bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative Explanations for Procedural Effects on Magnitude-Estimation Exponents for Taste, Invoking Adaptation, Context, and Volume Effects
Authors: O'Mahony Michael
Published: January 2007

Taste adaptation to residual stimuli from prior tastings was considered along with context and volume effects. These factors are proposed as alternative or supplemental explanations for the differences in the magnitude-estimation exponent (slope of the log-log plot of taste intensity versus solute concentration) that have been obtained by various workers using different stimulus presentation procedures.
Stroop Interference Based on the Synaesthetic Qualities of Auditory Pitch
Authors: Walker Peter , Smith Sylvia
Published: January 2007

The equivalence of perceptual experience across the sensory modalities, most vividly observed in synaesthetes, is rarely discussed in contemporary cognitive psychology. It is suggested, however, that the concepts and paradigms of human information processing are ideally suited to test, for example, the fundamental assumption that the synaesthetic qualities of a stimulus are rapidly and automatically encoded. In a preliminary experiment subjects were asked to rate each of four auditory tones on a series of 7-point scales defined by pairs of antonyms. The results confirmed that a pure auditory tone has a range of qualities, determined by its pitch, that are shared by stimuli in other modalities. The main experiment used a paradigm based on the Stroop interference effect. Here the 50 Hz and 5500 Hz tones served as incidental stimuli and the subjects were required to respond as quickly as possible by pressing one of two keys depending on which one of four possible words appeared in the centre of the screen. Subjects were found to respond more slowly when the qualities of the tone were incongruent with the synaesthetic qualities represented by the test word. The results confirm that synaesthetic qualities of pitch are rapidly and automatically encoded and that the products of this encoding automatically interact with the mechanisms responsible for identifying word meaning and/or with the post-identification decision processes.
Selective Looking and the Müller-Lyer Illusion: The Effect of Changes in the Focus of Attention on the Müller-Lyer Illusion
Authors: Goryo Ken , Robinson James O , Wilson John A
Published: January 2007

According to a selective looking paradigm subjects were required to attend to the inward-going or outward-going components of a combined Müller-Lyer figure in which both components were present and distinguishable by colour. The amount of the illusion was found to vary according to which component the subject attended. Subsidiary findings relate the amount of the illusion to fin angle, fin length, and length of shaft.
Sex and Age Differences in Choice Behaviour: The Object–Person Dimension
Authors: Jobson Steve , Watson John S
Published: January 2007

There is a popular belief that females are more socially oriented than males, while males are more nonsocially or object oriented than females. A 2 × 2 factorial design was employed to examine this, with independent variables of sex and age (young and older adults). The subjects were presented with six pairs of pictures, each consisting of an object and a person. Each presentation lasted 30 s; the time spent looking at each stimulus was taken as a measure of interest. The hypothesis that in this choice situation males and females would differ in their preference for object and person stimuli was confirmed. However, the sex difference was confined to young adults; older subjects of both sexes showed more (and equal) interest in the social stimuli than in the object stimuli. Masculinity and femininity scores on the Bem Sex Role Inventory showed some relationship with object–person preferences but failed to throw much light on the absence of a sex difference in older adults.
Estimation of Pendulum Length from Information in Motion
Authors: Pittenger John B
Published: January 2007

One hundred and five college students made estimates of the lengths of freely swinging pendulums mounted in an apparatus that masked all but the top few inches of the pendulum string. The law of pendulum motion shows that visible aspects of pendulum motion uniquely specify the length of the pendulum. Thus, information is available in the display that does, if observers are able to use it, allow accurate estimation of length. In three studies estimates were found to be linear functions of actual lengths, though with wide differences in slopes among individual observers. These results, together with statements made during post-experimental interviews, are interpreted as showing that observers use a rule to the effect that length is a linear function of ‘speed’, where speed appears to be a function of both period and angular velocity.
Locomotor Estimation of Distance after Visual Scanning by Children and Adults
Authors: Corlett John T , Patla Aftab E , Williams John G
Published: January 2007

Subjects (120 young adults and 120 children) were tested for their abilities to estimate visually the distance to a target 5 m away, then walk unaided by vision to that target as accurately as possible. Experimental groups were determined by visual scanning time (1, 5, or 10 s), delay between the end of visual scanning and the start of locomotion (0, 1, 3, or 5 s), and by age (9 year old children or young adult). Adults performed locomotor distance estimations based on visual scanning more accurately than children under all conditions. Increased scanning time resulted in more accurate performances by children but not by adults, and increased delays between the end of scanning and the start of locomotion caused decreases in accuracy for children only. These decrements were partially ameliorated by increased scanning time. The total time spent without vision after scanning the target (delay time plus walking time) was an important factor, with sharp increases in error for all delay conditions for children. The results are discussed in terms of trace decay effects and developmental aspects of visual guidance of locomotion.
Unstable Ocular Dominance and Reading Ability
Authors: Bigelow Elizabeth R , McKenzie Beryl E
Published: January 2007

An ocular anomaly, unstable ocular dominance, has been shown to be associated with poor reading performance in clinically selected subjects. A study is reported in which this anomaly was examined in a nonclinical sample. Two groups of children of similar reading performance and IQ but differing in chronological age were selected. The older children had a mean discrepancy between their reading and chronological age of 19 months. Unstable ocular dominance was more frequent in these poor readers. The hypothesis that this instability would lead to more errors and longer decision times for distinguishing left—right mirror-image figures was not supported. If unstable ocular dominance is to be established as anything other than a correlate of specific reading retardation, it is necessary to establish the processes through which it is operative. These have yet to be determined.
Visual Space as Physical Geometry
Authors: Rosar William H
Published: January 2007

The geometrical incongruence between patterns in visual space and structures and patterns of activity in the visual cortex, long known to investigators, serves as a criterion for evaluating physical theories of visual space. The problem of determining the geometry of the visual world (visual geometry) is compared with that of determining the geometry of the physical world (physical geometry). Theories as to the possible physical locus of visual space, whether in the brain or elsewhere, are reviewed, analyzed, and criticized accordingly. It is concluded that on the basis of congruence alone it would be predicted that visual space is not to be found in the brain, even though it is seemingly linked to it causally, as experimental neurology and neurophysiology demonstrate. Alternative theories as to the nature of visual space are considered, but are also found to be inadequate in explaining visual space in terms acceptable to contemporary science.
Visual Effects with a Miniature Leonardo's Window: Photographs and Real Scenes Fused Stereoscopically
Authors: Kalaugher Patrick G
Published: January 2007

The drawing on a conventional Leonardo's window will be seen by both of an observer's eyes unless one of them is occluded. But, by substituting a photographic colour transparency (in a suitably compact viewer) for the drawing, one eye can view the transparency whilst the other eye gains an unobstructed direct view of the scene. The transparency can then be stereoscopically fused with the directly-viewed scene. As the perspective of the transparency depends not on the observer's viewpoint but only on the position of the camera at the time of photography, altering the viewpoint causes the effective eye-base to vary, thus enhancing, suppressing, or sometimes even reversing the stereoscopic depth. With very simple equipment several visual effects can easily be demonstrated. Practical applications of the technique have been found, particularly in those engineering and geological situations in which it is useful to detect changes since a photograph was taken.
Signal Intensity, Task Context, and Auditory-Visual Interactions
Authors: Radeau Monique
Published: January 2007

A study is reported of the effect of signal intensity on immediate cross-modal bias between vision and audition. Each signal was presented at high or low intensity, giving rise to four conditions. The study also dealt with the effectiveness of instructions and task context in directing attention. Two kinds of task (pointing) contexts were compared: a constant or unimodal context in which the modality of the target signal was the same throughout a session, and a bimodal one in which it changed from trial to trial. In both conditions subjects were instructed that the signals might come from the same or from different positions, depending on the trial. For visual bias of audition the results show that a signal with high intensity was more biasing and less biased than one with low intensity. Auditory bias of vision did not reach significance in any of the four intensity conditions. Type of task context had no effect on the extent of bias, suggesting that a constant-task (unimodal) context was no more effective in directing attention than instructions alone.
Revisitation of the Family Tie between Münsterberg and Taylor-Woodhouse Illusions
Authors: Bressan Paola
Published: January 2007

Some observations suggest that, contrary to Taylor and Woodhouse's assumption, a strong relationship exists between the Taylor–Woodhouse and Münsterberg distortion illusions. An attempt is made to show that each of the major explanations put forward to account for the occurrence of the Münsterberg effect suits the Taylor–Woodhouse one as well.
Effect of Color on Judgments of Food Aroma and Flavour Intensity in Young and Elderly Adults
Authors: Christensen Carol M
Published: January 2007

The hypothesis was tested that subjects' judgments of food aroma and flavour strength will be increasingly influenced by food color as the chemosensory differences between foods become less apparent. Elderly ( n = 24) and young ( n = 22) adults were presented with pairs of food samples and instructed to indicate which sample had the more intense aroma or flavor. The chemosensory discriminations varied in difficulty, and the color of the food pairs was also manipulated so that either they were similarly colored, or the color strength differed so that it was either positively or inversely correlated with flavour strength. Overall, the results failed to support the hypothesis that color alters the perceived intensity of the food aroma or flavor. There was a weak trend toward a greater number of errors among sample pairs that varied in color, especially when color strength was inversely related to flavor strength. Elderly and young adult groups did not differ in chemosensory ability or in their responses to food color differences, although the elderly adults were significantly more certain of the accuracy of their chemosensory judgments.
Orientation and Alignment Misjudgement: New Geometrical Optical Illusions?
Authors: Yakimoff Naum
Published: January 2007

Misjudgement of orientation is demonstrated in drawings of tilted quadrangles with parallel diagonals. Apparent misalignment of apices and/or line-segment ends is shown in drawings of differently oriented rectangles, angles, and line segments.
Enhancing the Perception of Form in Peripheral Vision
Authors: Geiger Gad , Lettvin Jerome Y
Published: January 2007

Experiments are reported which show that the tachistoscopic presentation of a figure at the point of fixation makes salient the same figure where it occurs elsewhere in the visual field during the same flash. This induced saliency operates in all directions from the axis of gaze. If the eccentric figure is alone on a blank field the phenomenon is termed ‘eccentric enhancement’. The induced saliency of figures that are laterally masked within horizontal strings of figures that lie off the fixation point is termed ‘demasking’.
Positional Acuity without Monocular Cues
Authors: Morgan Michael J
Published: January 2007

The accuracy with which human observers can determine the spatial location of a shape boundary was measured by vernier alignment. The vernier targets were presented as random-dot stereograms, with varying amounts of camouflage in the monocular image. Camouflage decreased vernier acuity, but when the camouflage was broken by stereoscopic disparity, acuity was improved. In the limiting case when the shape boundaries were defined by disparity information alone, vernier thresholds (75% correct, binary forced-choice) were in the region of 40 s visual angle. This is poor acuity in comparison to vernier thresholds with monocular contour, but if the limited resolution acuity for stereopsis is taken into account, cyclopean and monocular positional acuities can be considered quite similar in relation to their respective resolution limits.
Pathways in Type-B (U-Shaped) Metacontrast
Authors: Reeves Adam
Published: January 2007

Rod and cone targets were crossed, in every combination, with rod and cone masks in flanking-bars metacontrast. Strong type-B (U-shaped) metacontrast was obtained in each condition, contrary to the claim that rod and cone masking are independent. In each condition, visibility declined steadily with stimulus-onset asynchrony (SOA) in trials in which target and mask appeared to be simultaneous, and increased with SOA in trials in which they appeared to be successive. The ‘U’ results from collapsing across these different types of trials, which may reflect distinct monotonic processes in masking. Under the light adaptation conditions used the time, Tmax, at which metacontrast was at a maximum was delayed by about 25 ms if rods, rather than cones, detected the target. Whether rods or cones detected the mask hardly altered Tmax.
Sensitivity to Perspective Structure While Walking without Vision
Authors: Rieser John J , Guth David A , Hill Everett W
Published: January 2007

Experiments are reported of the nonvisual sensitivity of observers to their paths of locomotion and to the resulting changes in the structure of their perspectives, ie changes in the network of directions and distances spatially relating them to objects fixed in the surrounding environment. In the first experiment it was found that adults can keep up to date on the changing structure of their perspectives even in the absence of sights and sounds that specify changes in self-to-object relations. They do this rapidly, accurately, and, according to the subjects' reports, automatically, as if perceiving the new perspective structures. The second experiment was designed to investigate the role of visual experience in the development of sensitivity to occluded changes in perspective structure by comparing the judgments of sighted adults with those of late-blinded adults (who had extensive life histories of vision) and those of early-blinded adults (who had little or no history of vision). The three groups performed similarly when asked to judge perspective while imagining a new point of observation. However, locomoting to the new point greatly facilitated the judgments of the sighted and late-blinded subjects, but not those of the early-blinded subjects. The findings indicate that visual experience plays an important role in the development of sensitivity to changes in perspective structure when walking without vision.
Snowhole Blues: Comments on Kinney and Corth
Authors: Trościanko Tom
Published: January 2007

Empirical observations are reported on illuminance and visibility in overcast snowscapes. Reasons for the improved visibility achieved with yellow goggles are discussed.
Perceived Orientation of Contour Quadrangles
Authors: Yakimoff Naum , Lolova Polina
Published: January 2007

One hundred subjects ranked the apparent tilt of ten quadrangles. A scale of perceived orientation was derived from a pair-comparison treatment of these data. The main characteristic determining estimated orientation of the quadrangles was the axis from which the sum of the squared distances to each point of the figure was minimal (the LS-axis). Judgements were also influenced by the orientation of an ‘axis of balance’, which ran through the centre of gravity and the lowermost apex of the quadrangle. Quadrangles with parallel LS-axes were systematically judged as differently tilted according to the difference in the orientation of their axes of balance. Both the LS-axis and the axis of balance are physical characteristics of an object that are of great importance for the optimal control of human action through vision.
Recognition of Positive and Negative Bandpass-Filtered Images
Authors: Hayes Tony , Morrone M Concetta , Burr David C
Published: January 2007

A study is reported in which the significance for vision of low- and high-spatial-frequency components of photographic positive and negative images was investigated by measuring recognition of bandpass-filtered photographs of faces. The results show that a 1.5 octave bandpass-filtered image contains sufficient visual information for good recognition performance, provided the filter is centred close to 20 cycles facewidth−1. At low spatial frequencies negatives are more difficult to recognize than positives, but at high spatial frequencies there is no difference in recognition, implying that it is the low-frequency components of negatives which present difficulties for the visual system.
Circular Vection as a Function of Foreground-Background Relationships
Authors: Ohmi Masao , Howard Ian P , Landolt Jack P
Published: January 2007

It has previously been reported that illusory self-rotation (circular vection) is most effectively induced by the more distant of two moving displays. Experiments are reported in which the relative effectiveness of two superimposed displays in generating circular vection as a function of (i) the separation in depth between them, (ii) their perceived relative distances, and (iii) which display was in the plane of focus was investigated. Circular vection was governed by the motion of the display that was perceived to be the more distant, even when it was actually nearer. However, actual or perceived distance was found to be not the crucial factor in circular vection because even when the distance between the two displays was virtually zero, vection was controlled by the display perceived to be in the background. When the displays were well separated in depth, vection was not affected by whether the near or the far display was in the plane of focus, nor by which display was fixed or pursued by the eyes.
The Effects of Display and Observer Strategy Variables on Bourdon Assimilation Illusions
Authors: Wenderoth Peter , O'Connor Tony
Published: January 2007

When a solid (filled-in) triangle is mirror-reflected about its vertex such that one angle arm and its reflection form a straight edge, this straight edge appears as a chevron bent in the direction of the other sides of the triangles, an effect directionally opposite to the well-known tilt illusion that occurs with outline angles. It has been proposed that these negative solid-angle illusions (assimilation effects) which occur in dual-angle (Bourdon-type) displays result from a failure to discriminate between the test (judged) edges and the bisectors of the solid angles. In dual-angle outline displays, near-zero effects have been attributed to the availability of collinearity cues. These hypotheses were tested in two experiments in which cues to collinearity were reduced by inserting gaps between the angles and in which collinearity information was increased by adding thick ‘necks’ to the displays. The results are consistent with predictions and implicate not only the nature of the angle display, but also the way in which observers perform the matching task in the production of assimilation effects.
The Perception of Continuous Curves in Dot Stimuli
Authors: Smits Jos T S , Vos Piet G
Published: January 2007

Two categorisation experiments are reported in which the perceptual phenomenon that some simple arrays of discrete dots appear as a continuous curve whereas others are perceived as an angular contour or as consisting of separate groups of dots was investigated. Triplets of dots were presented in the first experiment, and complete or incomplete regular dot polygons (ie dots positioned on the vertices of imaginary regular polygons) in the second. In both experiments the perception of a curve versus an angle was determined mainly by the relative orientations of the dots, ie by the angles between successive virtual lines, whereas the lengths of the virtual lines had relatively little influence. In experiment 2 the number of displayed dots was shown to be a second independent factor for perceiving continuity. These results are in agreement with results from experiments on dipole textures discrimination, and suggest the psychological existence and importance of virtual lines in the visual processing of dot stimuli.
The Influence of Auditory Stimulation on a Visual Oblique Effect
Authors: Johnstone Syren , Wenderoth Peter
Published: January 2007

It has previously been reported by Smets that there is an increase in the magnitude of the monocular oblique effect when a 70 dB(A), 1 kHz acoustic stimulus is presented contralaterally, but not ipsilaterally, to the viewing eye. This finding was interpreted as one which provided difficulties both for data-driven models of information processing and for the cortical simple cell explanation of the oblique effect. There are several logical and methodological difficulties in Smets's paper, and in the two experiments reported here the effect found by Smets was not replicated. The failure to observe the effect was robust under conditions that maximised the possibility of neural interaction. It is concluded that acoustic stimulation does not affect the magnitude of the oblique effect.
The Relative Contribution of Contact and Target Lines in the Magnitude of the Poggendorff Effect
Authors: Greene Ernest
Published: January 2007

It is well known that a set of parallel lines can cause misperception of the projected path of an oblique. Most studies of this effect have emphasized either the proximal or the distal stimulus components—the line with which the oblique makes contact, or the line that serves as the target of the projection. An experiment is reported in which the relative contribution of the contact and target lines was examined. The results indicate that rotation of either line can determine the magnitude of the projection error.
The Hidden Face of Kanizsa's Triangle: Apparent Movement of Subjective Figures in Three-Dimensional Space
Authors: Vallortigara Giorgio
Published: January 2007

Several demonstrations on the apparent movement in depth of subjective figures are presented. They include: (a) apparent rotational movement as a result of shape invariance or rigidity; (b) apparent rotational movement with three-dimensional subjective figures not accompanied by a brightness gradient; and (c) apparent rotational movement by kinetic occlusion.
Dependence of Apparent Movement of a Subjective Figure on the Perceptual Fate of Inducing Elements
Authors: Petersik J Timothy
Published: January 2007

In a series of demonstrations, two stimulus frames that contained subjective figures were alternated. It is shown that the perception of apparent movement of a subjective figure depends upon the configuration of the inducing stimuli and whether or not conditions of presentation favor the short-range or long-range process in apparent movement. Those conditions that favor the long-range process result in global apparent movement of the subjective figure. However, those conditions that favor the short-range process may prevent apparent movement of the subjective figure, or may result in a kind of apparent movement that is qualitatively different from that seen when similar physical contours are alternated. These results are interpreted in terms of the assumed differences between the short-range and long-range processes.
Perceptual and Task Factors in Fluent Braille
Authors: Millar Susanna
Published: January 2007

Hypotheses that fluent braille depends (i) on coding letters by global outline shape for all task and speed levels, or (ii) on lateral dot—gap density scanning in fast reading for meaning were tested with three groups of fluent braillists who differed in reading speeds.

In experiment 1, 90°-rotated (near to far) texts under vertical and horizontal finger orientation were used. Hypothesis (i) was not supported. Finger orientation interacted significantly with Speed and Task. Vertical finger orientation, which disrupts lateral scanning, slowed reading for comprehension more than for letter search, and differentially more for faster readers. Horizontal finger orientation, which instead disrupts the familiar finger—body relation, did not have differential effects. The findings support hypothesis (ii). In experiment 2, normal texts and texts containing a degraded dot in some letters were used. These are felt in searching for individual letter patterns, but would disrupt lateral scanning of expected dot—gap density patterns in reading for meaning. The results supported the predictions from hypothesis (ii), that degraded texts slow reading for meaning significantly more than for letter search, and more in the case of faster readers than for the slowest group. Findings were not consistent with hypothesis (i), which predicts that text degradation affects tasks equally, and affects the slowest rather than the fastest readers. The results suggest that perceptual coding in reading differs with task demands and speed.
Why There is No Error in the Direct Theory of Perception
Authors: Katz Stuart
Published: January 2007

According to Gibson's direct theory, perception is an achievement, not a process. Perceptual error, therefore, is the failure to perceive. Taken in isolation, this assertion leads to implausible consequences, but taken together with other assertions of Gibson, it may be understood, without contradiction, to mean that there is no absolute error in perception. Whether perception is successful or not is determined by the context in which the perceptual act occurs.
Individual Differences in Responses of Untrained Observers to Stroboscopic Apparent Motion
Authors: Finlay David C , Manning Mark L , Fenelon Barney
Published: January 2007

Two large groups of inexperienced subjects ( n = 208 and n = 50) and a small group of experienced subjects ( n = 5) were tested using time-till-breakdown as a measure of long-range apparent motion across a range of temporal frequencies. One group of inexperienced subjects was retested after one week and demonstrated quite stable patterns of response. Large intersubject variability was observed in terms of the amount of motion seen, with most inexperienced subjects reporting very little apparent motion. A raster display produced a peak frequency 1 Hz higher than a standard tachistoscope display. The role of experience was also examined with a small group of inexperienced subjects ( n = 8) tested once daily over five consecutive days. There was high intersubject variability and intrasubject consistency, demonstrating little influence of learning and experience. The results are discussed in terms of current ideas on the breakdown effect.
The Equiratio Taste Mixture Model Successfully Predicts the Sensory Response to the Sweetness Intensity of Complex Mixtures of Sugars and Sugar Alcohols
Authors: Frijters Jan E R , de Graaf Cees
Published: January 2007

The equiratio taste mixture model was originally developed for the prediction of psychophysical power functions of equiratio mixtures of substances that have a similar taste and that also exhibit mutual cross adaptation. Earlier studies have shown that the model is valid for mixtures of sugars and/or sugar alcohols. Two experiments are reported in which it is questioned whether the psychophysical functions of mixtures of higher physical complexity can be predicted by the model. In the first experiment the psychophysical power functions of binary and quaternary equiratio mixture types were determined experimentally and compared to those predicted by the generalized model. In the second, similar, experiment quaternary and eight-component mixture types were examined. The method of magnitude estimation, in combination with the sip and spit procedure, was used. The functions predicted by the model were almost identical to the functions established on the basis of the experimental data. These results reconfirm that the gustatory modality operates like an ‘averaging’ system when processing this kind of mixture. It is argued that for other kind of mixtures the model will predict incorrectly. The status of the equiratio mixture model is discussed.
The Horizontal—Vertical Delusion
Authors: Hinton Geoffrey E
Published: January 2007

Most people can correctly apply the concepts of horizontal and vertical in describing objects, but a simple demonstration shows that they are confused about how these concepts work. The nature of the confusion and its possible causes are briefly discussed.
Configurational Information in Face Perception
Authors: Young Andrew W , Hellawell Deborah , Hay Dennis C
Published: January 2007

A new facial composites technique is demonstrated, in which photographs of the top and bottom halves of different familiar faces fuse to form unfamiliar faces when aligned with each other. The perception of a novel configuration in such composite stimuli is sufficiently convincing to interfere with identification of the constituent parts (experiment 1), but this effect disappears when stimuli are inverted (experiment 2). Difficulty in identifying the parts of upright composites is found even for stimuli made from parts of unfamiliar faces that have only ever been encountered as face fragments (experiment 3). An equivalent effect is found for composites made from internal and external facial features of well-known people (experiment 4). These findings demonstrate the importance of configurational information in face perception, and that configurations are only properly perceived in upright faces.
Simulation of the Response of a Multichannel Nerve Array to Pulse Shapes Produced by Single-Channel Electrostimulation
Authors: Rattay Frank , Motz Hans
Published: January 2007

Results of experiments on single-channel electrostimulation of the cochlea which throw light on the performance of the central auditory nervous system (CANS) have recently been reported by Dobie and Dillier. Trains of pulses with different rise times could be distinguished by subjects with cochlea implants, even though time differences involved were very small. It was suggested by the authors that the information is carried to the CANS by an array of nerve fibres with characteristic time differences. In the present paper, simulations produced by means of a nerve model are reported and used to compute the patterns of action potentials evoked on the nerve array by different pulse trains. The changes in the patterns of the nerve responses resulting from the shape variations which have to be perceived by the CANS are examined.
Dynamic Occlusion and Motion Parallax in Depth Perception
Authors: Ono Hiroshi , Rogers Brian J , Ohmi Masao , Ono Mika E
Published: January 2007

Random-dot techniques were used to examine the interactions between the depth cues of dynamic occlusion and motion parallax in the perception of three-dimensional (3-D) structures, in two different situations: (a) when an observer moved laterally with respect to a rigid 3-D structure, and (b) when surfaces at different distances moved with respect to a stationary observer. In condition (a), the extent of accretion/deletion (dynamic occlusion) and the amount of relative motion (motion parallax) were both linked to the motion of the observer. When the two cues specified opposite, and therefore contradictory, depth orders, the perceived order in depth of the simulated surfaces was dependent on the magnitude of the depth separation. For small depth separations, motion parallax determined the perceived order, whereas for large separations it was determined by dynamic occlusion. In condition (b), where the motion parallax cues for depth order were inherently ambiguous, depth order was determined principally by the unambiguous occlusion information.
Real and Subjective Contour Poggendorff Illusions: No Differences Based on Eye Color
Authors: Beckett Peter A , Hurajt Stephen
Published: January 2007

Measures of illusion magnitude for a real contour and two subjective contour Poggendorff figures were obtained from a large number of dark-eyed and light-eyed undergraduates. Illusion magnitude varied as a function of figure type. However, eye color neither had a significant overall effect on illusion magnitude, nor did it interact with the figure-type variable. These data indicate that the presence of intersecting lines is not the basis of the iris-pigmentation effect reported by Coren and Porac.
Identification of Two-Tone Images; Some Implications for High- and Low-Spatial-Frequency Processes in Human Vision
Authors: Hayes Anthony
Published: January 2007

Unlike most multitone images, two-tone images such as print, geometric figures, and line drawings are as easy to interpret in photographic negative as in positive form. However, images derived from a multitone original in which intensity values are quantised to two levels are not. Bi-level quantised images, distinct from most other two-tone images, are shown to contain picture related components in their low spatial frequencies. Since it is the low-spatial-frequency components alone of negative images that present difficulties for vision, it is proposed that images which are as easy to interpret in negative as in positive form are those which are readily identified using only their high spatial frequencies.
Constant Errors in Judgements of Collinearity Due to the Presence of Neighbouring Objects
Authors: Hotopf W H Norman , Brown Susannah A
Published: January 2007

If a line (the pointer) is aligned with a dot (the target) that stands on another line (the induction line) which is at an angle to the pointer, the pointer and the dot may no longer appear collinear. Whether they do or not depends upon the angle formed by the pointer with the induction line: the smaller the angle, the greater the misalignment effect. Misalignment is always in the direction of the induction line, which is why this alignment illusion is called attraction-caused misalignment (attraction misalignment for short). Three experiments are described in which this illusion is explored further. In the first it is shown that the induction line can exert its influence even when not contiguous with the target, though the size of the effect varies inversely with the distance of the induction line from the target. In the second experiment it is demonstrated that a dot as well as a line can induce attraction misalignment and that similarity between the induction and target items increases misalignment. Evidence in support of the theory that the termination of the induction line, as well as the part contiguous with the target dot, may induce attraction misalignment is provided in the third experiment.
A New Visual Problem: Phenomenic Folding
Authors: Massironi Manfredo
Published: January 2007

It is possible to produce outline drawings that are perceived as representations of sheets or plates folded over themselves. However, only some of the many possible representations are immediately and necessarily perceived as such. Investigations were carried out to find out which elements must be included in a drawing if a subject is to perceive folding. Four necessary, though not individually sufficient, factors were detected. Other factors which are not necessary but which can intensify the perception of folding were also found. The four necessary factors are: (i) the existence of two phenomenically overlapping figures; (ii) at least one side of the upper figure must perfectly coincide with one side of the lower figure, this common side being defined as the folding line; (iii) the two phenomenically overlapping areas must be on the same side of the folding line; (iv) three segments must converge at the ends of the folding line. Some cognitive processes which appear to be involved in the phenomenon are also discussed.
Spatial and Orientation Specific Integration in the Tilt Illusion
Authors: Johnstone Syren , Wenderoth Peter
Published: January 2007

Lateral inhibition across a population of cells in visual cortex which are tuned to local orientation has been proposed and widely accepted as a basic process in the analysis of contour in the visual field. The tilt illusion is usually explained in terms of this inhibition. Experiments are reported which cast new light on the analysis of visual orientation. It is shown that tilt illusions may be obtained with very thin inducing annuli which are spatially remote from the test figure. In experiments in which remote crossed-grating plaids were used, an illusion which was pattern (global) rather than component (local) selective was seen. It is difficult to account for these observations in terms of local inhibitory mechanisms. Rather, the results support the existence of a secondary mechanism which is involved in basic orientation analytic processes. The relevance of these observations to models of visual contour analysis is discussed.
Angular Induction as a Function of Contact and Target Orientation
Authors: Greene Ernest , Pavlov George
Published: January 2007

The Poggendorff effect is seen as misalignment of two obliques, or misprojection of one, when the obliques are placed outside a set of parallel lines. To understand better the mechanisms behind this effect, the orientation of the lines which are normally parallel was systematically manipulated. The results indicate that projection bias is affected by the orientation of either line, is at a minimum where the line is orthogonal to the oblique, and is maximal at small angles. This is in line with classic theories which attribute the illusion to misperception of angular size. However, such explanations presuppose that in order to be effective the induction line must be proximal to the oblique so that an angle can be formed. Results are reported which show that the angle formed by the oblique and a line placed at a distance from the oblique, serving as the target of the projection, follows an angular rule of effectiveness similar to what is seen when the line is placed directly in contact with the oblique. The underlying process is described as ‘angular induction’.
Errors in Estimating the Orientation of Dot Patterns
Authors: Lánský P , Yakimoff Naum , Radil T , Mitrani L
Published: January 2007

The error in estimating the orientation of a dot pattern was measured as the difference between the orientation of the least-squared-distances line (LS-line) of the pattern and the orientation of a line adjusted by the subject to match the perceived orientation of the pattern. Analysis of the mean errors (averaged over ten subjects) obtained for one hundred patterns confirmed that the orientation of the LS-line represents the orientation of elongated dot-patterns. It is shown that estimated orientation was systematically biased towards the nearest 45° oblique meridian. This bias points to the importance of the ±45° directions as natural norms for left- and right-side tilt in the frontoparallel plane.
Measuring Attention Using Induced Motion
Authors: Gogel Walter C , Sharkey Thomas J
Published: January 2007

Attention was measured by means of its effect upon induced motion. Perceived horizontal motion was induced in a vertically moving test spot by the physical horizontal motion of inducing objects. All stimuli were in a frontoparallel plane. The induced motion vectored with the physical motion to produce a clockwise or counterclockwise tilt in the apparent path of motion of the test spot. Either a single inducing object or two inducing objects moving in opposite directions were used. Twelve observers were instructed to attend to or to ignore the single inducing object while fixating the test object and, when the two opposing inducing objects were present, to attend to one inducing object while ignoring the other. Tracking of the test spot was visually monitored. The tilt of the path of apparent motion of the test spot was measured by tactile adjustment of a comparison rod. It was found that the measured tilt was substantially larger when the single inducing object was attended rather than ignored. For the two inducing objects, attending to one while ignoring the other clearly increased the effectiveness of the attended inducing object. The results are analyzed in terms of the distinction between voluntary and involuntary attention. The advantages of measuring attention by its effect on induced motion as compared with the use of a precueing procedure, and a hypothesis regarding the role of attention in modifying perceived spatial characteristics are discussed.
A New Visual Illusion, and its Mechanism
Authors: Haig Nigel D
Published: January 2007

A new visual illusion is reported, in which a sine-wave grating appears to tilt when doubly sheared perpendicularly to the grating lines. It is shown that the illusory percept is related to the Münsterberg and Café Wall illusions. The probable mechanism at the root of all such illusions is postulated by reference to the neuroarchitecture of the retina and striate cortex.
Picture and Pattern Perception in the Sighted and the Blind: The Advantage of the Late Blind
Authors: Heller Morton A
Published: January 2007

Two experiments are reported on the contribution of visual experience to tactile perception. In the first experiment, sighted, congenitally blind, and late blind individuals made tactual matches to tangible embossed shapes. In the second experiment, the same subjects attempted tactile identification of raised-line drawings. The three groups did not differ in the accuracy of shape matching, but both groups of blind subjects were much faster than the sighted. Late blind observers were far better than the sighted or congenitally blind at tactile picture identification. Four of the twelve pictures were correctly identified by most of the late blind subjects. The sighted and congenitally blind performed at comparable levels in picture naming. There was no evidence that visual experience alone aided the sighted in the tactile task under investigation, since they performed no better than did the early blind. The superiority of the late blind suggests that visual exposure to drawings and the rules of pictorial representation may help tactile picture identification when combined with a history of tactual experience.
Perceived Causality Occurs with Stroboscopic Movement of One or Both Stimulus Elements
Authors: Gordon Ian E , Day Ross H , Stecher Erica J
Published: January 2007

It was shown by magnitude estimation that the perception of causality first described by Michotte (1946/1963) also occurs consistently and strongly with stroboscopic, ie apparent or phi, movement. This is so when the ‘causal’ movement is stroboscopic and the ‘caused’ movement real, when these movements are reversed, and when both movements are stroboscopic. The effect is not due to prior experience with Michotte-type displays.
Pigeon Pattern Perception: Limits on Perspective Invariance
Authors: Cerella John
Published: January 2007

Two experiments are reported in which the response of pigeons to perspective transformations of a pattern target was measured. In the first experiment an alphabet letter was taken as the pattern target (the ‘positive’) and the response to its perspective transforms was compared to the response to nontarget letters (‘negatives’) over the course of discrimination training. In the second experiment irregular quadrilaterals were used as positives and the responses to slight perspective deformations of the prototypes were compared to the responses to random transformations of the same magnitude under steady-state conditions. The amount of differential responding depended on the type of transformation. There was no differential response to targets rotated in the picture plane or around the horizontal axis in either experiment. There was differential response to small reductions and enlargements of the target. There was also differential response to translated targets, and this was seen irrespective of the amount of displacement. Results from targets rotated around the vertical axis were erratic, some target-plus-angle combinations elicited differential responding, but most did not. The erratic responses are attributed to symmetries in pattern elements that were abstracted as critical features. Pigeons therefore exhibit no true rotation invariance, limited size invariance, and complete shift invariance. It is argued that size invariance, but not position invariance, may depend on prior exposure to the alternatives.
Binaural and Monaural Localization of Sound in Two-Dimensional Space
Authors: Butler Robert A , Humanski Richard A , Musicant Alan D
Published: January 2007

Two experiments were conducted. In experiment 1, part 1, binaural and monaural localization of sounds originating in the left hemifield was investigated. 104 loudspeakers were arranged in a 13×8 matrix with 15° separating adjacent loudspeakers in each column and in each row. In the horizontal plane (HP), the loudspeakers extended from 0° to 180° in the vertical plane (VP), they extended from −45° to 60° with respect to the interaural axis. Findings of special interest were: (i) binaural listeners identified the VP coordinate of the sound source more accurately than did monaural listeners, and (ii) monaural listeners identified the VP coordinate of the sound source more accurately than its HP coordinate. In part 2, it was found that foreknowledge of the HP coordinate of the sound source aided monaural listeners in identifying its VP coordinate, but the converse did not hold. In experiment 2, part 1, localization performances were evaluated when the sound originated from consecutive 45° segments of the HP, with the VP segments extending from −22.5° to 22.5°. Part 2 consisted of measuring, on the same subjects, head-related transfer functions by means of a miniature microphone placed at the entrance of their external ear canal. From these data, the ‘covert’ peaks (defined and illustrated in text) of the sound spectrum were extracted. This spectral cue was advanced to explain why monaural listeners in this study as well as in other studies performed better when locating VP-positioned sounds than when locating HP-positioned sounds. It is not claimed that there is inherent advantage for localizing sound in the VP; rather, monaural localization proficiency, whether in the VP or HP, depends on the availability of covert peaks which, in turn, rests on the spatial arrangement of the sound sources.