bluuebunny/crossref_metadata_2025 huggingface dataset:
Transparency: Relation to Depth, Subjective Contours, Luminance, and Neon Color Spreading
Authors: Nakayama Ken , Shimojo Shinsuke , Ramachandran Vilayanur S
Published: January 2007

The perception of transparency is highly dependent on luminance and perceived depth. An image region is seen as transparent if it is of intermediate luminance relative to adjacent image regions, and if it is perceived in front of another region and has a boundary which provides information that an object is visible through this region. Yet, transparency is not just the passive end-product of these required conditions. If perceived transparency is triggered, a number of seemingly more elemental perceptual primitives such as color, contour, and depth can be radically altered. Thus, with the perception of transparency, neon color spreading becomes apparent, depth changes, stereoscopic depth capture can be eliminated, and otherwise robust subjective contours can be abolished. In addition, we show that transparency is not coupled strongly to real-world chromatic constraints since combinations of luminance and color which would be unlikely to arise in real-world scenes still give rise to the perception of transparency.

Rather than seeing transparency as a perceptual end-point, determined by seemingly more primitive processes, we interpret perceived transparency as much a ‘cause’, as an ‘effect’. We speculate that the anatomical substrate for such mutual interaction may lie in cortical feed-forward connections which maintain modular segregation and cortical feedback connections which do not.
Wallpaper Illusion: Cause of Disorientation and Falls on Escalators
Authors: Cohn Theodore E , Lasley David J
Published: January 2007

The wallpaper illusion, first described over a century ago, can occur when a person with normal binocular vision views a pattern that is periodic in the horizontal meridian of the visual field. Escalator treads present such a pattern. Evidence is presented favoring the view that disorientation experienced by escalator riders is caused by this illusion. Possibly some of the estimated 60 000 escalator falls occurring in the United States each year are linked to it.
Visual Processing of Stimulus Compounds in Newborn Infants
Authors: Slater Alan , Mattock Anne , Brown Elizabeth , Burnham Denis , Young Andrew
Published: January 2007

An experiment is described in which newborn infants' processing of stimulus compounds was investigated. After familiarization to two alternately presented stimuli which differed in colour and orientation, the newborns showed significant preferences for a stimulus which had a novel colour/orientation combination: the novel stimulus was produced by recombining features of the stimuli used for familiarization. This finding argues against the view that infants initially process separate components, or parts, of visual stimuli and are only able to attend to the correlations between them after about 3 months of age. Rather, the ability to process and remember stimulus compounds is present at birth.
Mirror-Reversal Phenomena in the Cutaneous Perception and Writing of Children
Authors: Nagata Yoko , Shimojo Shinsuke
Published: January 2007

When a letter is drawn on the forehead, it is perceived cutaneously as a mirror reversal of the experimenter-defined stimulus. An analogous mirror-reversal phenomenon is found in motor behaviour; eg, writing on the downward-facing horizontal surface of a table. We examined these mirror-reversal phenomena in tasks, performed by 4-year-old and 8-year-old children, involving cutaneous perception and motor-production. The children's tendencies toward mirror reversal in the two tasks varied with the orientation and position of the surface, but were similar to those of sighted and blind adult subjects. In addition, mirror reversal was independent of the left—right indifference often observed in young children in writing or visual-matching tasks. The implications of these findings are discussed in the context of a body schema used to guide sensorimotor functions.
Conflicting Figure-Ground and Depth Information Reduces Moving Phantom Visibility
Authors: Brown James M , Weisstein Naomi
Published: January 2007

Moving phantom visibility was measured in two experiments where the global figure-ground and depth relations within phantom-inducing patterns were manipulated. The local inducing environment where the illusion occurred was identical for all patterns. Phantom visibility was significantly reduced when occlusion cues specified the phantom-inducing parts of a pattern as ground. These results suggest conflicting figure – ground and depth information interferes with the representation and perception of phantoms as figure regions.
Similarity of Tactual and Visual Picture Recognition with Limited Field of View
Authors: Loomis Jack M , Klatzky Roberta L , Lederman Susan J
Published: January 2007

Subjects attempted to recognize simple line drawings of common objects using either touch or vision. In the touch condition, subjects explored raised line drawings using the distal pad of the index finger or the distal pads both of the index and of the middle fingers. In the visual condition, a computer-driven display was used to simulate tactual exploration. By moving an electronic pen over a digitizing tablet, the subject could explore a line drawing stored in memory; on the display screen a portion of the drawing appeared to move behind a stationary aperture, in concert with the movement of the pen. This aperture was varied in width, thus simulating the use of one or two fingers. In terms of average recognition accuracy and average response latency, recognition performance was virtually the same in the one-finger touch condition and the simulated one-finger vision condition. Visual recognition performance improved considerably when the visual field size was doubled (simulating two fingers), but tactual performance showed little improvement, suggesting that the effective tactual field of view for this task is approximately equal to one finger pad. This latter result agrees with other reports in the literature indicating that integration of two-dimensional pattern information extending over multiple fingers on the same hand is quite poor. The near equivalence of tactual picture perception and narrow-field vision suggests that the difficulties of tactual picture recognition must be largely due to the narrowness of the effective field of view.
Pre-Attentive Detection of a Target Defined by Stereoscopic Slant
Authors: Holliday Ian E , Braddick Oliver J
Published: January 2007

Does the visual system represent stereoscopic depth purely as a map of local disparities, or does it explicitly represent local relationships of disparity, such as disparity gradients? Experiments are reported in which visual search for a target containing the same disparity range as other elements in the display, but differing in the relationship of the disparities (stereo slant), was used to determine whether the target showed ‘pop-out’ like a unitary feature, or the serial search characteristic of feature conjunctions. Each stereo pair of elements was selected randomly from a range of outline parallelograms leaning to the right or to the left, so that the target could not be identified using any monocular shape cue.

Response times for detection of the target (present on 50% of the trials) were independent of the number of elements in the display. This result was confirmed by varying element size and spacing, and by using oblique crosses rather than parallelograms as stimuli. It is concluded that stereoscopically defined slant, or disparity gradient, can be processed and compared in parallel across the display, and acts in this respect as an explicit unitary visual property. This contrasts with findings in analogous experiments on movement, which show that targets defined by divergence or deformation of optic flow can only be identified by serial search.
Integration of Form across Saccadic Eye Movements
Authors: Hayhoe Mary , Lachter Joel , Feldman Jerome
Published: January 2007

To perceive a stable world, one must somehow be able to relate visual information from successive fixations. Little is known, however, about the nature of the integrative process. By using a task which requires the integration of spatial position information from different fixations, it is demonstrated that visual information from previous fixations is preserved in a world-centered representation which is precise enough to support judgements of geometric shape. It is also shown that successive views are aligned with respect to common visual features, indicating that visual stability may be normally accomplished by a visual matching strategy in combination with cancellation by an eye-position signal.
On the Variety of Percepts Associated with Dichoptic Viewing of Dissimilar Monocular Stimuli
Authors: Yang Yuede , Rose David , Blake Randolph
Published: January 2007

Upon dichoptic viewing of dissimilar patterns, several distinct perceptual states may be experienced over time. One state is exclusive monocular dominance, wherein the view of only one eye is seen in its entirety for some period of time. Another state is characterized by a mosaic-like collage consisting of portions of the view of each eye. Two other states involve simultaneous perception of both monocular images in their entirety. In one of these states, the two monocular stimuli appear to be superimposed without depth (a phenomenon we shall term ‘superimposition’). In the other state, the two monocular stimuli appear to be located at different depth planes (which we shall term ‘transparency’). This paper documents the stimulus conditions favoring these various perceptual states. Exclusive monocular dominance occurs most often when the two eyes view dissimilar patterns with the same spatial-frequency content, particularly when both patterns consist of low spatial frequencies. Superimposition also occurs most often when the two eyes view the same spatial frequencies, but predominantly when those spatial frequencies are high. Transparency is favored when the spatial-frequency difference between the eyes is great, particularly when the view of one eye consists of high spatial-frequency information.
Anatomy of a Flash. 2. The ‘Width’ of a Temporal Edge
Authors: Cogan Alexander I
Published: January 2007

In a previous study it has been found by using the Crawford masking paradigm with spatially coextensive stimuli that the end points of even a weak flash have a strong masking effect on the probe pulse, but no threshold elevation was observed when the probe was 100 ms or longer from flash onset and offset. The relationship between the strength of a temporal edge (eg the amplitude of a sudden increase in field luminance) and the duration of masking has not been systematically investigated. In the present experiments the duration of masking produced by a step of luminance as a function of step size was measured. With steps whose amplitude was between ten and five hundred times detection threshold, the duration of masking was about constant, ie 70 and 50 ms for on-responses and off-responses, respectively. This refractory period defined the ‘width’ of a temporal edge. Unless two suprathreshold unidirectional luminance changes are separated by an interval exceeding the width of a temporal edge, they are perceived as a single change in brightness. A linear systems analysis led to predictions for ramp stimuli that were confirmed by experiment.
Illusory Occluding Contours and Surface Formation by Depth Propagation
Authors: Takeichi Hiroshige , Watanabe Takeo , Shimojo Shinsuke
Published: January 2007

A novel kind of depth-spreading effect which should be distinguished in various aspects from the known interpolation, averaging, or ‘filling-in’ phenomena is reported. The demonstrations and experiments suggest that depth from an uncrossed disparity can be extrapolated from, not just interpolated between, illusory or real contours to form perceptually a background surface. In addition, the form of the illusory contour itself could be drastically changed in configuration and sharpness, contingently with perceptual background-surface formation. No such effects of surface and contour formation were observed in the crossed disparity case. Because the illusory contours were enhanced and perceived as illusory ‘occluding contours’, these effects may be closely related to the ‘occlusion constraints’ in the real world.
Spatial Gating Effects on Judged Motion of Gratings in Apertures
Authors: Power Roderick P , Moulden Bernard
Published: January 2007

Wallach has described in qualitative terms the movement of lines behind apertures. We related the data he obtained to the aperture problem, constructed a model of movement perception, and carried out tests of the model. Experiment 1 was a parametric study, and showed the conditions under which a reliable illusion (the barber pole illusion) of diagonal movement of lines along an aperture could be obtained, and when fluctuating judgements or veridical percepts were obtained. On the basis of this study a dipole model was constructed. The model was further developed and tested. In experiment 2 the effects of total area of stimulation were examined: diagonal gratings were viewed behind multiple apertures. In experiment 3 the effects of local signs were examined: diagonal gratings were viewed in an aperture which had edges cut in small steps and stairs, with the risers parallel to the grating, and the treads parallel to the direction of motion of the grating. Experiment 4 was designed to test a prediction about the motion aftereffect of dots near and far from the point of fixation, and the results confirmed the model. It was concluded that the model accounts for the barber pole illusion and, generally, for the movement of gratings in apertures.
Seeing Lumps, Sticks, and Slabs in Silhouettes
Authors: Willatsl John
Published: January 2007

Marr has suggested that we see three-dimensional (3-D) shapes in silhouettes because we make the implicit assumption that the viewed shapes are generalized cones. One difficulty with this suggestion is that it cannot deal with silhouettes of irregular 3-D shapes like clouds and trees; another is that it only applies to generalized cones with a relatively high length:width ratio. An alternative explanation, suggested by evidence from cross-cultural studies of language, from children's early speech, and from children's early drawings, is that the scene primitives actually used by humans are not generalized cones but ‘lumps’, ‘sticks’, and ‘slabs’, that is, primitives whose only shape properties are their relative extensions in 3-D space. In this paper it is proposed that the implicit assumption we make in interpreting silhouettes is that the extendedness of the silhouette reflects the extendedness of the viewed shape, so that a round region is seen as a lump and a long region is seen as a stick; and that such views seem “natural” because they are the views most likely to be encountered in normal environments. This account is more general than that of Marr because it explains how we interpret silhouettes of all kinds of 3-D shapes, even very irregular ones. Unlike Marr's account, it also deals with flat shapes like slabs and discs, and shows why it is difficult to see these shapes in silhouettes.
Visual Search: Detection, Identification, and Localization
Authors: Green Marc
Published: January 2007

In two studies, observers searched for a single oblique target in a field of vertical distractors. In one experiment, target detection and identification (left versus right tilt) were compared. In another experiment, detection and localization were compared for the left versus the right half of the display. Performance on all three tasks was virtually identical: if a target could be detected, it could also be identified and localized. A review of previous studies generally supports the conclusion that performance on the three tasks is similar. This argues against current search theories, which rest heavily on data showing differences in identification and localization.
Mobility of Normal Observers under Conditions of Reduced Visual Input
Authors: Eyeson-Annan Margo , Brown Brian
Published: January 2007

The importance in mobility performance of the rate of presentation of visual information, binocular versus monocular vision, the use of multiple rather than single reference points, and local motion parallax was investigated in two experiments. In each experiment ten subjects walked a triangular mobility course in a totally darkened room; the only visible targets were light emitting diodes (LEDs), mounted on poles, at the apices of the triangle. The LEDs were mounted so that one or two could be used in a trial; if two were used the distance between them was varied horizontally (in experiment 1) and vertically (in experiment 2). The subjects walked around the course under a range of conditions, including two ‘optimal trials’ in full light. The LEDs were flashed for 1 ms at frequencies of 0.5, 1 and 5 Hz in experiment 1 and at 1 and 5 Hz in experiment 2. Mobility was measured with the use of an ultrasonic locator system which measured the subject's position on the course 10 times per second.

The mean velocity of the subject in traversing the course was significantly reduced when the flash rate was slower, when the subject had one eye occluded, or when there was only one LED on the pole; when the spacing between the LEDs was varied, either vertically or horizontally performance was unaffected. These results imply that the frequency of updating of visual information is important in determining mobility performance, as are binocular cues, but that local motion parallax is not important. The number of LEDs on each pole had a significant effect on mobility performance: an ‘object’ (two lights) gave more information than a point reference.
The Pulfrich Pendulum Phenomenon in Stereoblind Subjects
Authors: Thompson Peter , Wood Vicky
Published: January 2007

The Pulfrich pendulum phenomenon, in which a pendulum swinging in the frontoparallel plane appears to swing in an ellipse when a neutral density filter is placed over one eye of the observer, was investigated in stereoblind subjects. It was found that such subjects can report the presence of the Pulfrich effect although they fail to fuse random-dot stereograms and fail to exhibit interocular transfer of the movement aftereffect. These findings suggest that ‘stereoblind’ subjects must retain some residual binocular mechanism for depth perception. Three possibilities are considered: (i) the stereoblind may be able to utilise contiguous temporal disparities as a cue for depth in the Pulfrich effect; (ii) they may retain some residual binocularity, sufficient to reveal the Pulfrich effect but not for other more demanding tasks for the binocular mechanisms; and (iii) they may retain some coarse magnocellular pathway disparity mechanism having lost their high-acuity parvocellular disparity system. There is little evidence to support any of these hypotheses, but the third shows promise.
Visual Recognition in the Peripheral Field: Letters versus Symbols and Adults versus Children
Authors: Zegarra-Moran Olga , Geiger Gad
Published: January 2007

The plot of the form-resolving field (FRF) was obtained by tachistoscopically presenting two figures in each stimulus, one in the center of gaze and the other in the peripheral field. The figures in the periphery were placed at various eccentricities in different presentations. The ensuing plot of average letter recognition as a function of eccentricity is the FRF. Only the horizontal components of the FRFs were used in the comparisons.

Three sets of figures were used as stimuli: regular-size letters, large-size letters, and symbols. Three groups of subjects were compared: adult ordinary readers, reading children, and pre-reading-age children. The last were tested with symbols only.

In letter recognition, the FRFs for young and adult ordinary readers are similar and fall off monotonically and symmetrically with eccentricity, hence conforming with the first Aubert—Foerster law (1857). However, the FRFs tested with symbols are narrower than those tested with letters of the same sizes and stroke widths, which is not in accordance with the first Aubert—Foerster law. In addition, the FRFs of symbols are different for each subject group. It is suggested that recognition in the peripheral field is not determined by visual acuity alone; rather, it is further confined or determined by the visual strategy employed to accomplish the task, and its associated distribution of lateral masking.
Time Estimation Methods—Do They Influence Prospective Duration Estimates?
Authors: Zakay Dan
Published: January 2007

The validity of an attentional model of prospective time estimation was tested in three experiments. In the first experiment two variables were manipulated: (1) nontemporal information processing load during the estimated interval, and (2) time estimation method, ie production of time simultaneously with the performance of a second task, or reproduction of time immediately upon termination of a task whose duration has to be measured. As predicted, a positive relationship between produced time length and information processing load demanded by a simultaneous task, and a negative relationship between reproduced time length and information processing load during the estimated interval, were found. The results were replicated in a second experiment in which verbal estimates of time were also measured and the objective duration of the estimated interval was varied. The pattern of results obtained for verbal estimates was similar to that obtained for reproduced ones. The results of a third experiment indicated that produced and reproduced times were positively correlated with clock time. The results are interpreted as supporting an attentional model of prospective time estimation.
What's the Difference between Men and Women? Evidence from Facial Measurement
Authors: Burton A Mike , Bruce Vicki , Dench Neal
Published: January 2007

Human subjects are able to identify the sex of faces with very high accuracy. Using photographs of adults in which hair was concealed by a swimming cap, subjects performed with 96% accuracy. Previous work has identified a number of dimensions on which the faces of men and women differ. An attempt to combine these dimensions into a single function to classify male and female faces reliably is described. Photographs were taken of 91 male and 88 female faces in full face and profile. These were measured in several ways: (i) simple distances between key points in the pictures; (ii) ratios and angles formed between key points in the pictures; (iii) three-dimensional (3-D) distances derived by combination of full-face and profile photographs. Discriminant function analysis showed that the best discriminators were derived from simple distance measurements in the full face (85% accuracy with 12 variables) and 3-D distances (85% accuracy with 6 variables). Combining measures taken from the picture plane with those derived in 3-D produced a discriminator approaching human performance (94% accuracy with 16 variables). Performance of the discriminant function was compared with that of human perceivers and found to be correlated, but far from perfectly. The difficulty of deriving a reliable function to distinguish between the sexes is discussed with reference to the development of automatic face-processing programs in machine vision. It is argued that such systems will need to incorporate an understanding of the stimuli if they are to be effective.
A General Correspondence Approach to Apparent Motion
Authors: Caelli Terry , Manning Mark , Finlay David
Published: January 2007

A general framework is considered for how different features of image parts determine the perceived direction of apparent motion between these parts as a function of their internalized feature weights. It is shown how the compatibility and constraints between pairwise part correspondences also play important roles in the types of perceived motion between parts; this process is modelled via a multivariate constraint-satisfaction procedure.
Extracting Prototypical Facial Images from Exemplars
Authors: Benson Philip J , Perrett David I
Published: January 2007

A computer graphic method for extracting a natural image of an individual's facial prototype, or average appearance, from a number of different images of that individual is presented. The process improves upon previous photographic and computational techniques. Synthesis of a person's average expression and pose from a sample of images is derived in an automatic and quantitative way. Possible uses of composite faces produced in this manner in psychological investigations of facial qualities (eg attractiveness) and in applied areas such as telecommunication are pointed out.
A Proximity-Contingent Stereoscopic Depth Aftereffect: Evidence for Adaptation to Disparity Gradients
Authors: Ryan Colin , Gillam Barbara
Published: January 2007

Prolonged inspection of a surface slanted in the third dimension of visual space typically results in a negative aftereffect such that, after adaptation, a surface in the fronto-parallel plane will appear slanted in the opposite direction. Binocular disparity is not necessary to generate such effects, since they can be obtained monocularly, presumably via adaptation to texture gradient. Six experiments demonstrated durable stereoscopic depth aftereffects in the absence of a texture gradient—by using discrete disparate objects rather than slanted surfaces— and demonstrated that adaptation was to the interobject disparity gradient rather than to the relative disparity of the objects per se. The disparity required to null the obtained aftereffects was inversely proportional to the horizontal separation of elements, for a constant disparity, and directly proportional to the separation of subsequently presented probes. When elements differed in depth (disparity), but were not laterally separated, nulling disparity was significant but invariant with changes in the horizontal separation of probe elements. In that case, adaptation was (i) either to the disparity gradient generated by the vertical separation of probe elements (of which the relative disparity component was tapped); or (ii) to relative disparity per se.
Coloured Speech Perception: Is Synaesthesia what Happens when Modularity Breaks Down?
Authors: Baron-Cohen Simon , Harrison John , Goldstein Laura H , Wyke Maria
Published: January 2007

Evidence was reported earlier from a single case that chromatic–lexical (CL) synaesthesia was a genuine phenomenon. A study is presented in which nine subjects were tested who also reported having coloured hearing. The following questions were addressed: (a) were these cases also genuine (ie consistent over time), (b) were they truly lexical, or rather variants of this condition, such as chromatic–graphemic (CG) or chromatic–phonemic (CP) synaesthesia, (c) did the experimental subjects show any commonalities between them, and (d) were they able to give information on a standard questionnaire about the phenomenology and ontogenesis of the condition? Subjects were asked to describe the colour sensation experienced on hearing items from a list of 130 words, phrases, and letters. The experimental group were not informed of any retest, but were retested more than one year later. A control group ( n = 9), matched for IQ, memory, age, and gender, were read the same list and asked to associate a colour with each list item. They were informed at the time of testing that they would be retested on a sample of items from the list a week later. 92.3% of the responses of the experimental group when retested one year later were identical to those given in the original test, compared with only 37.6% of the control subjects' responses (retested one week later). This confirmed the genuineness of these nine cases. All nine experimental subjects showed CG synaesthesia, none showing either CL or CP synaesthesia. Among the experimental group, some consistency was found in the colours evoked by hearing specific letters, suggesting the condition has a neurological basis. There was also evidence of a genetic sex-linked familial pattern underlying the condition. The importance of these distinct forms of synaesthesia for our understanding of the modularity of speech perception and colour vision is discussed.
Up–down Asymmetry in Vertical Induced Motion
Authors: Lott Lori A , Post Robert B
Published: January 2007

Induced motion (IM) is the illusory movement of an object in the direction opposite to the real motion of adjacent detail. One theory of IM suggests that it results, in part, from suppression of optokinetic nystagmus (OKN) by fixational (smooth-pursuit) effort. In several studies an asymmetry in human vertical OKN has been reported, with upward optokinetic stimulation eliciting higher OKN gain than downward motion. This provides a test of the nystagmus-suppression theory of IM. If suppression of OKN contributes significantly to IM, upward inducing stimuli should result in a greater magnitude of the illusion than should downward stimulus motion. Additionally, the asymmetry of vertical OKN should become more pronounced at higher stimulus velocities. Therefore, the asymmetry of vertical IM should be greater at higher inducing-stimulus velocities.

Twelve subjects viewed a large, random-dot stimulus, which moved either upward or downward at a velocity of 10, 40, or 70 deg s−1. Subjects fixated a horizontally moving laser spot and adjusted a rod to match the apparent slope of the motion path of the spot. IM magnitude was derived from these measures. Mean IM velocity was significantly higher with upward than with downward stimulation, and the difference was maximal at velocities of 40 and 70 deg s−1. The results are discussed within the context of the nystagmus-suppression theory and other theories of IM.
Illusory Contours from Pictorially Three-Dimensional Inducing Elements: Counterevidence for Parks and Rock's Example
Authors: Purghé Franco
Published: January 2007

In 1990 Parks and Rock claimed that, in pictorially three-dimensional (3-D) inducing patterns, an illusory figure does not emerge if a clear occlusion event is not present. A new pictorially 3-D pattern is presented which contradicts this claim. Two experiments were carried out. The first was aimed at ascertaining the presence of an illusory figure in the new 3-D pattern; the second was aimed at offering evidence that in Parks and Rock's pattern the disappearance of the illusory figure could be due to local interferences caused by the line elements in contact with the inducing borders. The results tend to contradict Parks and Rock's conclusions.
What Gives a Face its Gender?
Authors: Brown Elizabeth , Perrett David I
Published: January 2007

An experiment is reported in which the attribution of gender to isolated facial features and to faces whose features have been interchanged with those of a face of the opposite gender has been examined. Sixteen male faces were averaged to create a prototype male face and sixteen female faces averaged to create a prototype female face. The prototypes were then masked to exclude ears, neck, hair, and hairline. Individual features (brows, eyes, nose, mouth, and chin) and pairs of features (brows & eyes, eyes & nose, nose & mouth, mouth & chin) from the prototypes were then presented in isolation for classification according to their perceived gender. The results showed that, for the faces used, the brows & eyes, brows alone, eyes alone, the whole jaw, the chin, the nose & mouth, the mouth alone (in descending order), ie all the features except the nose, carried some information about gender when they were seen in isolation. In the second part of the experiment different features from one prototype face were grafted into the prototype of the opposite gender and the resulting composite faces classified by their perceived gender. The results of this feature substitution showed the jaw, brows & eyes, chin, and brows (in descending order) effecting significant change in perceived gender. The difference in gender information carried by feature(s) when they were viewed in isolation from that when they were substituted for each other is attributed to the role of configuration in the perception of the gender of a face.
Independent Effects of Lighting, Orientation, and Stereopsis on the Hollow-Face Illusion
Authors: Hill Harold , Bruce Vicki
Published: January 2007

Three experiments were conducted to investigate factors contributing to the ‘hollow face’ illusion. A novel method was employed in which the distance from the mask at which the illusion became apparent or disappeared, when retreating or approaching, respectively, was taken as a measure of the strength of the illusion. In all the experiments an effect of direction of observer's movement was found, demonstrating the stability of the initial percept.

Upright orientations were compared with inverted ones to investigate if the illusion reflects a bias towards a familiar percept. The direction of lighting was also varied. Independent main effects of orientation and lighting were found to be consistent with preferences both for upright faces and for top lighting. However, inverted faces also produced the illusion to some extent, suggesting a general preference for convexity. The role of stereopsis in resolving the illusion was tested by comparing monocular with binocular viewing conditions. Monocular viewing conditions gave rise to shorter distances, suggesting that the retinal disparities available with binocular viewing are important in disambiguating the illusion at small distances. The results are interpreted within the framework of a 22-dimensional sketch derived from independent modular processing of visual information.
The Familiar-Size Cue to Distance and Stereoscopic Depth Perception
Authors: Predebon John
Published: January 2007

The role of the familiar-size cue to distance in stereoscopic depth perception was examined in two experiments. In experiment 1 subjects judged the depth of a binocularly viewed interval, the far point of which was defined by either a familiar or an unfamiliar object, and in experiment 2 subjects adjusted the depth of the interval so that its extent appeared equal to the length of a vertical reference extent positioned on the surface of the object. Although familiar size influenced depth estimates (experiment 1) it did not influence matching judgments (experiment 2). The findings are discussed with reference to the issue of the nature of the familiar-size effects on judgments of stereoscopic depth.
The Perceived Strength of Motion-Defined Edges
Authors: Banton Tom , Levi Dennis M
Published: January 2007

Performance on visual tasks involving the use of motion-defined contours is likely to depend on stimulus strength, but presently there are no empirical or experimental assessments of motion-defined contour strength. Therefore, a matching method was used to estimate the strength of suprathreshold motion-defined edges on a luminance-contrast scale. The perceived strength of a motion-defined contour was expressed as an equivalent luminance contrast; this allowed the use of a single scale which accommodates diverse motion-defined stimuli. Motion-defined edge strength estimated in this manner was an inverted U-shaped function of dot density and dot velocity, and spanned at least a fivefold range of edge strengths. For one observer, maximum motion-defined edge strength was equivalent to 79% luminance contrast, at least thirteen times the contrast detection threshold. The results are interpreted via a simple two-stage model for perceiving motion-defined edges.
Misperception of Time-to-Collision by Drivers in Pedestrian Accidents
Authors: Stewart Douglas , Cudworth Christopher J , Lishman J R
Published: January 2007

The approach of an object can be monitored from its optic flow. More specifically, it has been postulated that time-to-collision at constant velocity is perceived by relating visual angle θ to its rate of change θ̇, time-to-collision being θ/θ̇.

This hypothesis is reappraised, and an alternative based on the parameters θ̇ and angular acceleration θ̈ is proposed. The expression 2 θ̇/θ̈ also specifies time-to-collision, with the benefits that it removes reliance on θ and permits time-to-collision to be determined from even momentary perception of an approaching point. This is supported by tests in which subjects responded to computer simulations of approaching objects. A further benefit is that if the object is accelerating rather than at constant velocity, time-to-collision is adjusted by 2 θ̇/θ̈, but not by θ/θ̇.

As time-to-collision increases, however, its cognitive derivation should transfer from optic flow to separate perceptions of distance and speed. It is proposed that when drivers of road vehicles are in potential collision with pedestrians their perception of distance is based primarily on familiar size, resulting in overestimation of size and therefore of time-to-collision with child pedestrians. This is supported by further computer simulations and is corroborated by predicting the effect of that overestimation on certain types of accidents, then testing from national accident statistics.

These analyses indicate that drivers' misperception of time-to-collision has a dramatic effect on the accident rate of child pedestrians. It is proposed that this could be greatly reduced by the provision of remedial measures.
Anisotropic Axes in Orientation Perception are Not Retinotopically Mapped
Authors: Buchanan-Smith Hannah M , Heeley David W
Published: January 2007

The effect of the posture of an observer on the pattern of meridional anisotropy for orientation acuity was examined. Orientation acuity was estimated for the two principal and for one oblique axis with three bodily postures: normal vertical sitting, vertical sitting with the head rotated to 45° from vertical, and prone. The test stimuli were sine-wave gratings covering a range of two octaves of spatial frequency, thin lines, and step edges. Acuity estimates were obtained by two different psychophysical procedures: a single-interval two-alternative forced choice, and a two-interval two-alternative forced choice. Both experimental procedures revealed a strong interaction between the shape of the function that describes the meridional variation of orientation acuity and the posture of the observer. The data are incompatible with models of the oblique effect in orientation perception that are based on a meridional anisotropy in neural properties early in the visual hierarchy.
How to Catch a Cricket Ball
Authors: Dienes Zoltan , McLeod Peter
Published: January 2007

A cricket or baseball fielder can run so as to arrive at just the right place at just the right time to catch a ball. It is shown that if the fielder runs so that d2(tan α)/d t2 = 0, where α is the angle of elevation of gaze from fielder to ball, then the ball will generally be intercepted before it hits the ground. This is true whatever the aerodynamic drag experienced by the ball. The only exception is if the ball is not approaching the fielder before he starts to run.
Gestalt Relations and Object Perception: A Developmental Study
Authors: Spelke Elizabeth S , Breinlinger Karen , Jacobson Kristen , Phillips Ann
Published: January 2007

We investigated whether adults and infants aged 3, 5, and 9 months perceive the unity and boundaries of visible objects in accord with the Gestalt relations of color and texture similarity, good continuation, or good form. Adults and infants were presented with simple but unfamiliar displays in which all three Gestalt relations specified either one object or two objects—perception of the objects was assessed by a verbal rating method in the adults and by a preferential looking method in the infants. The Gestalt relations appeared to influence the adults' perceptions strongly. However, the relations appeared to have no effect on the perceptions of 3-month-old infants and weak effects on the perceptions of 5-month-old and 9-month-old infants. The findings support the suggestion that developmental changes in object perception occur slowly. These changes, and the organizational phenomena to which Gestalt psychology called attention, may depend in part on the child's developing ability to recognize objects of particular kinds.
Binocular Rivalry Disrupts Stereopsis
Authors: Harrad Richard A , McKee Suzanne P , Blake Randolph , Yang Yuede
Published: January 2007

Does the shift from binocular rivalry to fusion or stereopsis take time? We measured stereoacuity after rivalry suppression of one half-image of a stereoacuity line target. After the observer signalled that the single stereo half-image had been suppressed, the other half-image was presented for a variable duration. Stereoacuity thresholds were elevated for 150–200 ms. A control experiment demonstrated that the threshold elevation was due to rivalry suppression per se, rather than masking effects associated with the rivalry-inducing target. Monocular Vernier thresholds, measured as the smallest identifiable abrupt shift in the upper line of an aligned Vernier target that had previously been suppressed by rivalry, were elevated for a much longer duration. This result shows that an appropriately matched stereo pair can break rivalry suppression more easily than can monocular changes in position. With the aid of a similar paradigm, we also measured the duration needed to detect a disparate feature in a random-dot stereogram after rivalry suppression of one half-image of the stereogram. Observers could correctly identify the location of the disparate feature (upper or lower visual field) when the other half-image was presented for a duration ranging from 150–650 ms. In the absence of the matching half-image, the first half-image was suppressed by the rival target for a far longer duration (a few seconds). These findings show that although stereopsis and fusion terminate rivalry, both are initially disrupted for a few hundred milliseconds by rivalry suppression.
Test of Balanced Transparency
Authors: Fukuda Mami , Masin Sergio C
Published: January 2007

It is implicitly or explicitly assumed in current transparency models that all the parts of a completely transparent surface have the same perceived degree of transparency. In general, the two experiments reported here have shown that this assumption is false. Consequently, any general transparency equation based on this assumption is unjustified. Separate transparency equations for the different parts of a transparent surface are instead justified. This indicates the need for a model of the overall judgment of transparency of these parts. In the second experiment the hypothesis that the judged degree of transparency of a whole transparent surface is a weighted average of the judged degrees of transparency of the different parts of this surface was tested. The results contradict this hypothesis and support the idea that the judgment of transparency of a whole surface and that of its parts depend on different stimulus conditions.
The Role of Wholistic/Configural Properties versus Global Properties in Visual Form Perception
Authors: Kimchi Ruth
Published: January 2007

A distinction has previously been proposed between global properties, defined by their position in the hierarchical structure of the stimulus, and wholistic/configural properties defined as a function of interrelations among component parts. The processing consequences of this distinction were examined in five experiments. In experiments 1–4 configural properties (closure and intersection) were pitted against component properties (line orientation and direction of curvature) and the results showed that discrimination and classification performance was dominated by the configural properties. In experiment 5 the relative perceptual dominance of type of property (configural/nonconfigural) and level of pattern structure (global/local) was examined. The results showed that classifications based on the configural property of closure were not affected at all by the level of globality at which this property varied. Global advantage was observed only with classifications based on line orientation. Taken together, the present results suggest that configural properties dominate discrimination and classification of visual forms, whereas the perceptual advantage of the global level of structure depends critically on the type of properties present at the global and local levels. These findings are also discussed in relation to findings on texture perception, and it is suggested that the perceptual system may be characterized by a predisposition for configural properties.
Aspect Graphs for Visual Recognition of Three-Dimensional Objects
Authors: Van Effelterre Thierry
Published: January 2007

Visual representation of three-dimensional (3-D) objects in our environment is a crucial question, for human as well as for machine vision. Some basics are reviewed of a viewer-centred model of 3-D objects, aspect graphs, which represents a 3-D object by all its topologically stable visible image contours (its aspects) and by the transitions between stable image contours (the visual events). This representation takes only geometrical information about discontinuities in depth and in surface orientation into account, and other clues, such as shadows, markings, texture, etc, are disregarded. Mathematical results give some insight into the relationships between the geometry of a 3-D object and the aspect of its image contours, the techniques used to compute an aspect graph effectively, and the state of the art of this type of model in computer vision. Current research is reviewed on viewer-centred representation in cognitive science that seems to indicate that aspect graphs could also have some relevance for human vision.
Cue Conflict and Stereoscopic Surface Slant about Horizontal and Vertical Axes
Authors: Ryan Colin , Gillam Barbara
Published: January 2007

The way in which a planar surface is defined or configured may affect its apparent slant about a given axis, and the magnitude of slant-axis anisotropies. The authors have previously suggested that (i) these within-axis and between-axis configuration effects may be attributable, in part at least, to the perspective—disparity conflict generated when geometrically frontoparallel configured surfaces are slanted stereoscopically; and (ii) that implicit contours, defined by line endings or conjunctions, may have effects analogous to those seen with explicit contours. These possibilities were directly examined in two experiments. In experiment 1, slant-axis anisotropy was progressively induced by adding horizontal lines to a vertical-line (zero anisotropy) grid under conditions of cue conflict; slants about the vertical (but not the horizontal) were attenuated—demonstrating a clear and systematic nexus between surface configuration and slant-axis anisotropy. The presence of regular implicit horizontals similarly and selectively attenuated the slant perceived about the vertical. In experiment 2, cue conflict was seen to exacerbate slant-axis anisotropy, but clearly could not fully account for it. There was an axis asymmetry in the effect of degrading implicit contours: degradation had a marked impact on perceived slant about the horizontal but not the vertical axis.
Detecting Changes in One's Own Velocity from the Optic Flow
Authors: Monen Jos , Brenner Eli
Published: January 2007

Experiments were designed to establish whether we can use the optic flow to detect changes in our own velocity. Subjects were presented with simulations of forward motion across a flat surface. They were asked to respond as quickly as possible to a step increase in simulated ego-velocity. The smallest change for which subjects could respond within 500 ms was determined. At realistic simulated speeds of locomotion, the simulated ego-velocity had to increase by about 50%. The threshold for detecting changes in simulated ego-velocity was hardly better than the threshold for detecting other changes in the acceleration of the dots on the screen. It made little difference whether the surface across which the subject appeared to move was built up of dots, lines, or triangles; neither did it matter whether subjects saw the same image with both eyes, or whether the simulation was presented in stereoscopic depth. The results show that we are very poor at detecting changes in our own velocity on the basis of visual input alone.