bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Curvature on Visual Interpolation
Authors: Takeichi Hiroshige
Published: January 2007

The effect of curvature on visual interpolation in partly occluded figures was examined. In experiments 1 and 2, the shape of a visually interpolated contour was measured by using a partially occluded triangle or a partially occluded circle as the target figure. The targets were cut off at both sides, with varying width from trial to trial. In experiment 1, the peak height, which was supposed to represent the shape of the interpolated contour, was measured for each target for each size of the visible part. A significant effect of curvature, as the difference in the peak height between the targets, was found when the width of the visible part was 10 to 20 min. The effect became stronger linearly with increasing length of the visible contour (the buildup effect). The effective curvature thus appeared to be measured along the visible contour in terms of the change of orientation. In experiment 2, the scale invariance of the buildup effect was examined with varying observation distance. It was found that the effect remained the same across scale if the effect was described in terms of visual angle of the visible arc, but not in terms of the proportion of the visible part to the whole figure. This suggests that the effect is derived from the visible contour, but not from the likelihood of the estimated shape of the partly occluded figure. It has been concluded that the curvature induces curved interpolation and that the curvature of the visible contour is measured along the contour as the change of orientation.
Amodal Completion and Vernier Acuity: Evidence of ‘Top-But-Not-Very-Far-Down’ Processes?
Authors: Mussap Alexander J , Levi Dennis M
Published: January 2007

Vernier thresholds were measured by means of a forced-choice paradigm for physically separated bars that were perceived either as separate or as amodally completed behind an occluder. The finding that thresholds were not reduced (improved) with amodal completion argues against an early neural code for amodal completion that is equivalent to physical completion of the vernier bars (ie neural propagation/interpolation) and limits the stage at which amodal representations could arise via bottom—up processes to neural sites located centrally with respect to those involved in position coding. An alternative explanation is also considered, that this result reflects the activity of top—down processes that mediate amodal completion by imposing grouping/organizational constraints upon earlier representations of position. In support of this proposition it was found that when tested by means of a non-forced-choice paradigm without feedback, observers demonstrated a reduced tendency to report the presence of a vernier offset when the bars were perceived as amodally completed (ie a shift in response bias occurred). This separability of vernier acuity and response bias suggests the existence of ‘top-but-not-very-far-down’ grouping processes whose influence does not extend to early representations of relative position.
Production and Interpretation of Pictures of Houses by Blind People
Authors: Heller Morton A , Kennedy John M , Joyner Tamala D
Published: January 2007

Subjects were exposed to a three-dimensional model of a house and were asked to draw it using a raised-line drawing kit. Independent groups of ten each of sighted controls, early-blind, and late-blind subjects were told to identify the vantage point of tangible pictures of the model, including side views, ‘bird's-eye’ views from above, and views involving linear perspective. The ease or difficulty of picture interpretation depended upon the nature of the tangible drawing, with much better performance being recorded for side views. Performance was poor for foreshortened 3/4 views. Early-blind subjects were particularly unlikely to recognize views from above. In a control experiment with blindfolded sighted subjects the influence of prior information was examined: some subjects were told that the drawings could consist of side view or bird's-eye, top view, or 3/4 view drawings. This experiment showed that performance can be greatly improved through prior information about the nature of the tangible pictures.
Visual Factors Affecting the Rod-And-Frame Illusion: Role of Gap Size and Frame Components
Authors: Antonucci Gabriella , Fanzon Daniela , Spinelli Donatella , Zoccolotti Pierluigi
Published: January 2007

In two studies the effect of the distance between the tip of the rod and the frame sides (gap) in the rod-and-frame (RF) illusion was examined and the effect of a full-square condition was compared with that of two different frame amputations.

In both studies, there were more rod-setting errors in the direction of the tilt of the inducing figure with a small gap than with a large one. These findings are consistent with the idea that in the case of small gap size local interactions contribute to determining the RF illusion. The actual length of the rod was varied in order to keep the gap constant across different frame tilts; therefore these findings cannot be due to the co-variation between gap size and frame tilt which is typical of standard apparatuses.

The effect of frame amputations was compared to the full-square condition. According to Wenderoth and Beh, amputations that maintain the two orthogonal contours of the square produce the typical angular function of the RF illusion. This prediction was confirmed in both studies. However, results indicate that the full square has a stronger illusory effect in the case of a small degree of tilt of the inducing stimulus, irrespective of gap size. It is suggested that this ‘square superiority’ effect is related to global, not local, mechanisms. To pursue Wenderoth and Beh's observations, amputations close to the vertical meridian were used in one experiment and those close to the horizontal meridian in the second experiment. Contrary to predictions, these conditions produced overlapping results.
Viewing Angle and the Perceived Orientation of Pictorial Elements: Geometric or Representational Effects?
Authors: Derȩgowski Jan B , Parker Denis M
Published: January 2007

The role of geometric shape properties in determining the perceived orientation (heading) change of picture elements was investigated in four experiments. In experiment 1 the systematic change in perceived heading of each of a depicted team of horses which projected irregular geometric shapes was measured. In experiment 2, involving silhouettes, the perceptual axes of these same horse shapes, together with those of a pair of enantiomorphic deltoid shapes, were derived. These derived shape axes were used in experiment 3, along with single oblique contours, to determine the degree of heading shift as a function of the complexity and orientation of the shape. The degree of heading shift was remarkably similar for both silhouette shapes and the single contours when the axes were oblique but, whereas vertical orientation was predicted to abolish heading shift, this was only true for the deltoid shapes. In experiment 4 a possible explanation of the nonpredicted heading shift for the vertically oriented horse silhouettes was investigated. Subjects' individual estimates of the axes of the horse shapes, rather than a group mean value, were used to set the horse shapes to the vertical. When viewing was from two positions no significant heading change with view was found. Taken as a whole the data suggest that the geometric properties of patterns, rather than their representative nature, determine the very obvious heading shift when pictures are viewed from different angles.
Life-Span Development of Odor Identification, Learning, and Olfactory Sensitivity
Authors: Cain William S , Stevens Joseph C , Nickou Connie M , Giles Amy , Johnston Ingrid , Garcia-Medina Maria Rosa
Published: January 2007

In the first of three studies, children (aged 8 to 14 years) were found to perform worse than young and middle-aged adults in unprompted identification of odors, with average performance much like that of elderly adults. Comparisons on other tasks, specifically odor threshold, prompted odor identification, and object naming (Boston Naming Test), across the life span (five groups) revealed that children have the same excellent olfactory sensitivity as young adults and merely lack odor-specific knowledge that accumulates slowly through life. Such knowledge apparently accumulates so slowly that age-associated discriminative losses, measurable by early middle age, begin to wear away gains obtained through experience before odors can become overlearned. In the second study, a novel adaptive psychophysical method, the step procedure, confirmed the equivalent sensitivity of children and young adults. In the third study, a paired-associate task illustrated the sluggish course of odor learning. Young adults outperformed children, though the youngest group, first graders, made up ground relatively fast. For children and adults, common odors facilitated performance relative to novel odors. The outcome highlighted the relevance of semantic factors in odor learning irrespective of age.
Depth Judgments of Triangular Surfaces during Moving Monocular Viewing
Authors: Reinhardt-Rutland Anthony H
Published: January 2007

When an observer judges the orientation in depth of a trapezoidal surface, the pictorial information of the surface is often more influential than motion information. Motion information might be more effective if pictorial information is simplified: this prompts the present study. Surfaces were triangular and pictorial information resided only in the visual lengths of the surfaces. In experiment 1, monocular observers viewed during head motions of 0 to 30 cm extent. Static judgments were somewhat dependent on visual length and tended to be frontal. Contrary to predictions, moving judgments were similarly affected: only 30 cm motion elicited near-veridical perception, as in previous studies with trapezoidal surfaces, although visual length had a residual effect. Experiment 2 involved investigation of whether visual length requires prior exposure to triangular surfaces to be effective; this was found not to be the case, which argues that observers rely on internal models of triangular surfaces. Depth perception appears to balance rapidity of processing against accuracy, in a way suggesting that ‘direct’ approaches are incomplete. Finally, it is argued that depth-from-motion simulations—influential in assertions that motion information is fully effective—depend on pictorial information.
Haptic Aftereffect of Curved Surfaces
Authors: Vogels Ingrid M L C , Kappers Astrid M L , Koenderink Jan J
Published: January 2007

A haptic aftereffect of curved surfaces is demonstrated. Two spherical surfaces were presented sequentially to human subjects. They rested one hand on the first (conditioning) surface. After a fixed conditioning period they transferred their hand to the second (test) surface and judged whether the test surface was convex or concave. In experiment 1 the curvature of the conditioning surface was varied; the subject's judgment of convexity or concavity of the test surface was strongly shifted in the direction opposite to the curvature of the conditioning surface (negative aftereffect). Therefore, subjects judged a flat surface to be concave after being exposed to a convex surface. After a conditioning period of 5 s the shift was about 20% of the curvature of the conditioning surface. In experiment 2 the duration of the conditioning period was varied; the magnitude of the aftereffect could be described by a first-order integrator with a time constant of 2 s. In experiment 3 the time interval between the conditioning period and the touching of the second surface was varied; the magnitude of the aftereffect could be described by an exponential decay with a time constant of 40 s. It is concluded that the haptic aftereffect of curved surfaces is an important effect that occurs almost instantaneously and lasts for an appreciable period.
Dependence of Relational Colour Constancy on the Extraction of a Transient Signal
Authors: Linnell Karina J , Foster David H
Published: January 2007

Human observers can correctly attribute changes in the appearance of a scene either to changes in the incident light or to changes in the spectral-reflectance properties of the scene. This ability was assessed as a function of the time course of illuminant and spectral-reflectance changes. Observers were presented with computer simulations of Mondrian patterns of 49 randomly selected Munsell papers. On each trial a Mondrian pattern was presented for 1 s; the pattern then changed either instantaneously or gradually into another Mondrian pattern, also presented for 1 s, which was related to the first either by an illuminant change or by an illuminant change accompanied by additional changes in the spectral-reflectance functions of the individual papers. Illuminant and spectral-reflectance changes were applied linearly in time (with respect to CIE coordinates) over intervals ranging from 0 to 7 s. Observers indicated whether there was a spectral-reflectance change. They were able to make reliable discriminations between illuminant and spectral-reflectance changes both when the changes were applied instantaneously and when they were applied gradually over time, but performance worsened progressively as the duration of the changes increased, that is, as their rate decreased. It is suggested that discrimination in this task depends on the extraction of a low-level transient signal which is generated in response to rapid changes in scene appearance and which is progressively attenuated as changes occur more and more gradually.
The Goldfish—A Colour-Constant Animal
Authors: Dörr Saskia , Neumeyer Christa
Published: January 2007

A series of either thirteen or fifteen coloured test fields with hues from blue through grey to yellow were presented on a black background. Goldfish were trained on a bluish-grey test field by food reward. In the training situation, the setup with the coloured papers was illuminated with white light. In the test situation, the colour of the illumination was changed to blue or yellow. In both test illuminations the goldfish preferred the training field in the same way as under white illumination despite the fact that this test field stimulated the cone types very differently from the training situation. As test fields were present that excited the cones in exactly the same way as under white light, but were not chosen, colour constancy can be concluded. By means of colour metrics, it was possible to quantify direction and strength of colour constancy.
Apparent Shape of the Mach Book
Authors: Clement Richard A
Published: January 2007

The Mach book is a two-dimensional figure which looks three-dimensional. Despite the impression of depth in the figure, the apparent shape has not been determined. It has been suggested that the book appears as part of a ‘cubic corner’, ‘as flat as possible’, or with each half rotated about its long diagonal. Alternative hypotheses as to the three-dimensional orientation of the book were tested by means of a probe-line technique. It was found that, although no hypothesis matched the results of all of the subjects, the probe-line settings of individual subjects were approximately linear or piecewise linear functions of the angles in the picture. The technique was also applied to asymmetric versions of the figure and it was found that the subjects modified their settings in accord with the constraint that the two halves of the figure must join in depth along their common edge. The findings are in agreement with models of the interpretation of line drawings in which local estimates of edge orientation in depth are formed, and subsequently checked for consistency.
Spatial Context in Recognition
Authors: Bar Moshe , Ullman Shimon
Published: January 2007

In recognizing objects and scenes, partial recognition of objects or their parts can be used to guide the recognition of other objects. Here, the role of individual objects in the recognition of complete figures and the influence of contextual information on the identification of ambiguous objects were investigated. Configurations of objects that were placed in either proper or improper spatial relations were used, and response times and error rates in a recognition task were measured. Two main results were obtained. First, proper spatial relations among the objects of a scene decrease response times and error rates in the recognition of individual objects. Second, the presence of objects that have a unique interpretation improves the identification of ambigous objects in the scene. Ambiguous objects were recognized faster and with fewer errors in the presence of clearly recognized objects compared with the same objects in isolation or in improper spatial relations. The implications of these findings for the organization of recognition memory are discussed.
Bilateral Symmetry Detection: Testing a ‘Callosal’ Hypothesis
Authors: Herbert Andrew M , Humphrey G Keith
Published: January 2007

At the end of the 19th century Mach observed that vertical symmetry is more easily perceived than is symmetry at other orientations, and proposed this resulted from bilateral symmetry in the visual system. Numerous studies of symmetry detection have been conducted, but none has been concentrated on Mach's proposal. Recent interpretations of Mach's hypothesis suggest the corpus callosum mediates the vertical-symmetry advantage. In this ‘callosal’ hypothesis it is suggested that the detectability of symmetry should be narrowly tuned around vertical, and that presentation of patterns away from fixation should disrupt the vertical advantage. We found that the vertical advantage was disrupted by presentation of patterns 1.2 deg from fixation, while detection of symmetry at other orientations was not disrupted. At fixation the orientation tuning was at least within ±10° of vertical. The detection of vertical symmetry at fixation was found to be anomalous in two subjects born without a corpus callosum as compared with controls, but relatively normal for presentation off fixation. The three experiments reported are in agreement with some of the predictions derived from the callosal hypothesis. It appears that the callosal hypothesis may account for the relative advantage of vertical symmetry at fixation, but other mechanisms must operate to detect symmetry at other orientations and positions.
Cortical Dynamics of Boundary Segmentation and Reset: Persistence, Afterimages, and Residual Traces
Authors: Francis Gregory , Grossberg Stephen
Published: January 2007

In previous work with a neural-network model of boundary segmentation and reset, the percept of persistence was linked to the duration of a boundary segmentation after stimulus offset. In particular, the model simulated the decrease of persistence duration with an increase in stimulus duration and luminance. Further evidence is revealed for the neural mechanisms involved in the theory. Simulations show that the model reset signals generate orientational afterimages, such as the MacKay effect, when the reset signals can be grouped by a subsequent boundary segmentation that generates illusory contours through them. Simulations also show that the same mechanisms explain properties of residual traces, which increase in duration with stimulus duration and luminance. The model hereby discloses previously unsuspected mechanistic links between data about persistence and afterimages, and helps to clarify the sometimes controversial issues surrounding distinctions between persistence, residual traces, and afterimages.
Properties of Complex Hallucinations Associated with Deficits in Vision
Authors: Schultz Geoffrey , Needham Walter , Taylor Robert , Shindell Steve , Melzack Ronald
Published: January 2007

Complex visual hallucinations are known to occur in individuals with impaired vision yet whose emotional and intellectual functions are within the normal range. These hallucinations, which were first reported by Charles Bonnet in 1760, have been described in many case studies, but have not been analyzed empirically to determine their major properties. In the present study, sixty complex hallucinators labeled as Charles Bonnet hallucinators were administered a questionnaire to determine the properties of their hallucinations. Combined use of multiple-correspondence analysis and hierarchical cluster analysis reveals a set of features that characterize the ‘typical’ Charles Bonnet hallucinatory experience: the hallucinators' experience occurs while they are alert and with the eyelids open; a sharply focused image appears suddenly, without any apparent trigger or voluntary control; the hallucination is present for seconds, does not move during this time, then suddenly vanishes. These features are discussed in terms of a ‘dimension’ of hallucinatory/perceptual experience, which ranges from discrete perceptual experiences to multiple, changing experiences. Possible mechanisms that underlie the Charles Bonnet hallucinations are discussed.
Haptic Unilateral and Bilateral Discrimination of Curved Surfaces
Authors: Kappers Astrid M L , Koenderink Jan J
Published: January 2007

Active haptic discrimination of cylindrically curved hand-sized surfaces was investigated. Unilateral discrimination (that is, with one hand, either the left or the right one) was compared with bilateral discrimination. In this latter condition, the right hand had to touch the right surface, and the left hand the left one. The importance of which surface of the pair is placed to the right of the observer and which to the left (the so-called placement order) was also investigated.

In comparison with existing studies, performance in the present experiments was better owing to the combined effects of a larger surface area and active instead of passive discrimination. The results show clearly that curvature discrimination does not follow a Weber law; performance is relatively better with the larger curvatures. For all subjects, unilateral discrimination was much better than bilateral discrimination. A partial cause of this difference is the influence of the placement order, which is very apparent in the results for the bilateral condition. These results cannot be fully explained but the findings suggest an influence of the object–observer relation on the perception of the object.
Spatial Interactions in Perceived Speed
Authors: Norman Hideko F , Norman J Farley , Todd James T , Lindsey Delwin T
Published: January 2007

Previous research has shown that the perception of motion within a local region is influenced by other motions within neighboring areas (eg induced motion). Here, a study is reported of the perceived speed of dots moving within a circular target region, which was surrounded by other motions within a larger surrounding area. The perceived speed of the central dots was found to be fastest when the surround was stationary; it became slower as the speed of motion in the surround was increased. This decrease in the perceived target speed with increases in surround velocity occurred regardless of whether the direction in which the surround moved was the same as or opposite to the motion of the target region. This result cannot be explained by using simple models of perceived speed that depend only upon such factors as the magnitude of relative motion between center and surround. The spatial area over which these motion interactions occur was also investigated.
The Role of Retinal versus Perceived Size in the Effects of Pitched Displays on Visually Perceived Eye Level
Authors: Post Robert B , Welch Robert B
Published: January 2007

Visually perceived eye level (VPEL) was measured while subjects viewed two vertical lines which were either upright or pitched about the horizontal axis. In separate conditions, the display consisted of a relatively large pair of lines viewed at a distance of 1 m, or a display scaled to one third the dimensions and viewed at a distance of either 1 m or 33.3 cm. The small display viewed at 33.3 cm produced a retinal image the same size as that of the large display at 1 m. Pitch of all three displays top-toward and top-away from the observer caused upward and downward VPEL shifts, respectively. These effects were highly similar for the large display and the small display viewed at 33.3 cm (ie equal retinal size), but were significantly smaller for the small display viewed at 1 m. In a second experiment, perceived size of the three displays was measured and found to be highly accurate. The results of the two experiments indicate that the effect of optical pitch on VPEL depends on the retinal image size of stimuli rather than on perceived size.
Disambiguating Complex Visual Information: Towards Communication of Personal Views of a Scene
Authors: Pomplun Marc , Ritter Helge , Velichkovsky Boris
Published: January 2007

Two experiments on the perception and eye-movement scanning of a set of six overtly ambiguous pictures are reported. In the first experiment it was shown that specific perceptual interpretations of an ambiguous picture usually correlate with parameters of the gaze-position distributions. In the second experiment these distributions were used for an image processing of initial pictures in such a way that in regions which attracted less fixations the brightness of all elements was lowered. The preprocessed pictures were then shown to a group of 150 naïve subjects for an identification. The results of this experiment demonstrated that in four out of six pictures it was possible to influence perception of other persons in the predicted way, ie to shift spontaneous reports of naïve subjects in the direction of interpretations that accompanied gaze-position data used for the preprocessing of initial pictures. Possible reasons for a failure of such a communication of personal views in two cases are also discussed.
A Comparison between Methods for Assessing the Resolution of Moving Targets (Dynamic Visual Acuity)
Authors: Long Gerald M , Johnson Dawn M
Published: January 2007

A comparison was made between two measures of visual functioning in a dynamic context that required the resolution of moving targets. Performance obtained on a traditional task of dynamic visual acuity, which involves the determination of the smallest target that can be resolved at a given target velocity, was compared with that obtained with an alternative task that essentially reverses the independent and dependent variables. Generally similar patterns of results were obtained across the two procedures, but the alternative procedure appears to offer several advantages such as greater ease of administration, improved precision of measurement, and more-direct assessment of underlying channel activity. The recommended use of the new procedure in future work involving dynamic acuity as well as particular variables that should be carefully controlled in such work (eg target duration and target size) are discussed.
Occlusion Constraints and Stereoscopic Slant
Authors: Häkkinen Jukka , Nyman Göte
Published: January 2007

In binocular vision horizontal magnification of one retinal image leads to a percept of three-dimensional slant around a vertical axis. It is demonstrated that the perception of slant is diminished when an occlusion interpretation is possible. A frontoparallel plane located in the immediate vicinity of a slanted surface in a location which allows a perception of occlusion reduces the magnitude of perceived slant significantly. When the same plane is placed on the other side, the slant perception is normal because there is no alternative occlusion interpretation. The results indicate that a common border between the occluder and a slanted surface is not a necessary condition for the reduction effect. If the edges are displaced and the edge of the slanted surface is placed in a location in which it could be occluded, the effect still appears.
Colour and Luminance Interact to Improve Pattern Recognition
Authors: Syrkin Gil , Gur Moshe
Published: January 2007

The authors have previously hypothesised that colour vision has evolved not only to encode colour per se but also, perhaps principally, to enhance luminance-based visual processing, so that for colour information to be fully effective, luminance as well as chromatic variations should be present in visual targets. Results of previous experiments, testing detection of spatial gratings and detection and perceived brightness of Mach bands support the hypothesis. Further experiments are reported in which the hypothesis was tested by using a higher-level task of pattern recognition. Subjects had to discriminate between luminance (isochromatic), isoluminant (chromatic), or combined colour/luminance ellipses and circles. It was found that the ability to discriminate between a circle and an ellipse was greatly enhanced when both colour and luminance variations were present as compared with the pure luminance or colour presentations. Summation-square analysis shows linear colour-luminance summation which can be modeled by a single-analyser model.
Can Illusory Motion Disrupt Tracking Real Motion?
Authors: Andrews Timothy J , McCoy Allison N
Published: January 2007

When rotating stripes or other periodic stimuli cross the retina at a critical rate, a reversal in the direction of motion of the stimuli is often seen. This illusion of motion perception was used to explore the roles of retinal and perceived motion in the generation of optokinetic nystagmus. Here we show that optokinetic nystagmus is disrupted during the perception of this illusion. Thus, when perceived and actual motion are in conflict, subjects fail to track the veridical movement. This observation suggests that the perception of motion can directly influence optokinetic nystagmus, even in the presence of a moving retinal image. A conflict in the neural representation of motion in different brain areas may explain these findings.
Coherence and Motion Transparency in Rigid and Nonrigid Plaids
Authors: Wright Michael J , Gurney Kevin N
Published: January 2007

Under a wide range of conditions, stimuli composed of two superimposed grating components with unequal rotation velocities (differing in sign and/or magnitude) gave a striking percept of a single, coherent, nonrigidly deforming plaid surface. Conversely, component angular velocities of the same sign and magnitude yielded rigidly rotating plaids. Rigidity and motion coherence were shown to be independent percepts, and coherent plaids were categorised unambiguously as rigid or nonrigid. Coherence and motion transparency were found to depend upon the relative orientation of components, and polar plots showed two lobes of high coherence for narrow intercomponent angles. There was a slight tendency for plaids with unequal component rotations to appear less coherent, but this was nonsignificant, once the effect of intercomponent angle was taken into account. Changes in the relative spatial frequency of components, relative contrast of components, and repeated presentation produced equivalent effects on coherence for rigid and nonrigid types of plaid motion. Manipulation of the terminators in the display by making the aperture diameters for the two component gratings unequal reduced coherence and increased transparency. The effect was the same for rigid and nonrigid plaids. Coherence in rigid and nonrigid plaids thus depends primarily on local processes and there is no strong interaction between rigidity and coherence.
The Motion Analogue of the Café Wall Illusion
Authors: Takeuchi Tatsuto
Published: January 2007

Detecting visual motion is computationally equivalent to detecting spatiotemporally oriented contours. The question addressed in this study is whether the illusory oriented contour in the space–space domain induces corresponding illusory motion perception. Two experiments were conducted. In experiment 1, the Café Wall pattern, which elicits a strong illusion of orientation (Café Wall illusion), was found to induce an illusion of motion when this pattern was converted to the space – time domain. The strength of the motion illusion depends on the mortar luminance and width, as for the Café Wall illusion. In experiment 2, the adaptation to this illusion of motion was found to induce a motion aftereffect in a static test, which indicates that a first-order-motion system contributes to the induction of the motion illusion. In fact, the motion-energy model was able to predict the strength of this motion aftereffect.
Three-Dimensional Caricatures of Human Heads: Distinctiveness and the Perception of Facial Age
Authors: O'Toole Alice J , Vetter Thomas , Volz Harald , Salter Elizabeth M
Published: January 2007

A standard facial-caricaturing algorithm was applied to a three-dimensional representation of human heads. This algorithm sometimes produced heads that appeared ‘caricatured’. More commonly, however, exaggerating the distinctive three-dimensional information in a face seemed to produce an increase in the apparent age of the face—both at a local level, by exaggerating small facial creases into wrinkles, and at a more global level via changes that seemed to make the underlying structure of the skull more evident. Concomitantly, de-emphasis of the distinctive three-dimensional information in a face made it appear relatively younger than the veridical and caricatured faces. More formally, face-age judgments made by human observers were ordered according to the level of caricature, with anticaricatures judged younger than veridical faces, and veridical faces judged younger than caricatured faces. These results are discussed in terms of the importance of the nature of the features made more distinct by a caricaturing algorithm and the nature of human representation(s) of faces.
Apparent Relative Motion from a Checkerboard Surround
Authors: Khang Byung-Geun , Essock Edward A
Published: January 2007

To better understand the Ouchi illusion in which a stationary picture generates illusory relative motion, the spatial properties of the constituent elements of the rectangular checkerboard background were examined. Results of experiment 1 revealed that the largest illusion was obtained with elements of approximately 20–30 min in width and 4–6 min in height, an orientation of the constituents that was orthogonal to that of the test grating, and a phase shift of the alternate stripes that was close to 180°. In experiment 2 it was found that the illusion increased in magnitude with increasing achromatic contrast but was minimal with a pattern of high chromatic contrast near isoluminance. In experiment 3, two test patches were presented simultaneously in the checkerboard background and were varied independently in their orientation to explore whether or not their motions were perceived as coherent (common fate). Patches having identical orientations, and nearly orthogonal to the surround, were synchronized more strongly than those having reflected orientations. Hysteresis related to the gain control of spatially overlapping visual units differing in their polarity (ON/OFF) was discussed as a possible cause of this phenomenon.
Motion-Blur Illusions
Authors: Gosselin Frédéric , Lamontagne Claude
Published: January 2007

The still-radii illusion, the figure-of-eight illusion, the band-of-heightened-intensity illusion and the dark-blurred-concentric-circles illusion have remained, until now, isolated relatively ill-explained phenomena. A single algorithmic model is proposed which explains these four visual illusions. In fact, this model predicts phenomena produced by motion of any gray-shaded patterns relative to the eyes (termed ‘motion-blur illusions’). Results of a computer simulation of the model are presented. A novel instance of the proposed class of illusions, which can be readily experienced by the reader, is introduced to illustrate the generality of the model.
Fractal Timing of Verbal Transforms
Authors: Tuller Betty , Ding Mingzhou , Kelso J A Scott
Published: January 2007

The paper deals with the timing pattern of perceptual change elicited by multiple repetitions of a syllable (the verbal-transformation effect). We show that the distribution of the dwell time, the time spent perceiving a given phonemic form before switching to another form, obeys a power law with an exponent valued between 1 and 2. This result is robust, occurring for meaningless syllables and for English words of different initial phonemic salience. Experiment 2 demonstrates that subjects are aware of the temporal dynamics of perceptual change. On the basis of these results, it is argued that within this paradigm the notion of a mean dwell time is ill defined and there is apparently no characteristic time scale for perceptual change.
Depth Perception during Diplopia is Direct
Authors: Ziegler Lynn R , Hess Robert F
Published: January 2007

Although depth is experienced with targets at large disparities when they are seen as double or diplopic, whether that depth is as direct as with fused targets has been a matter of considerable uncertainty. Researchers have often claimed that judgments of the depth of diplopic targets during simple near/far tasks rely upon indirect associations with eye-muscle proprioception or a copy of the vergence drive signal. We designed a four-alternative task that could not be performed without a direct appreciation of depth. Observers judged the depths of each of two Gabor stereo pairs presented simultaneously. Disparities were always above each observer's measured diplopia threshold. The signs of the disparities were varied independently and observers reported the perceived depth near and far for each target. Our results demonstrate conclusively that depth during diplopia requires neither proprioception nor an efferent copy but is direct.
Predicting the ‘Where’ and Resolving the ‘What’ of a Moving Target: A Dichotomy of Abilities
Authors: Long Gerald M , Vogel Cheri A
Published: January 2007

Anticipation timing (AT) and dynamic visual acuity (DVA) were assessed in a group of college students ( n = 60) under a range of velocity and duration conditions. Subjects participated in two identical sessions 1 week apart. Consistently with previous work, DVA performance worsened as velocity increased and as target duration decreased; and there was a significant improvement from the first to the second session. In contrast, AT performance improved as velocity increased, whereas no improvement from the first to the second session was indicated; but increasing duration again benefited performance. Correlational analyses comparing DVA and AT did not reveal any systematic relationship between the two visual tasks. A follow-up study with different instructions on the AT task revealed the same pattern of AT performance, suggesting the generalizability of the obtained stimulus relationships for the AT task. The importance of the often-overlooked role of stimulus variables on the AT task is discussed.
A Jittered Squares Illusion and a Proposed Mechanism
Authors: Sowden Paul T , Watt Simon J
Published: January 2007

A new visual illusion is reported in which randomly positioned squares that are perfectly aligned with the horizontal and vertical appear slightly rotated about their midpoints (‘jittered’) relative to each other. Possible mechanisms for the illusion have been explored in a series of three experiments. Experiment 1 showed that, unlike the Münsterberg illusion, the Jittered Squares illusion persists at isoluminance. Experiment 2 indicated that the degree of rotation from vertical and horizontal, of rows and columns of squares in which the edges of individual squares remain perfectly aligned with vertical and horizontal, changes the perceived strength of the illusion such that the strongest effect is found at rotations of ±10° to ±15°. Experiment 3 revealed that the illusion is dependent upon the spatial extent of the gaps between the squares, such that it becomes weaker as the separation increases. On the basis of the findings it is suggested that the jittering results from the extraction of obliquely oriented contours by an integrator mechanism when the difference in orientation, between the edges of the individual squares and the global orientation of a contour made up of a number of edges of individual squares, is not too dissimilar. It is proposed that a mechanism such as simultaneous orientation contrast between these global contours and the vertical and horizontal edges of the individual squares causes the squares to appear rotated away from the orientation of the extracted contours, leading to the perceived jittering.
Auditory Apparent Motion between Sine Waves Differing in Frequency
Authors: Strybel Thomas Z , Menges Michele L
Published: January 2007

The effects of frequency differences between the lead and lag stimuli on auditory apparent motion (AAM—the perception of continuous changes in the location of a sound image over time) were examined in two experiments. In experiment 1, three standard frequencies (500, 1000, and 5000 Hz) and three SOAs (40, 60, and 100 ms) were tested. Both standard frequency and stimulus onset asynchrony (SOA) were constant throughout a session. Eleven comparison frequencies were tested within each session, with the range dependent on the standard frequency. At standard frequencies of 500 and 1000 Hz, AAM was heard when the frequencies of the lead and lag stimuli were within 100 Hz of each other. At 5000 Hz, the range of frequencies producing AAM increased with SOA. In experiment 2, two standards (500 and 5000 Hz) were tested with a wider range of SOAs (10–210 ms) varied within a session, and a narrower range of comparison frequencies. Here, comparison frequency was constant throughout a session. At 500 Hz, the SOAs producing AAM did not depend on comparison frequency. At 5000 Hz, the SOAs producing AAM increased with comparison frequency, consistent with Korte's third law of visual apparent motion.
Measurement of the Texture-Coherence Limit for Bandpass Arrays
Authors: Wilkinson Frances , Wilson Hugh R
Published: January 2007

Casual observation suggests that when the elements of a visual array are packed at a sufficiently high density they cohere to generate the percept of a texture. This ‘texture-coherence limit’ has been quantified by using arrays composed of Gabor functions, sixth Gaussian derivatives, or differences of Gaussians. In all cases the texture-coherence limit was a power-law function of the size of the elements as quantified by their space constants with an exponent averaging 0.7. Furthermore, the texture-coherence limit was independent of both element spatial frequency and contrast over a considerable range. A quantitative fit to the data is provided by a model in which the texture-coherence limit is determined by activation of complex cells, which pool a spatial range of subunit inputs, throughout the stimulus region. Possible extensions to two dimensions are considered.
The Analysis of Orientation-Dependent Time Costs in Visual Recognition
Authors: Leek E Charles
Published: January 2007

How does the visual system recognise stimuli presented at different orientations? According to the multiple-views hypothesis, misoriented objects are matched to one of several orientation-specific representations of the same objects stored in long-term memory. Much of the evidence for this hypothesis comes from the observation of group mean orientation effects in recognition memory tasks showing that the time taken to identify objects increases as a function of the angular distance between the orientation of the stimulus and its nearest familiar orientation. The aim in this paper is to examine the validity of this interpretation of group mean orientation effects. In particular, it is argued that analyses based on group performance averages that appear consistent with the multiple-views hypothesis may, under certain circumstances, obscure a different theoretically relevant underlying pattern of results. This problem is examined by using hypothetical data and through the detailed analysis of the results from an experiment based on a recognition memory task used in several previous studies. Although a pattern of results that is consistent with the multiple-views hypothesis was observed in both the group mean performance and the underlying data, it is argued that the potential limitations of analyses based solely on group performance averages must be considered in future studies that use orientation effects to make inferences about the kinds of shape representations that mediate visual recognition.
Effects of Pattern Orientation and Number of Symmetry Axes on the Detection of Mirror Symmetry in Dot and Solid Patterns
Authors: Wenderoth Peter , Welsh Sebastian
Published: January 2007

It has been postulated that as the number of axes of symmetry in a pattern increases, so pattern ‘goodness’ increases. Recently, a distinction was made between two different theoretical accounts of regularity or ‘goodness’ in relation to patterns with mirror symmetry: the ‘transformational’ and the ‘holographic’ models. It was argued that the former predicts a ‘goodness’ ordering of four > three > two > one whereas the latter predicts four > two > three > one, where ‘>’ means greater regularity or goodness. In three experiments, we have tested these predictions. In experiment 1, we measured percentage correct and reaction time to dot patterns which had one, two, three, or four axes of symmetry and were flashed for 150 ms. Experiment 2 was identical except that patterns were presented for 2000 ms. In experiment 3, dot patterns were replaced by solid shapes which also had one, two, three, or four axes of symmetry. Although it was found that stimuli with four axes clearly allowed superior performance to that of stimuli with one axis, results obtained with stimuli with two and three axes were almost identical and in between those obtained with one and four axes. The data thus support the suggestion that extra axes add ‘goodness’ to symmetrical patterns but not in a monotonic fashion.
Haptic Perception of Texture Gradients
Authors: Holmes Emily , Hughes Barry , Jansson Gunnar
Published: January 2007

To pick up 3-D aspects of pictures is arguably the most difficult problem concerning tactile pictorial perception by the blind. The aim of the experiments reported was to examine the potential utility of texture gradients in this context. Since there is no theoretical basis for predicting absolute values of 3-D properties from 2-D patterns read by the finger pads, the abilities of participants to perceive gradients lying between known maxima and minima were assessed. Experiment 1 involved blindfolded sighted participants making verbal magnitude estimations of texture-gradient magnitudes corresponding to plane surfaces at different slants. In experiment 2 the participants' task was to orient a surface at a slant corresponding to the texture gradients depicted tactually, and experiment 3 required early-blind participants to attempt the same task. The results revealed that participants can scale the magnitudes of texture gradients with high precision and that they can also accurately produce surface slants from depictions, providing the extreme conditions are clearly defined and there are opportunities for learning. Texture gradients appear as informative to the blind as they do to the sighted. To what extent these data can be generalised to other gradients and textures or to other projections of 3-D scenes remains to be investigated.