bluuebunny/crossref_metadata_2025 huggingface dataset:
The Unit Membrane, the Endoplasmic Reticulum, and the Nuclear Pores are Artefacts
Authors: Hillman Harold , Sartory Peter
Published: January 2007

It is shown on the basis of solid geometry that the trilaminar appearance of membranes described by Robertson must be an artefact, although the membranes themselves are not. However, considerations of solid geometry as well as observations on living cells indicate that the endoplasmic reticulum and nuclear pores are artefacts resulting from preparation for electron microscopy. Suggestions for their genesis are proposed.
Op Art and Visual Perception
Authors: Wade Nicholas J
Published: January 2007

An attempt is made to list the visual phenomena exploited in op art. These include moiré fringes, afterimages, Hermann grid effects, Gestalt grouping principles, blurring and movement due to astigmatic fluctuations in accommodation, scintillation and streaming possibly due to eye movements, and visual persistence. The historical origins of these phenomena are also noted.
Apparent Movement, Eye Movements and Phoria When Two Eyes Alternate in Viewing a Stimulus
Authors: Ono Hiroshi , Gonda Gail
Published: January 2007

Three experiments were conducted to test the hypothesis that the apparent movement of a stimulus when the two eyes, are alternately occluded can be explained by phoria and Hering's principles of visual direction. In experiments 1 and 2, the direction of apparent movement, eye position, and eye movements were measured when eye movements did and did not occur. In experiment 3, the magnitude of apparent movement and the extent of phoria were compared. Results from experiments 1 and 2 indicated that the direction of apparent movement could be predicted from the direction of phoria, in conjunction with Hering's principles, and was not contingent on eye movements. In experiment 3, a high positive correlation ( r = 0.95) between the magnitude of apparent movement and the extent of phoria was obtained.
The Use of Numerical and Graphical Statistical Methods in the Analysis of Data on Learning to See Complex Random-Dot Stereograms
Authors: Cleveland William S , Guarino Roberta
Published: January 2007

Several numerical and graphical statistical methods are illustrated in an analysis of data from an experiment that investigated a hypothesis of Julesz that giving a person a priori information about the structure of a complex random-dot stereogram reduces the time needed to perceive it when it is viewed. The data are divided into two groups, one consisting of those observers who received no cue or verbal cues (NV) and the other consisting of those who received verbal-visual cues (VV). A quantile-quantile plot shows that the NV times (mean = 7.6) are longer than the VV times (mean = 5.6). By using probability plots, it is shown that the perception times have an exponential probability distribution. A hypothesis test based upon this distribution is used to show that the differences between the NV and W times has significance slightly below 0.05.
Spatial-Frequency Masking with Briefly Pulsed Patterns
Authors: Legge Gordon E , Cohen Michael A , Stromeyer Charles F
Published: January 2007

Spatial-frequency masking was studied with briefly pulsed (25 ms) vertical gratings. The mask was a noise grating, and the test pattern was a sinusoidal grating. A low-frequency band of noise masked a low- but not high-spatial-frequency test grating when the patterns were presented simultaneously. A high-frequency band of noise did not mask a low-frequency test grating when the patterns were presented simultaneously or when the mask was presented after the test pattern (backward masking). Masking was, however, observed when the mask or test pattern was of sufficiently high contrast so that the stimuli had nonlinear distortion and thus produced DC shifts of the field luminance.
Monocular versus Binocular Contrast Thresholds for Movement and Pattern
Authors: Rose David
Published: January 2007

The superiority of binocular vision over monocular vision has been compared for the detection of stationary sinusoidal grating patterns, and for the detection of the apparent movement induced by rapidly phase-reversing such gratings. The thresholds for binocular and monocular pattern perception were in the ratio 1: 2 1/2, as found by previous workers. For apparent movement, however, binocular thresholds were lower than monocular thresholds by a factor of 1 ·9; for every subject tested ( n = 20) the ratio for movement detection was larger than the ratio for pattern detection. The effects of combining inputs from the two eyes cannot be explained solely by linear summation models, but may in some circumstances depend on the nonlinearities of certain types of nerve cell.
The Penrose Triangle and a Family of Related Figures
Authors: Draper Stephen W
Published: January 2007

Starting from a study of the Penrose triangle, the theory is advanced that our perception of the relative spatial positions of parts of a figure is mediated by a set of significant directions (or axes). Illustration and exploration of the theory in this paper revolves around examples drawn mostly from a family of figures related to the Penrose triangle. This family is defined partly in terms of the common nature of its members' anomalies, and partly by the feature that they are seen as configurations of ‘beams’. This feature and the conditions for it are also examined by the use of examples.
Binocular Utilization of Monocular Cues That are Undetectable Monocularly
Authors: Julesz Bela , Oswald Hans-Peter
Published: January 2007

The latency time of tracking dynamic random-dot stereograms can be shortened by as much as 100 ms when monocular cues are added by introducing a difference in dot density between target and surround. It has been tacitly assumed that perception time will be reduced only if the added monocular cues are above the detection threshold for each eye. However, the experiments reported here clearly show that stereoscopic performance as measured by an eye tracking task can be greatly enhanced by added monocular cues that cannot be detected. Observers were instructed to track a suddenly displaced vertical bar (portrayed as a dynamic random-dot stereogram) while their eye movements were recorded by EOG. The bar had either a given binocular disparity or zero binocular disparity with respect to its surround. For the target with a disparity (in a wide range), the latency time of tracking decreased by more than 30 ms (10%) as density difference increased from 0 to 4%, whereas in the control conditions with no stereoscopic cues (zero disparity) subjects were unable to track the bar at all within that range of density difference. Thus stereopsis is greatly aided by minimal monocular cues that by themselves elude monocular detection.
Reaching in the Dark
Authors: Wishart Jennifer G , Bower T G R , Dunkeld Jane
Published: January 2007

Reaching for noise-making objects presented in darkness declines, then recovers, during infancy. The most probable explanation of this U-shaped function would seem to involve changes in reaching, changes in the perception of success, and changes in the body schema. There is no need to postulate any U-shaped change within the auditory system.
A Distinctive Characteristic of Pictorial Perception: The Zoom Effect
Authors: Hagen Margaret A , Elliott Harry B , Jones Rebecca K
Published: January 2007

To investigate the role of flat surface information for the plane of projection in pictorial perception, three studies were designed in which varying amounts of such information were made available to adult subjects. The first study tested preferences for true or modified linear perspective under conditions of presence or absence of surface texture cues for the plane of projection. In the second and third studies, the absence of texture cues for the plane was coupled with the addition of motion parallax and binocular information respectively. It was found that adults showed a consistent preference for parallel perspective in pictures when the flat-surface information was provided either by visible texture or by motion parallax; but no consistent preference for either true or modified perspective in the absence of all three sources of flatness information or when the flat surface information was given only by binocular cues in the absence of visible surface texture or head motion.
Motion Parallax as an Independent Cue for Depth Perception
Authors: Rogers Brian , Graham Maureen
Published: January 2007

The perspective transformations of the retinal image, produced by either the movement of an observer or the movement of objects in the visual world, were found to produce a reliable, consistent, and unambiguous impression of relative depth in the absence of all other cues to depth and distance. The stimulus displays consisted of computer-generated random-dot patterns that could be transformed by each movement of the observer or the display oscilloscope to simulate the relative movement information produced by a three-dimensional surface. Using a stereoscopic matching task, the second experiment showed that the perceived depth from parallax transformations is in close agreement with the degree of relative image displacement, as well as producing a compelling impression of three-dimensionality not unlike that found with random-dot stereograms.
The Site of Binocular Rivalry Suppression
Authors: Blake Randolph , Overton Randall
Published: January 2007

Two experiments were performed to localize the site of binocular rivalry suppression in relation to the locus of grating adaptation. In one experiment it was found that phenomenal suppression of a high-contrast adaptation grating presented to one eye had no influence on the strength of the threshold-elevation aftereffect measured interocularly. Evidently information about the adaptation grating arrives at the site of the aftereffect (presumably binocular neurons) even during suppression. In a second experiment 60 s of grating adaptation was found to produce a short-term reduction in the predominance of the adapted eye during binocular rivalry. These findings provide converging lines of evidence that suppression occurs at a site in the human visual system after the locus of grating adaptation and, hence, after the striate cortex.
The Cheshire Cat Effect
Authors: Duensing Sally , Miller Bob
Published: January 2007

Designing a binocular-rivalry exhibit for the Exploratorium resulted in the observation of some interesting phenomena. Under conditions of binocular rivalry, motion in the field of one eye can trigger suppression of the other visual field as a whole or in parts. This suppression sometimes occurs only in the area of motion. Subparts of a suppressed area often remain in the visual field. Conversely, moving an object into the suppressed area of a visual field can elicit dominance of that object alone, with the rest of the field remaining suppressed. The suppression of partial areas of the visual field of each eye can occur simultaneously.
Attentive Fields: Valid Scientific Constructs or Elusive Theoretical Entities: A Reply to Pressey
Authors: Bross Michael
Published: January 2007

Pressey conveys the impression that we misunderstood and misapplied his construct of attentive field. In this rejoinder it is argued that by Pressey's own definition and application of this construct his theory should be able to account for our results.
Pattern and Flicker Detection Examined in Terms of the Nasal — Temporal Division of the Retina
Authors: Blake Randolph , Mills Jamie
Published: January 2007

Contrast thresholds for the detection of flicker and the detection of pattern were measured for nasal and temporal retinae of each eye separately. While confirming that these two types of thresholds can differ, depending on spatial frequency, the results provide no support for hemiretinal or hemispheric asymmetries in the distribution of the putative pattern and movement channels.
The Effects of Verbal Meaning and Response Categorisation on the Fragmentation of Steadily Fixated Patterns
Authors: Swanston Michael T
Published: January 2007

Studies of steady visual stimulation have suggested that the subjective meaning of a stimulus may determine the form and degree of its perceptual fragmentation. This was tested for steady fixation by presenting a letter of the alphabet (‘L’) in a sequence of other letters which were either normally oriented or inverted. No evidence was found for greater stability in the former case. An investigation of the categorisation of subjective disappearances showed that, although the stability of pattern components was not determined by reporting these singly or in conjunction, the disappearances of the whole pattern were significantly increased by reporting only these as opposed to reporting disappearances of each component. Response to simulated subjective disappearances also showed that the effect was due to the nature rather than the number of response categories. In the final experiment all subjects fixated a rotated letter, after half had received pretraining in the recognition of rotated letters. No effects of the pretraining were apparent, for either level of response categorisation, and it was concluded that the processes underlying subjective disappearances in steady fixation are not modified by the meaningfulness of a stimulus. The involvement of central processes was, however, indicated by the effects of response categorisation and the influence of simulated disappearances on pattern stability in a trial subsequent to their presentation.
Depicted Angle of Forms and Perception of Line Drawings
Authors: Kaess Dale W , Deregowski Jan B
Published: January 2007

Subjects were presented with projections of either rectangular or elliptic forms which appeared either on their own or upon the following figures: (a) a face of a portrayed cube, (b) a parallelogram identical with (a), and (c) a rectangle of equal width and area to (a). Four different angles of projection were used for both the forms and for the background figures.

In the composite figures these angles were varied independently. The subjects were required to judge the width of the forms. The forms were judged to be wider when presented on backgrounds (a) and (b) than when presented on background (c) or alone, especially at greater angles of projection. This suggests that the implicit-shape constancy effect is independent of relational effects resulting from the frame surrounding the form.
The Computation of Binocular Edges
Authors: Mayhew John E W , Frisby John P
Published: January 2007

A computational model is described which effects the binocular combination of monocular edge information. The distinctive features of the model are: (i) it identifies edge locations in each monocular field by searching for zero crossings in nonorientated centre-surround convolution profiles; (ii) it selects amongst all possible binocular point-for-point combinations of edge locations only those which satisfy a (quasi-)collinear figural grouping rule; (iii) it presents a concept of the orientated and spatial-frequency-tuned channel as a nonlinear grouping operator. The success of the model is demonstrated both on a stereo pair of a natural scene and on a random-dot stereogram.
Visual Sensitivity to the Shape and Size of a Moving Object: Implications for Models of Object Perception
Authors: Beverley Kenneth I , Regan David
Published: January 2007

Subjects adapted to rectangular targets whose opposite edges moved in opposite directions at any given instant (as when an object moves directly towards or away from the head). The distance that adaptation spread from the vertical edges was up to three times less when the horizontal edges were also moving than when the horizontal edges were stationary. Furthermore, for a square target (1 deg × 1 deg), adaptation spread least when the horizontal edges moved at the same speed as the vertical edges, whereas for a target whose height was half its width (0·5 deg × 1 deg) adaptation spread least when the horizontal edges moved at half the speed of the vertical edges.

We propose that the human visual system acts as though it contains detectors sensitive to the size and shape of an object and that these detectors enhance this sensitivity to shape and size by comparing the velocities of the horizontal and vertical edges. When a nonrotating solid object moves in three dimensions its shape severely restricts the possible relationships between the velocities of the vertical and horizontal edges of its retinal image. Our hypothetical detectors utilise these geometrically determined velocity relationships as a basis for their selective sensitivity to shape.

More speculatively, object perception and the perception of shape and size in everyday vision might involve visual sensitivity to the relationship between the velocities of an object's edges as well as sensitivity to the locations of these edges: the visual system may recognise which of the many edges in the visual field belong to a single object by comparing the velocities of orthogonal pairs of edges.
Motion Aftereffect: A Global Mechanism for the Perception of Rotation
Authors: Cavanagh Patrick , Favreau Olga Eizner
Published: January 2007

Observers adapted to motion by looking at rotating logarithmic spirals. They were tested with a stationary mirror image of the adapting spiral in which all contours were at 90° to those of the first spiral. Motion aftereffects were reported in the contrarotational direction—that is, observers who had seen clockwise rotating motion reported seeing counterclockwise aftereffects. These aftereffects lasted one-third as long as the aftereffects obtained when the adapting spiral was used as the test figure. These two aftereffects were shown to have different storage properties, thereby indexing the operation of at least two different mechanisms. We interpret the motion aftereffect that is obtained with the mirror-image stimulus as indicative of the existence of global rotation detectors.
Perception at the Blind Spot and Tilt Aftereffect
Authors: Cumming Geoff , Friend Hans
Published: January 2007

Black and white stripes were used to induce a tilt aftereffect near the blind spot. Stripe fragments on either side of the blind spot were seen as being completed across the blind spot, but the magnitude of the tilt aftereffect they induced suggested that the perceptually ‘filled-in’ portions of the stripes did not contribute to the aftereffect. So perceptually filled-in lines seem not to be fully potent percepts.
The Effects of Spatial and Temporal Factors on the Perception of Stroboscopic Rotation Simulations
Authors: Petersik J Timothy
Published: January 2007

In the present two experiments subjects viewed discontinuous, i.e. stroboscopic, simulations of a transparent sphere partially filled with randomly positioned luminous dots and rotating about the y axis in depth. Over a range of stimulus conditions, such simulations elicited coherent sensations of continuous rotation and internal volume of the sphere. By manipulating both spatial and temporal variables in the simulations, it was attempted to define the boundary conditions for which corresponding elements of a simulation are perceptually paired from frame to frame to yield coherent sensations of rotation and depth. The results indicated that the process that matches or pairs corresponding elements in a three-dimensional simulation cannot be identified with the process that matches corresponding elements in similar two-dimensional displays. Furthermore, temporal factors influenced the perception of these simulations more than did spatial factors, and rotation-judgment accuracy and perceived depth were different functions of temporal frequency. Over a range of temporal frequencies, such three-dimensional simulations are apparently processed in a manner similar to that in which objects undergoing real motion are processed.
The Selective Impact of Verbally Communicated Criteria in Orientation Judgements by Young Children
Authors: McGonigle Brendan O , Chalmers Margaret
Published: January 2007

In a series of tests requiring judgements of orientation, the impact of a verbally transmitted equivalence criterion (e.g. “Pick me out the one exactly the same as this one”) was compared with one which specified the ‘identity’ of the target as a ‘standing up’ or ‘lying down’ pattern. When a subset of four-year-olds was given the latter instruction, their performance improved dramatically (although all stimuli were lying flat on a horizontal surface) but reverted to a previous (low) level when equivalence instructions were reintroduced. The results suggest that findings from equivalence tests cannot be used to make unambiguous inferences concerning the competence of young children to make identification judgements.
A New Illusion and Possible Links with the Münsterberg and Fraser Illusions of Direction
Authors: Taylor Steve P , Woodhouse J Margaret
Published: January 2007

In the course of an investigation of the Münsterberg illusion, a new illusion has been produced. The illusion is reduced to its simplest form and possible links to the original Münsterberg and Fraser illusions are suggested.
The Binocular: Monocular Sensitivity Ratio for Movement Detection Varies with Temporal Frequency
Authors: Rose David
Published: January 2007

Binocular sensitivity to the movement or flicker visible in a phase-reversing grating pattern is higher by a factor of about 1·7 to 2·0 compared with monocular sensitivity, at low rates of phase reversal. This factor decreases as the temporal frequency of the phase reversal increases, especially above 10 Hz. For different observers, the ratio may be higher or lower overall with gratings of spatial frequency 5 cycles deg−1 than with 0·5 cycle deg−1 gratings.
Faces, Vases, Subjective Contours, and the McCollough Effect
Authors: Meyer Glenn E , Phillips Debra
Published: January 2007

A version of the face—vase pattern was constructed with the use of subjective contours. The McCollough effect was viewed on this pattern and it was found that perceptual alteration (face to vase) does not weaken the strength of the effect's hues while a complete perceptual rearrangement (faces/vases to concentric rectangles) does.
Figure Embeddedness as a Function of the Orientation of Embedding-Field Contours
Authors: Appelle Stuart
Published: January 2007

The ‘oblique effect’ was studied with the use of an embedded-figures task in which the percentage of contextual or embedding contours aligned in the same orientations as those comprising the hidden forms was systematically varied. For hidden forms comprised either of horizontal and vertical contours, or of oblique (45° and 135°) contours, search times increased markedly as the percentage of aligned contextual contours increased. Although the rate at which embeddedness increased was the same for both orientations, search times were consistently greater for locating obliquely oriented targets ( p < 0–05), and search time variance was significantly greater ( p < 0–025) on trials in which the hidden form was oblique. The results suggest that the laws of organization governing embeddedness apply equaly to oblique and horizontal—vertical orientations, but perceptual processing of oblique orientations is poorer. The relationship between search time and aligned contour is discussed in terms of the dual processes of extraction and synthesis in visual search.
Relation of Brightness to Threshold for Light-Adapted and Dark-Adapted Rods and Cones: Effects of Retinal Eccentricity and Target Size
Authors: Drum Bruce
Published: January 2007

‘Equal-brightness' functions of retinal eccentricity and target diameter were measured by a matching procedure, and compared with the corresponding threshold functions for four different adaptation conditions: light-adapted cones (LAC), dark-adapted cones (DAC), light-adapted rods (LAR) and dark-adapted rods (DAR). The separation between log brightness matches and log thresholds decreased with eccentricity and increased with target size for all adaptation conditions, but overall separation was substantially greater for the DAR condition than for the other three.

A two-channel model of achromatic brightness is proposed to explain the results. The model assumes ‘strong’ and ‘weak’ channels, which contribute unequally to brightness. These channels are tentatively identified with tonic and phasic classes of retinal ganglion cells.
A Dichoptic Edge Effect Resulting from Binocular Contour Dominance
Authors: Welpe Edwin , von Seelen Werner , Fahle Manfred
Published: January 2007

If one eye sees a bright field on a dark surround while a homogeneous background is presented to the other eye, then a distinct dark zone appears at the outer borders of the field.

If the surround is coloured, then the zone is of corresponding hue. The effect disappears if the edge of the field can be fused with a bar of appropriate contrast. The influence of parameters such as pattern contrast and size were studied quantitatively. A model is proposed relating the effect to receptive-field organisation and the fusion process.
The Dominance of Touch by Vision: Occurs with Familiar Objects
Authors: Power Roderick P
Published: January 2007

In a study of visual dominance based on Rock and Victor's experiments, observers examined well-known objects while receiving conflicting tactual and visual information. In experiment 1 observers simultaneously felt a circular 20 cent coin and looked at it through a lens which transformed the visual image to an oval with axes in the ratio 1:1·8. In experiment 2 another sample of observers felt well known cubic objects—dice—and looked at them through lens systems which made the visual images: (i) rectangular with sides in the ratio 1:1–3; (2) diamond-shaped with 72° smaller angles; (iii) rectangular with sides in the ratio 1:1·8; and (iv) a parallelogram with side lengths in the ratio 1:1·8 and with 60° smaller angles. Although there was some conflict between the observers' cognitions and their percepts, effectively all reported that the target objects were like or felt like their visual images, demonstrating that the dominance of vision over touch is far stronger than has been recognised.
An Examination of Intertrial Interval and Gender Influences on Sucrose Detection Thresholds Established by a Modified Staircase Procedure
Authors: Kunka Matthew , Doty Richard L , Settle R Gregg
Published: January 2007

The influence of intertrial interval durations ranging from 7 to 30 s upon sucrose detection thresholds of sixteen subjects was investigated by means of a modified staircase procedure with intertrial rinses. In addition, the influence of the sex of the subject was examined. Neither the intertrial interval nor the sex of the subject significantly affected sucrose detection thresholds. The results suggest that, in sucrose detection threshold studies using the present procedure, one can employ intertrial intervals as short as 7 s without significantly affecting the threshold value.
The Poggendorff Illusion: An Illusion of Linear Extent?
Authors: Greist-Bousquet Suzanne , Schiffman Harvey R
Published: January 2007

In the standard version of the Poggendorff figure a transversal intersects two parallel verticals and the segment of the transversal between the two intersection points, A and B, is not shown. The two portions of the transversal outside the parallels then seem to be misaligned. Besides this illusion of direction, there is also an illusion of size, the distance AB being underestimated in the standard figure. The influence of configural components in determining this spatial distortion of the Poggendorff figure was examined by having subjects reproduce the inner oblique (at 45°) extent AB in variations of the figure. This distance was found to be underestimated in Poggendorff variations which contained parallel (vertical) components that formed an acute angle with AB; and the underestimation increased as the number of these components present in the figure increased. The distance AB was found not to be significantly distorted in figures which contained only those parallel (vertical) components that formed an obtuse angle with AB, yet their presence in the figure tended to counteract the underestimation. When the transversals were omitted, the underestimation was found to increase. The findings are interpreted in support of an explanation that reduces the Poggendorff effect to those factors which mediate the Müller-Lyer illusion.
The Effect of the Nature of the Surround on the Perceived Lightness of Grey Bars within Square-Wave Test Gratings
Authors: White Michael
Published: January 2007

The perceived lightness of grey bars within grey–white and grey–black square-wave test gratings was measured in the presence of different surrounding regions (plain black, plain white, or black–white square-wave gratings). The results for the grey–white test gratings are explained in terms of three separate processes: (i) lightness contrast; (ii) lightness assimilation resulting from the limited ability of the visual system to deal with grating contrast at higher spatial frequencies; and (iii) lightness assimilation resulting from lateral inhibition between pattern detecting channels mediating the perception of the gratings in the test regions and the surrounds. The results for the grey–black test gratings were explained without reference to the third process. It is concluded that techniques involving lightness assimilation could provide investigators with a sensitive new method of investigating the specificities of the inhibitory interactions underlying pattern perception.
Self-Referent and Movement Cues in Coding Spatial Location by Blind and Sighted Children
Authors: Millar Susanna
Published: January 2007

The study tested the hypothesis that movement and self-referent information differ, and that children can use both to code unseen locations. In one experiment blindfolded sighted children made more errors with changed than with unchanged accessing movements, despite unchanged reference conditions. Rotation decreased accuracy further, although most responses were to the correct side. Age did not interact with experimental conditions. In another experiment blind children and matched blindfolded controls were less accurate with changed movements; and rotations were more difficult still. Visual experience, but not age, interacted with conditions. The blind showed significantly more self-reference (responses to the original side in rotations), and were somewhat worse also with changed movements alone but did not differ from controls when movements and references were unchanged.

The results support the hypothesis that movement and self-referent information differ. Visuospatial experience and task conditions rather than age seem to determine the extent to which children use either form of information.
Apparent Rotation of a Line Superimposed upon Radially Expanding and Contracting Backgrounds
Authors: Swanston Michael T , Wade Nicholas J
Published: January 2007

An oblique line superimposed on a vertical or horizontal grating appears to rotate when the whole pattern is expanded or contracted. The apparent rotation occurs with head movements towards or away from a stationary grating, or with zooming a grating relative to a stationary observer. The magnitude and direction of the apparent rotation is dependent upon the relative inclination of the line to the grating and is most pronounced with a relative orientation of 45°.
Orientation Selectivity of the Human Visual System as a Function of Retinal Eccentricity and Visual Hemifield
Authors: Beaton Alan , Blakemore Colin
Published: January 2007

An adaptation method was used to determine the specificity of orientation-selective channels in the human visual system at different retinal eccentricities (up to 16 deg) in both hemifields of each eye. For a vertical test grating, the elevation in contrast threshold produced by adapting to a high-contrast grating of the same spatial frequency but variable orientation was equated with the contrast levels of a vertical adapting grating that produced equivalent effects ( equivalent-contrast transformation). This enabled comparisons to be made between the orientation tuning of the aftereffect at different retinal loci. For the spatial frequency employed (3 cycles deg−1), no systematic change in orientation selectivity was found as a function of either retinal eccentricity or the hemifield (and hence the cerebral hemisphere) stimulated.
The Sensitivity of Binocular Rivalry Suppression to Changes in Orientation Assessed by Reaction-Time and Forced-Choice Techniques
Authors: O'Shea Robert P , Crassini Boris
Published: January 2007

Binocular rivalry was induced between two orthogonal square-wave gratings of the same spatial frequency, luminance, contrast, and field size, presented dichoptically. One of the gratings could be instantly replaced by a third grating differing only in orientation. In one experiment subjects were required to respond as soon as an orientation change was noticed, and to withold response to catch trials (no orientation change). When orientation changes were made to the visible grating, reaction time was found to be a U-shaped function of the magnitude of orientation change. When orientation changes were made to the grating undergoing binocular-rivalry suppression, an overall increase in reaction time was found with the increase being greater for large orientation changes (an asymmetrical U-shaped function). In another experiment subjects were required to detect the direction of a change in orientation in a two-alternative forced-choice procedure. Thresholds were thus obtained for 75% correct performance. It was found that thresholds for orientation changes made to the visible and invisible fields were identical from 20° to 70° orientation change. Outside this range thresholds were higher when orientation changes were made to the field suppressed by binocular rivalry. It is argued that the orientation functions obtained in the two experiments may represent incomplete suppression of either form or transient information during binocular rivalry.
False Perspectives
Authors: Gillam Barbara
Published: January 2007

Textbook accounts of perception frequently contain grossly wrong perspective drawings and/or statements about perspective which misrepresent the available monocular information about distance and size, as well as giving the unfortunate impression that perspective alone elicits only a weak impression of recession. An early example of such a false perspective is the ‘Ames window’, which is not a correct rendering of a slanted window.
High Fundamental Spatial Frequencies and Edges have Different Perceptual Consequences in the ‘Group/End-to-End’ Movement Phenomenon
Authors: Petersik J Timothy , Grassmuck Jane
Published: January 2007

A subject viewing two alternating frames, each containing, say, three vertical stripes in a horizontal row, displaced laterally by one cycle in one frame with respect to the other, perceives either the three stripes moving left-right-left in unison (group movement) or one stripe moving from one end of the display to the other and the two overlapping stripes stationary (end-to-end movement). At suitable temporal parameters of presentation (frame duration, interstimulus interval) the perception of the display is bistable. Experiments have shown that the relative strengths of these alternative movement sensations depend upon the fundamental spatial frequency of the display and upon stimulus waveform. Square-wave stimuli, which have energy at high spatial frequencies, had effects opposite to those produced by increases in fundamental spatial frequency. Amblyopes differed from normal viewers only in the perception of the square-wave stimuli.
Meridional Variation in Visual Acuity of Hooded Rats Reared in a Carpentered Environment
Authors: Dean Paul , Horlock Phillip , Strachan Ian M
Published: January 2007

Resolution acuity in people is frequently better for horizontal and vertical gratings than for obliques. An animal model of this oblique effect might be of help in elucidating its underlying neural mechanisms. Rats were chosen because laboratory rats are reared in a ‘carpentered environment’ apparently similar to those proposed to cause the oblique effect in people, and because electrophysiological experiments suggest that orientation selective units in rats' visual cortex may prefer horizontal and vertical stimuli. The acuity of eight laboratory-reared hooded rats was measured with high-contrast horizontal, vertical, and oblique gratings. The animals learned to detect low-frequency square-wave gratings with slightly fewer errors if they were horizontal or vertical than if they were oblique, but the effects of grating orientation on acuity were not significant. Refraction of the rats' eyes gave no evidence of astigmatism. These results suggest that the rat may not be a good animal model for studying the mechanisms that underlie meridional variations in acuity in people, and raise questions concerning both the neural bases of resolution acuity, and the validity of the ‘carpentered environment’ hypothesis.
Cortical Anatomy, Size Invariance, and Spatial Frequency Analysis
Authors: Schwartz Eric L
Published: January 2007

In a recent application of an algorithm developed in computer and optical pattern recognition, Cavanagh has suggested that a composite of spatial frequency mapping and complex logarithmic mapping would provide a translationally, rotationally, and size-invariant mechanism for human vision. In this work, Cavanagh has not made explicit the fact that this transformation is composite, that is, that the first step (global Fourier analysis) is perceptually, anatomically, and physiologically inconsistent with primate vision, but that the second step (complex logarithmic mapping) is actually embodied in the anatomy of the primate retinostriate projection. Moreover, it is the complex logarithmic remapping step which is entirely responsible for the computational simplification of the symmetries of size and rotation invariance. These facts, which have been extensively discussed in a recent series of papers, are briefly reviewed and illustrated. Furthermore, it is shown that the architecture of the retinostriate map may provide an example of computational anatomy in vision, such that the spatial representation of a stimulus in the brain may be of direct functional significance to perception, and to the nature of certain visual illusions.
Inhibitory Circuits Accounting for Development of Visual Cortical Mappings, Stimulus Preferences, and Psychophysical Performance
Authors: Dobson Vernon G
Published: January 2007

A developmental rationale is proposed for the circuitry underlying the generation of fine retinotopic mappings, the quantitative range of simple-cell stimulus preferences, and the psychophysical performance of the visual system. It is assumed that the retina consists of a mosaic of partially overlapping elements, or hyperfields, which are laid down in a sunflower-seed pattern. These hyperfields project to a corresponding rectilinear mosaic of hypercolumns in the cortex, according to a pattern of chemoaffinities. Each hyperfield, in turn, consists of a sunflower-seed mosaic of nonoverlapping ganglion-cell receptive-field centres, which project to a matching rectilinear mosaic of minicolumns in the corresponding hypercolumn. Retinotopic order is produced in the hyperfield-hypercolumn mapping by radially symmetric inhibitory links, between cortical cells more than two minicolumns apart, which operate on Hebb-modifiable retinocortical excitatory afferent fibres. Under this mapping, hyperfield radii map onto parallel rows of minicolumns (orientation columns), and concentric semicircles of ganglion-cell receptive fields map onto spatial-frequency columns, crossing orientation columns at right angles. The ‘scatter’ in this mapping is equivalent to one local average receptive-field diameter. Orientation-related stimulus preferences are produced by asymmetrical inhibitory links between cells more than two minicolumns apart, in the same spatial-frequency columns. A third network of inhibitory circuits, with Hebb-modifiable synapses, is assumed to operate between cells in the same or immediately adjacent minicolumns. This network enhances stimulus selectivity and sensitivity in simple and hypercomplex cells, and is responsible for adaptation aftereffects and sensory information storage.
Optical Information and Practice in the Discrimination of 3-D Mirror-Reflected Objects
Authors: Kaushall Philip , Parsons Lawrence M
Published: January 2007

Two studies of the discrimination of three-dimensional mirror-reflected objects were concerned with the influence of practice and stimulus information for shape, specifically binocular information and perspective transformations. In the first study subjects made ‘same-different’ responses to successively presented pairs of real objects, under binocular and monocular viewing conditions. In the second study subjects viewed object pairs on a rotating turntable, in five different displays. Neither binocular information nor perspective transformations contributed to isomorph discrimination. In both studies mental rotation and other less well specified strategies were employed. After practice, in contrast to previous reports, five of the six subjects in these studies produced reaction times unrelated to the orientation difference between the objects. These practice effects may reflect either extremely rapid rotation rates, the detection of rotationally invariant features, or the use of multiple strategies.
Research on Monocular Depth Perception between 1884 and 1914: Influence of the German Unfallversicherungsgesetz and of the Jurisdiction of the Reichsversicherungsamt
Authors: Hell Wolfgang
Published: January 2007

The German Unfallversicherungsgesetz (Accident Insurance Law) of 1884 granted annuities to all employees in case of an industrial accident resulting in a partial or permanent disability. The amount of the annuity was to be assessed “according to the remaining working capacity”. The application of this requirement of the law to the loss of one eye influenced the research on monocular depth perception, in particular by providing impetus to research into adaptation to monocularity during the following thirty years. The failure of this research to produce unequivocal results and a decision of the Reichsversicherungsamt (German Insurance Board) restricting its own jurisdiction put an end to this line of research.
The Relationship between Texture Gradient and Perceived Slant-in-Depth: Direct or Mediated?
Authors: Epstein William
Published: January 2007

Judgments were obtained of the surface texture and rotation in depth of a briefly-exposed monocularly-viewed rectangular grid rotated in depth and a set of projective equivalents of the grid presented in the frontalparallel plane. The judgments were secured when the grids were presented alone and when they were followed by a masking textured surface after interstimulus intervals (ISIs) ranging from 0 to 120 ms. In the absence of the mask judged texture varied corresponding to the variations of optical texture both for the rotated rectangular grids and the frontalparallel projections. Judgements of orientation in the absence of the mask varied corresponding to the variations in objective orientation for the rectangular grid and corresponding to the projective equivalent rotations for the frontalparallel projections. Introduction of the mask at ISI = 0 led to disruption of discriminative gradient and orientation judgments. The degree of disruption decreased as ISI increased. These findings were interpreted as supporting a mediational hypothesis of the relationship between optical texture and perceived slant-in-depth. In contrast to the direct perception hypothesis advanced by Gibson, the mediational hypothesis assigns an important role to the perceptual representation of the optical gradient. When the formation of this representation is arrested by processing of the mask, the relationship between optical texture and perceived slant-in-depth is disrupted.
A Note on the Basis of Reversed Perspective
Authors: Moray Gerta , Moray Neville
Published: January 2007

Glasser's and Humphrey's explanation of the origin of reversed perspective in Byzantine and other arts is supported by the results of an experiment in which observers judged the back line of a ‘footstool’ drawing to be equal in length to the front line when it was actually shorter than the latter. Thus a correctly drawn parallelogram appears to be in reversed perspective where it is the top of an object whose side is shown and which therefore provides cues for its depth.
Classification of Impossible Objects
Authors: Sugihara Kōkichi
Published: January 2007

A mathematical scheme is proposed for the classification of impossible objects. Impossible objects are usually defined from a psychological point of view as mental images of ‘solid objects’ which cannot exist in a real three-dimensional world. From the mathematical point of view, however, various kinds of impossibility can be observed in such objects, and they are classified according to the kinds of impossibility they possess. Since impossible objects are treated in a purely mathematical way, the results afford a powerful basis for the psychological study of human visual perception of impossible objects. Several psychological problems arising from the present results are also discussed.
The Effect of Familiar Size at Familiar Distances
Authors: Fitzpatrick Virginia , Pasnak Robert , Tyer Zita E
Published: January 2007

The effect of familiar size as a distance cue was tested with familiar objects at familiar distances. Experiment 1 showed that there were no uncontrolled distance cues available and that in their absence the retinal image did not affect depth or size perception. Under these conditions, size and distance judgments were essentially indeterminate and independent of each other. In experiment 2 a paradigm was employed which allowed a direct determination of whether equivalent changes either in size of a familiar object or in its true distance produced equivalent changes in its perceived distance. The results showed that there were no uncontrolled distance cues, and that subjects perceived the familiar object as having its familiar size. Moreover, changing the retinal image of the objects had almost exactly the same effect on their perceived distance as did changing their true distance. Hence, familiar size does effectively govern the perception of distance when there are no competing cues.
Brightness Effects in Diffuse and Sharp Illusory Figures of Similar Configuration
Authors: Parks Theodore E
Published: January 2007

The relative frequencies of ‘bright’, ‘dark’, and ‘neither’ reports were similar for diffuse, as compared to sharp-edged illusory circles and rings, whether viewed directly or peripherally, suggesting in this case a shared source of at least part of their illusory brightness alteration.
The Perception of Musical Rhythms
Authors: Longuet-Higgins H Christopher , Lee Christopher S
Published: January 2007

There are many musical sequences in which the rhythm is evident from the mere durations of the notes. A simple theory is proposed of how a listener may infer the rhythm of such a sequence by comparing the note lengths. It is assumed that the listener forms an idea of the rhythm as the sequence unfolds, constructing and eliminating metrical hypotheses in the light of what he hears. The theory, which differs in some important respects from earlier proposals, has been implemented as a computer program. The program has been tested on a wide variety of musical examples, and its successes and failures are discussed in detail.
Eye Dominance and Stereopsis
Authors: Weinman John , Cooke Vicky
Published: January 2007

The contribution of eye dominance to the large individual differences found in the speed of stereoscopic fusion has been examined. The degree of sensory dominance was measured and correlated with the time taken to perceive depth in three random-dot stereograms of varying complexity. A significant positive correlation was found with the simple stereogram and nonsignificant positive correlations were obtained with the two more complex stereograms. The results indicate that a high degree of eye dominance can significantly interfere with the speed of fusion of simple stereograms.