bluuebunny/crossref_metadata_2025 huggingface dataset:
Border Locking and the Café Wall Illusion
Authors: Gregory Richard L , Heard Priscilla
Published: January 2007

The Café Wall illusion (seen on the tiles of a local café) is a Münsterberg chequerboard figure, but with horizontal parallel lines which may have any luminance separating the rows of displaced squares. These (the ‘mortar’ lines) display marked wedge distortion which is especially affected by: contrast of the squares (‘tiles’); width of the ‘mortar’ lines, and their luminance which must not be significantly higher than that of the light squares or lower than that of the dark squares for distortion to occur. An experiment is described from which quantitative data have been obtained by varying these parameters. It is suggested that contiguous regions of different luminance (and contiguous colour regions) are normally held in spatial register by locking from common luminance boundaries. The Café Wall illusion is attributed to this border locking producing inappropriate contour shifts from neighbouring regions of contrasting luminance when separated by narrow gaps of neutral luminance. Further implications on the border-locking notion are discussed.
Assessment of Depth Perception in Cats
Authors: Mitchell Donald E , Kaye Martin , Timney Brian
Published: January 2007

A behavioural method is described for the assessment of depth perception of kittens. Measurement is made of the smallest separation in depth that can be discriminated between two adjacent stimuli under both monocular and binocular viewing conditions. Normal animals can discriminate much smaller separations in depth when using two eyes than with monocular viewing, implying the presence of a cue to depth that is uniquely available with binocular viewing. The test provides a quick and reliable way of screening animals for stereopsis.
A Test for Contrast-Polarity Selectivity in the Tilt Aftereffect
Authors: Magnussen Svein , Kurtenbach Wolfgang
Published: January 2007

The tilt aftereffect (TAE) was studied with adapting and test stimuli consisting of black or white bars (experiment 1), and of luminance edges (experiment 2). Both experiments failed to demonstrate selectivity of the TAE to the polarity of luminance contrast.
Flexibility in the Choice of Distinctive Features in Visual Search with Blocked and Random Designs
Authors: Corcoran Derek W J , Jackson Alistair
Published: January 2007

An experiment is reported which demonstrates that the features used to detect a character in arrays of similar forms are a function of the stimulus context in which the target is embedded. With the use of blocked and randomised design it was shown that prior knowledge of the background aided search when the feature which was relevant for one background was irrelevant for another, but no significant effect of prior knowledge was obtained when the same feature was useful for the backgrounds.
A New Motion Illusion
Authors: Schulman Paul H
Published: January 2007

Two instances of a new illusion of motion were discovered. In the first, when observers tracked a spot of light moving vertically in a field of stationary vertical lines, the lines appeared to move in the same direction as the spot. If observers did not track the spot, the lines appeared stationary. The second instance was designed to see if the same illusion would occur when the spot appeared to move as a result of induced motion. In this display a vertically moving grid of horizontal lines surrounded a stationary vertical line. A stationary spot of light could be projected on the line. If the subject fixated the spot, both spot and line appeared to move against the grid. If the spot was absent, the line appeared to move along with the grid. The implications of this illusion for theories of induced motion are discussed.
Individual Differences in the Visual Component of Prism Adaptation
Authors: Melamed Lawrence E , Beckett Peter A , Halay Michael
Published: January 2007

The centrality of individual differences in the visual component of perceptual adaptation was examined in a massed-practice—terminal-exposure, prism-viewing paradigm. With positive (adaptive) adjustments in the judgment of the visual straight-ahead, target-pointing aftereffects were found to be equivalent to the sum of the visual and proprioceptive (head—arm) aftereffects. For subjects showing negative visual adjustments to prism exposure, the target-pointing aftereffect was not significantly different from the change in proprioception alone. Implications of these findings for hypotheses concerning the process of perceptual adaptation are discussed.
Symmetry Perception and Spatial-Frequency Channels
Authors: Julesz Bela , Chang Jih-Jie
Published: January 2007

It is known that the sum of a random-dot array with vertical bilateral symmetry and one with horizontal bilateral symmetry appears as a random array. Here we show that if the vertically and horizontally symmetrical arrays are spatially filtered, so that their respective spectra are 2 octaves apart, then their superposition does not appear random, but both symmetries can be simultaneously perceived. The low-band array has a stronger perceptual weight than the high-band array. These demonstrations give further evidence that frequency channels are before symmetry perception.
The Oblique Effect of Stimulus Identification Considered with Respect to Two Classes of Oblique Effects
Authors: Essock Edward A
Published: January 2007

Two classes of oblique effects are proposed. Oblique effects demonstrated in paradigms reflecting the basic functioning of the visual system are termed class 1, and those obtained in paradigms reflecting stimulus encoding and memory are termed class 2. The present experiments examine the class 2 oblique effect that has been obtained on reaction time (RT) tasks. Three RT tasks with different response requirements (identification, detection, and classification) were conducted to determine the basic conditions necessary for the production of the class 2 RT oblique effect. The results indicate that the source of the class 2 oblique effect obtained in RT paradigms is a greater confusability between the 45° oblique lines than between the horizontal and vertical lines when identification of orientation is required.
Vision, Visibility, and Perception in Driving
Authors: Hills Brian L
Published: January 2007

Recent research is reviewed and its implications discussed. ‘On-the-Spot’ accident investigations have confirmed that errors of perception by the driver are a major contributory factor to accidents. However, the available evidence suggests that few of these are attributable to reduced or defective vision, since at best only a weak relationship has been found between a driver's level of vision (or visual performance) and his accident rate. A number of reasons for this general finding are considered, including driver compensation. For all drivers, the rapid fall in visual acuity with angular distance from the centre of vision presents particular problems, giving special significance to eye-movement patterns and the problems of visual search. Numerous physical and psychophysical restrictions on visibility could lead to the ‘looked, but failed to see’ type of accident, but their relative importance requires evaluation. There is now much evidence that the driver is quite often operating beyond his visual or perceptual capabilities in a number of key driving situations, including overtaking, joining or crossing a high-speed road, and a number of nighttime situations. It is concluded that ‘expectancy’, based on experience in both the long and the short term, has a profound influence on driver perception and assessment of risk. For all drivers, serious errors of judgement from time to time would seem inevitable. In general, these do not lead to accidents because of, among other things, the safety margins added by the driver and adjustments made by other road users. Thus, despite his limitations and fallibilities, the average driver is involved in surprisingly few serious incidents, particularly in view of the rapid rate of decisionmaking that is required. However, the present accident rate should not be accepted as inevitable and various countermeasures are discussed.
The Microstructure of Dual-Task Interaction. 4. Sleep Deprivation and the Control of Attention
Authors: Fisher Shirley
Published: January 2007

The experiment was designed to investigate attention-switching behaviour in sleep-deprived subjects and involved the same dual-task paradigm reported in earlier studies. The task specified by instructions to be the main task, was the five-choice serial-response task; the secondary task was an auditory-verbal digit task which occurred at random time intervals.

Analysis of the intervals in which the two tasks concurred gave a different result. Sleep-deprived subjects seemed less able to control the fine structure of the interval and tended to persist in producing serial responses at the expense of the secondary-task response. The evidence supported the view that both sleep-deprived and control subjects were not able to process information in parallel and, thus, the difference in interval patterning was due to the difference in attention-switching processes. The possibility that sleep deprivation might result in loss of attentional control is considered briefly.

A surprising result was that, in terms of overall response rates, the sleep-deprived group, although slower, preserved the dual-task priority structure better than the control group, who slowed on both tasks in the combined condition. The control result was different in this respect from control data from previous research, but it is important that within the sleep-deprived group there was evidence that ability to preserve the priority structure was unaffected.
Perceived Spatial Frequency of Flickering Gratings: A Local Spatial Distortion
Authors: Nyman Göte , Rovamo Jyrki
Published: January 2007

Perceived spatial frequency of a low-frequency grating increases if the grating contrast is temporally modulated at about 4 to 16 Hz. The amount of increase can be up to 50% as estimated by a grating-match technique. It is shown here that the illusion is not a simple spatial-frequency shift phenomenon but also involves local spatial distortions. This was discovered by using the method of distance match, in which the perceived length of a spatial period or its multiples was estimated in a flickering grating. The results indicate that the illusory increase in perceived spatial frequency does not predict the perceived period length of a grating in a simple reciprocal manner. The decrease in the apparent period length is restricted to distances covering only one or two spatial cycles. This points out that care should be taken in interpreting various illusory changes in spatial frequency simply as shifts of frequency. The results are interpreted as demonstrating the operation of a size-analyzing mechanism which has a limited spatial bandwidth and which is sensitive to flicker-induced disturbances.
Control Stimuli in Investigations of the Acute-Angled and Obtuse-Angled Müller-Lyer Illusions
Authors: Adam June , Bateman Layna
Published: January 2007

Over the past decade, attention has been drawn to the importance of intertip distance (the distance between the tips of the arrowheads or featherheads) as a possible determinant of the Müller-Lyer illusion. Investigation of this stimulus property for the arrowhead and featherhead components of the Müller-Lyer figure has indicated that the two components exhibit a lack of symmetry, a conclusion supported by other studies using rather different approaches to the investigation of symmetry. This article argues that the control stimuli used in previous investigations are inadequate. It is proposed that in addition to the conventional straight-line control stimulus, in which the standard shaft is stripped of the oblique inducing lines, H-shaped figures in which the inducing lines are vertical should be included. Results are reported of an experiment in which both types of control stimuli are used to investigate the effects of intertip distance, and the spatial separation of that distance from the standard shaft, upon the arrowhead and featherhead figures.
Binocular Moiré Fringes and the Vertical Horopter
Authors: Tyler Christopher W
Published: January 2007

Binocular moiré fringes observed in grating stimuli are analyzed in terms of the processes of binocular fusion, the vertical horopter, and the perception of vertical.
Adaptation to a ‘Spatial-Frequency Doubled’ Stimulus
Authors: Thompson Peter , Murphy Brian J
Published: January 2007

The perceived spatial frequency of low-frequency sinusoidal gratings is elevated when the gratings are temporally modulated sufficiently rapidly. Although this phenomenon is usually called ‘spatial-frequency doubling’, the magnitude of this spatial-frequency elevation depends on the spatial and temporal parameters of the grating and may be less than or greater than doubling. Adaptation to such a pattern produces contrast-threshold elevation whose spatial-frequency tuning is centred upon the grating's real rather than perceived spatial frequency. These results suggest that spatial-frequency elevation occurs later in the visual system than adaptation or that these two processes are independent of one another, at least under the conditions of these experiments.
The Effect of Similarity between Line Segments on the Correspondence Strength in Apparent Motion
Authors: Ullman Shimon
Published: January 2007

The correspondence between line segments in apparent motion is shown to be affected by the similarity between them. Increase in orientation difference or in length ratio between lines in a competing motion configuration decreases the probability of perceived apparent motion between them. The results suggest the existence of a built-in preference metric that may reflect a measure of matching likelihood between elements in three-dimensional space.
Does Integration Produce Masking or Protect from it?
Authors: Navon David , Purcell Dean
Published: January 2007

To examine the role of integration in pattern masking, possible disruptive effects of integration were minimized by using a mask that overlaid completely all targets. Exposure durations were 10 ms, so under energy summation the target area was much darker than the rest. In another condition the mask was red and targets were blue, so under energy summation the target area could also be distinguished by hue. Masking magnitude increased with delay of mask onset, and it was established by four independent criteria that integration was negligible in the condition which produced most masking. It is deduced that integration is not necessary for masking; furthermore it is suggested that integration never produces masking, but rather may or may not protect from a disruptive effect of interruption. The argument is that were the visual system to have better visual resolution, it would suffer more given the same masking parameters. It is argued that type B masking functions arise from a combination of the facilitatory effect of integration and the detrimental effect of interruption.
Perception of an Illusory Contour as a Function of Processing Time
Authors: Reynolds Robert I
Published: January 2007

The temporal development of illusory contour figures was investigated with the use of backward masking to control the duration of processing. The integration of an illusory triangle is elicited after 100 ms of processing time. When a pattern yielding the impression of a brick background is added to the display the triangle is elicited after 100 ms, held as a viable construct for the next 200 ms, and then is no longer perceived. When the brick pattern is drawn so as to appear transparent, a sequence of four qualitatively different percepts arise, culminating in the perception of a triangle located behind the transparent pattern. These findings are consistent with a hypothesis-testing model in which the construct ‘triangle’ interacts with an increasing number of features of the stimulus array; at each interaction it may or may not be found to be consistent with the sensory evidence newly taken into account.
The Contributions of F C Müller-Lyer
Authors: Day Ross H , Knuth Hannelore
Published: January 2007

Translations of Müller-Lyer's two papers on visual illusions, “Optical illusions” (1889) and “Concerning the theory of optical illusions: On contrast and confluxion” (1896), are accompanied by a brief biographical note and a commentary.
The Many Illusions of the Müller-Lyer: Comparisons of the Wings-in and Wings-out Illusions and Manipulations of Standard and Dot Forms
Authors: Greist-Bousquet Suzanne , Schiffman Harvey R
Published: January 2007

The assumed role of peripheral distortion mechanisms in both wings-in and wings-out Müller-Lyer illusions was investigated by requiring subjects to reproduce the central extent of standard Müller-Lyer figures and dot variations. Illusory magnitude of the line and dot variations was also examined with increasing wing length and wing angle. A reduction in the overestimation for the wings-out illusion occurred with the removal of intersecting lines; the dot variations evidenced a significant overestimation effect. In contrast, no reliable decrease in underestimation was found with the removal of intersecting lines in the wings-in illusion, and both standard and dot variations were significantly underestimated. These results support a conclusion that the wings-in and wings-out Müller-Lyer illusions are two distinct illusions, and may be differentially determined at the loci of distortion within the visual system.

Parallel changes in illusory magnitude were noted with configural manipulations of standard and dot wings-out illusions. However, standard and dot forms of the wings-in illusion were not equivalently affected by equivalent configural manipulations, which suggests that they are different illusions. Thus, the use of the wings-in dot variation to separate empirically peripheral from nonperipheral distortion mechanisms may be ill-advised.
Are the Obtuse Angles the Key Components of the Poggendorff Illusion?
Authors: Wenderoth Peter , Johnson Michael
Published: January 2007

An experiment is reported which confirms and extends a previous finding that amputations of the Poggendorff figure do not necessarily result in large positive effects with obtuse-angle stimuli, and small or even negative effects with acute-angle stimuli. Indeed, the acute-angle effects found were significantly greater than the obtuse-angle effects, and the full Poggendorff error was not explicable in terms of the linear summation of the component-angle effects. An ‘alignment displacement effect’ reported earlier by Hotopf and Obonai was shown to occur, but could not be an important component of the Poggendorff illusion.
Intensity, Spatial Frequency, and Temporal Frequency Determinants of Apparent Motion: Korte Revisited
Authors: Caelli Terry , Finlay David
Published: January 2007

The authors have earlier found support for the notion that apparent motion (AM) is mediated by a low-pass temporal-frequency filter operating over the spatial domain of the AM sources. Experiments have been carried out to test how this response is changed, or unchanged, through varying the source intensities or contrasts. The results indicate no intensity or contrast effects on the spatiotemporal limits for AM. These results are related to the early formulations of Korte and indicate that there is no amplitude-modulation or contrast-sensitivity function for AM—as there is for threshold movement detection. The filter mechanism seems to be largely restricted to the spatiotemporal domain.
A Study of Interocular Transfer of Spatial Adaptation
Authors: Bjørklund Roald A , Magnussen Svein
Published: January 2007

The threshold-elevation aftereffect was measured ipsiocularly and interocularly following grating adaptation of one eye. The functions relating aftereffect magnitude to adapting contrast and adaptation time were similar under the two testing conditions, with interocular transfer remaining fairly constant; decay times were similar for ipsiocular and interocular aftereffects of comparable magnitude, and their frequency selectivities were the same. It is concluded that the stimulus-response characteristics of monocular and binocular spatial channels are fundamentally similar.
An Attempt at Correlating Visuomotor-Induced Tilt Aftereffect and Ocular Cyclotorsion
Authors: Courjon Jean Hubert , Jeannerod Marc , Prablanc Claude
Published: January 2007

Subjects were exposed to an optical rotation of visual reafferences from hand movements. This is known to produce visuomotor adaptation. An experiment is reported where it also induced a perceptual aftereffect measured as a displacement of the apparent vertical and as an ocular cyclotorsion, both in the direction of the optical rotation. No correlation could be found between the two phenomena which can be considered as independent adaptive responses to the visuomotor conflict.
Visually Induced Tilt Affects Form Perception
Authors: McAdie Patricia J , Steinbach Martin J
Published: January 2007

A large visually moving field, which induces a sensation of tilting, affects the perception of form with virtually no change in the orientation of the retinal image. This effect is both quantitatively and qualitatively different from the effect of the induced tilt on a vertical line, suggesting a higher-order visual-vestibular interaction.
Illusory Brightness and the Ends of Petals: Change in Brightness without Aid of Stratification or Assimilation Effects
Authors: Kennedy John M
Published: January 2007

A series of petals arrayed around a central region induces an illusory brightness effect that is systematically related to the angle formed by the petals and the perimeter of the illusory brightness. As the petals veer to become tangents the illusory brightness decreases. The effect is not contingent on illusory stratification, or assimilation between the petals.
Thresholds for Seeing Visual Phantoms and Moving Gratings
Authors: Mulvanny Patrick , Macarthur Rodger , Sekuler Robert
Published: January 2007

Moving visual phantoms look like real gratings and generate movement aftereffects as do real gratings. Three experiments have been carried out to test whether phantoms resemble real gratings in other ways. Changes in the spatiotemporal frequency of an inducing grating affect the minimum contrast at which it will induce phantoms, but only insofar as the changes affect the visibility of the inducing gratings. Changes in the areal extent of the inducing grating and in the extent of the gap across which phantoms must be induced alter the visibility of the phantoms but, again, only to the extent that the changes affect the visibility of the inducing gratings themselves. Phantoms induced by high-contrast gratings may be cancelled by gratings of near-threshold contrast when the latter are presented 180° out of phase with the inducing gratings. It is concluded that the appearance of phantoms is governed solely by the detectability of their inducing gratings, but that the effects of phantoms on pattern-sensitive channels are not the same as are the effects of real gratings. The pattern characteristics of phantoms thus do not represent a spread of energy from inducing to phantom regions of visual space or their neural representations.
Characterisation of Human Behaviour during Odour Perception
Authors: Laing David G
Published: January 2007

Factors which govern the optimum perception of odours have not yet been defined. This has hindered the development of standard methods and instruments for measuring olfactory responses. As an initial step towards defining these conditions, inhalation rates and volumes, number of sniffs, and sniff duration were measured for twenty-three humans in odour-threshold and odour-intensity tests with pentyl acetate, 1-butanol, and diethylamine. Measurements were made with the aid of a hot-wire anemometer concealed within the outlet of an air-dilution olfactometer. Individuals varied markedly in their sampling techniques but maintained their characteristic sniffing patterns with different odours and olfactory tasks. Only three parameters consistently varied with odour concentration: total volume of odour sampled, total sampling time, and number of sniffs. Maximum inhalation rate was remarkably stable and was independent of the type, concentration, and pleasantness of odour. Values recorded for sniff volumes and inhalation rates indicate that most olfactometers in use do not accommodate human inhalation requirements during a sniffing episode. The many common characteristics in the varied sampling techniques of different subjects suggest that the techniques are close to those providing optimum odour perception. Whether these are inherited or developed through habit or experience is not known.
Effects of Visual Angle on Perspective Reversal for Ambiguous Patterns
Authors: Borsellino Antonio , Carlini Franco , Riani Massimo , Tuccio Maria Teresa , De Marco Angelo , Penengo Piero , Trabucco Aurelia
Published: January 2007

Reversal rates of an ambiguous figure (the Necker cube) were studied for different pattern sizes covering a range of visual angles θ from ∼1 to 62 deg. A large number of reversals was obtained for each observer and each pattern in order to examine the statistical distributions of reversal times. A pronounced flattening of the statistical distributions (represented throughout by a gamma distribution) and a growth of the mean duration of each percept, with increasing pattern size was found. A plateau in the range of θ between 5 and 20–30 deg was observed. For larger values of θ two kinds of observers have been identified: for ‘fast’ observers the inversion rate is little affected by θ, whilst for ‘slow’ observers, the mean reversal time increases strongly with θ. A tentative model, based on three different contributions to the duration of the alternation process, is proposed: a constant term, independent of θ, and two terms dependent on θ—a retinal term, and a cortical one. The last term is interpreted as due to the spreading of excitation with the characteristic of a filling-in process.
The Role of the Vertical Dimension in Stereoscopic Vision
Authors: Longuet-Higgins H Christopher
Published: January 2007

It is shown how the full three-dimensional structure of a scene may in principle be computed from a correlated pair of retinal images, when all that is known about the orientations of the two eyes is that the planes of their horizontal meridians accurately coincide. The vertical dimension plays a crucial role in the theory; visible points which lie on the horizontal meridian supply no information about the angle of convergence or the direction of gaze.

(i) If the scene contains three or more nonmeridional points, not all lying in a vertical plane, then their positions in space are fully determined by the horizontal and vertical coordinates of their images on the two retinas.

(ii) If just two nonmeridional points are visible, or more than two, lying in a vertical plane, then their retinal images admit, in general, just two distinct three-dimensional interpretations. One of these is usually unrealistic; but a choice between them may be perceptually difficult if the vertical plane containing the points is nearly perpendicular to the interocular axis.

These results suggest that vertical disparities may play an important role in the binocular perception of absolute depth. Elsewhere (Mayhew, this issue) this suggestion is found to provide a quantitative explanation of Ogle's ‘induced effect’.
Velocity Constraints on Apparent Rotational Movement
Authors: Farrell Joyce E , Larsen Axel , Bundesen Claus
Published: January 2007

The visual illusion of apparent rigid rotation was produced by sequential alternation of two views of the same object in different orientations. The minimum stimulus-onset asynchrony required for the appearance of rigid rotation was a linearly increasing function of the angular difference in orientation between the two views. Variation in the size of the object affected the zero-intercept of the function, but the slope was virtually constant. The slope invariance suggests that the appearance of rigid rotation is constrained by an upper bound on the apparent angular velocity of the object as a whole, rather than a bound on the linear velocity of its parts.
Equation Counting and the Interpretation of Sensory Data
Authors: Richards Whitman A , Rubin John M , Hoffman Donald D
Published: January 2007

Many problems in biological information processing require the solution to a complex system of equations in many unknown variables. An equation-counting procedure is described for determining whether such a system of equations will indeed have a unique solution, and under what conditions the solution should be interpreted as ‘correct’. Three examples of the procedure are given for illustration, one from auditory signal processing and two from vision.
The Disparity Gradient Limit for Binocular Fusion: An Answer to J D Krol and W A Van de Grind
Authors: Burt Peter , Julesz Bela
Published: January 2007

The observations reported earlier by the authors are shown to support the view that the constraints for fusion are stimulus-centered and not observer-centered, thus justifying the reformulation of the disparity limits for binocular fusion in terms of a gradient limit which is disputed by Krol and van de Grind.
The Extent of Panum's Area and the Human Cortical Magnification Factor
Authors: Hampton David R , Kertesz Andrew E
Published: January 2007

The horizontal extent of Panum's fusional area was measured by means of a single-vertical-line stimulus placed at thirty-two locations throughout the peripheral visual field. These results were transformed by using known values of the human cortical magnification factor (CMF), and the hypothesis that variations in the magnitude of Panum's area may be accounted for by variations in the CMF was tested. It was found that the increase in Panum's area with increasing stimulus eccentricity correlates well with the CMF, but that variations in the extent of Panum's area as a function of angular position around the line of sight do not correspond well with the CMF.
Light Source Position in the Perception of Object Shape
Authors: Berbaum Kevin , Bever Todd , Chung Chan Sup
Published: January 2007

The apparent relief of monocularly viewed surfaces reversed when the order of light and shade was reversed relative to the position of a lamp observed the moment earlier. The pattern of shading was reversed either by illuminating from a direction opposite to that of the apparent direction of illumination or by inverting the illuminating image relative to the light source. The combination of both of these manipulations restores the original juxtaposition of light source and shading and reestablished accurate perception of relief. These results demonstrate that the perception of the relief of physical surfaces depends upon the remembered position of an apparent light source.
Interruption of Dot Processing by a Backward Mask
Authors: Liss Philip , Reeves Adam
Published: January 2007

A white target field with 0–10 randomly positioned black dots was presented for 20 ms, and followed by a patterned mask with a duration of 200 ms. Subjects reported target numerosity, with strict or lax criteria. Numerosity functions, and control forced-choice discrimination results, supported an interruption model for backward masking by pattern, even for stimulus onset asynchronies as short as 50 ms. When the same targets were degraded by reducing their contrast, but not otherwise masked, results supported an integration model.
Locus of Habituation in the Human Newborn
Authors: Slater Alan , Morison Victoria , Rose David
Published: January 2007

There is some controversy concerning the youngest age at which an infant will habituate to a visual stimulus or will prefer a novel to a familiar pattern. One suggestion has been that apparently successful reports of habituation and dishabituation in the newborn baby are attributable to retinal adaptation. This interpretation was tested in two experiments. In both experiments monocular conditions of viewing were used: newborns were habituated with one eye as the ‘seeing’ eye, and posthabituation novelty preferences investigated with the other eye. Significant preferences were found both for a novel colour (experiment 1) and for a novel shape (experiment 2), which implies that a retinal-adaptation model can be ruled out. It is suggested that the habituation effects and the subsequent novelty preferences found in the experiments are most reasonably interpreted as a function of memory formation, and evidence is presented for the storage of visual experience from birth. The results also demonstrate some form of binocular interaction in the newborn.
On the Plausibility of Superman's X-Ray Vision
Authors: Pittenger John B
Published: January 2007

Requirements that a vision system must meet to make Superman's x-ray vision possible are stated, and two solutions are proposed. In one, emitted x-rays carry the information to Superman's eyes; in the other, emitted rays make objects transparent to a second type of ray. Further subjects lending themselves to this type of research are superhearing, the biomechanics of leaping tall buildings, or being faster than a bullet.
The Role of Motion in Infants' Perception of Solid Shape
Authors: Owsley Cynthia
Published: January 2007

Previous research has shown that infants as young as the first few months of life perceive several aspects of the three-dimensional environment. Yet we know relatively little about the visual depth information which serves as a basis for their spatial capacities. A study is reported in which a visual habituation procedure was used to examine what types of optical depth information four-month-old infants find useful in visually perceiving solid (three-dimensional) shape. Results imply that in the absence of binocular depth cues four-month-olds rely on kinetic depth information to perceive solid shape.
Parallel-Alleys and Distance-Alleys on Horopter Plane in the Dark
Authors: Indow Tarow , Watanabe Toshio
Published: January 2007

On each of three frontoparallel planes at distances of about 98, 186, and 276 cm from the subject, two series of light points running horizontally in the dark, one above the other, were constructed by six subjects: a P-alley in which the two series appear as two straight lines that are parallel, and a D-alley in which each pair of points appear equally separated in the vertical direction. Luneburg's mapping functions between visual space and physical space have been used to obtain estimates of K (curvature) and σ (a constant related to depth perception). In addition, ratios of perceptual distances were assessed by four out of the six subjects with eleven triplets of points on the alleys and values of K were estimated (and the fits of theoretical equations were tested) without the use of the mapping functions. In contrast to experiments with P-alleys and D-alleys on the horizontal plane, K was not unequivocally negative in either of the two experiments.
Two Channels for Flicker in the Human Visual System
Authors: Moulden Bernard , Renshaw Judy , Mather George
Published: January 2007

The human visual system contains a large number of narrowly-tuned spatial-frequency-specific channels. Does it contain an analogous set of channels tuned to a narrow range of temporal frequency? On the basis of data gathered with the use of a threshold elevation technique it is argued that human sensitivity to flicker can be accounted for by assuming the existence of just two filters, one a low-pass filter peaking gently at around 6 Hz and one a band-pass filter peaking at around 9 Hz. Similar data gathered from studies of interocular transfer suggest that at least some of the mechanisms involved are binocular, rather than being purely monocular as has previously been suggested.
The Relationship between Space and Time in the Perception of Stimuli Moving behind a Slit
Authors: Casco Clara , Morgan Michael
Published: January 2007

When a shape defined by a set of dots plotted along its contour is presented in a sequence of frames within the boundaries of a slit, and in each frame only one dot (featureless frame) or two dots (feature frame) are displayed, a whole moving dotted shape is perceived. Masking techniques and psychophysical measures have been used to show that a dynamic random-dot mask interferes with shape identification, provided the interframe interval is greater than about 15 ms, and there are no stimulus features for recognition in individual frames. A similar pattern of results was obtained when the observer had only to detect the movement of a single dot or a pair of dots against a dynamic-noise background. It is concluded that the visual system can resolve the correspondence problem in both apparent movement (one moving dot) and aperture viewing (featureless-frame condition) by extracting motion before the extraction of features in each frame. However, the results also show that where feature identification in each frame is possible, it can also be used to identify the moving targets.
Diverting Subjects' Concentration Slows Figural Reversals
Authors: Reisberg Daniel , O'Shaughnessy Mark
Published: January 2007

Earlier research has shown that subjects are slower to discover the alternative construal of ambiguous geometric figures if they are simultaneously engaged in distractor tasks. Results are reported which show that this effect slows reversals subsequent to the first reversal, and is therefore not merely slowing the discovery of the alternative construal. In addition, the magnitude of the distraction effect seems unchanged through the successive reversals. The results are discussed in terms of their implications for figural reversal and of their implications for the role of mental resources in perceiving.
The Effect of Feature Displacement on Face Recognition
Authors: Haig Nigel D
Published: January 2007

Human beings possess a remarkable ability to recognise familiar faces quickly and without apparent effort. In spite of this facility, the mechanisms of visual recognition remain tantalisingly obscure. An experiment is reported in which image processing equipment was used to displace slightly the features of a set of original facial images to form groups of modified images. Observers were then required to indicate whether they were being shown the “original” or a “modified” face, when shown one face at a time on a TV monitor screen. Memory reinforcement was provided by displaying the original face at another screen position, between presentations. The data show, inter alia, the very high significance of the vertical positioning of the mouth, followed by eyes, and then the nose, as well as high sensitivity to close-set eyes, coupled with marked insensitivity to wide-set eyes. Implications of the results for the use of recognition aids such as Identikit and Photofit are briefly discussed.
Aggregation and Unit Formation in the Perception of Moving Collinear Lines
Authors: Gillam Barbara , Grant Theodore
Published: January 2007

The degree to which collinear lines are treated as a unit in resolving rotary motion in depth was investigated with the use of parallel projection to make direction of motion ambiguous. The proportion of time that the collinear lines appeared to rotate in the same direction was used as an index of their perceptual coherence. When the gap between the lines was small, there was strong grouping of the lines with respect to direction of motion as well as appearance of rigidity for the configuration. For larger gaps the grouping for direction of motion was maintained, but the lines appeared to have different axes of rotation leading to an appearance of nonrigidity. It is concluded that line elements can be aggregated for the resolution of certain properties without constituting a unit in any general sense.
Temporal Integration and Contrast Sensitivity in Foveal and Peripheral Vision
Authors: Rovamo Jyrki , Leinonen Lea , Laurinen Pentti , Virsu Veijo
Published: January 2007

Spatial contrast sensitivity functions and temporal integration functions for gratings with dark surrounds were measured at various eccentricities in photopic vision. Contrast sensitivity decreased with increasing eccentricity at all exposure durations and spatial frequencies tested. The decrease was faster at high than at low spatial frequencies, but similar at different exposure durations. When cortically similar stimulus conditions were produced at different eccentricities by M-scaling, contrast sensitivity became independent of visual field location at all exposure durations tested. The results support the view that in photopic vision spatiotemporal information processing is qualitatively similar across the visual field, and that quantitative differences result from retinotopical differences in ganglion cell sampling. For gratings of constant retinal area temporal integration (improvement of contrast sensitivity with increasing exposure duration) was more extensive at high than at low retinal spatial frequencies but independent of cortical spatial frequency and eccentricity. For M-scaled gratings temporal integration was more extensive at high than at low cortical spatial frequencies but independent of retinal spatial frequency and eccentricity. The results suggest that the primary determinant of temporal integration is not spatial frequency but grating value that is calculated as AF2 square cycles (cycle2), where A is grating area and F spatial frequency.
Exorcising the Double-Nail Confusion: A Reply to Ono
Authors: Krol Jodi D , Van de Grind Wim A
Published: January 2007

Contrary to the claims of Ono it is argued that the principles and rules of direction vision do not account for the double-nail illusions, and that the ‘ghost’ concept is hidden rather than exorcised in Ono's approach.
A New Visual Illusion: Flickering Fields are Localized in a Depth Plane behind Nonflickering Fields
Authors: Wong Eva , Weisstein Naomi
Published: January 2007

Flickering regions of the visual field are perceived to lie well behind regions which are not flickered. The depth segregation is not due to luminance differences since the average temporal luminance across all the regions was equal. This depth effect produced by flicker is not dependent on the texture of the visual field; nor does it depend on a specific configuration of the flickering and nonflickering areas. It is optimal at a temporal frequency around 6 Hz, which suggests that visual channels responding maximally to high temporal frequencies are involved in the segregation of perceptual regions in depth.
Kinetic Occlusion by Apparent Movement
Authors: Anstis Stuart M , Ramachandran Vilayanur S
Published: January 2007

A small square and a large triangle below it were presented in the first frame. These were switched off and replaced by a triangle alone in the second frame, shifted horizontally and upwards. The triangle appeared to move obliquely, as expected, but most observers also saw the square moving horizontally and hiding behind the triangle, although there was no stimulus corresponding to it in the second frame. The visual system invokes the occlusion ‘hypothesis’ in order to explain the otherwise mysterious disappearance of the square. The experiment suggests that apparently intelligent solutions can be rapidly computed by the visual system.
Visual Half-Field Symmetry in Orientation Perception
Authors: Magnussen Svein , Landrø Nils Inge , Johnsen Tore
Published: January 2007

The perception of orientation in the left and right visual half-fields has been investigated. No evidence for interfield differences was obtained for the discrimination of single lines by line matching or in magnitude of the systematic orientation distortion in orientation contrast and rod-and-frame experiments. Furthermore, increasing the time interval between test and comparison lines in successive matching provides no evidence for a differential operation of short-term spatial memory in the two hemispheres. It is concluded that hemispheric asymmetries do not arise at the level of sensory processing of spatial signals.
Errors in the Stereoscopic Separation of Surfaces Represented with Regular Textures
Authors: Ninio Jacques , Mizraji Eduardo
Published: January 2007

Stereograms containing two similar or dissimilar linear textures, either on the same surface or at two different depths, were tested on seventy subjects. Whereas random textures usually produced correct percepts, regular textures consistently led to errors of stereoscopic interpretations, including a reversal of hollows into bumps, dissociation of single surfaces into two layers, and errors in relative positioning of two surfaces. Horizontal—vertical textures tended to be seen as flatter and further away from the observer than diagonal ones. Continuous textures tended to be seen closer than discontinuous ones. In the interpretation of the results, the possibility is raised that different textures are processed independently and that the brain has no reliable method for combining the conclusions into a rigorous global percept.
Contrast and Spatial Frequency Components in Visual Preferences of Newborns
Authors: Morison Victoria , Slater Alan
Published: January 2007

A preferential-looking procedure was used to investigate newborns' responses to square-wave gratings varying in spatial frequency and contrast. A preliminary study confirmed that the gratings used in the experiment were suprathreshold. In the experiment newborns' preference for a grating of 0.1 cycle deg−1 within the peak contrast sensitivity range was examined. Reduction in the contrast of this grating led to a transfer of the preference to a high-contrast grating of the same space-averaged luminance with a spatial frequency outside this range (0.42 cycle deg−1). The findings are discussed with reference to the role of the contrast sensitivity function in pattern preferences of newborns: it is suggested that contrast and spatial frequency interact in determining pattern preferences.
Shape and Contour: The Points of Maximum Change are Least Useful for Recognition
Authors: Kennedy John M , Domander Ramona
Published: January 2007

Attneave hypothesized that recognition of a shape would be best if the eye was given those parts of the shape most different from a straight line, ie regions of maximum direction change (MAX points). Experiments are reported which show that MIN points—the points midway between MAX points—are actually better for shape recognition. But by far the best parts of the shape for recognition were found to be the regions intermediate between MAX points and MIN points. It is suggested that these regions are especially suitable for shape extrapolation and interpolation because they are evenly distributed.
Eye Movements and Illusions of Alignment
Authors: Findlay John M , Hotopf W H Norman
Published: January 2007

Extraction of the location of a target in the visual periphery is a fundamental visual process which may be manifested both in conscious judgements of location, such as decisions about alignment, and in the processing required to execute an eye movement to a peripheral target. In both cases, location judgement is affected by the neighbouring visual configuration. An experiment is reported in which the amplitude of saccadic eye movements has been measured to study the effect of a configuration consisting of a single ‘induction line’. The results demonstrate systematic effects of this line on the size of the saccade which are closely similar to those previously found in an alignment task.