bluuebunny/crossref_metadata_2025 huggingface dataset:
Projective Invariance and Picture Perception
Authors: Niall Keith K , Macnamara John
Published: January 2007

Four experiments test the assumption that, in the visual perception of pictures, observers have reliable and direct access to the equivalence of shapes in projective geometry. The assumption is that perception of projective equivalence is the basis of shape constancy (‘the projective thesis’).

Observers matched or reproduced abstract planar shapes under conditions of rotation in the picture plane, and pictured rotation in depth. Departure from projective equivalence was assessed in each study by measuring the planar analogue of cross ratio. Projective equivalence was not found to be perceived uniformly where Euclidean equivalence was not judged uniformly, either in recognition tasks or in production tasks. When the projective thesis is put to a suitably general test, confidence in the thesis is undermined.
Anomalous Contours and Illusion of Angularity: Phenomenal and Theoretical Comparisons
Authors: Pinna Baingio
Published: January 2007

Many experimental comparisons between real and anomalous contours have proven the functional equivalence of the two conditions; however, there are some contradictory findings. One of these is obtained by analyzing the anomalous contours in the light of a new illusion, called the ‘illusion of angularity’. A circle becomes a polygon when it covers the centre of a radial arrangement of black stripes, and a polygon changes its perceptual shape depending on its orientation with respect to the same radial arrangement. Phenomenally, it appears like a very pointed polygon, in which every side is concave or, alternatively, a shape that looks like a circle with angles added in the spaces between the radial stripes, or a polygonal shape in which every side is convex.

The reciprocal anomalous counterparts of these conditions, obtained by removing the geometrical/polygonal contours, reveal different results. In the first case, one sees a perfect circle; in the second case, a polygon with blunted vertices, or a circular shape with angular protrusions; in the third case, a deformed circle.

These results are inconsistent with some theoretical models proposed to explain the emergence of anomalous contours, namely, all the top-down models expressed in terms of cognitive constructions and perceptual hypotheses, or in terms of global figural organizations. Rather, these comparisons suggest a different interpretation for the two phenomena (the illusion of angularity and anomalous contours). This interpretation is based on dynamic interactions or on network computations that synthesize both real and anomalous contours.
Combining Binocular and Monocular Curvature Features
Authors: Stevens Kent A , Lees Marek , Brookes Allen
Published: January 2007

A study is reported of the perception of visual surfaces in wire-frame stimuli generated by combinations of monocular surface contours and binocular disparity that provide differing information about 3-D relief. Observers vary considerably in the relative contribution made by the binocular and monocular cues to the perception of overall 3-D form. Without training, many observers may entirely fail to perceive surface curvature from the binocular disparity patterns, interpreting the form of the surface only according to the monocular information. For other observers, both cues contribute to the end percept, with the monocular interpretation dominating where the disparity information indicates planarity and with disparity dominating where disparity information suggests curvature and the monocular interpretation suggests planarity. Where stereo and monocular interpretations indicate inconsistent surface curvature features at a common location, more complex resolution strategies are suggested.
The Influence of Dimensionality on Eye Fixations
Authors: Abed Farough
Published: January 2007

Eye fixation patterns were explored for sixty adult subjects, each of whom viewed one of three stimuli, either in a three-dimensional model format or in a two-dimensional photographic format. The stimuli consisted of one symmetrical and two asymmetrical color representational drawings displayed in the form of a photograph or of a model. Total fixation times (in ms) were computed for seven portions of each stimulus: top, bottom, left, right, foreground, middle ground, and background. Results indicated that for all stimuli, subjects viewing the 3-D model spent significantly more time fixating the foreground and significantly less time fixating the background than subjects viewing the 2-D photograph. For the two asymmetrical stimuli subjects in the two groups differed significantly in their fixation patterns for the left/right variables. It was concluded that eye fixation patterns vary as a function of dimensionality.
Perceptual Fade-Out Occurs in the Binocularly Viewed Ganzfeld
Authors: Gur Moshe
Published: January 2007

The conviction that time-varying signals are essential for normal visual perception was recently challenged by Bolanowski and Doty who observed that no ‘blankouts’ occurred in the binocularly viewed Ganzfeld. They suggested that monocularly perceived fading is caused by the eye in darkness suppressing the non-Ganzfeld-viewing eye. In the present paper, fade-out perception under monocular and binocular Ganzfeld viewing is compared, and the effect of the free eye on the Ganzfeld-viewing eye is tested directly. Results show that fading takes place under both monocular and binocular viewing. The data reenforce the view that transient inputs are necessary for maintaining visual perception. It is also shown that there are two Ganzfeld-related phenomena—fade-out and blackout. Fade-out, a slow gradual loss of brightness and of saturation perception, is observed by all subjects under both monocular and binocular viewing, and is affected by the light intensity and wavelength. It is probably retinal in origin. Blackout, a brief intermittent loss of all visual sensation, is experienced by some subjects in the monocular Ganzfeld only and is not appreciably affected by the light intensity or wavelength. It may be caused by a central blocking of all input to the perceiving stage.
Numerosity Estimation as a Function of Stimulus Organization
Authors: Ginsburg Norman
Published: January 2007

It was proposed that stimulus organization of a set of homogeneous items can best be measured by using the mean distance to nearest neighbours. Patterns of dots were generated that fell on four different positions along the cluster continuum, from highly regular, through random, to clustered. When thirty subjects were asked to judge numerosity, their estimates decreased signicantly as cluster measures increased. Four possible interpretations of the effect of organization on numerosity perception are discussed.
The Charles Bonnet Syndrome: ‘Phantom Visual Images’
Authors: Schultz Geoffrey , Melzack Ronald
Published: January 2007

The Charles Bonnet syndrome is a condition in which individuals experience complex visual hallucinations without demonstrable psychopathology or disturbance of normal consciousness. An analysis of the sixty-four cases described in the literature reveals that the syndrome can occur at any age though it is more common in elderly people. Reduction in vision, due to peripheral eye pathology as well as pathology within the brain, is associated with the syndrome. Individual hallucinatory episodes can last from a few seconds to most of the day. Episodes can occur for periods of time ranging from days to years, with the hallucinations changing both in frequency and in complexity during this time. The hallucinations may be triggered or stopped by a number of factors which may exert their effect through a general arousal mechanism. People, animals, buildings, and scenery are reported most often. These images may appear static, moving in the visual field, or animated. Emotional reaction to the hallucinations may be positive or negative. Several theories have been proposed to account for the hallucinations. This paper highlights the sensory deprivation framework, with particular emphasis on the activity in the visual system after sensory loss that produces patterns of nerve impulses that, in turn, give rise to visual experience.
Temporal Integration of Spatially Filtered Visual Images
Authors: Parker Denis M , Lishman J Rowland , Hughes James
Published: January 2007

Factors which govern the temporal integration of spatial information were examined in a group of five experiments. A series of high-pass and low-pass spatially filtered versions of a visual scene were generated. Observers' ratings of these filtered versions of the scene for perceived image quality indicated that quality was determined both by the bandwidth of spatial information and the presence of high-spatial-frequency edge information. When sequences of three different versions of the scene were presented over an interval of 120 ms the perceived quality of the resulting composite image was determined both from the ratings of the individual components of that sequence and from the order in which these components were presented. When the order of spatial information in a sequence moved from coarse to fine detail the perceived quality of the composite image was significantly better than when the order moved from fine to coarse. This evidence of a coarse-to-fine bias in pattern integration was further investigated with a detection paradigm. The pattern of errors once again indicated that temporal integration of spatial information was superior when a coarse-to-fine mode of information delivery was employed. Taken together the data indicate that the pattern-integration mechanism has an inherent order bias and does not accumulate spatial information so efficiently when the ‘natural’ coarse-to-fine order is violated.
Cooperative Representation of Visual Borders
Authors: Stuart Geoffrey W , Bossomaier Terence R J
Published: January 2007

Recently it has been reported that the visual cortical cells which are engaged in cooperative coding of global stimulus features, display synchrony in their firing rates when both are stimulated. Alternative models identify global stimulus features with the coarse spatial scales of the image. Versions of the Munsterberg or Café Wall illusions which differ in their low spatial frequency content were used to show that in all cases it was the high spatial frequencies in the image which determined the strength and direction of these illusions. Since cells responsive to high spatial frequencies have small receptive fields, cooperative coding must be involved in the representation of long borders in the image.
The Müller-Lyer Illusion Mark II
Authors: Degoldi Brett R , Day Ross H
Published: January 2007

A new illusion of size is described. A passage of print occupying about half a standard A4 sheet appeared larger than the same passage when the sheet was cropped immediately above and below it. This illusion is demonstrated and explained in terms of perceptual compromise between the vertical extent of the printed passage and the sheet of which it is an intrinsic feature. In this sense it is held to be essentially the same as the Müller-Lyer illusion of extent in which the spaces between the apexes are intrinsic to the figure.
Spectral Content as a Cue to Perceived Auditory Distance
Authors: Little Alex D , Mershon Donald H , Cox Patrick H
Published: January 2007

Changes in the spectral content of wide-band auditory stimuli have been repeatedly implicated as a possible cue to the distance of a sound source. Few of the previous studies of this factor, however, have considered whether the cue provided by spectral content serves as an absolute or a relative cue. That is, can differences in spectral content indicate systematic differences in distance even on their first presentation to a listener, or must the listener be able to compare sounds with one another in order to perceive some change in their distances? An attempt to answer this question and simultaneously to evaluate the possibly confounding influence of changes in the sound level and/or the loudness of the stimuli are described in this paper. The results indicate that a decrease in high-frequency content (as might physically be produced by passage through a greater amount of air) can lead to increases in perceived auditory distance, but only when compared with similar sounds having a somewhat different high-frequency content, ie spectral information can serve as a relative cue for auditory distance, independent of changes in overall sound level.
An Exploratory Study of Syncretic Experience: Eidetics, Synaesthesia and Absorption
Authors: Glicksohn Joseph , Salinger Orna , Roychman Anat
Published: January 2007

Synaesthesia and eidetic imagery are both syncretic experiences entailing a dedifferentiation of perceptual qualities. In this paper the correlation between synaesthesia and eidetic imagery is explored. Ten subjects selected for possible eidetic and/or synaesthetic ability were tested in a battery of tasks that tap structural and typographic eidetic imagery, and colour—hearing and colour—mood synaesthesia. It was found that both structural and typographic eidetic imagery were correlated with measures of synaesthesia, indicating a relationship between the two phenomena.
Haptic Dominance in Form Perception: Vision versus Proprioception
Authors: Heller Morton A
Published: January 2007

An experiment placed vision and touch in conflict by the use of a mirror placed perpendicular to a letter display. The mirror induced a discrepancy in direction and form. Subjects touched the embossed tangible letters p, q, b, d, W, and M, while looking at them in a mirror, and were asked to identify the letters. The upright mirror produced a vertical inversion of the letters, and visual inversion of the direction of finger movement. Thus, subjects touched the letter p, but saw themselves touching the letter b in the mirror. There were large individual differences in reliance on the senses. The majority of the subjects depended on touch, and only one showed visual dominance. Others showed a compromise between the senses. The results were consistent with an attentional explanation of intersensory dominance.
The Perception of Movement and Depth in Moiré Patterns
Authors: Spillmann Lothar
Published: January 2007

Moiré patterns can produce striking movement effects and in more complex stimuli can induce vivid stereoscopic depth. The physical rules underlying these phenomena are reviewed and their relationship to psychophysics is discussed.

First, it is shown how moirés in ‘optical line interference’ patterns are created by superimposing periodic visual stimuli, eg gratings, and shifting them relative to each other. When two gratings are presented in this manner, small differences in spatial frequency, orientation, and speed are magnified. This magnification has prompted the use of moiré patterns both in industry and in art where their enhanced sensitivity to misalignment and spatial distortion has been widely exploited.

Next, it is demonstrated how enhanced depth in ‘stereoscopic interference’ patterns is produced by presenting grating stimuli in two (or more) depth planes. The perceived depth effect in the resulting moiré pattern can be elicited similarly by binocular disparity and motion parallax.

Finally, it is described how perceived movements occurring in different directions and at different depths are the basis for the perceptual ‘irritations’ that fascinate observers in complex moiré patterns. The use of moirés for the noninvasive examination of the human retina by aliasing is discussed.
Selective Attention and Temporal-Order Judgment
Authors: Jaśkowski Piotr
Published: January 2007

A procedure originally introduced by Sternberg and coworkers was used to examine the effect of selective attention on temporal-order judgment. Two-response and three-response paradigms were employed. As in Sternberg et al's work, a shift of psychometric functions for the two-response paradigm was found that suggested shorter latency for the stimulus to which attention was directed. However, no shift was noted for the three-response paradigm. This discrepancy can be explained by the assumption that the shift obtained for the two-response paradigm results from an artifact caused by a specific task. The artifact occurs because the instruction to attend to a particular stimulus induces a response bias when the subject is forced to guess in situations where he/she cannot recognize the temporal order of stimuli. The artifact disappears with the three-response paradigm where the subject has the additional option to respond “simultaneous”.
Limits on the Comprehension of Rotational Motion: Mental Imagery of Rotations with Oblique Components
Authors: Pani John R
Published: January 2007

Mental imagery of rotational motion across variation in the orientation of a square to an axis of rotation, the orientation of the axis to the environment/viewer, and the starting orientation of the rotation were investigated in three experiments. The experimental method included specifying the particular rotations that subjects should consider and obtaining exact predictions of the outcomes of the rotations. When the square was normal to the axis and the axis was normal to the environment/viewer, performance was excellent. When either of these relationships was oblique, performance was quite good. When both of these relationships were oblique, nearly every subject made large errors on every problem. The difficulty of the double-oblique rotations was reduced when the initial orientation of the square was not canonical. Current views of the comprehension of rotational motion are discussed. It appears that the comprehension of rotational motion can be understood as an organization of the symmetric space traced out by the motion. People succeed in organizing this space when it is aligned with a principal spatial reference system.
Mirror Image Reversal: Is what we See what we Present?
Authors: Morris Reg C
Published: January 2007

Many psychological explanations have been advanced to explain left—right reversal in mirror images, but Gregory and Haig have each proposed a physical explanation for the reversal: the first is based upon the physical rotation used to present the surface of the object to the mirror, and the second on the classical optics of reflection. These physical explanations are considered together with an explanation based on object symmetry. The apparent reversal of directional coordinates (eg left and right) that occurs in the mirror images of most objects is distinguished from reversals achieved by physical or mental rotation. It is also distinguished from the object—image match that can be achieved by mental or physical rotation of some symmetrical objects. It is concluded that the left—right reversal is not specifically optical, but is determined by multiple factors, including object symmetry, the conventional and gravitational positioning of top and bottom and back and front, and our greater familiarity with right—left than with top—bottom or back—front reversals.
Temporal-Order Judgment and Reaction Time to Stimuli of Different Rise Times
Authors: Jaśkowski Piotr
Published: January 2007

Point of subjective simultaneity and simple reaction time were compared for stimuli with different rise times. It was found that these measures behave differently. To explain the result it is suggested that in the case of temporal-order judgment the subject takes into account not only the stimulus onset but also other events connected with stimulus presentation.
Occlusion and the Distortion of Alignment in Three-Dimensional Space
Authors: Daniels Victoria , Gordon Ian E
Published: January 2007

When observers are asked to align two rectangular stimuli oriented at 45° to the visual axis there is a slight tendency to set the more distant stimulus closer to the eye than its true coplanar position. However, when a large rectangular surface is interpolated between the two oblique stimuli and the observer, errors of alignment become relatively much larger. The displacement caused by the interpolated stimulus occurs both when the display is viewed monocularly and when it is viewed binocularly. Reducing the obliquity of the rectangles results in smaller judgment errors and increasing obliquity increases errors; this is true with and without occlusion. The addition of texture elements to the surfaces of the rectangles reduces judgment errors significantly, but only under conditions of occlusion. It is possible that misalignments recorded for three-dimensional displays have something in common with the two-dimensional Poggendorff illusion.
Coordination of what and where in Visual Attention
Authors: Duncan John
Published: January 2007

Performance often suffers when two visual discriminations must be made concurrently (‘divided attention’). In the modular primate visual system, different cortical areas analyse different kinds of visual information. Especially important is a distinction between an occipitoparietal ‘where?’ system, analysing spatial relations, and an occipitotemporal ‘what?’ system responsible for object recognition. Though such visual subsystems are anatomically parallel, their functional relationship when ‘what?’ and ‘where?’ discriminations are made concurrently is unknown. In the present experiments, human subjects made concurrent discriminations concerning a brief visual display. Discriminations were either similar (two ‘what?’ or two ‘where?’ discriminations) or dissimilar (one of each), and concerned the same or different objects. When discriminations concerned different objects, there was strong interference between them. This was equally severe whether discriminations were similar—and therefore dependent on the same cortical system—or dissimilar. When concurrent ‘what?’ and ‘where?’ discriminations concerned the same object, however, all interference disappeared. Such results suggest that ‘what?’ and ‘where?’ systems are coordinated in visual attention: their separate outputs can be used simultaneously without cost, but only when they concern one object.
The Relative Effectiveness of Serial and Parallel Viewing of Line Drawings Depicting Possible and Impossible Objects
Authors: Tambouratzis Tatiana , Wright Michael J
Published: January 2007

In a series of experiments, subjects were asked to make judgments concerning the three-dimensional constructibility of line drawings depicting possible and impossible objects. A spectrum of objects was employed in which complexity as well as, for impossible objects, the cause and saliency of the contradiction in three-dimensional structure varied widely. The line drawings were presented under varying viewing conditions and exposure times.

It was found that line drawings of possible objects were more often correctly identified than those of impossible ones. Parallel (simultaneous) viewing was more efficient than serial viewing (in which a line drawing moved behind a narrow stationary aperture). The orientation of the aperture did not cause differences in the subjects' performance. Line-drawing complexity and contradiction in three-dimensional structure were not found to be significant for accurate recognition. Finally, no consistent effect of exposure duration on performance could be determined in the range 60–1000 ms.
Postural Sway and Perception of the Upright Stance Stability Borders
Authors: Blaszczyk Janusz W , Hansen Paul D , Lowe Deborah L
Published: January 2007

Decline in the perception of the borders of postural stability due to increase in sway was evaluated in young and elderly subjects. Ranges of lateral and anteroposterior postural sway were measured in eleven young and eleven elderly subjects during maximum voluntary excursions of center of gravity while leaning forward, backward, left, and right. In both age groups, displacement of the center of gravity out of the reference position resulted in increases in the range of sway in the plane corresponding to the direction of lean. Young subjects who further displaced their center of gravity within the base of support also exhibited significantly elevated anteroposterior sway range while leaning forward and backward, both in eyes-closed and in eyes-open experimental conditions. The elderly subjects, however, showed greater mediolateral oscillation of center of gravity while leaning forward with their eyes open. No significant intergroup differences in the anteroposterior sway range during leans in the mediolateral plane were found. However, a greater mediolateral component of sway range at lateral borders of stability was observed in the young adults. Analysis of signal-to-noise ratios indicated a greater decline in stability control in the elderly, due to impairment of perception of postural stability borders.
Auditory Looming Perception: Influences on Anticipatory Judgments
Authors: Rosenblum Lawrence D , Wuestefeld A Paige , Saldaña Helena M
Published: January 2007

Several studies in the auditory-perception literature hint that listeners may be able to anticipate the time of arrival of an approaching sound source. Two experiments are reported in which listeners judged the time of arrival of an approaching car on the basis of various portions of its auditory signal. Subjects pressed a computer key to indicate when the car would have just passed them, assuming that the car maintained a constant approach velocity. A number of variables were tested including (a) the time between the offset of the signal and the virtual time of passage, (b) duration of the signal, and (c) feedback concerning judgment accuracy. Results indicate that increasing the time between signal offset and virtual time of passage decreases judgment accuracy whereas the actual duration of the signal had no significant effect. Feedback significantly improved performance overall.
Configurational Factors in the Perception of Unfamiliar Faces
Authors: Hole Graham J
Published: January 2007

Young et al (1987) have demonstrated that the juxtaposition of top and bottom halves of different faces produces a powerful impression of a novel face. It is difficult to isolate perceptually either half of the ‘new’ face. Inversion of the stimulus, however, makes this task easier. Upright chimeric faces appear to evoke strong and automatic configurational processing mechanisms which interfere with selective piecemeal processing. In this paper three experiments are described in which a matching paradigm was used to show that Young et al's findings apply to unfamiliar as well as to familiar faces. The results highlight the way in which minor procedural differences may alter the way in which subjects perform face-recognition tasks.
Impact of Quality of the Image, Orientation, and Similarity of the Stimuli on Visual Search for Faces
Authors: Kuehn Sally M , Jolicoeur Pierre
Published: January 2007

Evidence from a series of visual-search experiments suggests that detecting an upright face amidst face-like distractors elicits a pattern of reaction times that is consistent with serial search. In four experiments the impact of orientation, number of stimuli in the display, and similarity of stimuli on search rates was examined. All displays were homogeneous. Trials were blocked by distractor type for three experiments. In the first experiment search rates for faces amidst identical faces rotated by 180° were examined. No advantage was evidenced in searching for an upright face. The impact of the quality of the face representation was examined in the second experiment. Search rates are reported for a line-drawn and a digitized image of a face amidst identical faces rotated by 180°. Search was faster for digitized than for line-drawn faces. The findings of the first experiment for orientation were replicated. In the third and fourth experiments the impact of disrupting the facial configuration in distractors was examined and performance was contrasted for blocked and mixed trials, respectively, with the same stimulus set. Reaction times increased with the number of distractors in the display in all but the nonface condition, which produced a shallow slope suggestive of parallel search. Search amidst other distractors appeared to involve the conjoining of a specific set of features with specific spatial relations. The hierarchy of relevant configural dimensions was inconsistent across these two experiments, suggesting that the symmetry, top-down order of features, orientation of the face, and predictability of the distractor type may have an interactive effect on search strategies.
Spatial Content and Spatial Quantisation Effects in Face Recognition
Authors: Costen Nicholas P , Parker Denis M , Craw Ian
Published: January 2007

It has recently become apparent that if face images are degraded by spatial quantisation, or block averaging, there is a nonlinear acceleration of the decline in accuracy of recognition as block size increases. This suggests recognition requires a critical minimum range of object spatial frequencies. Two experiments were performed to clarify the phenomenon. In experiment 1, the speed and accuracy of recognition for six frontoparallel photographs of faces were measured. After familiarisation training sessions, the images were shown for 100 ms with 11, 21, and 42 pixels per face, horizontally measured. Transformations calculated to remove the same range of spatial frequencies were performed by means of quantisation, a Fourier low-pass filter, and Gaussian blurring. Although accuracy declined and speed increased in a significant, nonlinear manner in all cases as the image quality was reduced, it did so at a faster rate for the quantised images. In experiment 2, faces rated as being typical were shown at 9, 12, 23, and 45 pixels per face and with appropriate Fourier low-pass versions. The nonlinear decline was confirmed and it was shown that it could not be attributed to a ceiling effect. A further condition allowed quantised and Fourier low-pass conditions to be compared with an unstructured-noise condition of equal strength to that of the quantised images. These gave comparable, but slightly less impaired, recognition than the quantised images. It can be inferred from these results that the removal of a critical range of at least 8–16 cycles per face of information explains the step decline in recognition seen with quantised images. However, the decline found with quantised images is reinforced by internal masking from pixelisation.
Anomalous and Luminance Contours Produce Similar Angular Induction Effects
Authors: Greene Ernest , Verloop Marja
Published: January 2007

One can shear a pattern of lines to produce an anomalous contour which has a perceptual influence similar to that of a straight line segment. Illusion effects have been found with configurations which contain these anomalous contours, as well as cross adaptation with respect to luminance contours. We have found that sheared-line contours will bias judgment of collinearity, ie perceived alignment, of a luminance contour. The angular induction effects are similar to those reported for interactions between luminance contours, and the same equation can be used to model both kinds of data. The results of this experiment support the neuroreductionist view that anomalous and luminance contours are processed at the same level of the nervous system. Additionally, we suggest that with both types of contour the perceptual system registers and responds to the alignment of local brightness differentials.
Visual Perception of Intentional Motion
Authors: Dittrich Winand H , Lea Stephen E G
Published: January 2007

A series of experiments were performed to investigate how motion sequences provide information about the intentional structure of moving figures or actors. Observers had to detect simulations of biologically meaningful motion within a set of moving letters. In the first two experiments a factorial design was used, with type of instruction as a between-subject factor and six movement parameters (number of items, speed and directness of target and distractors, and ‘relentlessness’ of target movement) as within-subject factor; in the final two experiments, the visibility of the goal towards which the target moved and the use of a tracking movement to distinguish the target were varied. In such displays search time increases with increasing number of stimuli. It was found that (a) the more direct the motion, the more likely it was to be interpreted as intentional; (b) intentional motion was much easier to detect when the target moved faster than the distractors than when it moved more slowly; (c) recognition of intentionality was impaired but not abolished if the goal towards which the target was moving was invisible; and (d) participants did not report intentional movement when the target was distinguished by brightness rather than the manner in which it moved. We argue that the perception of intentionality is strongly related to observers' use of conceptual knowledge, which in turn is activated by particular combinations of features. This supports a process model, in which intentionality is seen as the result of a conceptual integration of objective visual features.
Prospective Control in Catching by Infants
Authors: van der Meer Audrey L H , van der Weel F R Ruud , Lee David N
Published: January 2007

Catching a moving object requires the ability to predict the future trajectory of the object. To test whether infants can use visual information predictively, reaching for a toy moving at different speeds was investigated in six infants around 11 months of age. The toy was occluded from view by a screen during the last part of its approach. Gaze arrived at the exit side of the screen and the hand started to move forward before the toy had disappeared behind the occluder; these actions were prospectively geared to certain times before the toy would reappear. In addition, hand-movement duration was found to be related to the time of reappearance of the toy—the information used to regulate duration of hand movement being picked up before the toy disappeared behind the occluder. In a longitudinal experiment, the development of predictive reaching was investigated in two infants between the ages of 20 and 48 weeks. At all ages studied, gaze anticipated the reappearance of the moving toy. However, anticipation with hand movement of the disappearance of the toy and the ability to gear actions prospectively to the time (instead of distance) the toy was away from certain points on the track developed relatively late and marked the transition to successfully catching faster-moving toys.
Local and Global Factors in Visual Occlusion
Authors: Boselie Frans
Published: January 2007

Although interest in the phenomenon of visual occlusion is of very long standing, only a small number of experimental studies have been reported, and available theories fail to give satisfactory explanations of the data. In this paper the efficacy of local factors in organising the perception of globally regular occlusion patterns is explored. Three experiments are reported in which the relative contribution of local and global factors to the salience of percepts is investigated. It is demonstrated that local factors play a very important role in the perception of these kinds of patterns.
The Hermann Grid Illusion: A Tool for Studying Human Perceptive Field Organization
Authors: Spillmann Lothar
Published: January 2007

Psychophysical research on the Hermann grid illusion is reviewed and possible neurophysiological mechanisms are discussed. The illusion is most plausibly explained by lateral inhibition within the concentric receptive fields of retinal and/or geniculate ganglion cells, with contributions by the binocular orientation-specific cortical cells. Results may be summarized as follows: (a) For a strong Hermann grid illusion to be seen bar width must be matched to the mean size of receptive-field centers at any given retinal eccentricity. (b) With the use of this rationale, the diameter of foveal perceptive-field centers (the psychophysical correlate of receptive-field centers) has been found to be in the order of 4–5 min arc and that of total fields (centers plus surrounds) 18 min arc. These small diameters explain why the illusion tends to be absent in foveal vision. (c) With increasing distance from the fovea, perceptive-field centers increase to 1.7 deg at 15 deg eccentricity and then to 3.4 deg at 60 deg eccentricity. This doubling in diameter agrees with the change in size of retinal receptive-field centers in the monkey. (d) The Hermann grid illusion is diminished with dark adaptation. This finding is consistent with the reduction of the center—surround antagonism in retinal receptive fields. (e) The illusion is also weakened when the grid is presented diagonally, which suggests a contribution by the orientation-sensitive cells in the lateral geniculate nucleus and visual cortex. (f) Strong induction effects, similar to the bright and dark spots in the Hermann grid illusion, may be elicited by grids made of various shades of grey; and by grids varying only in chroma or hue.

Not accounted for are: the illusory spots occurring in an outline grid ie with hollow squares, and the absence of an illusion when extra bars are added to the grid. Alternative explanations are discussed for the spurious lines connecting the illusory spots along the diagonals and the fuzzy dark bands traversing the rhombi in modified Hermann grids.
The Use of Pigmentation and Shading Information in Recognising the Sex and Identities of Faces
Authors: Bruce Vicki , Langton Steve
Published: January 2007

An investigation of what can be learned about representational processes in face recognition from the independent and combined effects of inverting and negating facial images is reported. In experiment 1, independent effects of inversion and negation were observed in a task of identifying famous faces. In experiments 2 through 4 the question of whether effects of negation were still obtained when effects due to the reversal of pigmentation in negative images were eliminated was examined. By the use of images of the 3-D surfaces of faces measured by laser, and displays as smooth surfaces devoid of pigmentation, only effects of inversion were obtained reliably, suggesting that the effects observed in experiment 1 arose largely through the inversion of pigmentation values in normal images of faces. The results of experiment 5 suggested that the difference was not due to the different task demands of experiments 2–4 compared with those of experiment 1. When normally pigmented face images were used in a task making similar demands to that of experiment 4, independent effects of inversion and negation were again observed. When a task of sex classification was used in experiments 6 and 7, clear effects of negation as well as inversion were observed on latencies, though not accuracies, of responding. The results are interpreted in terms of the information content of pigmentation relative to shape from shading in different face-classification tasks. The results also reinforce other recent evidence demonstrating the importance of image intensity as well as spatial layout of face ‘features’.
Three-Dimensional Illusory Objects Produced by Rotation in Depth
Authors: Kojo Ilpo , Liinasuo Marja , Rovamo Jyrki
Published: January 2007

Rotation of a Kanizsa triangle in depth around its vertical axis causes a perception of a three-dimensional object with a flat, rigid illusory triangle between the inducing discs. When the inducing discs of a Kanizsa triangle were made thicker, the illusory triangle between the discs also became thicker. In the experiments both computer animation and real inducers made of plastic were used. The method promoted border perception in a three-dimensional illusory figure. We suggest that the perception of three-dimensional illusory objects is due to a process which is also used in the perception of real three-dimensional objects.
Spatial Reference Systems in the Comprehension of Rotational Motion
Authors: Pani John R , Dupree Davido
Published: January 2007

In certain simple rotations of objects, the orientation of the axis and planes of rotation can determine whether people are able to visualize the motion or perceive it as simple and coherent. This finding affords the opportunity to investigate the spatial reference systems used to define the orientation of the axis and planes of rotation. The results of two experiments suggest that the permanent environment is the primary reference system, apart from the rotating object, used for this purpose. Subjects also were able to use a local spatial environment to determine the orientation of the motion; some subjects were particularly adept at this. The viewer perspective, in contrast, was irrelevant as a reference system in these experiments. These results argue strongly for the primacy of environmental reference systems in the perception and imagination of orientation and extend the set of findings common between the comprehension of rotational motion and orientation-sensitive form perception.
Dichoptically Viewed Colour Aftereffects Produced by Monocular Adaptation
Authors: Delorme André
Published: January 2007

Colour aftereffects were observed in dichoptically viewed achromatic striped patterns after a 25 s period of monocular adaptation to an homogeneous coloured field of red, green, or blue. Three test conditions of dichoptic viewing were used. In condition 1, black line patterns were viewed dichoptically on fused white backgrounds. Stimuli used in condition 2 were similar except that they were white line patterns on black backgrounds. Last, condition 3 was realised with the same stimulus patterns utilised in condition 1, except that the mode of dichoptic viewing produced a juxtaposition rather than a fusion of the two white backgrounds containing the line patterns. Some colour aftereffect was obtained for each colour-adaptation condition and in each test condition. It consisted in a negative colour aftereffect (NCA) in the adapted eye (the colour seen was roughly the complementary of the adaptation colour) and/or a positive colour aftereffect (PCA) in the unadapted eye (the colour seen tended rather to be similar in hue to the adaptation colour). In fact, the following four kinds of responses were obtained: (i) two colour aftereffects, one seen by each eye, ie a NCA involving the adapted eye and a PCA involving the unadapted eye; (ii) a NCA involving the adapted eye only; (iii) a PCA involving the unadapted eye only; (iv) no colour aftereffect at all. Results obtained in different test conditions permitted us to assert that both kinds of colour aftereffect could be produced with white patterns on dark backgrounds as well as with black patterns on white backgrounds and did not require binocular fusion of the white backgrounds. Hypothetical physiological explanations of these aftereffects are available.
The Perception of Luminosity on Different Backgrounds and in Different Illuminations
Authors: Bonato Frederick , Gilchrist Alan L
Published: January 2007

Observers were presented with target surfaces of varying luminance and asked to report whether they appeared luminous or opaque. In one experiment the targets were presented against three backgrounds, white, gray, and black. In another experiment the targets were presented within Mondrian patterns that were either brightly or dimly illuminated. The results indicate that, across a variety of conditions, a target begins to appear luminous when its luminance is about 1.7 times that of a surface that would appear white in the same illumination, whether or not a white surface is available in the visual field for comparison. Defined in this way the luminosity threshold exhibits the two main kinds of constancy characteristic of surface grays, constancy with respect to changes in the illumination level and constancy with respect to changes in the reflectance of the immediate background. This finding, while challenging a range of potential rules, places the problem of defining the conditions that produce luminosity squarely within the problem of lightness perception for opaque surfaces.
Motion Aftereffects with Random-Dot Chequerboard Kinematograms: Relation between Psychophysical and VEP Measures
Authors: Wist Eugene R , Gross Jörg D , Niedeggen Michael
Published: January 2007

A random-dot chequerboard kinematogram was used to investigate the effect of motion adaptation both on evoked potentials and on motion aftereffects (MAEs). The experimental paradigm used allowed simultaneous measurement of both variables. Each adaptation period was followed by a series of 5 short test stimuli to which evoked potentials were recorded. Motion aftereffects were observed in the intervals between test stimuli. An inverse relationship between mean N2–P1 amplitude and mean reported MAEs was found as a function of adaptation durations of 1.4, 5.6, and 17.5 s. When the shortest and longest adaptation durations were compared, this relationship held for thirteen of fourteen subjects tested when adaptation-motion and test-motion directions corresponded and for twelve of fourteen subjects when they were opposed. The possibility that the effect of motion adaptation on N2–P1 amplitude was due to local luminance-contrast adaptation is discussed and shown to be unlikely. The suitability of this paradigm for the combined psychophysical and electrophysiological assessment of disturbances in motion perception is discussed.
Structural Description Theories: Is RBC/JIM a General-Purpose Theory of Human Entry-Level Object Recognition?
Authors: Kurbat Matthew A
Published: January 2007

A long-standing problem in structural description theories of object recognition has been the lack of concrete proposals for parts, methods of dividing objects into parts, and relations between parts. Biederman's RBC theory and Hummel and Biederman's JIM model are seminal works because they present one of the first concrete solutions to this very difficult problem: RBC/JIM in turn played a major role in turning object recognition into a burgeoning research area.

Here, a review of RBC/JIM as the state-of-the-art structural description theory of recognition is presented. A main conclusion is that there are strong limitations on the scope of objects which RBC/JIM can represent, and hence recognize, because mechanisms for dividing objects into parts and representing parts are not general purpose. Nevertheless, RBC/JIM has promise as a model of geometric object recognition, and there are other directions that may be pursued in the interest of developing a more general-purpose theory.
Integration by Association: Combining Three-Dimensional Cues to Extrinsic Surface Shape
Authors: Stevens Kent A
Published: January 2007

Surface shape is visually derived from multiple sources of three-dimensional (3-D) information. The apparent unity of the percept creates an assumption that there are perceptual processes that resolve and combine the different channels of information within some common 3-D representation. However, integration by the explicit conversion of the information from different sources into a common representation is computationally difficult and unnecessary. An alternative, integration by association, is discussed and related to a variety of experimental results on 3-D-cue conflict.