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At least 1,063 records · Page 59Linked to original sources
PubMed1977

Effect of distance information and range on two indices of visually perceived distance.

Subjects made verbal reports of the perceived distance of near visual targets and indicated their distances by pointing at them with an unseen hand. The targets were presented under three stimulus conditions: monocular, binocular, and multicue. Two ranges of target distance were studied in separate experiments: 11-39 cm and 21-33 cm. When reciprocals of both response distance and target distance were plotted, all functions were approximately linear. The verbal and manual responses (distance indices) differed greatly, but were found to be related by a constant transform. The range of target distances had no effect on either index. The standard deviation of the manual response was about half that of the verbal response. Stimulus condition had a large effect, with the multicue condition producing the greatest change in indicated distance. and the monocular condition the least. The results are discussed with reference to the definition of perceived distance, and hypothesis concerning the integration of distance information.

Adult↗
PubMed1977

Expanding angles? Systematic distortions of space involving angular figures.

Using simple, single angular figures, including figures containing only one line, we have shown systematic misestimations of distance defined by these figures. These misestimations are not related to the absolute distance per se, but are related both to the size of the angle defining the distance, and to the part of the angle defining it. Some implications of these findings are discussed.

Adolescent↗
PubMed1978

Illusory dilatation of square surfaces.

The aim of the present research was to study illusory dilatation of surfaces isolating some factors contributing to this phenomenon. A series of displays (8.5 cm x 8.5 cm) was prepared: a white square card and five square cards with a uniform pattern of black dots, increasing gradually. The displays were presented to two different groups of subjects, according to the method of paired comparisons and according to the method of limits (under conditions of reduced viewing) respectively. The subjects were asked to evaluate the relative magnitude of the displays. The textured cards significantly differed from the white standard and also among themselves. Up to a threshold, as the dots increase, the surfaces expand as well.

Distance Perception↗
PubMed1978

Central and peripheral object distances as determinants of the effective visual field in early infancy.

While visually fixating on a central, coloured object, thirty-six infants aged between two and five months were presented with a peripheral target to the right or to the left of midline. Both objects were presented at two distances: either 30 or 90 cm from the infant. The extent of the effective visual field was measured by the presence and the latency of saccadic shifts of gaze from the fixation object toward the target object placed at varying degrees of eccentricity. The effective visual field expanded between two and four months. Near peripheral targets were detected at greater angles of eccentricity than those more distant, but this effect was modified both by age and by the distance of central fixation. For two- and three-month infants the effective visual field was most reduced when the central fixation object was placed at 30 cm and the target object at 90 cm. The ability to respond to peripheral objects more distant than the fixation object develops after three months.

Age Factors↗
PubMed1978

Perspectives in open spaces. A geometrical application of the Thouless index.

A geometrical model for computing 'general perspectives' is discussed. It is based on the power function r = p(d/t) 1 -i, where i is the Thouless index for the phenomenal regression to the real object, r is the real size of the object, p is the apparent size, d is the distance between the subject and the object, and t is the distance between the subject and the projection plane. This model assumes that i is invariant for different distances and this was verified in seventy children and adults at distances of 15 or 120 m. A computer program draws families of curved perspectives which are well-fitted to the actual shape of large visual alleys produced by experiment in open fields.

Adult↗
PubMed1978

Illusory contours and the ends of lines.

A series of lines pointing towards a central region induces an illusory brightness effect that is systematically related to the angle formed by the lines and the contour of the illusory brightness. As the lines veer to become tangents the illusory brightness decreases.

Adult↗
PubMed1979

Recalibration of the convergence system.

Adaptation to convergence-altering prism spectacles was studied. The subjects were trained for 8 min with either convergence-increasing or convergence-decreasing prisms. Before and after training they estimated the distance to a binocular dot varying in the stimulus it provided to convergence. Both the preadaptation and postadaptation estimates showed that the reciprocal of estimated target distance is linearly related to convergence. Further there was a consistent change in the direction of adaptation expected from the preadaptation to the postadaptation test. This change was accounted for in terms of a recalibration of the effective absolute convergence level.

Adaptation, Ocular↗
PubMed1979

Scanning visual images: implications for the representation of space.

This study investigated whether reaction time to detect an item within an image increases as a monotonic function of the relative or the absolute distance from the starting item to the probed item with the image. It was found that when relative probed distances were manipulated and absolute distances kept constant and, conversely, when absolute distances were manipulated and relative distances kept constant, reaction times were invariant across relative distance but increased as a function of increasing absolute distance. This result may be interpreted either in terms of operations within an imaginal representation or in terms of operations on propositional statements underlying the image.

Adult↗
PubMed1980

The influence of visual pattern on perceived speed.

The two experiments to be described are concerned with the instability of the relationship between objective and subjective speed as experienced by the driver of a motor vehicle. A number of factors that contribute to the instability are outlined, one of the most important of which is considered to be rectilinear speed adaptation. The hypothesis is made that by deliberately distorting the spatial geometry of the visual field it should be possible to counteract the effects of sensory adaptation. The first experiment tests the hypothesis on a motion simulator and confirms the possible value of such a technique. The second experiment describes a field study in which the proven technique is applied to a stretch of motorway at a site where the accident rate was exceptionally high owing to excessive speed. The observed reduction of relevant accidents at this and a number of other motorway sites where the system has been installed is discussed.

Accident Prevention↗
PubMed1980

Control stimuli in investigations of the acute-angled and obtuse-angled Müller-Lyer illusions.

Over the past decade, attention has been drawn to the importance of intertip distance (the distance between the tips of the arrowheads or featherheads) as a possible determinant of the Müller-Lyer illusion. Investigation of this stimulus property for the arrowhead and featherhead components of the Müller-Lyer figure has indicated that the two components exhibit a lack of symmetry, a conclusion supported by other studies using rather different approaches to the investigation of symmetry. This article argues that the control stimuli used in previous investigations are inadequate. It is proposed that in addition to the conventional straight-line control stimulus, in which the standard shaft is stripped of the oblique inducing lines. H-shaped figures in which the inducing lines are vertical should be included. Results are reported of an experiment in which both types of control stimuli are used to investigate the effects of intertip distance, and the spatial separation of that distance from the standard shaft, upon the arrowhead and featherhead figures.

Adult↗
PubMed1980

Infant response to impending optical collision.

Young infants withdraw their heads when shown a display simulating a rectangle rotating towards their faces. The head withdrawal is specific to that transformation and is not elicited by a similar transformation which does not specify approach. This is possible evidence of an unlearned ability to pick up information about change of position in the third dimension.

Distance Perception↗
PubMed1980

The effect of similarity between line segments on the correspondence strength in apparent motion.

The correspondence between line segments in apparent motion is shown to be affected by the similarity between them. Increase in orientation difference or in length ratio between lines in a competing motion configuration decreases the probability of perceived apparent motion between them. The results suggest the existence of a built-in preference metric that may reflect a measure of matching likelihood between elements in three-dimensional space.

Distance Perception↗
PubMed1981

The Poggendorff illusion: an illusion of linear extent?

In the standard version of the Poggendorff figure a transversal intersects two parallel verticals and the segment of the transversal between the two intersection points, A and B, is not shown. The two portions of the transversal outside the parallels then seem to be misaligned. Besides this illusion of direction, there is also an illusion of size, the distance AB being underestimated in the standard figure. The influence of configural components in determining this spatial distortion of the Poggendorff figure was examined by having subjects reproduce the inner oblique (at 45 degrees) extent AB in variations of the figure. This distance was found to be underestimated in Poggendorff variations which contained parallel (vertical) components that formed an acute angle with AB; and the underestimation increased as the number of these components present in the figure increased. The distance AB was found not be significantly distorted in figures which contained only those parallel (vertical) components that formed an obtuse angle with AB, yet their presence in the figure tended to counteract the underestimation. When the transversals were omitted, the underestimation was found to increase. The findings are interpreted in support of an explanation that reduces the Poggendorff effect to those factors which mediate the Müller-Lyer illusion.

Distance Perception↗
PubMed1981

Are the obtuse angles the key components of the Poggendorff illusion?

An experiment is reported which confirms and extends a previous finding that amputations of the Poggendorff figure do not necessarily result in large positive effects with obtuse-angle stimuli, and small or even negative effects with acute-angle stimuli. Indeed, the acute-angle effects found were significantly greater than the obtuse-angle effects, and the full Poggendorff error was not explicable in terms of the linear summation of the component-angle effects. An 'alignment displacement effect' reported earlier by Hotopf and Obonai was shown to occur, but could not be an important component of the Poggendorff illusion.

Adolescent↗
PubMed1981

Perceived loudness and visually-determined auditory distance.

Three experiments were conducted to determine whether variations in the perceived distance to a test sound could influence its loudness in the absence of physical changes in sound-level. The phenomenon of visual capture provided the means for manipulating apparent distance. A 'dummy' loudspeaker was used to vary the apparent source location of a short noise stimulus while the true source of this sound remained fixed (and hidden) with respect to the observer. Sound-levels from 40 to 75 dB(A) were presented to independent groups of observers in either anechoic or semi-reverberant acoustical environments. In general, reported loudness increased with perceived distance. This finding has implications for conceptualizing the phenomenon of loudness constancy.

Acoustics↗
PubMed1982

Effect of brightness on perceived distance as a figure-ground phenomenon.

Two experiments were performed to compare the effects of brightness on perceived distance in the situations in which a target appeared either as figure (experiment 1) Or as ground (experiment 2). In experiment 1 the stimulus array consisted of two small homogeneous target regions and a homogeneous surrounding region common to both; in experiment 2 it consisted of two large homogeneous target regions and a textured surrounding region. Subjects were asked to indicate which of the two targets appeared nearer and to make a verbal judgment of perceived depth between them. The results showed that the target having the greater brightness contrast with the surround is apt to be judged nearer when the targets appear as figure, and farther when they appear as ground. These findings support Egusa's hypothesis that the effect of brightness on perceived distance can be attributed to figure-ground differentiation between the target region to be judged and its direct surround.

Distance Perception↗
PubMed1983

Optic-flow and cognitive factors in time-to-collision estimates.

Time-to-collision (Tc) estimates were obtained from twenty-four subjects who viewed film clips for varying lengths of time. The film clips showed the view from a moving car travelling towards a stationary target car, but ended 100 m before reaching the target. Viewing time varied from 2 to 6 s, approach velocity from 40 to 100 km h-1, and Tc from 3.6 to 9.0s. It was hypothesised that, if time were needed to calculate Tc, the accuracy of Tc estimates would increase with viewing time up to some maximum. However, the results showed no effect of viewing time, and this was taken to indicate that estimates were based upon information directly available from the changing optic array at the eye of the observer. A significant velocity effect was found, accuracy increasing with velocity. Since velocity was inversely correlated with Tc, this probably implies that accuracy decreases with increasing Tc. Sex differences were found, with males giving higher and more accurate estimates than females. The relevance of these findings to the nature of Tc information is discussed.

Adolescent↗
PubMed1984

Learning spatial dimensions with a visual sensory aid: Molyneux revisited.

The relationship between sensory aid research and several areas of perceptual learning has been explored with five experiments on learning the use of the Binaural Sensory Aid, an electronic sensor in which pitch specifies distance and interaural amplitude difference (IAD) specifies direction. The training task required reaching to objects in near space, with tactile error feedback. Perceptual learning for both dimensions was demonstrated within 72 trials, giving a level of performance comparable to the use of a natural sound source, although performance with the direction cue did not reach asymptote until a second training session. Training was unaffected by various kinds of regularity in the spatial target sequences, or by a reduction in the number of spatial target locations until only two locations were used; at this point directional accuracy declines. Training only one dimension at a time did not produce additional improvement of performance on that dimension, but did impair generalization of the direction cue. Learning of the pitch-distance dimension was generally better than that of the IAD dimension, possibly because of its greater discriminability with this device. Generally, the pattern of results indicates that in learning to use such devices subjects readily determine the sensory dimensions of the codes and have considerable ability to generalize to new locations.

Distance Perception↗