bluuebunny/crossref_metadata_2025 huggingface dataset:
Do Sensitivity Drifts Occur for Stimuli other Than Sodium Chloride? A Preliminary Investigation
Authors: O'Mahony M , Dunn M
Published: January 2007

Solutions of sodium chloride, sucrose, tartaric acid, and quinine sulphate were each presented in successive ascending series, both with and without interstimulus tapwater rinses, to six subjects. A tendency for detection and recognition thresholds to be raised on successive ascending series was noted for all stimuli. The effects were explained in terms of adaptation to stimulus residuals. When water rinses were taken between tastings, significantly lower thresholds were noted for sodium chloride and glucose. Although this trend did occur for tartaric acid and quinine sulphate, it was not significant. The literature was examined and seen to show similar trends.
Nulling the Movement Aftereffect: Evidence for Pattern Specificity
Authors: Mayhew J E W
Published: January 2007

A microtextured surface such as a homogeneously illuminated tracing-paper screen provides an excellent test surface for the movement aftereffect. When it is moved against the aftereffect at the appropriate velocity, a null occurs and the screen appears stationary. However, if patterned illumination is superimposed on the homogeneous field, the nulling breaks down. The pattern appears to move in one direction, driven by the aftereffect, and the screen can be clearly seen moving in the opposite direction. This breakdown begins to occur at luminances just above threshold for the detection of the pattern. The implication is that two populations of motion detectors are involved. Evidence in support of this postulate is presented.
Monophasic Temporal Modulation Increases Apparent Spatial Frequency
Authors: Virsu V , Nyman G
Published: January 2007

There are three different types of flicker—monophasic, diphasic, and polyphasic—and they have different spatial consequences with gratings. Monophasic flicker does not alter the spatial phase in time, but spatial phase changes are caused by the other two types. The effects of sinusoidal monophasic flicker on the apparent spatial frequency of sinusoidal gratings were studied in the present experiments by simultaneous spatial-frequency matches. Monophasic temporal modulation increased apparent spatial frequency. The stimulus conditions for producing a maximum effect were (a) a relatively low spatial frequency, (b) a relatively high level of light adaptation, (c) an intermediate temporal frequency (4–8 Hz), and (d) an intermediate contrast. The largest apparent increases exceeded 30%. The magnitude of the spatial effect was correlated with data on temporal resolution and contrast sensitivity collected under the same conditions. The spatial effect had a high correlation with the critical flicker-fusion frequency, and the contrast-sensitivity enhancements caused by the flicker followed functions similar to those of the spatial effect when the spatial frequency and the level of adaptation were varied. We interpret the spatial effect of low-frequency monophasic flicker as evidence that there are channels for spatial frequency in human vision whose spatial tuning depends on the spatial distribution of sensitivity in the receptive fields of single neurones. Flicker at intermediate temporal frequencies decreases the functional effectiveness of centre—surround antagonism, and makes channels otherwise responsive to high spatial frequencies responsive to low spatial frequencies. As the central decoding of channel outputs can be assumed invariant, an increase in the apparent spatial frequency follows from the change of tuning properties if the channels mediate the perception of spatial frequency. An analysis of the variability of spatial frequency matches indicated that spatial frequency discrimination, if considered in relative terms, is independent of the spatial frequency, the mean luminance, and the contrast of gratings within broad ranges of variation.
L'enregistrement des Mouvements Oculaires Par le Reflet Cornéen. Analyse des Erreurs Systématiques de la Localisation du Regard
Authors: Bullinger A
Published: January 2007

On analyse des erreurs de localisation du regard dans la technique du reflet cornéen en prenant le centre de la pupille comme lieu de fixation du regard. Deux facteurs principaux sont mis en évidence et on analyse les corrections nécessaires pour améliorer la précision.
On Training Sensitivity to Painting Styles
Authors: Silverman Jen , Winner Ellen , Rosenstiel Anne K , Gardner Howard
Published: January 2007

A training study was conducted with ten-year old children (1) to determine the steps through which children pass in learning to sort paintings by style; (2) to investigate the relationship between this and other perceptual and performing skills. Subjects who initially focused on subject matter cues learned to sort paintings by style; a substantial proportion of the subjects succeeded in consistently applying a multidimensional analysis, by means of which various compositional components were first independently assessed and their cumulative effects then evaluated. Moreover, the subjects passed through a consistent set of stages en route to style sensitivity. Posttesting revealed that sensitivity to style is more likely to be enhanced if subjects have had intensive exposure to a small set of highly distinctive styles than if they have gained a superficial familiarity with a wide variety of styles; that the classification skills leading to style sensitivity are related to certain discriminative capacities utilized in the sciences; and that subjects trained to attend to certain features of painting show a modest change in their own style of representational drawing. The findings are discussed in terms of the cognitive capacities emerging during the middle years of childhood.
Outline Picture Perception by the Songe of Papua
Authors: Kennedy John M , Ross Abraham S
Published: January 2007

The Songe of Papua New Guinea have little or no indigenous pictorial art. Nevertheless, Songe subjects of both sexes of varying ages and degrees of Western contact were able to identify a wide range of outline drawings depicting objects, animals, and human forms. ‘Kinetic’ scenes and outline drawings portraying colour and texture discontinuities presented some difficulty for the Songe, especially for those over forty years old. Informants over forty in general made significantly more errors than those under forty. It was noted that this has been found in research in many other cultures.
Lines that Affect Speed of Visual Scanning
Authors: Frith Uta
Published: January 2007

Scanning from left to right through arrays of shapes is slower with vertical than with horizontal lines. The reverse is true for scanning from top to bottom. Thus, lines lying across the direction of scan appear to act as barriers.
Relationship between Selection Accuracy and Exposure in Visual Search
Authors: Solman Robert T
Published: January 2007

The physical similarity between the target and the irrelevant items, and the number of irrelevant items, were varied to obtain curves relating accuracy of target location to exposure, and reaction time to exposure. Two groups of subjects searched circular displays where similarity differed for each group, and number and exposure varied within groups. The results indicated that the relationships between accuracy and exposure were the more informative since they directly reflected processing, particularly when the exposure was very brief. These time versus accuracy curves were negatively accelerated, showing rapid increases in accuracy for approximately 50 ms with very slow (if any) increases for longer exposures. As it was not possible to account for these accuracy variations in terms of simple serial or parallel models of information processing, they were seen as reflecting processing by preattention and focal attention. Further analysis suggested that the times required for preattentive processing were brief and have a probability distribution.
Psychophysical Hallucinations of Orientation and Spatial Frequency
Authors: Georgeson Mark A
Published: January 2007

After inspection of vertical sinusoidal gratings at least three distinct types of subjective or ‘hallucinated’ patterns can be seen on a uniform test field. One type, here called horizontal streaming (H), is already well-known from the work of MacKay. A second type (V) looks like a roughly sinusoidal grating about 15 octaves above the adapting spatial frequency. Under optimal conditions a second vertical component appears at about 2 octaves below the adapting frequency. The third category of aftereffect consists of diagonal lines (D) at two orientations (about ±40° from vertical). The spatial-frequency band at these two orientations appears to be fairly broad, but roughly similar to the adapting frequency. The duration and strength of D increased, while V declined, at higher adapting spatial frequencies. D and V were increasing functions of adapting contrast, while H appeared abruptly only after the highest adapting contrast. H, D, and V are thus all functionally distinct.

A schematic model of cortical organization is proposed to account for these phenomena. Pattern channels selective for a given orientation are grouped together with movement channels selective for the orthogonal direction. Antagonism between channels within such ‘modules’ accounts for the streaming effect (H). Inhibition between modules tuned to different orientations and spatial frequencies accounts for the D and V effects: after adaptation of channels in one module, neighbouring module(s) are released from inhibition to produce a spurious response which is seen as a grating-like object in the adapted part of the visual field. During flickering adaptation a ‘hallucinated’ lattice can be seen superimposed on the adapting grating. It apparently consists of Fourier components more remote from the adapting pattern than D and V are. This disinhibitory effect is strong confirmation of the inhibitory model. The regular and highly organized matrix of channels implied by these experiments may constitute a cortical hypercolumn conducting a coarse, piecewise Fourier transformation of the retinal image.
On Interocular Transfer of the Movement Aftereffect in Individuals with and without Normal Binocular Vision
Authors: Wade Nicholas J
Published: January 2007

The duration of the movement aftereffect was measured in twenty-four normally binocular subjects and in eighteen subjects who lacked stereopsis as a consequence of childhood strabismus. Aftereffects were generated monocularly and binocularly, and compared to those which occurred after adaptation of one eye and testing with the other. Normal subjects were categorized on two indices of eye dominance, which involved sighting and rivalry tests. The monocular-aftereffect durations were slightly longer when the dominant eye was used, and interocular transfer from the dominant eye to the nondominant eye was greater than the transfer in the reverse direction; however, these differences were not statistically significant. The results from the strabismic subjects suggested that they fell into two distinct groups: one group (seven of the eighteen subjects) experienced no interocular transfer in either direction; the other group did yield some interocular transfer, and it was generally greater after adaptation of the dominant eye and testing the nondominant eye than in the reverse direction. Six of the seven subjects who failed to show any transfer still had misalignment of the visual axes, but this was not the case in any of the subjects exhibiting transfer.
Dominance of Touch by Vision: Generalization of the Hypothesis to a Tactually Experienced Population
Authors: Power Roderick P , Graham Anne
Published: January 2007

It is now held that in conditions where there is conflicting sensory information vision dominates touch. The present study was designed to place boundary conditions on the generality of the hypothesis by comparing the performance of tactually experienced subjects—potters—with university students on a form-perception task in which a square was optically distorted so as to appear rectangular. Subjects examined the square haptically and visually, and matched it by touch or vision. Although potters were more accurate than students when not permitted vision, tactual judgements of both were dominated by vision when they were presented with conflicting information. In a supplementary study longer, more active exploration and emphasis on the necessity of matching by touch had no differential effect. In a third study it was found that a range effect produced by the comparison stimuli could explain the lesser accuracy of the students when they were making haptic judgements. The generality of the hypothesis that vision dominates touch is strengthened by our failure to refute it.
A Dynamic Ponzo Illusion: Induced Direction of Rotation in Depth
Authors: Hershberger Wayne , Laughlin Nellie , Nitschke Werner
Published: January 2007

Observers viewed parallel projections of a five-rung gate rotating in depth about its vertical center rung and judged the direction of apparent rotation. The background of a Ponzo illusion superimposed upon these parallel motion projections affected the direction of apparent rotation, with that end of the gate approaching the apex of the background appearing to recede from the viewer. This result is consistent with the thesis that the static Ponzo illusion is, at least in part, an illusion of depth.
The Magic Number 4 ± 0: A New Look at Visual Numerosity Judgements
Authors: Atkinson Janette , Campbell Fergus W , Francis Marcus R
Published: January 2007

Visual numerosity judgements were made for tachistoscopically presented linear arrays of dots or lines. The interelement interval (which could be specified in spatial frequency terms) was constant for a given array but varied across conditions. A clear limit in the accuracy of numerosity judgements was found to be set at 4 for regularly spaced elements with spatial frequencies below approximately 10 cycles/deg (element and interelement interval of 0·05 deg). This limit in terms of accuracy is accompanied by a fast and almost constant response time for arrays of 4 or less, compared to response times for arrays of more than 4 elements. The limit in accuracy falls to 2 elements rather than 4 for spacing narrower than 0·05 deg although with such spacing the elements are still easily resolved. The limit of 4 is found if the stimulus is a bright afterimage, lasting for approximately 60 s. This result suggests that the limit is independent of the time allowed for a single fixation and is a perceptual limit rather than a limit in some memory buffer. ‘Numerosity’ units are proposed to account for the results.
Sun Figure: An Illusory Diffuse Contour Resulting from an Arrangement of Dots
Authors: Kennedy John M
Published: January 2007

A set of black dots grouped on a white background to create an impression of radiating lines which fade towards the centre makes possible a percept of a central glow.
Vision with Isoluminant Colour Contrast: 1. A Projection Technique and Observations
Authors: Gregory Richard L
Published: January 2007

An optical technique is described for projecting two-colour pictures with controlled brightness contrast, which may be set to zero—at isoluminance. Colour registration is maintained without adjustment or special setting up. It is suggested that colour- and brightness-contour registration in the visual channel is a problem which may be solved neurally by master brightness signals locking slave colour signals. The projection apparatus allows the supposed master brightness signals to be removed—at isoluminance—when contour disturbances should occur. Observations of this kind are reported.
The Detection of Line Segments
Authors: Bacon Jon , King-Smith P Ewen
Published: January 2007

Many simple cells of the visual cortex have long narrow receptive fields, which are strongly excited by lines oriented along their long axis. In the present psychophysical analysis, we assume that there are similar independent ‘subunits’ which contribute, by probability summation, to the detection of a line. If a line segment is shorter than the subunit length, then extending the line length will increase the sensitivity of all the subunits affected by the line, and a relatively large increase in visual sensitivity will occur, corresponding to this ‘physiological summation’ within subunits. However, for a line segment which is much longer than the subunit length, the main effect of extending line length is to stimulate more subunits, resulting in a relatively small increase in sensitivity owing to probability summation. Thus a study of sensitivity (reciprocal threshold) as a function of line length may be used to test the subunit model and to estimate the subunit length. Here we use a quantitative model to demonstrate that sensitivity/line length data may be well fitted, assuming independent subunits having a constant length of 8·6′—in good agreement with the length of Andrews' ‘ff’ units.
Stability of Wilkinson's Linear Model of Prism Adaptation over Time for Various Targets
Authors: Wallace Benjamin
Published: January 2007

Prism adaptation as measured by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS) was assessed as a function of amount of exposure time and target specificity, whether an exposure and a test target background were the same or different, to determine the validity of Wilkinson's linear model (NA = PS+ VS). With few exceptions the model was found to hold well up to 40 min of prism viewing regardless of type of exposure background. In addition target specificity affected magnitude of the NA component of adaptation but not the PS and the VS components.
Spatial-Frequency Adaptation and Afterimages
Authors: Smith Robert A
Published: January 2007

The contribution of afterimages to spatial-frequency adaptation was studied by comparing a number of different fixation paradigms designed to maximize or minimize afterimages. While it is clear that adaptation is not an afterimage artifact, nevertheless afterimages are produced at low spatial frequencies and can considerably distort the results of adaptation experiments unless steps are taken to eliminate them.
Measurement of Visual Preferences in Cats
Authors: Emerson Victor F , Timney Brian
Published: January 2007

A technique is described for measuring visual preferences in cats. The method involves a self-presentation paradigm, but provides strict control of the visual field and orientation of contours in the field. Two procedures are presented: a single-choice design and a multiple-choice design, both of which use duration of self-produced exposure as the dependent measure. Although both procedures may serve as indices of preference order, the multiple-choice method is preferable for measuring preference strength. The application of the technique as a behavioural index of the effects of early environmental manipulation is suggested. Preliminary data from two normal cats indicate that, although homogeneous illumination is reinforcing, the presence of features, especially oriented contours, appears to increase the ‘interest’ value of the presentation.
A Behavioural Technique for the Rapid Assessment of the Visual Capabilities of Kittens
Authors: Mitchell Donald E , Giffin Fred , Timney Brian
Published: January 2007

A behavioural method is described for the measurement of various visual spatial acuities in kittens as young as thirty days of age. Examples are given of applications of the technique to measurement of the visual acuity for gratings in normal kittens as well as to studies of the time course of behavioural recovery from the effects of early monocular visual deprivation.
Hyperbolic Geometry as an Alternative to Perspective for Constructing Drawings of Visual Space
Authors: Finch Dennis
Published: January 2007

It is demonstrated by the use of drawings: (i) that two-point perspective drawings based on projective geometry possess systematic distortions, and (ii) that these distortions can be eliminated in drawings based on hyperbolic geometry.
The Phenomena of the Disembodied Eye or is it a Matter of Personal Geography?
Authors: Corcoran Derek W J
Published: January 2007

When a bilaterally asymmetrical figure is drawn on the skin at various bodily positions, the observer often reports that the figure he ‘sees’ is reversed. On the head and neck, for example, figures drawn to the front of an imaginary line through the centre of the head, approximately in line with the ear canal are seen as reversed, and those to the rear of this line as correctly orientated. Different bodily locations such as the palm were tried and the orientation was found to depend in most instances upon the direction in which the surface faced. Several possible theories were tested against the data.
Individual Differences in the Selection and Use of Features for Classifying Visual Stimuli
Authors: Chantrey David F
Published: January 2007

Two experiments were performed to investigate the classification of pot-like outlines by human judges. In experiment 1, seventy-two pot-like shapes, drawn by using all possible combinations of values of four pot ratios, were classified by twenty subjects and by a computer program. The shapes varied only in quantitative features and possessed no all-or-none characteristics. In experiment 2, 256 shapes traced from drawings of existing pots were classified by fifteen judges. The pots varied in both quantitative and all-or-none features. The results showed that there were differences between judges in the weightings they assigned to different features, and the judges themselves could be classified according to the weightings they gave the features. There were even differences in the way different judges used all-or-none features for classifying. Possible mechanisms are suggested for the basis of these differences
Eye Movement Strategies Involved in Face Perception
Authors: Walker-Smith Gail J , Gale Alastair G , Findlay John M
Published: January 2007

Recordings were made of the eye fixations of three subjects in two tasks involving black-and-white photographs of faces. In the first task, subjects matched a test face with a previously viewed target face; in the second task, subjects compared two simultaneously presented faces. The eye movements were recorded with a corneal reflection technique.

Each subject showed an individual fixation strategy for the tasks; in particular each subject had one or more preferred facial features which were viewed foveally in both tasks. The subjects also showed some tendency to use a regular sequential pattern of eye movements. However, the sequences used differed from one task to the other. Although some aspects of the results support the scanpath hypothesis of Noton, it is suggested that an alternative interpretation is possible.
Technique d'enregistrement et d'analyse des mouvements oculaires
Authors: Bullinger André , Kaufmann Jean-Louis
Published: January 2007

The aim of this article is to describe an apparatus registering eye movements, that alleviates the constraints that are usually necessary to control head movements. In a second part, the errors observed in gaze localisation by using the pupilar referential are analysed. Finally, means of increasing precision in the determination of visual fixation and facilitating the analysis of the registered images are proposed. These means comprise: (i) the use of an algorithm enabling the calculation of a correspondence grid of distortion for any one visual fixation, (ii) the use of a fixed standard dependent on the apparatus enabling the permanent determination of the position of the head, (iii) the possibility of analysing the registered images in a semiautomatic way by means of a ‘writing tablet’ and a computer of the PDP 8 series. Only four calibration points are necessary to determine all the useful parameters for the registering procedure and the analysis proposed.
Spatial Effects in Speech Perception in the Absence of Spatial Competition
Authors: Hublet Claude , Morais José , Bertelson Paul
Published: January 2007

Two synthetic speech syllables, differing in pitch, were presented over one loudspeaker situated at one of the following azimuths: 0° (in front of the subject); 45°, 90°, and 135° to the left or to the right; and 180°. The subject's task was to report the high-pitch syllable. The pattern of performance can be described in terms of two component effects: a decreasing anterior—posterior gradient, and right-side advantage. Competition between messages from one direction only appears to be as effective in determining auditory spatial effects as competition between spatially distinct sources.
Developmental Constraints of Motion Detection Mechanisms in the Kitten
Authors: Flandrin Jean-Marc , Jeannerod Marc
Published: January 2007

The influence of deprivation procedures on the development of motion detection mechanisms has been studied in twenty-two kittens. Superior colliculus neurons did not acquire direction selectivity and normal ocular dominance in animals reared in the dark or in stroboscopic light. Neuron immaturity persisted in spite of a five week additional recovery period in normal conditions. Exposure to unidirectional visual motion for 10 h during the fifth week of postnatal age produced an asymmetric development of the two superior colliculi. Finally, unilateral neonatal ablation of visual cortex permanently impaired development of the ipsilateral superior colliculus. In the same or in different animals, development of optokinetic nystagmus, a typical visuomotor response, was similarly influenced by the global or selective deprivation procedures. These results suggest that motion detection mechanisms (both afferent and efferent) strongly depend upon constraints imposed by the visual world during the first weeks of life.
Illusory Line Linking Solid Rods
Authors: Ware Colin , Kennedy John M
Published: January 2007

A solid object—a frame enclosing rods—can be seen as having an illusory ‘line’ joining the tips of the rods.
Müller-Lyer Illusions: Their Origin in Processes Facilitating Object Recognition
Authors: Warren Richard M , Bashford James A
Published: January 2007

Perspective theories for the Müller-Lyer illusions have considered them to reflect constancies normally permitting the viewer to compensate for distance in estimating the true size of three-dimensional objects. Our experiments suggest a rather different perspective theory involving object recognition.

A novel experimental procedure was used. Each of the separate groups of thirty subjects viewed only one of nineteen experimental drawings based on the Müller-Lyer figures. They judged the overall length of the shaft and divided it into subjectively equal quarters. The major findings were that the effect of each component angle was generally independent of other angles and independent of any overall perspective appearance of the figure. The shortening effect produced by an acute angle was limited to the contiguous quarter, whüe the lengthening effect of an obtuse angle extended undiminished from the contiguous quarter to the next quarter.

Perspective photographs are shown, demonstrating that these angle-induced changes in apparent length can compensate selectively for the different perspective distortions occurring for the component parts of a single three-dimensional object. Such expansions and contractions provide no direct help in estimating overall size or distance of the object. But they do make possible recognition of the actual shape of the object and its orientation to the viewer, as well as producing errors when judging the length of Müller-Lyer figures.
Metacontrast as Measured under a Signal Detection Model
Authors: Hernandez Linda L , Lefton Lester A
Published: January 2007

Metacontrast is assessed both by percent accuracy and by the dichotomous sensitivity and criterion measures of a signal-detection model in a forced-choice detection task. The results showed a monotonic increase in sensitivity with increasing mask delay, and an abrupt shift of subjects' response criterion at an 80 ms interstimulus interval. The results are discussed in terms of the interpretational advantages of a signal-detection approach to metacontrast investigation.
The Perception of Brief Temporal Intervals: Power Functions for Auditory and Visual Stimulus Intervals
Authors: Bobko Douglas J , Thompson Jack G , Schiffman Harvey R
Published: January 2007

Two experiments were performed to examine the role of method of estimation and the employment of a standard stimulus on the judged duration of auditory and visual stimuli presented for brief temporal intervals (0.25 to 5.0 s). The results indicate that the relationship between judged and physical duration is nearly direct and linear. Psychophysical methodology and stimulus modality exerted little influence on the obtained power functions.
Visual Motion Aftereffect Induced by Simulated Rectilinear Motion
Authors: Denton Gordon G
Published: January 2007

Visual motion aftereffect characteristics comparable to those associated with rotary and translatory movement of a test field are demonstrated for simulated rectilinear motion of the observer. The intensity and time duration of the phenomenon are shown to be positively correlated. The implications of this for individual observers are considered. The results of this experiment are correlated with those for adaptation and for recovery from adaptation that were obtained from the same group of observers. The findings are shown to support the hypothesis that visual motion aftereffect is a manifestation of the adaptation recovery function of velocity sensitive mechanisms.
The Effect of Visual Frame of Reference on a Judgement of Plane Stimulus Orientation by Children
Authors: Elliott John M , Connolly Kevin J
Published: January 2007

Three studies are reported with children aged [Formula: see text] to [Formula: see text] years and also with educationally subnormal children, in which it was found that up to about 7 years children's selection of one of a pair of line stimuli as ‘falling over’ is affected by the nature of the visual surround contours provided. Both the form of the stimulus surround and the presence or absence of a baseline tilted 45° relative to the horizontal were found to affect the children's judgements. The plane (horizontal or vertical) in which the stimuli were presented had no effect on the results.

It is argued that while the results show the influence of the visual surround on children's comprehension of ‘falling over’, this may not be wholly explicable in terms of surround contour matching, as conventionally correct judgements were obtained in the absence of all straight line contours in the immediate surround.
Illusory Contours Can Arise in Dot Figures
Authors: Kennedy John M , Ware Colin
Published: January 2007

Frisby and Clatworthy have suggested that subjective contours depend on special contrast effects acting at the tips of lines and at right angles to the lines. Their suggestion depends in part on the absence of such contours in dot figures. However, if the dots are grouped regularly and make a ‘good figure’, strong subjective contours appear, including a pattern comparable to Kanizsa's triangle. The kind of contrast explanation required for these figures would be one in which individual dots create small contrast effects which are only manifest in perception when the effects are grouped together, by Gestalt form indicators, overlap cues, or the like.
Interocular Transfer in Individuals with Strabismic Amblyopia; A Cautionary Note
Authors: Hess Robert
Published: January 2007

Interocular transfer of the adaptation aftereffect was measured and correlated with residual binocular function for two strabismic amblyopes who represent different types of neural loss. The results indicate that for these two subjects there is paradoxical correlation between efficacy of interocular transfer and residual binocular function.
Development of Sensitivity to Information Provided by Cast Shadows in Pictures
Authors: Yonas Albert , Goldsmith Lynn T , Hallstrom Janet L
Published: January 2007

The shadow cast by an object in a two-dimensional picture can specify for the observer the spatial relations between that object and its surroundings, and also the shape and size of the object itself. Some sensitivity to this information is present even in three-year-old children. Experiment 1 provided evidence that three- and four-year-old children can rely on the shape of the shadow cast by an object to judge the shape of the object. In experiment 2, with adults and three- and four-year-old children, the location of the shadow cast by an object influenced the perceived depth and height off the ground plane of the object. Although even the three-year-old children were sensitive to the location of the cast shadows, there was evidence of improvement with age in judging the distance and size of the object. The three-year-olds were not able to judge the object's size when the location of the cast shadow provided the only differential information for size. In contrast, they were significantly better in judging size when the location of the object, rather than the location of the shadow, was varied.
Iris Pigmentation and Visual-Geometric Illusions
Authors: Coren Stanley , Porac Clare
Published: January 2007

Blur or degrading of the retinal image has been shown to be a factor in the formation of visual-geometric illusions where intersecting line elements are present. Light irises allow more scattered light within the eye, which results in more image degradation than found in dark-eyed subjects. Measurements on 755 observers show that illusion magnitude varies as a function of iris pigmentation for a configuration with intersecting line elements (Müller — Lyer illusion), but not for a configuration devoid of such features (Ebbinghaus illusion).
Infant Recognition of Mother's Voice
Authors: Mehler Jacques , Bertoncini Josiane , Barriere Michele , Jassik-Gerschenfeld Dora
Published: January 2007

Each of a group of one-month-old infants was reinforced, contingent upon nonnutritive sucking, with its mother's voice and the voice of a stranger. In this experiment, two conditions were applied. Under the first, the mother's speech was aimed at communicating with the infant, while, under the second, the mother's speech lacked prosodic and intonational aspects of normal speech. It was shown that infants will suck more for their mother's voices under the intonated condition only. It was concluded that a young infant prefers its own mother's voice provided the mother speaks normally.
Explaining Imaginal Inference by Operations in a Propositional Format
Authors: Wilton Richard N
Published: January 2007

Solving problems by imaginal inference often seems inefficient for an organism that is manipulating propositions. One explanation for the apparent inefficiency is that the problems are being solved not in propositional format but by operations in an analogue format. Imaginal inference might then be the most efficient method compatible with the limitations inherent in the analogue format. In the present paper an alternative rationale is given for the use of imaginal inference by explaining how the processes involved in mental problem solving are related to those in perception: it is suggested that the mechanisms used in problem solving have evolved from a perceptual system in which hypotheses about events in the sensory field are generated from an internal representation of the world. This thesis denies that perception is passive and suggests that the capacity for thought is limited by its evolutionary dependence on mechanisms specialized originally for perception. Acceptance of the thesis implies that the capabilities of a propositional format in problem solving would be limited. This limitation could account for the apparently inefficient use of that format in imaginal inference.
Perspectives in Open Spaces: A Geometrical Application of the Thouless Index
Authors: Battro Antonio M , Reggini Horacio C , Karts Carlos
Published: January 2007

A geometrical model for computing ‘general perspectives’ is discussed. It is based on the power function r = p(d/t)1- i, where i is the Thouless index for the phenomenal regression to the real object, r is the real size of the object, p is the apparent size, d is the distance between the subject and the object, and t is the distance between the subject and the projection plane. This model assumes that i is invariant for different distances and this was verified in seventy children and adults at distances of 15 to 120 m. A computer program draws families of curved perspectives which are well-fitted to the actual shape of large visual alleys produced by experiment in open fields.
Moirés Maintained Internally by Binocular Vision
Authors: Piggins David
Published: January 2007

Moiré patterns in depth are reported when spatially periodic stimuli are viewed stereoscopically. Near-vertical square-wave gratings with horizontal disparity effected by orientation difference produce a ‘venetian blind’ effect. A single grating is observed divided into horizontal layers, the number of layers being a direct function of orientation difference. Lines within each layer are slanted with respect to the frontoparallel plane, becoming more so with increasing orientation difference. Subjects with stereo deficits report a decreased effect. Quantitative reports implicate stereoscopic mechanisms responsible for this unique, internal preservation of moiré patterns.
Chromatic Induction Effects in the Hermann Grid Illusion
Authors: McCarter Andrea
Published: January 2007

The chromatic Hermann grid illusion was investigated in sixteen subjects, with variation of the lightness contrast between the chromatic inducing squares and the background, and the saturation and hue of the inducing squares. Subjects made magnitude estimates of the sharpness and clarity of perceived dots at the intersections of the grid, and matched the appearances of the dots with Munsell chips. A chromatic induction effect was found to occur in the absence of lightness contrast, but the sharpness of the illusory dots increased with increasing lightness contrast ( p < 0.001). The saturation of the perceived dots increased with increases in the saturation of the inducing squares ( p <0.05), and was higher for the longer wavelengths than for the shorter wavelengths ( p < 0.005). Neural units with center-surround arrangements responding differentially to light of the same color in the center and the surround, e.g. red off-centers and red on-surrounds, could account for the chromatic induction effect.
Does Visual Texture Discrimination Precede Binocular Fusion?
Authors: Frisby John P , Mayhew John E W
Published: January 2007

Various stereoscopic demonstrations are presented which indicate that visual texture discrimination is based on processes which occur after, or at the same time as, the binocular combination of images from the two eyes. Monocularly invisible texture regions can become apparent, and monocularly visible regions can be hidden, by the processes of binocular fusion.
Induced Motion as a Function of the Speed of the Inducing Object, Measured by Means of Two Methods
Authors: Gogel Walter C
Published: January 2007

Induced motion is illustrated by the apparent motion imparted to a stationary disc by the horizontal motion of an enclosing frame. The present study examined the effect of frame speed, with a constant extent of frame motion, on the magnitude of induced motion for average frame speeds varying from 0·17 to 2·85 deg s−1. The induced motion was measured by two methods. (i) The observer adjusted the horizontal distance between comparison posts to indicate the extent of the horizontal induced motion in a physically stationary disc. (ii) The observer adjusted the slant of a comparison rod to indicate the apparent path of motion of the disc physically moving straight up and down in phase with the horizontal motion of the surrounding frame. The latter method requires the observer to integrate two apparent components of motion of the disc, one from its physical vertical motion and the other from its induced horizontal motion. The results from both methods show that substantial amounts of induction occurred at all of the frame speeds. The vector addition of apparent motions from real and from induced motion obtained from the second method, and the substantial amounts of induction found with the high frame speeds are interpreted to indicate that the processes underlying the perception of real and induced motion are essentially the same.
Spatial Localization under Conflict Conditions: Is There a Single Explanation?
Authors: Warren David H
Published: January 2007

Visual–auditory (VA) and visual–proprioceptive (VP) localization conflict paradigms were varied to explore the comparability of the conflict situations. In experiment 1 various attempts were made to decrease the dominance of visual information over proprioceptive and auditory target information. Pairing auditory with proprioceptive information against conflicting visual information did not lessen the visual dominance, nor did dimming the visual field. A ‘cognitive’ manipulation, in which the subject was led to doubt the reliability of the visual information, reduced visual dominance over audition but not visual dominance over proprioception. This difference between the two conflict situations was further explored and corroborated in experiment 2. In experiment 3 no attempt was made to lead the subject to believe that paired discrepant targets were related, and the visual dominance of audition was strong while the visual dominance of proprioception did not occur.

The apparent differences between the VA and the VP conflict situations are discussed with regard to the feasibility of generating a unitary explanation of localization conflict results. Several further factors are discussed that must be explored before undertaking such a unitary formulation.
Salt Taste Detection: An R-Index Approach to Signal-Detection Measurements
Authors: O'Mahony Michael , Gardner Laura , Long Denise , Heintz Christi , Thompson Barbara , Davies Mary
Published: January 2007

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal – noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could not see the stimuli yet to be presented, indicating a lack of systematic sensitivity drift. The simultaneous measurement of more than one signal strength with reference to a common noise stimulus was seen to be a viable and sensitive procedure. Comparison of flow-wise and sipwise presentation of stimuli using R-indices, indicated that the former elicited greater subject sensitivity to NaCl taste.
Surfaces with Steep Variations in Depth Pose Difficulties for Orientationally Tuned Disparity Filters
Authors: Mayhew John E W , Frisby John P
Published: January 2007

Surfaces possessing steep variations in depth present severe difficulties for orientationally tuned filter models of stereopsis. These difficulties are discussed in connection with a random-dot stereogram depicting a surface with steep horizontal corrugations. As expected on theoretical grounds, we find that a vertical ±45° orientationally filtered version of this stereogram cannot be fused. Moreover, it is demonstrated that a horizontal ±45° filtered version can be fused only with difficulty and its stereo percept is poor compared to that of the unfiltered original. It is concluded that orientated filters seem ill-designed to mediate the extraction of disparity cues, at least in the cases under consideration.
Adaptation Effects on the Apparent ‘Squareness’ of Square-Wave Gratings
Authors: Nachmias Jacob
Published: January 2007

Adaptation to a 9 cycles deg−1 sine wave makes the apparent brightness profile of a 3 cycles deg−1 square wave look less ‘square’ even when it does not look like that of a sine wave. Adaptation to a 3 cycles deg−1 sine wave has no noticeable effect. Hypotheses based on ‘excitation patterns’ across spatial-frequency-selective channels can account for these results; it is not clear whether variations in local light adaptation can also account for them.
Perception of Relative Velocity: A Revision of the Hypothesis of Relational Determination
Authors: Epstein William , Cody William J
Published: January 2007

The conventional formulation of the hypothesis of relational determination asserts that the perceived relative velocities of two or more objects depend upon their relative rates of displacement with respect to stationary referents in the visual field. Experiment 1 showed that this formulation is too restrictive by demonstrating the transposition-of-velocity effect under conditions in which two light spots moved in the absence of static visible contours and traversed unequal path lengths. Experiment 2 showed that angular velocity per unit of relative angular extent, and not relative linear or perceived extent, of the respective motion paths influences perceived relative velocity in nonarticulated space. The retinal dimensions of static visible frameworks were shown in experiment 3 to influence perceived relative velocity in a direction consistent with the conventional formulation of the relational-determination hypothesis, but the weight of the evidence suggested a reformulation along the following lines: the perceived relative velocities of two objects are significantly affected by the proportions of the retinal projections of the respective movement fields traversed by the two objects in the same unit of time, even when the motion fields consist only of the objects' motion paths.
What is Suppressed during Binocular Rivalry?
Authors: Blake Randolph , Westendorf David H , Overton Randall
Published: January 2007

To answer the question ‘What is suppressed during binocular rivalry?’ a series of three experiments was performed. In the first experiment observers viewed binocular rivalry between orthogonally oriented patterns. When the dominant and suppressed patterns were interchanged between the eyes observers continued seeing with the dominant eye, indicating that an eye, not a pattern, is suppressed during rivalry. In a second experiment it was found that a suppressed eye was able to contribute to stereopsis. A third experiment demonstrated that the predominance of an eye could be influenced by prior adaptation of the other eye, indicating that binocular mechanisms participate in the rivalry process.
Spatial Anisotropy in Intramodal and Cross-Modal Judgments of Stimulus Orientation: The Stability of the Oblique Effect
Authors: Lechelt Eugene C , Verenka Angeline
Published: January 2007

Visual and haptic judgments of stimulus orientation were examined intramodally and cross-modally by having subjects reproduce standard stimulus orientations simultaneously with their inspection or after a delay. For all conditions, an oblique effect was obtained, i.e. vertical and horizontal orientations were reproduced reliably more accurately than oblique orientations. Although intramodal differences were large, with haptic errors being greater than visual errors, cross-model differences were small. Furthermore, while for intramodal conditions simultaneous visual reproductions were reliably more accurate than delayed reproductions but haptic reproductions were more accurate when delayed, cross-modal errors were reliably greater with simultaneous reproductions, regardless of whether the standard orientation was visual or haptic. The modality differences reflect basic differences in stimulus information processing and the stability of the oblique effect across the experimental conditions suggests that perceptual spatial anisotropic effects are strongly influenced by experiential factors.