer longer viewing distances at the computer workstation.

Computer Terminals↗
PubMed2002

Stereoacuity at distance and near.

PURPOSE: Because previous studies have reported conflicting evidence, we examined a possible difference in stereoacuity between distance and near, in particular using a random-dot display. We compared distance and near stereoacuities using identical presentation formats at the two distances. METHODS: Twelve young adults with low, stable refractive errors and apparently normal binocular vision participated. Stereoacuity was determined with a Mentor B-VAT II using Random Dot E (BVRDE) and Contour Circles (BVC) stereograms presented on a standard monitor (25 x 19.3 cm) at 518 cm (distance-habitual) and a small monitor (2.0 x 1.4 cm) at 40 cm (near-habitual). To examine whether accommodation-convergence influenced stereoacuity, testing at 40 cm was repeated with the addition of +2.50 DS lenses and base-in prisms (near-compensated) that created the same accommodation and convergence demands as for distance-habitual viewing. RESULTS: The two stereotests produced similar findings. Stereoacuity was not significantly different for distance-habitual and near-habitual viewing of the BVRDE (p = 0.43) and BVC (p = 0.79) stereotests. Near-compensated stereoacuity was worse than near-habitual (BVRDE, p = 0.005; BVC, p = 0.004) and distance-habitual (BVRDE, p = 0.05; BVC, p = 0.003) for both stereotests. Because near stereoacuity with yoked prisms (control condition) was the same as without prism (near-habitual), prism-induced optical distortions cannot account for the difference. CONCLUSIONS: Stereoacuity was not different at distance and near under normal viewing conditions. The conflict between subject knowledge of target proximity and the optically-induced relaxation of accommodation and convergence, or an inaccurate accommodative-convergence response, might have caused poor near-compensated stereoacuity.

Accommodation, Ocular↗
PubMed2003

Is binocular contrast sensitivity at distance compromised with multifocal soft contact lenses used to correct presbyopia?

PURPOSE: The purpose of this investigation was to determine whether new experimental multifocal optical designs incorporating diffractive/refractive optics for correction of presbyopia in a soft contact lens would compromise binocular contrast sensitivity at distance while achieving 20/20 binocular visual acuity at near. METHODS: Thirty presbyopic volunteers were fitted with Acuvue Bifocal soft lenses, two (FO1 and 3B1) experimental diffractive/refractive multifocal soft lenses separately and in combination as a pair and soft spherical lenses. Visual performance was evaluated via binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity after 1 week of lens wear. RESULTS: The experimental lenses FO1 and the combination FO1/3B1 performed as well for binocular contrast sensitivity, binocular distance high-contrast visual acuity, and binocular distance low-contrast visual acuity as the habitual presbyopic correction and the spherical soft distance correction. A strong correlation (r = 0.73 and 0.53, respectively) was found between binocular contrast sensitivity and binocular distance low-contrast visual acuity with experimental FO1 and FO1/3B1 lenses. However, the correlation (r = 0.37 and 0.60, respectively) between binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity with FO1 was weaker than that with the combination FO1/3B1 lenses. Subjective responses support the objective data. DISCUSSION: The data show that experimental FO1 lens and the experimental combination of the FO1/3B1 lenses can be prescribed to not compromise distance binocular contrast sensitivity.

Adult↗
PubMed2006

Distance and near visual acuity in infantile nystagmus.

PURPOSE: Infantile nystagmus (IN) has been reported to decrease with convergence. However, previous studies reported equivocal results regarding a corresponding improvement in acuity with near viewing. The aim of this study was to determine whether visual acuity improves with near viewing in patients with IN. METHODS: In the first experiment, visual acuities were measured using clinical test charts at standard test distances of 3 or 6 m and 40 cm and using S Charts at 3.75 m and 40 cm. In the second experiment, visual acuities were measured using a Bailey-Lovie chart at distance and a Lighthouse modified ETDRS near card held by each subject at his or her preferred working distance. S-chart acuities were obtained again at 3.75 m and 40 cm for comparison. Horizontal eye movements were recorded using infrared limbal reflection for 20 of the 34 subjects in the first experiment and for all 20 subjects in the second experiment. RESULTS: The S-chart acuities measured at distance and near were almost all within 0.1 logMAR (logarithm of the minimum angle of resolution) in experiments 1 and 2. Clinically measured acuity averaged nearly one line better at 40 cm than at distance in experiment 1, but the mean difference between near acuity using the ETDRS card and distance acuity using the Bailey-Lovie chart was less than one letter in experiment 2. No consistent relationship existed between the changes in visual acuity with viewing distance and the subject's eye movements. CONCLUSION: Despite a reduction of nystagmus at near distances in many patients with IN, the visual acuity at near does not improve significantly. These results imply that visual acuity in patients with IN is determined primarily by sensory limitations rather than by the moment-by-moment characteristics of these patients' eye movements.

Adolescent↗
PubMed1989

Vertical disparity, egocentric distance and stereoscopic depth constancy: a new interpretation.

There has long been a problem concerning the presence in the visual cortex of binocularly activated cells that are selective for vertical stimulus disparities because it is generally believed that only horizontal disparities contribute to stereoscopic depth perception. The accepted view is that stereoscopic depth estimates are only relative to the fixation point and that independent information from an extraretinal source is needed to scale for absolute or egocentric distance. Recently, however, theoretical computations have shown that egocentric distance can be estimated directly from vertical disparities without recourse to extraretinal sources. There has been little impetus to follow up these computations with experimental observations, because the vertical disparities that normally occur between the images in the two eyes have always been regarded as being too small to be of significance for visual perception and because experiments have consistently shown that our conscious appreciation of egocentric distance is rather crude and unreliable. Nevertheless, the veridicality of stereoscopic depth constancy indicates that accurate distance information is available to the visual system and that the information about egocentric distance and horizontal disparity are processed together so as to continually recalibrate the horizontal disparity values for different absolute distances. Computations show that the recalibration can be based directly on vertical disparities without the need for any intervening estimates of absolute distance. This may partly explain the relative crudity of our conscious appreciation of egocentric distance. From published data it has been possible to calculate the magnitude of the vertical disparities that the human visual system must be able to discriminate in order for depth constancy to have the observed level of veridicality. From published data on the induced effect it has also been possible to calculate the threshold values for the detection of vertical disparities by the visual system. These threshold values are smaller than those needed to provide for the recalibration of the horizontal disparities in the interests of veridical depth constancy. An outline is given of the known properties of the binocularly activated cells in the striate cortex that are able to discriminate and assess the vertical disparities. Experiments are proposed that should validate, or otherwise, the concepts put forward in this paper.

Depth Perception↗
PubMed1989

The effect of accommodative hysteresis on apparent distance.

The influence of accommodative hysteresis on monocular distance perception was examined in 18 visually normal young adults. Tonic accommodation and apparent distance were measured immediately before and after a 10 minute period of sustained focus at either the accommodative nearpoint or farpoint. Separate sessions were used for the two sustained focus conditions. On each session, apparent distance was assessed for both a highly effective and a non-effective accommodative target viewed at a constant optical distance of 3D. Sustained focus at the nearpoint resulted in a significant increase in the apparent distance of the highly effective accommodative target, as well as in tonic accommodation. Sustained focus at the farpoint yielded a slight decrease in tonic accommodation, but no significant alteration in the apparent distance of the highly effective accommodative target. No tendency for change in the apparent distance of the non-effective accommodative target was observed under either the nearpoint or farpoint condition. The results suggest that accommodative distance information is linked to the level of monocular blur-driven accommodative innervation necessary for clarity of focus.

Accommodation, Ocular↗
PubMed2002

Assessing auditory distance perception using virtual acoustics.

In most naturally occurring situations, multiple acoustic properties of the sound reaching a listener's ears change as sound source distance changes. Because many of these acoustic properties, or cues, can be confounded with variation in the acoustic properties of the source and the environment, the perceptual processes subserving distance localization likely combine and weight multiple cues in order to produce stable estimates of sound source distance. Here, this cue-weighting process is examined psychophysically, using a method of virtual acoustics that allows precise measurement and control of the acoustic cues thought to be salient for distance perception in a representative large-room environment. Though listeners' judgments of sound source distance are found to consistently and exponentially underestimate true distance, the perceptual weight assigned to two primary distance cues (intensity and direct-to-reverberant energy ratio) varies substantially as a function of both sound source type (noise and speech) and angular position (0 degrees and 90 degrees relative to the median plane). These results suggest that the cue-weighting process is flexible, and able to adapt to individual distance cues that vary as a result of source properties and environmental conditions.

Adult↗
PubMed2006

Distance stereoacuity in intermittent exotropia.

BACKGROUND: Studies of distance stereoacuity in intermittent exotropia suggest that normal stereoacuity corresponds to good control of the deviation and that reduced or negative stereoacuity signifies poorer control. AIM: : To evaluate distance stereoacuity in intermittent exotropia using the Frisby Davis Distance stereo test (FD2). METHODS: Children with intermittent exotropia where the near angle was less than or equal to distance were eligible for recruitment. Standardised prospective data collection included FD2 distance stereoacuity. This was a longitudinal study in which outcomes are reported for baseline, last follow-up (> or =6 months before any surgery) or preoperative and last postoperative visits for those undergoing surgery. RESULTS: 110 children with intermittent exotropia had FD2 stereoacuity tested at baseline: 70 comprehended the test. Mean (standard deviation (SD)) age was 4.6 (1.7) years (range 2-10 years). 41/70 (59%) showed positive responses: mean (SD) stereoacuity 30 (12) s of arc. The mean follow-up period before any surgery was 13 months (range 6-27 months). At follow-up, mean (SD) stereoacuity was 24 (11) s of arc. Preoperative and postoperative stereoacuity were not significantly different from those not undergoing surgery. CONCLUSION: This study was the first to report distance stereoacuity in intermittent exotropia using the FD2 stereo test: patients with intermittent exotropia can achieve normal levels of distance stereoacuity, but a considerable proportion, despite comprehending, showed a negative response. This suggests that using the FD2, distance stereoacuity in intermittent exotropia is either absent or normal rather than reduced. Possible reasons for this and its implications are discussed.

Child↗
PubMedDate not supplied

Reliability of distance estimation by doctors and patients: cross sectional study.

OBJECTIVE: To assess the reliability and accuracy of distance estimated by doctors and patients. DESIGN: Comparison between estimated and measured distances of six familiar sites around Guy's Hospital, London. SUBJECTS: 100 hospital consultants and 100 patients. MAIN OUTCOME MEASURES: Median (range) of estimated distances, and mean (SD) of the difference between estimated and measured distances. RESULTS: Both doctors and patients gave a wide range of estimates of distance. The estimates differed by up to 14.6-fold from the measured distances, and the difference between minimum and maximum estimates was up to 62.5-fold. CONCLUSION: Doctors and patients were inaccurate at estimating distances, which implies that estimates of distances walked are not reliable indicators of a person's health.

Cross-Sectional Studies↗