bluuebunny/crossref_metadata_2025 huggingface dataset:
Levels of Feature Analysis in Processing Visual Patterns
Authors: Ward Lawrence M , Wexler David A
Published: January 2007

In this paper, a revised Pandemonium-like model of visual-feature processing is formulated and a preliminary test of its feasibility is reported. The model differentiates visual-feature processing into a series of hierarchical stages organized by increasing complexity, with the output of each stage going both to the next higher stage, and directly to a more central processor. In the experiment, subjects sorted decks of cards into piles according to the presence or absence of a target stimulus which differed from nontargets in a variety of different features; detection of a feature was sufficient for detection of a target. The data generally supported the revised Pandemonium model, in that targets which differed from nontargets in features thought to be low in the hierarchy were processed faster than targets whose difference was in a high level feature. An extension of the revised model did somewhat less well in predicting the results of sorting for targets in which detection of any one of several features was sufficient for target detection.
Binocular Convergence as a Determinant of Reaching Behavior in Infancy
Authors: von Hofsten Claes
Published: January 2007

Reaching behavior in eighteen- to thirty-two-week-old infants was studied as a function of binocular convergence. The infant looked at the object to be reached for through prism arrangements which changed convergence only. The reaches obtained were nearly always directed at the virtual object defined by convergence. Corrections of the reaches, if any, were made rather late and often not before the hand arrived at the place of the virtual object.
Stereopsis and the Representation of Space
Authors: Klein Raymond
Published: January 2007

Four stereoblind and four normal subjects were tested on a mental rotation task. It was hypothesized that, if stereopsis is an important input for building up the perceptual system that represents three-dimensional space, then subjects lacking it ought to be deficient at mental rotations in depth. Stereoblind subjects were equally efficient at picture-plane and depth rotations, and were nonsignificantly better than normal subjects at rotations in depth. It was concluded that in the absence of stereopsis other cues are sufficient for the development of the ‘three-dimensional’ perceptual system. A puzzling paradox was raised, however, by the finding that the introspections of the two groups differed markedly.
Distortions and Disappearances of Geometrical Patterns
Authors: Wade Nicholas J
Published: January 2007

Prolonged observation of a stationary grating has a number of perceptual consequences. Initially the lines appear well-resolved and straight. The lines then take on a wavy and oscillating appearance, which is followed by scintillation of the pattern. The scintillations are often accompanied by cloudy disappearances of the grating. A streaming or scintillating aftereffect is visible subsequently, upon viewing a homogeneous surface. The literature concerning these effects is reviewed and several experiments are reported which examined the apparent waviness and scintillating disappearances. The basis for the apparent waviness remains unresolved. It is suggested that the scintillations are produced by small involuntary eye movements over the contours and that the associated disappearances might be due to binocular rivalry.
Storage of Spatially Specific Threshold Elevation
Authors: Thompson Peter G , Movshon J Anthony
Published: January 2007

The decay of several visual aftereffects may be prolonged by interposing a period of light-free or pattern-free viewing between adaptation and testing. We demonstrate that this storage phenomenon can be observed using the threshold elevation aftereffect that follows inspection of a high-contrast grating pattern. Control experiments comparing thresholds for vertical and horizontal gratings after adaptation to a vertical grating reveal that the stored aftereffect, like its unstored counterpart, is pattern-selective. Storage is equally pronounced with stimuli that are detected by pattern-analyzing or movement-analyzing visual channels. Unlike other aftereffects, the threshold-elevation aftereffect requires that the storage period be light-free; no storage is seen if a blank field is inspected between adaptation and testing. The results are discussed with respect to the nature of visual aftereffects, and possible cognitive or physiological models of storage.
Visualization of Compound Scenes
Authors: Beech John R , Allport D Alan
Published: January 2007

Subjects listened to descriptions of familiar objects and the spatial relations between them and attempted to visualize these objects as a composite scene. The time taken to generate a composite visual image, measured from the end of the verbal description, increased dramatically and linearly with the number of objects in the scene. As this relationship was independent of the rate of presentation of the verbal description, over a wide range, it could not be due to the visualization process cumulatively lagging behind the verbal description. Our evidence indicates that this relationship is due to some process, necessary to the subjective visualization of a composite array as a whole, which commences only after the verbal description is complete.
Size and Position Invariance in the Visual System
Authors: Cavanagh Patrick
Published: January 2007

The encoding of simple features such as lines and angles leads naturally to size and position invariance when these features are analyzed symbolically in terms of structure and connectedness. No such analysis is possible for a spatial frequency encoding, however, as all a priori indications of pattern unity are lost. An additional transformation of spatial frequency information is therefore demonstrated that automatically derives a size invariant representation of form. The feasibility of the transform scheme in the visual system is outlined with a hypothetical processing sequence. It is found that the organization of cells in the striate cortex shows a marked similarity to an intermediate stage of the proposed sequence.
Importance of Relative Width Differences and Instructions on Shape Constancy Performance
Authors: Kaess Dale W
Published: January 2007

Adult subjects were instructed to select either the wider physical or the wider perspective shape of two rotated rectangles. With equal differences between the physical and perspective widths, responses were governed by instructions and by the magnitude of the differences between widths of the forms. However, with unequal differences between physical and perspective widths of the two rectangles, responses were governed primarily by the magnitude of the differences. Regardless of instructions, responses were to the dimension with the greater difference between widths. The results suggest that performance in the shape constancy experiment is a function of relative dimensional discriminability, as defined by instructions, and relative differences of widths between forms presented for comparison.
Another Optical—Geometrical Illusion
Authors: Vicario Giovanni B
Published: January 2007

A new optical—geometrical illusion is described. The parallelism of short rows of dots is affected by some unknown factor, so that the rows appear as pivoting on their middle point. Some explanations of the illusion are considered, but with no success.
The Perception of Motion: Michotte Revisited
Authors: Weir Sylvia
Published: January 2007

This paper extends the range of artificial-intelligence vision programs to the domain of moving objects, using the work of Michotte as a source of data for a computer program which purports to ‘see’ the action types he examined. Given the thesis that internal descriptions of a nonlinguistic type provide the basis for a constructive, knowledge-based theory of perception, the properties of a symbol-manipulating system capable of supporting this are explored as a challenge to the Michotte notion of “direct perception without interpretation”.
Apparent Movement of Successively Generated Subjective Figures
Authors: Petersik J Timothy , Hicks Kenyon I , Pantle Allan J
Published: January 2007

In the present studies a pair of random-dot frames was constructed so that two areas in the first frame (f1) were correlated with two areas in the second frame (f2). The alternation of the pair of frames (an f1-f2 sequence) gave rise to two subjective figures. When two pairs of random-dot frames (an f1-f2 sequence and an f3-f4 sequence), each of which produced two subjective figures in different locations, were themselves alternated, the subjective figures from the f1-f2 sequence interacted with the subjective figures from the f3-f4 sequence to produce apparent movement. With any one of the four general kinds of displays which we constructed, subjects usually perceived only one of two types of subjective-figure movement. The type of movement that was perceived with a given display depended primarily upon the degree of change (across the interval between an f1-f2 and an f3-f4 sequence) of the internal structure of the successively generated subjective figures. Relative intensity differences between the subjective figures and their backgrounds influenced the type of apparent movement seen, whereas variations in the density of elements in a display did not. We tentatively propose a two-stage model to explain the apparent movement of the subjective figures: the first stage is assumed to generate the subjective figures by means of a cross-correlation of the intensity distributions of the two frames within an f1-f2 sequence and within an f3-f4 sequence; on the basis of inputs from the first stage, the second stage generates apparent movement signals for the subjective figures.
Stereopsis Masking in Humans is Not Orientationally Tuned
Authors: Mayhew John E W , Frisby John P
Published: January 2007

A stereopsis signal carried by an oriented random texture and masked by a similar noise texture is not unmasked when the orientation of the noise is rotated. This result is discussed in connection with the orientational tuning of local and global stereopsis processes.
Analysis of the Detection of a Moving Line
Authors: King-Smith P Ewen
Published: January 2007

A model is proposed to explain the effects of line motion on visual sensitivity. The model incorporates recent evidence for parallel ‘pattern’ and ‘flicker’ systems. An element of either system consists of a spatial filter followed by a temporal filter; the characteristics of these filters were derived from previous psychophysical measurements. The model may be used to demonstrate why visual sensitivity to optimum triangular-wave motion is greater than for optimum square-wave motion, which, in turn, is greater than for on-off presentation. The predictions of the model are in reasonable agreement with threshold-amplitude data for triangular-wave and square-wave motion; the model is also consistent with threshold-frequency data for small-amplitude sinusoidal motion.
Illusory Dilatation of Square Surfaces
Authors: Bazzeo Aurora , Zanuttini Lucia
Published: January 2007

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 × 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.
Contrast Summation Effects and Stereopsis
Authors: Mayhew John E W , Frisby John P
Published: January 2007

Contrast thresholds for stereopsis were measured for a variety of bandpass-filtered random-dot stereograms in a series of experiments. The principal finding was that contrast thresholds for stereopsis from ‘complex’ stereograms composed of mixtures of (a) two widely different spatial frequencies or (b) two or more widely different oriented random textures, are considerably lower than would be expected if stereopsis from such stimuli is mediated by the first component to rise above its own stereopsis contrast threshold. Instead, it appears that stereopsis comes about whenever the supradetection-threshold contrast of a stereogram exceeds a certain level, regardless of whether this contrast is provided by a single component or by a mix of two different ones. The implications of these findings for models of stereopsis are discussed.
The Relationship between Brightness Contrast and Illusory Contours
Authors: Jory Max K , Day Ross H
Published: January 2007

One group of subjects rated differences in brightness and another the clarity of illusory contours for eight figure — ground combinations of the Kanizsa and Ehrenstein patterns made from Munsell papers. For four combinations there was a difference in Munsell value (brightness) between figure and ground and for another four no difference. For the latter the pattern was derived from differences in hue or colour quality. For the combinations with a Munsell value difference the ratings of both brightness difference and contour clarity were high and for those of uniform value both were low. The results are interpreted as supporting the argument that illusory contours derive primarily from contrast-induced differences in brightness and possibly in colour between contiguous, physically uniform regions.
Sensory Conditions for the Occurrence of the Neon Spreading Illusion
Authors: van Tuijl Harrie F J M , de Weert Charles M M
Published: January 2007

The neon effect, i.e. an illusion of light projected onto a homogeneous lattice, may occur in line patterns made up of elements of different color or brightness. Particular luminance relations between the different line elements in the pattern and between these line elements and their background appear to be critical for the occurrence of the effect.
Three-Dimensional Perception of Planar Line Segments
Authors: Hoyer Horst W
Published: January 2007

Two-dimensional line drawings can be perceived as three-dimensional images if they are viewed through a grating of parallel lines placed a short distance above the drawing. The position in space of the images is a function of the angle between the lines in the drawing and those in the viewer grating.
Salt Taste Adaptation: The Psychophysical Effects of Adapting Solutions and Residual Stimuli from Prior Tastings on the Taste of Sodium Chloride
Authors: O'Mahony Michael
Published: January 2007

The paper reviews how adaptation to sodium chloride, changing in concentration as a result of various experimental procedures, affects measurements of the sensitivity, intensity, and quality of the salt taste. The development of and evidence for the current model that the salt taste depends on an adaptation level (taste zero) determined by the sodium cation concentration is examined and found to be generally supported, despite great methodological complications. It would seem that lower adaptation levels elicit lower thresholds, higher intensity estimates, and altered quality descriptions with predictable effects on psychophysical measures.
The Effect of Spatial Frequency and Contrast on Visual Persistence
Authors: Bowling Alison , Lovegrove William , Mapperson Barry
Published: January 2007

The visual persistence of sinusoidal gratings of varying spatial frequency and contrast was measured. It was found that the persistence of low-contrast gratings was longer than that of high-contrast stimuli for all spatial frequencies investigated. At higher contrast levels of 1 and 4 cycles deg−1 gratings, a tendency for persistence to be independent of contrast was observed. For 12 cycles deg−1 gratings, however, persistence continued to decrease with increasing contrast. These results are compared with recently published data on other temporal responses, and are discussed in terms of the different properties of sustained and transient channels.
Exposure-Time and Spatial-Frequency Effects in the Tilt Illusion
Authors: O'Toole Brian I
Published: January 2007

The exposure durations of a vertical test line and a tilted inducing grating were varied and the tilt illusion thus generated was found to change as a function of this variation. Significant direct effects (acute-angle expansion) and indirect effects (acute-angle contraction) were found to occur at times consistent with Andrews's estimate of the time course of inhibition in the visual system when the inducing grating had a spatial frequency of 10 cycles deg−1. However, a 2 · 71 cycles deg−1 grating gave significant effects at exposure durations of 10 as well as 1000 ms, while in a further experiment a 10 · 91 cycles deg−1 grating gave significant effects at 1000 ms only. These results seem to suggest that orientation interactions thought to be due to inhibition (direct effect) and disinhibition (indirect effect) may occur within both sustained and transient channels with concomitant differences in time constants.
A Computational Study of a Period of Infant Object-Concept Development
Authors: Prazdny Slava
Published: January 2007

Piaget has distinguished a number of distinct stages in the development of the concept of an enduring external object during infancy. I present a theory of a class of behaviours at one of these stages embodied in a working computer program. The behaviour of this program matches a class of perceptual behaviours of infants between about twelve and twenty weeks of age in a number of experimental situations studied by Bower. The theory argues that these behaviours are a result of the interaction between the perceptual and conceptual levels of the system, and the way in which conflicts between competing descriptions of an object are resolved. I locate the cause of several features of the behaviours in the procedures for managing the changing representation of the world, and the system's way of treating transitions between the states of an object (for example, moving to stationary). The basic conceptual primitives of the analysis are objects and events, not motion and place, as argued by Bower, or the infant's previous activity, as argued by Piaget. I argue that adequate explanations of experimental findings such as these require the construction of fairly detailed computational models.
Slant Underestimation: A Model Based on the Size of the Viewing Aperture
Authors: Perrone John A
Published: January 2007

By analyzing the projection plane in terms of the projected size of different elements on a surface, it is shown how the direction of the perpendicular, from the station point to the surface, is an important variable in the derivation of the slant angle. It is also shown that the test surfaces used in traditional slant-perception experiments contain no information about this direction. A model is proposed which is based on the idea that the direction of the line from the eye to one edge of the viewing aperture is mistaken for the perpendicular, and two options are derived to show how the information in the optical array could be interpreted on the basis of the perpendicular lying in this new direction. It is shown that both of these options are dependent upon the size of the field of view of the test surface and both are underestimations as long as half of the angle measuring the field of view is less than the actual slant of the surface. The model is tested against some data from previously reported experiments and is found to provide a close fit.
The Effect of Blurring on Intersecting-Line Illusions
Authors: Stuart Geoffrey W , Day Ross H
Published: January 2007

It was observed by chance that illusions in patterns consisting of criss-crossing lines, such as the Orbison and Hering illusions, are markedly reduced when the patterns are blurred. In the first of two experiments the reduction with blurring was confirmed for four patterns but failed to occur in patterns lacking criss-crossing lines. In the second experiment the reduction was shown to be due mainly to the reduced luminance contrast in blurred patterns, thus confirming earlier findings on the effect of contrast on this group of illusions. Theoretical implications are discussed.
The Double-Nail Illusion: Experiments on Binocular Vision with Nails, Needles, and Pins
Authors: Krol Jodi D , van de Grind Wim A
Published: January 2007

When two nails or similar slender objects are held straight ahead at reading distance, one a few centimetres behind the other and aligned at the same eye level, they are seen side by side rather than one behind the other. A quantitative study of this ‘double-nail’ illusion shows that the objects are judged to be at the positions of the so-called apparent or ghost images known from fusional theories of stereopsis. Most recent fusional theories assume that apparent images are suppressed by neuronal interactions, and the usual absence of percepts corresponding with apparent images is often quoted as an argument against ‘projection’ theories of stereopsis. The double-nail illusion shows, however, that percepts which correspond with apparent images do occur. The results are interpreted in terms of a neuronal-network type of fusional theory, in which the interpretation that corresponds with the minimum overall disparity is assumed to dominate. The following parameters were varied in the experiments: length, width, colour, and contrast for each of the nails; and fixation point position; and the orientation of the nail carrier. The results show that identity of the stimuli is not a necessary condition for the illusion. A stable vergence can be enforced by the double-nail illusion, and with additional nails multistable states of vergence can be obtained.
The Detection of Auditory Visual Desynchrony
Authors: Dixon Norman F , Spitz Lydia
Published: January 2007

Subjects were presented with a film and its soundtrack through apparatus which enabled asynchrony between picture and sound to be increased. It was found that asynchrony is more easily detected when sound precedes picture, and for a hammer hitting a peg than for someone speaking. These preliminary results suggest that we learn to tolerate the asynchrony between hearing and vision produced by the slower transmission of sound than of light.
A Versatile Colour Stimulus Generator
Authors: Wittebrood Jos E M , Wansink Marty G , de Weert Charles M M
Published: January 2007

An inexpensive colour-picture generating system is described and a few applications are indicated. The basic equipment comprises a microprocessor; a colour television monitor with R, G, and B inputs; and a number of video memories. The most important characteristic of the apparatus is the way in which video memories are used in combination with a set of colour registers and very fast digital/analog converters. The equipment permits display of any kind of figure with a maximum of eight colours simultaneously present. Figures may be generated point by point by the experimenter, or by computer. Colours can be changed continuously with the R, G, and B channels each receiving one out of 256 possible values.
Pursuit Eye Movements and the Depth-Movement Phenomenon in Dynamic Visual Noise
Authors: Leguire Lawrence E
Published: January 2007

The ability to generate voluntary pursuit eye movements in the absence of retinal-contour motion cues was assessed on the basis of observers' perceptions of depth and motion when they viewed dynamic visual noise with a filter over one eye. The results indicated that the depth-movement phenomenon yielded robust pursuit with the velocity an inverse function of filter density. These data suggest that retinal-contour motion cues are not necessary and that perceived motion is sufficient to drive pursuit.
Consistency of Response during Steady Visual Simulation
Authors: Swanston Michael T , Wade Nicholas J
Published: January 2007

The indication of subjective states during steady visual stimulation by means of key depressions has been assumed to be free of systematic bias. However, it is shown that the reported visibility of simple stimuli may be determined by the level of categorisation employed before the initiation of an overt response. In particular, the duration of unitary disappearance of a stimulus is found to be greater when this is the only category of change to be reported than when the same measure is derived from concurrent reports of the disappearance of its parts. The correspondence of findings both with afterimages and with steady fixation shows that peripheral factors such as eye movements cannot provide an adequate explanation. Experiments comparing part/whole categorisation of the visibility of single lines suggest caution in the acceptance of previous studies designed to indicate underlying neurophysiological mechanisms in subjective disappearances.
The Motion-Induced Contour
Authors: Klymenko Victor , Weisstein Naomi
Published: January 2007

An outline projection of a rectangular solid object, rotating in depth, produces a moving rotating in depth illusory contour across the empty region where an edge would normally be located even though it is not physically present. Observers see a contour demarcating the junction of the two frontal surfaces of the object when it undergoes the figural transformations of rotation-in-depth. Two experiments, in which several types of temporal change were compared, demonstrated that translation, flicker, or no motion are ineffective in producing the contour compared to rotation-in-depth. Also the four lines constituting the two inducing vertices of the object were sufficient to produce the motion-induced contour during rotation-in-depth. Three demonstrations further clarifying the nature of the motion-induced contour are also reported.
Spatial Induction of Illusory Motion
Authors: Gogel Walter C , Griffin Bernard W
Published: January 2007

Induced motion is not limited to continuous motions presented on a frontoparallel plane. Experiments were conducted to investigate several varieties of induced motion to which theories of induced motion must apply. The observer indicated the perceived path of motion of a vertically moving test point to which induced motion at right angles to the physical motion was added by the motion of two inducing points. In experiment 1 all motions (both apparently and physically) were in a frontoparallel plane. It was found that discrete displacement as well as continuous motion of the test and inducing points produced substantial amounts of induction. In experiment 2 the inducing points were continuously moved in stereoscopic distance rather than remaining in an apparent frontoparallel plane. A large amount of apparent motion in depth was found in the vertically moving test point and was interpreted as an induced motion in depth. In experiment 3 an alternative interpretation of the phenomenon of experiment 2, in terms of an apparent vergence for the two images of the test point, was investigated and found to be unlikely. In experiment 4, with all the points moving continuously in a frontoparallel plane, eye motions as well as induced motions were measured, with the observer fixating either the test point or an inducing point. Substantial amounts of induction were obtained under both conditions of fixation. The consequences of these findings for theories of induced motion are discussed.
Binocular Adaptation That Cannot Be Measured Monocularly
Authors: Wolfe Jeremy M , Held Richard
Published: January 2007

The tilt aftereffect (TAE) is used to demonstrate the existence of a purely binocular process in human vision. A purely binocular process is a process that can be activated only by matched inputs to the two eyes. It is insensitive to monocular stimulation. The TAE can be produced by exposure to a bipartite field with the top tilted to the left of vertical, the bottom to the right. After such adaptation a pair of colinear lines appears bent in the opposite direction. A cyclopean random-dot stereogram can be used as an adapting stimulus. It produces a 2° TAE when a cyclopean test stimulus is used and a 1° TAE when a binocular but noncyclopean test stimulus is used. If the same noncyclopean pattern is viewed monocularly, no TAE is measurable. The TAE does not transfer from cyclopean adaptation to monocular testing. Apparently, cyclopean stimuli activate a ‘purely binocular process’ that cannot be activated by either eye alone.
Study of Unaided Cross-Eyed Stereopsis
Authors: Hamori Eugene , Broad Roy D , Reed Calvin E
Published: January 2007

The learning of the skill of unaided cross-eyed stereopsis was investigated on a group of young adults. Both pictorial and random-dot stereograms were used; small stereograms were viewed at normal reading distance and large projected stereograms were viewed in an auditorium. The results suggest that this direct stereoscopic technique can be learned within a few minutes by almost everyone in the population represented by the test group. The calculated eye-convergence angles for various conditions of cross-eyed stereoscopic viewing indicate that little eye discomfort is caused by this factor when the stereograms are located at a sufficient distance from the viewers. The comments of subjects support this conclusion. The unexpected prevalence of the aptitude for this skill should have practical application in the unaided three-dimensional visualization of computer-generated stereograms.
Letter Identification in Words and Non-Words, with Variation in Visual Angle and Delay of Position Cue
Authors: Solman Robert T
Published: January 2007

Two experiments are described in which subjects were required to report the name of a single position-cued ‘critical’ letter in a tachistoscopically displayed string of four letters. The stimulus characters were arranged to form three types of letter strings: (i) strings in which the letters did not form words; (ii) words in which contextual constraint of the critical letters was minimised; and (iii) words in which contextual constraint of the critical letters was maximised. The serial position of the letter to be identified in each string was cued at delays of −500, −100, and +500 ms, in experiment 1 and at delays of −510 and +510 ms in experiment 2, and in both experiments one group of subjects responded to letter strings which subtended a horizontal visual angle of 3·95 deg, while a second group responded to strings which subtended 1·02 deg. Correct identifications of critical letters showed that the presentation of words resulted in superior performance. This ‘word superiority effect’ is consistent with earlier findings implying that it has a perceptual locus. For the stimuli which subtended the large visual angle the word advantage was detrimentally affected only when the position of the critical letter to be identified was cued either 500 or 510 ms prior to the display of the letter string.
An Alternative Explanation of the Infant's Difficulty in the Stage III, IV, and V Object-Concept Tasks
Authors: Neilson Irene
Published: January 2007

Traditional explanations of the infant's difficulty in the stage III, IV, and V object-concept tasks have centred on the fact that the object is made to disappear. It is argued that this emphasis is mistaken. Two experiments are reported which demonstrate that infants continue to have difficulty in these tasks when tested with transparent occluders. The implications of these findings for alternative explanations of the infant's difficulty in the stage III, IV, and V tasks are considered.
Rehabilitation of a Classical Notion of Panum's Fusional Area
Authors: Krol Jodi D , van de Grind Wim A
Published: January 2007

It is argued that (1) the work of Burt and Julesz does not challenge the classical notion of Panum's fusional area; (2) their disparity gradient concept is contradicted by some of their own findings as well as by those of Krol and van de Grind; (3) their results can be accounted for by the classical concept of Panum's fusional area if eye vergence is taken into account; (4) the explanations suggested by Burt and Julesz for the depth perception aspects of Panum's limiting case and the double-nail illusion are based on unwarranted generalisation of results concerning binocular direction vision.
An Effective Paradigm for Conditioning Visual Perception in Human Subjects
Authors: Davies Peter , Davies Geoffrey L , Bennett Spencer
Published: January 2007

Repeated pairing of an auditory conditioned stimulus with a weak visual unconditioned stimulus produced extended image sequences and visual responses conditioned to the tone alone. The experiment is set into the context of Pavlov's view of Helmholtz's “unconscious inference” thus providing experimental evidence linking the higher mental process of perception with classical conditioning.
A Model of the Development of the Early Infant Object Concept
Authors: Luger George F , Bower T G R , Wishart Jennifer G
Published: January 2007

A computational model is proposed for the early stages of development of the object concept in infancy. Stages in development are represented as a sequence of grammars or rewrite rules that parse a set of perceptual phenomena. The infant's changes between developmental stages can be described by differences between the grammar rules that model each stage. The program replicates five studies by Bower et al on the development of the object concept and reaffirms the primacy of rest and motion parameters as explanatory invariants in early object-concept development.
Illusory Contour Lightness: A Neglected Possibility
Authors: Parks Theodore E , Rock Irvin , Anson Richard
Published: January 2007

When the area occupied by a typical sharp-edged illusory figure is outlined physically, some illusory lightness survives within the contours as an example of figure-ground contrast. This general phenomenon may therefore account for the direction of the apparent alteration in lightness found within many illusory figures, but it cannot account for the magnitude of that alteration.
Individual Variation in Directional Bias in Visual Perception
Authors: Annett Marian
Published: January 2007

Directional biases in visual perception were examined for individual differences in sixty-five subjects on two tasks. One task required judgments of the onset asynchrony of pairs of dots presented at random, either one dot in each visual field, or both in the left visual field (LVF), or the right visual field (RVF). The second task required the recall of four letter strings presented randomly in either visual field. Dot-asynchrony judgments were influenced by two main biases: first, an outward from the centre bias in both visual fields, and second, a lateral bias which was significantly from left to right (L—R) in the total sample. A substantial minority of subjects were biased to judge the dots as occurring in right to left (R—L) order.

Accuracy of letter report decreased fairly consistently from L—R in the RVF but varied in the LVF. Some subjects showed a L—R report gradient, some a R—L gradient, and some a U-shaped recall pattern. Significant correlations between measures of L—R and R—L biases on the two tasks show that the biases have some stable foundation. The findings suggest that there are directional biases affecting visual perception which are due neither to learned reading habits, nor to cerebral specialization of function.
The Multiple Determination of Illusory Contours: 1. A Review
Authors: Halpern Diane F , Salzman Billie
Published: January 2007

Four theories of illusory-contour perception are reviewed—brightness contrast (simultaneous contrast, assimilation, and dissimilation), depth/completion, partial activation of neural feature analyzers, and the diffuse—sharp dichotomy. It is concluded that the processes and mechanisms involved in illusory-contour perception most likely depend upon the stimulus elements used in the illusory-contour display.
Reaching for Rattles: A Preliminary Study of Contrast Sensitivity in 7–10 Month Old Infants
Authors: Atkinson Janette , French Jennifer
Published: January 2007

Contrast sensitivity for a 3 cycles deg−1 sinusoidal grating in 7–10 month old infants was tested by presenting gratings and uniform fields on cylinders, with the former providing auditory reinforcement when the infant picked them up. The method shows that a contrast as low as 7.5% can commonly be detected at this age, compared with 1–2% for adults under comparable conditions. However, as the development of hand preferences interferes with the task as an indicator of visual sensitivity, it is concluded that this method is not in its present form suitable for vision testing on a wide scale or in a clinical setting.
Apparent Reversal Frequencies in Squares and Trapezia: The Effect of Invariant and Variant Information
Authors: Mitchell Rex , Power Roderick P
Published: January 2007

Three studies of apparent reversals (ARs) in rotating rectangular and trapezoid arrays are reported, together with a mathematical analysis. Study 1 explores the effect of different degrees of outline suppression on the frequency and distribution of ARs in squares and trapezia. Study 2 examines how modifications in both types of array reduce AR frequency, demonstrates a manipulation whereby ARs in rotating squares are eliminated, and suggests that ARs in squares and trapezia are of different origins. In the mathematical analysis, an invariant characteristic of the transformations of rotating rectangles is reported, and from this a numerical index is developed that expresses the extent to which a rotating trapezium may appear to pause just before each point of oscillation. In study 3 it is shown that this measure is a better predictor of AR frequencies than the heuristic proposed by Braunstein.
Gustatory Responses to Nongustatory Stimuli
Authors: O'Mahony Michael
Published: January 2007

Subjects were required to give taste responses to days of the week and states of the USA, as well as colour responses. Some consistency of response was obtained over three sessions held at two-week intervals. The implications of such consistency of response to nongustatory stimuli for psychophysical taste description are discussed.
Global Factors in the Hermann Grid Illusion
Authors: Wolfe Jeremy M
Published: January 2007

Most explanations of the Hermann grid illusion are local in nature. For example, in Baumgartner's model the effect is generated by the response of cells having concentric on—off or off—on receptive fields. Such models predict that the magnitude of the illusion at a given intersection should be the same whether that intersection is viewed in isolation or in conjunction with other intersections in a grid. Two experiments are reported. The first demonstrates that illusion magnitude grows with the number of intersections. The second shows that this growth is seen when the intersections are arranged in an orderly grid but not when they are placed irregularly. These results suggest that a purely local model for the Hermann grid illusion is not a complete explanation. Global factors must be involved.
Complex and Simple Proportions and the Aesthetic Attractivity of Visual Patterns
Authors: Boselie Frans
Published: January 2007

It is hypothesized that a figure with sides and angles in complex ratios (that is, other than 1:1) makes an aesthetic impression only when the complex ratios entail simple ones. An experiment is reported in which twelve pairs of line drawings were presented in which one drawing (A) always contained one or more 1:1 ratios, whereas in the other drawing (B) such simple ratios could not be indicated. In seven pairs the A pattern was preferred significantly. In this context, the alleged aesthetic appeal of the golden section is discussed.
Binocular Summation on Fused Annular Backgrounds
Authors: Cogan Alexander I , Silverman Gerald , Chan Hoover
Published: January 2007

A paradigm has been proposed to test the hypothesis that binocular fusion results in simple summation, S, of monocular photopic luminances: S = Δ LBM( L)/Δ LB(2 L) = 1, where Δ LBM and Δ LB are threshold luminances for a monocular and a binocular increment, appearing on a fused background of luminance L or 2 L, respectively. This prediction was tested psychophysically, with background size as parameter. Thresholds were measured for a brief (20 ms) foveal flash centered on a luminous disk encircled by a massive black annulus serving as a fusion lock. The flash was presented binocularly, or monocularly, at 30 and 60 cd m−2 background luminances. The diameter of the disk was varied from 3 min to 40 min visual angle. The size of the flash was constant (6 min diameter), except for the smallest disk (3 min diameter). All thresholds varied as a function of background size (the known ‘sensitization effect’). The summation index S did not vary with background size. A mean value S = 0.9 was found; this is consistent with the notion that summation of the order of 90% occurs during binocular fusion. We surmise that even a weak monocular test flash makes fusion less than perfect.
The ‘Shrinking Circle Illusion’ is a Shrinking Ellipse
Authors: Bradley Drake R , Godiksen Emil B
Published: January 2007

Twenty-four subjects judged the size of the horizontal and vertical extents of the path traversed by a circularly rotating target. The target was rotated at velocities ranging from 0.18 to 1.13 cycles s−1, and observed with smooth pursuit eye movements or by fixating a point in the center of the path. It was found that underestimation of the target path increased with velocity, and was more pronounced for the horizontal than vertical component of the target path. These effects were quite strong during smooth pursuit, but weak during fixation. In previous research on the ‘shrinking circle illusion’ the vertical component of the path was not measured. The present findings indicate that the apparent shape of the path is elliptical, and that the eccentricity of this ellipse increases with velocity during smooth pursuit.
Human Orientation with Restricted Sensory Information: No Evidence for Magnetic Sensitivity
Authors: Fildes Brian N , O'Loughlin Bernard J , Bradshaw John L , Ewens Warren J
Published: January 2007

Baker claimed that people are able to orientate themselves to particular geographical locations as a result of sensitivity to the Earth's magnetic field. These claims were disputed by Gould and Able. A study involving a greater number of subjects ( n = 103) and more stringent control over environmental sensory cues was carried out to resolve this disagreement. Subjects responded, both with a direct pointing response and with a verbal judgement in terms of an imagined clock face, to the targets of north, home, and the City of Melbourne. In statistical terms, subjects were not able to orientate towards any target by use of either response. No evidence was found for a magnetic sense in humans as claimed by Baker.
Upside-down Presentation of the Johansson Moving Light-Spot Pattern
Authors: Sumi Shigemasa
Published: January 2007

In a film produced by Johansson, a group of moving spots, corresponding to lights attached to the main joints of a walker or a runner, gives instantly a vivid impression of a person walking or running. Even when this film was inverted and run backward, some sort of human movement was still perceived. It was perceived more frequently as an upright image of a person moving forward in a very strange manner than as an inverted image of a person moving backward. Such strangeness seemed to arise from the fact that the actor's arms were perceived as legs and vice versa. The phase relations typical of the Johansson pattern are therefore still present when the film is inverted and run backward, leading to the perception of biological motions though these motions are very strange.
Learning Spatial Dimensions with a Visual Sensory Aid: Molyneux Revisited
Authors: Warren David H , Strelow Edward R
Published: January 2007

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.
Rivalry with Continuous and Flashed Stimuli as a Measure of Ocular Dominance across the Visual Field
Authors: Leat Susan J , Woodhouse J Margaret
Published: January 2007

Two measures of sensory ocular dominance were compared. Both involved dichoptic presentation of orthogonal gratings—a situation which results in binocular rivalry. The gratings were presented briefly in experiment 1 and continuously in experiment 2 and by the predominance of one grating over the other a quantitative estimation of ocular dominance was obtained in both cases. Comparison of the results showed that (a) binocular rivalry suppression was present for exposures of 250 ms and (b) the briefly presented gratings were a more sensitive test for ocular dominance than conventional continuously presented stimuli.

The variation of dominance over the horizontal meridian of the visual field was considered. For many subjects a consistent different in the ocular dominance in the two halves of the visual field, and therefore of the cortex, was found. Some showed dominance of the ipsilateral eye in each hemisphere while others showed dominance of the contralateral eye. It was found that there is, in fact, a continuum of types of dominance pattern amongst individuals.
Contextual Effects in Infant Visual Perception
Authors: Bomba Paul C , Eimas Peter D , Siqueland Einar R , Miller Joanne L
Published: January 2007

A familiarization/preference technique was used to assess the ability of three- and four-month-old infants to discriminate line segments that differed in orientation. Discrimination was found to be significantly better, as evidenced by a greater preference for the novel stimulus, when the line segments were embedded in a redundant contextual frame than when they were presented alone. However this effect could not always be unambiguously interpreted; under some stimulus conditions, a strong stimulus preference may have caused the novelty effect. It is concluded that perception in infants is, at least in part, organized and, as in adults, involves more than a simple feature-by-feature analysis of information.
The Role of Pattern and Flicker Mechanisms in Determining the Spatiotemporal Limits of Velocity Perception. 2. The Lower Movement Threshold
Authors: Harris Michael G
Published: January 2007

For slowly-drifting foveally-presented gratings of 1 cycle deg−1 and above, continuous movement can be perceived at stimulus velocities greater than about 1 min visual angle s−1, irrespective of spatial frequency, providing stimulus contrast is greater than 0.01. For coarser gratings, the minimum perceivable rate of drift is determined by the detectability of the stimulus and is strongly dependent upon both spatial frequency and contrast.