bluuebunny/crossref_metadata_2025 huggingface dataset:
Infants' Reactions to Visual Movement of the Environment
Authors: Delorme André , Frigon Jean-Yves , Lagacé Carole
Published: January 2007

It has been demonstrated many times that the posture of infants is affected by movement of the visual environment. However, in previous studies, measurements taken with infants less than 10 to 12 months of age have always been recorded with the infants in a sitting position. An experiment is reported in which the postural reactions to a sinusoidal movement of the visual environment were recorded in infants 7 months of age and older standing with support. Fifty subjects divided into five groups (mean age 7.15 to 48.6 months) participated in the experiment. The groups differed in age and motor ability. Movement of the visual environment was achieved by means of a floorless room that could be moved sinusoidally in the anteroposterior axis. The subjects had to stand holding a horizontal bar fixed to a force-measurement platform. For each subject, measurements were made during four 60 s intervals: two with movement of the room and two with the room stationary. For all groups, reactions in the anteroposterior axis were stronger than in the lateral axis and this was true for both stimulus conditions. Comparison of the differences between the movement and stationary conditions in the anteroposterior axis, as a function of age, shows that the youngest infants seemed paradoxically to give stronger reactions when the room was stationary than when it was moving; the inverse was true for older infants and this difference increased with age. An analysis of the data with fast Fourier transforms reveals that the majority of subjects showed a pattern of postural reactions where the dominant (peak) frequency was identical to the peak frequency of room movement. The results of the present experiment lead to the conclusion that young infants react posturally to movements of their visual environment as soon as they are able to stand without help. Also, the best synchronization is found in infants that have just learned to stand without help. These results confirm that ‘visual proprioception’ assumes a leading role in the learning of a new stance.
Verbal Transformations in the Aged
Authors: Roivainen Eka
Published: January 2007

The susceptibility of aged persons to verbal transformations was studied in an experiment with ambiguous verbal stimuli (‘reversible words’). Twenty-five subjects, aged 64 to 86 years, participated in the experiment. The results indicate that the aged are somewhat less susceptible to verbal reversals than are young adults, but there seem to be no age differences in the type of illusory forms heard. These results differ from those of experiments with nonreversible words, which show a very low rate of transformation and a total absence of transformations into meaningless forms in the aged. It is hypothesized that the reversibility of repeated ambiguous patterns is a general phenomenon arising from satiation, whereas transformations of repeated unambiguous verbal stimuli, involving phonetic distortions, are based on specific speech-perception mechanisms that are absent in the aged.
The Importance of Alignment in Blind Subjects' Use of Tactual Maps
Authors: Rossano Matt J , Warren David H
Published: January 2007

An experiment was conducted to test for the presence of alignment effects (previously found in sighted map users) in blind and visually impaired subjects using tactual maps. The term ‘alignment effects’ refers to the fact that when points represented as further up on a map do not correspond to points forward from the user in the environment, errors in the directional judgments made by subjects are greatly increased. The results show that alignment effects do exist in blind and visually impaired map users. Blind subjects encoded maps using the ‘up equals forward’ rule, and demonstrated some similarity to sighted subjects in the types of errors made. There was also some indication of improved performance over repeated trials. Differences between blind and sighted subjects were also found and were tentatively attributed to visual experience with object transformations and/or representational variables. Subject background variables were also investigated and some relationships between background of the subject and performance were drawn.
Emmert's Law in the Ames Room
Authors: Dwyer Jonathan , Ashton Roderick , Broerse Jack
Published: January 2007

The Ames distorted room illusion, in which the perceived sizes of objects placed within the room differ from their objective sizes, has been used to support arguments for indirect perception. A study is reported in which Emmert's law of the apparent size of after-images was examined in relation to the Ames room's illusory alteration of apparent and actual distances. Size judgments of afterimages projected into the Ames room were compared with control conditions in which both actual and apparent afterimage projection distances were reproduced. Results indicate that Emmert's law may not provide a simple geometrical relationship between proximal image size and actual viewing distance, and that the processes involved in making afterimage size judgments are similar to those processes involved in making size judgments of ‘real world’ objects.
Perception of Structure from Two-, Four-, or Eight-Dot Oscillatory Motion: Restoration of Rigidity with the Aid of Structural Information
Authors: Ishiguchi Akira
Published: January 2007

The motion of two dots corresponding to the two endpoints of an oscillating rigid pendulum produces the perception of an elastic rod, not a rigid one. The possibility that structural information about a rigid object whose motion is simulated plays an important role in the perceptual restoration of the rigidity is examined. Two experiments are reported in which the motion of the endpoints of rigid objects (two endpoints for a rod, four for a sheet, and eight for a board) was displayed. Rigid structure was restored whenever structural information could be used to activate a knowledge data-base on the properties of the objects.
Vernier Acuity with Opposite-Contrast Stimuli
Authors: O'Shea Robert P , Mitchell Donald E
Published: January 2007

Vernier acuity has usually been tested with stimuli of the same contrast polarity (SC). This traditional vernier acuity was compared to that obtained with stimuli of opposite-contrast (OC) in which one target was brighter than the background and the other was darker. For both bar and dot targets vernier acuity with OC stimuli was about half as good as with SC stimuli. There were large individual differences in the size of the disadvantage with OC stimuli, although thresholds remained within the hyperacuity range. There were also individually-differing biases to see a dark vernier stimulus on one or the other side of a bright stimulus. Differences between OC and SC vernier acuities persisted over a wide range of interstimulus spacings, widths, and contrasts. At extremes of these spatial manipulations acuities became similar, but only because SC acuities were degraded to the level of OC acuities. Subjects showed little improvement in OC vernier acuity, even after 50 000 trials. It is concluded that finest judgements of spatial position arise in a level of the visual system at which light and dark stimuli are treated independently.
Perceptual Information for the Timing of Interceptive Action
Authors: Tresilian James R
Published: January 2007

Time-to-contact is an important quantity for controlling activities which involve the timing of interactions with objects and surfaces in motion relative to an observer. Two alternative means for obtaining perceptual information that might be used to obtain the time-to-contact required to correctly time an interaction have been contrasted: a method based on the perception of distance and velocity, and a method due to Lee involving a perceptual variable called tau. A monocular version of the first method is presented and shown to place a highly unrealistic and arbitrary limitation on the capabilities of the visual system. The second method is reviewed and its limitations discussed. Several means by which these limitations can be overcome are presented. Recently reported results from experiments which involved catching self-luminous balls in the dark are interpreted in terms of timing information available to the subject, and the notions of intermodal and multimodal timing information are introduced. Finally, the possibility that timing information is available to an observer which does not involve the variable tau is considered. It is concluded that many questions regarding the perception of time-to-contact remain unresolved and that much empirical research remains to be done.
Shape from Shading in Different Frames of Reference
Authors: Howard Ian P , Bergström Sten S , Ohmi Masao
Published: January 2007

It has often been reported that, in the absence of information about the direction of illumination, people interpret surface convexities and concavities in accordance with the assumption that illumination comes from above. However, ‘above’ could mean with reference to gravity, the head or the retina. Yonas et al reported that four-year-old infants use the head more than gravity as the frame of reference in interpreting surface relief but that seven-year-olds make about equal use of the two frames of reference. The potency of these two frames of reference when acting separately and when pitted against each other was measured on adult subjects. For all subjects the ‘assumption’ about the direction of illumination was predominantly with respect to the head. The gravitational frame was used only when the headcentric frame was irrevelant, and then not consistently.
Ambiguity in 3-D Patterns Induced by Lighting Assumptions
Authors: Papathomas Thomas V , Gorea Andrei
Published: January 2007

A bistable pattern is shown with white and black bars with horizontal and vertical orientations which produce an impression of thin slabs stacked up in depth either toward or away from the observer. It is postulated that the ambiguity is induced by the observer's assumption of the direction of the light source.
Static Depth Cues Do Affect the Perceived Direction of Motion
Authors: Mowafy Lyn
Published: January 2007

Models of motion perception usually assume that the visual system references spatial displacements to retinal coordinates, and not to three-dimensional coordinates recovered by a parallel process. The present studies investigated whether moving elements viewed in the context of a static random-dot stereogram could lead to the appearance of motion in depth. Observers judged the velocity of a monocular element translating horizontally in the stereo context as ‘same as’ or ‘different to’ that of a standard. Based on velocity constancy, if there was apparent motion in depth, the relative velocity judgments would yield a predictable pattern of errors.

The first experiment compared two stereo contexts: a sloped surface versus a fronto-parallel plane at zero disparity. The results indicated an overall increase in the perceived velocity of the element moving in the sloped surface context. A similar pattern of results was found when surfaces differing in incline were compared. Experiment 2 explored the case of fronto-parallel planes at crossed and uncrossed disparities. Here depth differences did not systematically affect observers' judgments. It was concluded that in some cases motion analysis can be affected by three-dimensional disparity information and not by angular displacement alone.
Structural Information Processing in Peripheral Vision
Authors: Kawabata Nobuo
Published: January 2007

Structural visual information processing was investigated in peripheral vision. Perceptual completion, as observed at the blind spot, occurred across a vertical blank stripe in a test pattern, presented in the peripheral visual field. That is, a shape, organized by structural processing, was perceived under critical visual conditions when it was presented in peripheral vision. The results indicate that structural processing, as indicated by perceptual completion, occurs in the peripheral visual information handling process. The results suggest that structural processing of shape information is built into the peripheral visual system and reduces the information load on the higher visual processes under conditions in which visual information is not adequate.
Reaction Time Measures of Feature Saliency in Schematic Faces
Authors: Fraser Ian H , Craig Greg L , Parker Denis M
Published: January 2007

Two separate paradigms utilizing measurements of reaction time were employed to study facial feature saliency in schematic line drawn faces. In the first paradigm the speed of response to the omission of different facial components was measured, and in the second, the speed of response to feature substitution was measured. In both paradigms the facial features were presented in a random temporal sequence in order to minimise preferential scanning strategies. The two separate paradigms reflected the feature hierarchy most commonly found in the literature, ie the outline and eyes are more salient than the nose and mouth in terms of both speed of processing and error rate. In a third study the feature substitution paradigm was used to investigate the effects of feature saliency on the perception of emotional faces. The results suggest a change in the eyes/mouth hierarchy so that the mouth becomes the most salient feature in the surprised, happy, and sad target faces. This reverse in hierarchy, however, was not evident with the angry target face. These results are discussed in terms of changes in the focus of ‘attention’ and/or changes in ‘processing efficiency’.
Outlined Elements, Regular Elements and Coincidences in Illusory-Figure Patterns
Authors: Parks Theodore E
Published: January 2007

When elements in a pattern which would otherwise produce an illusory figure are modified by outlining or by increasing their regularity (in accordance with a proposed measure of the latter quality), the illusory effect is much reduced. Both results reflect the principle that ‘coincidences’ in a display play little or no role in the process of segmentation when other circumstances tend to force critical edges to ‘belong’ to individual elements of the display.
The Internal Clock: Evidence for a Temporal Oscillator Underlying Time Perception with Some Estimates of its Characteristic Frequency
Authors: Treisman Michel , Faulkner Andrew , Naish Peter L N , Brogan David
Published: January 2007

Evidence for the proposition that human time perception is determined by an internal clock is largely indirect. It would strengthen the case for this hypothesis if a model for the internal clock were available from which predictions could be derived and tested, and if the basic parameter of such a model, the frequency at which the clock runs, could be estimated. A model for an internal temporal pacemaker is briefly described and its properties are explored by computer simulation. Results are obtained that provide a basis for predicting that, under appropriate conditions, interference between an imposed rhythm and the frequency of a temporal oscillator may cause perturbations in temporal judgment which are related to the characteristic frequency of that oscillator. Experimental data are reported which appear to demonstrate such an interference pattern. These results allow some estimates of the characteristic frequency of the temporal oscillator to be obtained.
Predicting the Future Position of a Moving Target
Authors: Peterken Carolyn , Brown Brian , Bowman Ken
Published: January 2007

Three experiments were conducted to examine the processes underlying the prediction of the future position of a moving target. A target moved horizontally across a computer screen at constant velocity, disappearing partway across the screen, and subjects responded when they estimated the target would have passed a point on the far side of the screen, had it continued on its path. The first experiment demonstrated that visual tracking of the target is not necessary for successful position estimation. In the second experiment, the time over which the prediction was made rather than the interval for which the target was visible, the distance over which the prediction was made, or the velocity of the target, was found to affect performance. Finally, performance was not affected when markers were placed parallel to the trajectory of the target; the presence of gratings which masked portions of the target's path did not affect subjects' performance. The previous literature suggests that the spatial interval over which predictions are made is the important variable; we find that temporal factors are the major determinants of prediction.
Sine of an Illusion
Authors: Day Ross H , Stecher Erica J
Published: January 2007

In an informally observed sine-wave figure in which the vertical extent between contours was constant, apparent extent in the crest and trough (the ‘turns’) appeared greater than in the straight oblique sections of the figure. This observation was confirmed in two experiments in which the vertical extents were matched by two vertically arranged dots. It was found that in a turn the apparent extent was greater than the true extent, but in a straight section both extents were about equal. These outcomes were confirmed when the two sections were each separated from the figure and presented alone. The illusion is explained in terms of a perceptual compromise between the vertical extent and the greater overall dimensions of the section at the turn of the sine-wave figure and is thereby held to be the same in principle as the Müller-Lyer illusion.
Perceived Depth Scales with Disparity Gradient
Authors: Bülthoff Heinrich , Fahle Manfred , Wegmann Michael
Published: January 2007

Perceived difference in depth between two adjacent stimuli decreases with increasing disparity gradient even if the disparity stays constant, ie when the stimuli approach each other along paths within fronto-parallel planes. This depth scaling effect is more pronounced with line stimuli than with two isolated points or two small symbols and is insignificant for easily discriminable symbols. The decrease in perceived depth is more pronounced for horizontal orientation than for oblique or vertical orientation. The ratio of perceived depth difference to displayed disparity difference also decreases when the distance between the stimuli increases at a constant gradient in depth. This is to say that we are more correct in our depth estimates for steep gradients in depth when the euclidean distance between the stimuli is short.
Origins of the Proprioceptive Function of Vision: Visual Control of Posture in One Day Old Domestic Chicks
Authors: Butterworth George , Henty Cliff
Published: January 2007

Recently hatched domestic chicks control their upright bipedal posture, at least in part, with respect to the flow of visual information at the retina, as do human infants when they first acquire control of the head, of sitting, and of standing. Some implications of the similarity of the proprioceptive function of vision in chicks and in humans for the origins and development of postural control are discussed.
Evidence for a Common Motion Mechanism of Luminance-Modulated and Contrast-Modulated Patterns: Selective Adaptation
Authors: Turano Kathleen
Published: January 2007

Selective adaptation effects were measured with contrast-modulated patterns and sine-wave gratings in order to determine the extent to which the two patterns are processed by common mechanisms. Direction-specific adaptation effects were measured for a contrast-modulated adapting pattern and a test pattern. The contrast-modulated adapting pattern was composed of a sine-wave grating of 8 cycles deg−1 whose contrast was spatially modulated by a sinusoid of 1 cycle deg−1 at one of four levels: 100%, 60%, 30%, or 0%. The results showed that contrast-modulation thresholds for contrast-modulated gratings were raised by 0.3 to 0.5 log units following adaptation to a contrast-modulated grating moving in the same direction as the test pattern, relative to thresholds obtained following adaptation to a contrast-modulated grating moving in the opposite direction. Cross-adaptation effects were also measured with a sine-wave adapting pattern and a contrast-modulated test pattern. The sine-wave adapting pattern was a sine-wave grating of 1 cycle deg−1 whose contrast was set to one of three levels: 16.4%, 1.25%, or 0%. The contrast-modulated test pattern was a sine-wave grating of 8 cycles deg−1 whose contrast was modulated by a sinusoid of 1 cycle deg−1. The results revealed that contrast-modulation thresholds for contrast-modulated gratings were raised by approximately 0.25 log units following adaptation to moving sine-wave gratings, relative to thresholds obtained following adaptation to a uniform field. Cross-adaptation effects were also obtained with a contrast-modulated adapting pattern and a sine-wave test pattern. The results support the view that signals generated from luminance-domain stimuli and from contrast-domain stimuli are processed by a common motion mechanism.
Rapid Discrimination of McCollough Effects
Authors: Humphrey G Keith , Gurnsey Rick , Fekete Eva
Published: January 2007

The McCollough effect is a colour aftereffect that is contingent on pattern orientation. Three experiments were conducted to establish whether such aftereffect colours could serve as a basis for discrimination in several rapid discrimination tasks. In the first experiment it was investigated whether aftereffect colours could act like a simple ‘feature’ in a visual search task involving a difficult orientation discrimination. Without McCollough adaptation, the time taken to detect a ‘target’ among ‘distractors’ increased substantially as the number of distractors increased. With adaptation, detection time was essentially independent of the number of distractors, indicating that the nature of the task changed from a difficult orientation discrimination to a simple discrimination based on differences in aftereffect colours. The second and third experiments employed a difficult four-alternative forced-choice procedure in which subjects were required to discriminate a monochromatic patch of square-wave grating oriented at 45° from three others oriented at 135° (and vice versa). The gratings were presented very briefly (67–333 ms) followed by a 500 ms mask. Subjects performed the task with and without McCollough adaptation. Performance was strikingly better after adaptation: colour aftereffects could be used to make the discrimination even at exposure durations as short as 67 ms. The third experiment demonstrated that this enhanced performance was indeed due to perceived colour differences (rather than a possible contrast difference). The results of the three experiments are discussed in relation to proposals about the locus of the McCollough effect.
Texture-Based Tasks are Little Affected by Second Tasks Requiring Peripheral or Central Attentive Fixation
Authors: Braun Jochen , Sagi Dov
Published: January 2007

Experiments are described in which observers attempted to perform concurrently two separate visual tasks. Two types of tasks were used: the identification of a T-shaped or L-shaped letter target, and the detection or localization of a texture element of unique orientation (texture target) within a dense texture. Combining these tasks to form various task pairs, performance as a function of stimulus onset asynchrony (SOA) was established separately for each task in a pair. In addition, performance was measured when each task was carried out by itself. When paired, two identification tasks (T or L) on (two) letter targets required a significantly larger SOA than either identification task by itself. This outcome suggests the involvement of serial performance and competition for a limited resource, confirming that letter identification requires attentive fixation. However, when the identification of a central letter target was paired with the localization (upper or lower hemifield) of an eccentric texture target, performance in the pair was comparable to performance of each task by itself. This suggests parallel performance and a lack of conflict over resources. The outcome was similar when the identification of an eccentric letter target was paired with the detection (present or absent) of an eccentric texture target. These results are consistent with the possibility that localization and detection of a textural singularity do not require attentive fixation.
The Detectability of Geometric Structure in Rapidly Changing Optical Patterns
Authors: Lappin Joseph S , Norman J Farley , Mowafy Lyn
Published: January 2007

Human vision is sensitive to the coherent structure and motion of simple dot patterns undergoing rapid random transformations, even when the component dots are widely separated spatially. A study is reported in which visual sensitivity to translations, rotations, expansions, pure shear, and additive combinations of these transformations was investigated. Observers discriminated between coherent (correlated) movements, in which all the component dots moved simultaneously in corresponding directions and distances, and incoherent (uncorrelated) movements, in which the movements of individual dots were statistically independent.

In experiment 1 the accuracy of coherence discrimination was found to be similar for all four of the basic transformations and to increase linearly with the distance of the movements. The discriminability of coherent versus incoherent motion was also found to be similar to the detectability of any motion, suggesting that concurrent movements of individual dots are visually interrelated. In experiments 2 and 3 the visual independence of these four groups of transformations was tested by comparing the accuracy of coherence discrimination of each of the transformations presented alone with that when added to background motions produced by each of the four transformations. Coherence discriminations were less accurate when the target transformation was added to another background transformation, indicating that these transformations are not visually independent. Rotations and expansions, however, were visually independent. In experiment 3 qualitatively similar effects for patterns of several different sizes and dot densities were found. In general, an impressive visual sensitivity to globally coherent structure and motion under several different geometric transformations was observed in these experiments. A basic theoretical issue concerns the local visual mechanisms underlying this sensitivity.
Some Observations on the Perception of Marroquin Patterns
Authors: Earle David C
Published: January 2007

Demonstrations are presented to show that the perception of structure in Marroquin patterns is disrupted if the dots comprising the pattern have opposite contrast polarity, and also if the dots comprising the pattern are separated in stereoscopic depth. It is also demonstrated that the perception of structure in a Marroquin pattern is made possible if the pattern is separated in stereoscopic depth from ‘noise’ dots, where the pattern structure cannot be perceived in either half of the unfused stereogram. In these respects the perception of Marroquin patterns is similar to the perception of Glass patterns. These findings are thus consistent with the proposal that the perception both of Marroquin and of Glass patterns is based on the construction of virtual lines.
The Apparent Shape of Afterimages in the Ames Room
Authors: Broerse Jack , Ashton Roderick , Shaw Craig
Published: January 2007

When observers project afterimages of circular patterns onto a surface slanting away from them the images are reported as being oval in shape. In this paper it is reported that this does not occur when similar afterimages are projected onto the slanting rear wall of an Ames room. Instead of appearing as ovals, the afterimages remain circular. It appears as though the actually-slanted rear wall of the room not only looks as if it is normal to the line of vision, but also that it functions as if it was in such an orientation as far as a projection surface for afterimages is concerned. While these results are consistent with Emmert's law and with traditional accounts of shape and size constancy, they raise once again the age-old issue of whether the ‘image on the retina’ constitutes an object of perception that can be described in terms of its shape or size.
Neon Flank and Illusory Contour: Interaction between the Two Processes Leads to Color Filling-in
Authors: Takeichi Hiroshige , Shimojo Shinsuke , Watanabe Takeo
Published: January 2007

Two aspects of neon color spreading, local color spreading (neon flank) and illusory contour, were investigated by dichoptic viewing. Neon flank was not observed under appropriate dichoptic stimulation, suggesting that input to the process for local color spreading is based on monocular configuration. However, illusory contours were formed according to the interocularly combined configuration rather than according to each monocular configuration, suggesting that input to the process responsible for illusory contours should be ocularly-nonselective and binocular, rather than monocular. The possibilities of artifacts such as those arising from interocular rivalry were appropriately eliminated, and thus, it is tentatively concluded that the process underlying local color spreading is monocularly driven, whereas the process underlying illusory contours is binocularly driven. Furthermore, a new demonstration is presented that indicates that interocularly-induced illusory contours ‘capture’ and extend the monocularly-induced local color spreading, resulting in global color spreading (neon color spreading). These results support our hypotheses that neon color spreading involves two separable processes in the early visual processing, the feature detection process (for local color spreading) and the illusory contour process, and that these two processes interact with each other at later stages of cortical processing. The relation of local color spreading and illusory contours to surface separation is also discussed.
Curvature is a Basic Feature for Visual Search Tasks
Authors: Wolfe Jeremy M , Yee Alice , Friedman-Hill Stacia R
Published: January 2007

A curved target can be found efficiently among straight distractors in a visual search task. This could reflect the status of curvature as a basic feature for visual search. Alternatively, curvature could be detected as a locus of high variation in orientation. In a series of experiments it is shown that efficient search for curvature is possible even if local variation in orientation is eliminated as a cue. This suggests that curvature is part of the set of basic features for visual search and that this set is derived relatively late in the course of visual processing.
The Reversed Müller-Lyer Illusion and Figure—Ground Organization Theory
Authors: Taya Raiten , Ohashi Yasuhiro
Published: January 2007

When the shaft is shortened and reaches neither of the vertices of the two pairs of wings, a reversed Müller-Lyer illusion is observed: a shaft between inward-pointing wings appears to be longer than a shaft between the outward-pointing wings. In this paper it is examined whether this illusion can be explained in terms of figure—ground organization. A circle was used as the focal area, instead of a shaft or a pair of dots, so that the figure—ground character could be seen more definitely in this focal area.

The apparent size of the focal circle was measured under different conditions with three variables (enclosure, wings direction, and depth). The focal circle appeared to be largest in the condition where the circle should appear most readily as a hole, ie in the single, wings-in, space condition. The circle appeared to be smallest in the condition where the circle should appear most readily as a disc, ie in the separate, wings-out, object condition. This is consistent with an explanation of the usual, as well as the reversed, Müller-Lyer illusion in terms of figure—ground organization theory.
Changes in Infants' Ability to Switch Visual Attention in the First Three Months of Life
Authors: Atkinson Janette , Hood Bruce , Wattam-Bell John , Braddick Oliver
Published: January 2007

The abilities of 1-month-old and 3-month-old infants to shift their gaze from a central target to a peripheral target were compared in four experiments. In experiment 1 targets matched in mean luminance to the background were presented to infants in the periphery at varying levels of contrast. The contrast thresholds for target detection were found to be significantly different for 1-month-olds compared with 3-month-olds. With targets set close to these contrast thresholds, correct refixations and the latency for shifting attention were examined in experiment 2. Two conditions were used: a peripheral target was presented against a homogeneous background (noncompetition); and in the second condition, the patterned target appeared at one of two lighter peripheral windows set against a darker background (competition). Although there was no difference between the two age groups in the latency for shifting visual attention, 1-month-olds were found to make more directional errors in the competition condition. The competition effect of two potential targets on latencies was examined in experiment 3. In the competition condition, two identical peripheral patterned targets were presented to the infants. The 3-month-olds refixated more quickly to one of the double targets in the competition condition than to a single peripheral target, whereas 1-month-olds were slowed down by a double target display. Finally, in experiment 4 the ability of the infants to process and disengage from a central stimulus and to refixate towards a similar peripheral target was examined. This type of competition disrupted both the direction of the first eye movement and the latency to shift attention in both age groups. However, the effect was significantly greater for the 1-month-olds. Taken together, the results of these experiments demonstrate the greater disruption of fixation-shift behaviour in 1-month-olds compared with 3-month-olds when competing visual stimuli are used. This developmental change is explained in terms of maturation of executive cortical orienting systems over the first months of life.
Action Categories and the Perception of Biological Motion
Authors: Dittrich Winand H
Published: January 2007

Johansson filmed walkers and runners in a dark room with lights attached to their main joints and demonstrated that such moving light spots were perceived as human movements. To extend this finding the detection and recognition of Johansson displays of different kinds of movements under three light-spot conditions were studied to determine how human actions are perceived on the basis of biological-motion information. Locomotory, instrumental, and social actions were presented in each condition, namely in normal Johansson (light attached to joints), inter-joint (light attached between joints), and upside-down Johansson. Subjects' verbal responses and recognition times were measured. Locomotory actions were recognised better and faster than social and instrumental actions. Furthermore, biological motions were recognised much better and faster when the light-spot displays were presented in the normal orientation rather than upside down. Recognition rate was only slightly impaired under the inter-joint condition. It is argued that the perceptual analysis of actions and movements starts primarily on an intermediate level of action coding and comprises more than just the similarity of movement patterns or simple structures. Additionally, coding of dynamic phase relations and semantic coding take place at very early stages of the processing of biological motion. Implications of these results for computer vision, perceptual models, and mental representations are discussed.
Comparison of Nine Methods of Indicating the Direction to Objects: Data from Blind Adults
Authors: Haber Lyn , Haber Ralph Norman , Penningroth Suzanna , Novak Kevin , Radgowski Hilary
Published: January 2007

Nine methods of indicating the direction to object locations were tested on twenty blind adult subjects. The task was to indicate the location of active auditory targets distributed in a semicircle with a 1.7 m radius around the subject. Target location, practice, and feedback were systematically varied for each method. The greatest accuracy and lowest variability were found for pointing methods that used body parts (directing the nose at the target, facing it with the chest, and pointing with the index finger) and extensions of body parts (pointing with a hand-held cane or with a short stick). Two less accurate methods involved rotating a dial. The least accurate methods involved drawing and a verbal description in terms of clockface labels. Method interacted significantly with target location, and with individual differences. In general, the body-part and extension method were affected less than other methods by target location and individual differences. The findings suggest that a pointing response that uses a body part or an extension of a body part is the best choice for experimental or diagnostic measurement of object location by blind subjects. Differences between the results of this study of blind subjects and auditory localization accuracy in sighted subjects are discussed, and the implications for spatial processing in the blind are considered.
Is a Perceived Shape Based on its Retinal Image?
Authors: Rock Irvin , Linnett Christopher M
Published: January 2007

Although the processing of phenomenal shape might be supposed to begin at an early stage, with the shape of the retinal image of an object, it is possible that it does not begin until a later stage at which the locations of the parts of the object have been perceived. Such perceived locations are based on a compensation or constancy mechanism that takes account of eye position. Ordinarily these two possible bases of shape perception—retinal image and perceived location—are confounded. To separate them the parts of a shape were presented sequentially, during which time the eyes were in motion. The eye movement did not alter phenomenal locations of the parts vis-à-vis one another but did yield an entirely different composite retinal image of the parts. Another method employed was to change the location of each sequentially presented part with respect to a displacing frame of reference. By and large the results indicate that the composite shape perceived is based on the perceived location of the parts of the object with respect to one another, rather than on the composite retinal image.
Sex Discrimination: How Do We Tell the Difference between Male and Female Faces?
Authors: Bruce Vicki , Burton A Mike , Hanna Elias , Healey Pat , Mason Oli , Coombes Anne , Fright Rick , Linney Alf
Published: January 2007

People are remarkably accurate (approaching ceiling) at deciding whether faces are male or female, even when cues from hairstyle, makeup, and facial hair are minimised. Experiments designed to explore the perceptual basis of our ability to categorise the sex of faces are reported. Subjects were considerably less accurate when asked to judge the sex of three-dimensional (3-D) representations of faces obtained by laser-scanning, compared with a condition where photographs were taken with hair concealed and eyes closed. This suggests that cues from features such as eyebrows, and skin texture, play an important role in decisionmaking. Performance with the laser-scanned heads remained quite high with 3/4-view faces, where the 3-D shape of the face should be easiest to see, suggesting that the 3-D structure of the face is a further source of information contributing to the classification of its sex. Performance at judging the sex from photographs (with hair concealed) was disrupted if the photographs were inverted, which implies that the superficial cues contributing to the decision are not processed in a purely ‘local’ way. Performance was also disrupted if the faces were shown in photographic negatives, which is consistent with the use of 3-D information, since negation probably operates by disrupting the computation of shape from shading. In 3-D, the ‘average’ male face differs from the ‘average’ female face by having a more protuberant nose/brow and more prominent chin/jaw. The effects of manipulating the shapes of the noses and chins of the laser-scanned heads were assessed and significant effects of such manipulations on the apparent masculinity or femininity of the heads were revealed. It appears that our ability to make this most basic of facial categorisations may be multiply determined by a combination of 2-D, 3-D, and textural cues and their interrelationships.
Voluntary and Stimulus-Induced Attention Detected as Motion Sensation
Authors: Hikosaka Okihide , Miyauchi Satoru , Shimojo Shinsuke
Published: January 2007

Attention may be drawn passively to a visually salient object. We may also actively direct attention to an object of interest. Do the two kinds of attention, passive and active, interact and jointly influence visual information processing at some neural level? What happens if the passive and active attentions come into conflict? These questions were addressed with the aid of a novel psychophysical technique which reveals an attentional gradient as a sensation of motion in a line which is presented instantaneously. The subjects were asked to direct attention with voluntary effort: to the side opposite to a stimulus change, to an object with a predetermined colour, and to an object moving smoothly. In every case the same motion sensation was induced in the line from the attended side to the unattended side. This voluntary attention, however, can easily and quickly be distracted by a change in the periphery, though it can be regained within a period of 200 to 500 ms. The results suggest that the line motion can be induced in voluntary (top-down) as well as stimulus-driven (bottom-up) situations, thus indicating the truly attentional nature of the effect, rather than it being some kind of retinotopic sensory artifact or response bias. The results also suggest that these two kinds of attention have facilitatory effects acting together on a relatively early stage of visual information processing.
Apparent Relative Size and Depth of Moving Objects
Authors: Kaneko Hirohiko , Uchikawa Keiji
Published: January 2007

The effects of the relative velocities of moving objects on their apparent relative size and depth were investigated with the aid of square patterns generated on a CRT display by a microcomputer. The observer matched the apparent sizes of squares, arranged in two or more rows that moved with different velocities, and made judgments of the apparent relative depth of the rows. In many conditions, squares moving more slowly were perceived as larger in size than those moving faster, regardless of the kind of depth responses, but in some conditions which contained strong depth cues the size responses seemed to be affected by perceived depth. The size-change effect of moving objects is discussed from the viewpoint of size–depth relationship.
Parallelism and the Perception of Illusory Contours
Authors: Albert Marc K
Published: January 2007

The role of symmetry in the perception of illusory contours has been a subject of controversy ever since Kanizsa proposed his theory of illusory contours based on Gestalt principles. Today it is widely agreed that illusory contours do not necessarily occur more readily with inducers that can be ‘amodally’ completed to symmetrical objects than with inducers that cannot. But the question of whether symmetrical inducers produce weaker illusory contours than do unsymmetrical ones is still controversial.

A novel determinant of illusory contour strength, parallelism, is proposed. Experiments are reported which indicate that illusory contours induced by ‘blobs’ which have boundaries that are nearby and parallel to the illusory contour are weaker than illusory contours induced by blobs that do not have this property. It is suggested that the display that has been most widely used by researchers to support their claims for a weakening of illusory contours with symmetrical inducers is weak primarily because of parallelism.
Discrimination of the Shape of the Masked Inducing Figure Precedes Perception of the Illusory Triangle
Authors: Muise J Gerard , LeBlanc Renaud S , Blanchard Louis C , de Warnaffe Alain
Published: January 2007

Using the Kanizsa triangle in a free-inspection paradigm, Gellatly has shown that subjects report seeing an illusory triangle while apparently not phenomenally aware of the inducing areas. It is argued that Gellatly's procedure may induce response processes which camouflage early sensory processes.

By forcing subjects to choose between two response alternatives, it was shown that when they could just perceive the illusory triangle, they could also correctly discriminate the shape of the inducing elements. Under the free-inspection procedure, the duration threshold for seeing the illusory triangle was about 9 ms while the threshold for discriminating the shape of the inducing elements was about 2 ms.

A static representation of the dynamic procedure used by Gellatly has been derived, which shows a novel effect of contour completion across boundaries resulting in a ghostly white triangle.
Visual Alchemy: Stereoscopic Adaptation Produces Kinetic Depth from Random Noise
Authors: Nawrot Mark , Blake Randolph
Published: January 2007

Observers perceive incoherent motion and no hint of depth when viewing stochastic motion, in which stimulus elements move in all possible directions. As earlier work has shown, depth can be specified by introducing a brief interocular delay between the presentation of corresponding animation frames of this ‘noise’ to the left and right eyes. A study is reported in which observers were adapted to a stereoscopic display consisting of coherent planes of motion at different depths. This stereoscopic adaptation caused incoherent depthless motion to take on the qualities of structure and depth, and it could nullify the depth induced by interocular delay. The findings are interpreted within the context of a neural model consisting of units selectively responsive to different directions of motion at different planes of depth.
Obliquity Integration: Variations on a Theme of Delbœuf
Authors: Vicario Giovanni B , Vidotto Giulio , Zambianchi Elena
Published: January 2007

An optical—geometrical illusion, described by Delbœuf and not familiar to specialists, is investigated. The results of two experiments show that the divergence between a bar filled with parallel slanting lines and a line drawn above it is clearly related to this angle of the lines which fill the bar. The illusion is already present when this angle is 10°, reaches its maximum at 20°, decreases at 30°, and almost disappears at 40°. These results are similar to those found for the tilt illusion, are slightly different from those found for the rod-and-frame illusion, and differ greatly from those found for the Zöllner illusion. The other variables considered—the distance between the slanting lines filling up the bar, the distance between the upper line and the bar, and the width of the bar—do not influence the illusion as much. Since either the line appears as diverging from the bar, or the bar seems inclined in relation to the line, the illusion should be considered a complex one. The small oblique lines inside the bar induce obliquity in the opposite sense in the display, but which of the elements is seen as diverging from the other depends on which of the two is established as the frame of reference.