bluuebunny/crossref_metadata_2025 huggingface dataset:
Shock-Tube Studies in Exothermic Systems
Authors: Strehlow Roger A.
Published: March 2004

Three types of behavior are possible: (1) planar incident shocks, with reaction, may be produced and studied; (2) detonation may be initiated by longitudinal nonsteady processes; or (3) distinct transverse instabilities may appear. Case (2) occurs when the incident shock velocity is adjusted to be less than the Chapman-Jouguet velocity. Here, if a reaction occurs, it leads to nonsteady processes which may initiate detonation. Examples are presented to discuss the inherent limitations of this case, and to show that reaction kinetic processes may be studied even though nonsteady flow processes are occurring. Cases (1) and (3) occur when the shock is adjusted to be above the Chapman-Jouguet velocity, usually in diluted mixtures. Case (3) instabilities (which negate the quantitative study of reaction kinetics) are always observed when the reaction zone length becomes of the order of, or less than, the tube diameter. Case (1) behavior is observed for longer reaction zone length, even though there are also recorded cases of unstable flow under these circumstances. An acoustic theory of transverse waves is used to discuss the possible occurrence of case (1) and case (3) flows.
The Role of Facial Colour and Luminance in Visual and Audiovisual Speech Perception
Authors: McCotter Maxine V , Jordan Timothy R
Published: March 2004

We conducted four experiments to investigate the role of colour and luminance information in visual and audiovisual speech perception. In experiments la (stimuli presented in quiet conditions) and 1b (stimuli presented in auditory noise), face display types comprised naturalistic colour (NC), grey-scale (GS), and luminance inverted (LI) faces. In experiments 2a (quiet) and 2b (noise), face display types comprised NC, colour inverted (CI), LI, and colour and luminance inverted (CLI) faces. Six syllables and twenty-two words were used to produce auditory and visual speech stimuli. Auditory and visual signals were combined to produce congruent and incongruent audiovisual speech stimuli. Experiments 1a and 1b showed that perception of visual speech, and its influence on identifying the auditory components of congruent and incongruent audiovisual speech, was less for LI than for either NC or GS faces, which produced identical results. Experiments 2a and 2b showed that perception of visual speech, and influences on perception of incongruent auditory speech, was less for LI and CLI faces than for NC and CI faces (which produced identical patterns of performance). Our findings for NC and CI faces suggest that colour is not critical for perception of visual and audiovisual speech. The effect of luminance inversion on performance accuracy was relatively small (5%), which suggests that the luminance information preserved in LI faces is important for the processing of visual and audiovisual speech.
Recognising Facial Expression from Spatially and Temporally Modified Movements
Authors: Pollick Frank E , Hill Harold , Calder Andrew , Paterson Helena
Published: March 2004

We examined how the recognition of facial emotion was influenced by manipulation of both spatial and temporal properties of 3-D point-light displays of facial motion. We started with the measurement of 3-D position of multiple locations on the face during posed expressions of anger, happiness, sadness, and surprise, and then manipulated the spatial and temporal properties of the measurements to obtain new versions of the movements. In two experiments, we examined recognition of these original and modified facial expressions: in experiment 1, we manipulated the spatial properties of the facial movement, and in experiment 2 we manipulated the temporal properties. The results of experiment 1 showed that exaggeration of facial expressions relative to a fixed neutral expression resulted in enhanced ratings of the intensity of that emotion. The results of experiment 2 showed that changing the duration of an expression had a small effect on ratings of emotional intensity, with a trend for expressions with shorter durations to have lower ratings of intensity. The results are discussed within the context of theories of encoding as related to caricature and emotion.
Do Expertise and the Degree of Perception—Action Coupling Affect Natural Anticipatory Performance?
Authors: Farrow Damian , Abernethy Bruce
Published: March 2004

Two experiments using a temporal occlusion paradigm (the first with expert and novice participants and the second with participants of intermediate skill) were conducted to examine the capability of tennis players to predict the direction of an opponent's service in situ. In both experiments two different response conditions, reflecting differing degrees of perception–action coupling, were employed. In a coupled condition players were required to make a movement-based response identical to that which they would use to hit a return of service in a game situation, whereas in an uncoupled condition a verbal prediction of service direction was required. Experiment 1 provided clear evidence of superior prediction accuracy under the coupled response condition when ball flight was available, plus some limited evidence to suggest that superior prediction accuracy under uncoupled response conditions might hold true if only advance (pre-contact) information was available. Experiment 2 showed the former finding to be a robust one, but was unable to reveal any support for the latter. Experiment 1 also revealed that expert superiority is more apparent for predictions made under natural (coupled) than uncoupled response-mode conditions. Collectively, these findings suggest that different perceptual processes may be in operation in anticipatory tasks which depend on skill level, the type of information presented, and degree of perception–action coupling inherent in the task requirements.
Spatial Variations of Visual—Auditory Fusion Areas
Authors: Godfroy Martine , Roumes C , Dauchy P
Published: March 2004

The tolerance to spatial disparity between two synchronous visual and auditory components of a bimodal stimulus has been investigated in order to assess their respective contributions to perceptual fusion. The visual and auditory systems each have specific information-processing mechanisms, and provide different cues for scene perception, with the respective dominance of space for vision and of time for hearing. A broadband noise burst and a spot of light, 500 ms in duration, have been simultaneously presented to participants who had to judge whether these cues referred to a single spatial event. We examined the influence of (i) the range and the direction of spatial disparity between the visual and auditory components of a stimulation and (ii) the eccentricity of the bimodal stimulus in the observer's perceptual field. Size and shape properties of visual–auditory fusion areas have been determined in two dimensions. The greater the eccentricity within the perceptual field, the greater the dimension of these areas; however, this increase in size also depends on whether the direction of the disparity is vertical or horizontal. Furthermore, the relative location of visual and auditory signals significantly modifies the perception of unity in the vertical plane. The shape of the fusion areas, their variation in the field, and the perceptual result associated with the relative location of the visual and auditory components of the stimulus, concur towards a strong contribution of audition to visual–auditory fusion. The spatial ambiguity of the localisation capabilities of the auditory system may play a more essential role than accurate visual resolution in determining fusion.
Recognising the Usual Orientation of One's Own Face: The Role of Asymmetrically Located Details
Authors: Brédart Serge
Published: March 2004

Our ability to recognise the usual horizontal orientation of our own face (mirror orientation) as compared with another very familiar face (normal orientation) was examined in experiment 1. Participants did not use the same kind of information in determining the orientation of their own face as in determining the orientation of the other familiar face. The proportion of participants who reported having based their judgment on the location of an asymmetric feature (eg a mole) was higher when determining the orientation of their own face than when determining that of the other familiar face. In experiment 2, participants were presented with pairs of manipulated images of their own face and of another familiar face showing conflicting asymmetric features and configural information. Each pair consisted of one picture showing asymmetric features of a given face in a mirror-reversed position, while the facial configuration was left unchanged; and one picture in which the location of the asymmetric features was left unchanged, while the facial configuration was mirror-reversed. As expected from the hypothesis that asymmetric local features are more frequently used for the judgment of one's own face, participants chose the picture showing mirror-reversed asymmetric features when determining the usual orientation of their own face significantly more often than they chose the picture showing normally oriented asymmetric features when determining the orientation of the other face. These results are explained in terms of competing forward and mirror-reversed representations of one's own face.
Effects of Partial Occlusion on Perceived Surface Segregation
Authors: Masin Sergio Cesare
Published: March 2004

Tests are reported of the possibility that local information from contour junctions and from corners of intersecting surfaces is used for perceived surface segregation. Stimuli were two intersecting squares with small disks occluding different parts of the squares. The perceived segregation of the squares from one another decreased as the amount of occlusion of parts of the squares increased. This segregation was less when disks occluded parts of contours than when disks occluded parts entirely inside the squares. Occlusion of parts of contours reduced segregation independently of whether contour junctions or corners were visible or invisible, both where the intersecting surfaces were transparent squares and when they were outlined squares. The present findings show that local information from contour junctions or from corners is not used for surface segregation, and confirm that this segregation is determined by global processes of grouping of areas and of extrapolation of contours.
Motion, Flash, and Flicker: A Unified Spatiotemporal Model of Perceived Edge Sharpening
Authors: Hammett Stephen T , Georgeson Mark A , Barbieri-Hesse Gillian S
Published: March 2004

Blurred edges appear sharper in motion than when they are stationary. We proposed a model of this motion sharpening that invokes a local, nonlinear contrast transducer function (Hammett et al, 1998 Vision Research38 2099–2108). Response saturation in the transducer compresses or ‘clips’ the input spatial waveform, rendering the edges as sharper. To explain the increasing distortion of drifting edges at higher speeds, the degree of nonlinearity must increase with speed or temporal frequency. A dynamic contrast gain control before the transducer can account for both the speed dependence and approximate contrast invariance of motION sharpening (Hammett et al, 2003 Vision Research in press). We show here that this model also predicts perceived sharpening of briefly flashed and flickering edges, and we show that the model can account fairly well for experimental data from all three modes of presentation (motion, flash, and flicker). At moderate durations and lower temporal frequencies the gain control attenuates the input signal, thus protecting it from later compression by the transducer. The gain control is somewhat sluggish, and so it suffers both a slow onset, and loss of power at high temporal frequencies. Consequently, brief presentations and high temporal frequencies of drift and flicker are less protected from distortion, and show greater perceptual sharpening.
Boundary Completion in Illusory Contours: Interpolation or Extrapolation?
Authors: Shipley Thomas F , Kellman Philip J
Published: March 2004

Most computational and neural-style models of contour completion (ie illusory and occluded contours) are based on interpolation: the filling in of an edge between two visible edges. The results of three experiments suggest an alternative conception, that units are formed as a result of extrapolation from visible edges. In three experiments, subjects reported illusory contours between standard illusory-contour inducing elements and forms that do not, by themselves, induce illusory contours. We suggest that these forms are not a special case of inducing elements but that they represent a different class— receiving elements. Receiving elements are forms that can receive an illusory contour but cannot generate one, and they can alter contour formation. In experiment 1, receiving elements increased the judged clarity of illusory contours. In experiment 2, illusory edges were seen to connect to corners, line ends, and even the edges of circles. Boundary formation in motion displays also appears to be based on extrapolation. In experiment 3, subjects reported that small moving dots altered the formation of spatiotemporally defined boundaries. Implications for higher-order operator and network models of boundary formation are discussed.
Prior Knowledge about Display Inversion in Biological Motion Perception
Authors: Pavlova Marina , Sokolov Alexander
Published: March 2004

Display inversion severely impedes veridical perception of point-light biological motion (Pavlova and Sokolov, 2000 Perception & Psychophysics62 889–899; Sumi, 1984 Perception13 283–286). Here, by using a spontaneous-recognition paradigm, we ask whether prior information about display orientation improves biological motion perception. Participants were shown a set of 180° inverted point-light stimuli depicting a human walker and quadrupeds (dogs). In experiment 1, one group of observers was not aware of the orientation of stimuli, whereas the other group was told beforehand that stimuli will be presented upside down. In experiment 2, independent groups of participants informed about stimulus orientation saw the same set of stimuli, in each of which either a moving or a static background line was inserted. The findings indicate that information about display inversion is insufficient for reliable recognition of inverted point-light biological motion. Instead, prior information facilitates display recognition only when it is complemented by additional contextual elements. It appears that visual impressions from inverted point-light stimuli remain impenetrable with respect to one's knowledge about display orientation. The origins of orientation specificity in biological motion perception are discussed in relation to the recent neuroimaging data obtained with point-light stimuli and fragmented Mooney faces.
Velocity Dependence of the Interocular Transfer of Dynamic Motion Aftereffects
Authors: Tao Ran , Lankheet Martin J M , van de Grind Wim A , van Wezel Richard J A
Published: March 2004

It is well established that motion aftereffects (MAEs) can show interocular transfer (IOT); that is, motion adaptation in one eye can give a MAE in the other eye. Different quantification methods and different test stimuli have been shown to give different IOT magnitudes, varying from no to almost full IOT. In this study, we examine to what extent IOT of the dynamic MAE (dMAE), that is the MAE seen with a dynamic noise test pattern, varies with velocity of the adaptation stimulus. We measured strength of dMAE by a nulling method. The aftereffect induced by adaptation to a moving random-pixel array was compensated (nulled), during a brief dynamic test period, by the same kind of motion stimulus of variable luminance signal-to-noise ratio (LSNR). The LSNR nulling value was determined in a Quest-staircase procedure. We found that velocity has a strong effect on the magnitude of IOT for the dMAE. For increasing speeds from 1.5 deg s−1 to 24 deg s−1 average IOT values increased about linearly from 18% to 63% or from 32% to 83%, depending on IOT definition. The finding that dMAEs transfer to an increasing extent as speed increases, suggests that binocular cells play a more dominant role at higher speeds.
The Effects of Different Aperture-Viewing Conditions on the Recognition of Novel Objects
Authors: Króliczak Grzegorz , Goodale Melvyn A , Humphrey G Keith
Published: March 2004

The process of learning the structure of novel objects involves the selective use of information available in the distal stimulus. By allowing participants to explore the object within a limited field of view, we were able to examine more rigorously what regions of the object are actually selected in the learning process. Participants explored objects either by moving a circular aperture over a stationary novel object (the aperture-movement condition), or by moving the object behind a stationary aperture (the object-movement condition). Given the differences in how the spatial layout of object parts is revealed in the two study conditions, we expected that exploration would be more systematic in the aperture-movement condition than it would be in the object-movement condition, and would lead to better object recognition. We show evidence that in the aperture-movement condition exploration patterns were more related to the structure of the object and, as a consequence, the aperture-movement condition resulted in more accurate recognition in a later old–new discrimination test.
Monocular Discs in the Occlusion Zones of Binocular Surfaces Do Not Have Quantitative Depth—A Comparison with Panum's Limiting Case
Authors: Gillam Barbara , Cook Michael , Blackburn Shane
Published: March 2004

Da Vinci stereopsis is defined as apparent depth seen in a monocular object laterally adjacent to a binocular surface in a position consistent with its occlusion by the other eye. It is widely regarded as a new form of quantitative stereopsis because the depth seen is quantitatively related to the lateral separation of the monocular element and the binocular surface (Nakayama and Shimojo 1990 Vision Research30 1811–1825). This can be predicted on the basis that the more separated the monocular element is from the surface the greater its minimum depth behind the surface would have to be to account for its monocular occlusion. Supporting evidence, however, has used narrow bars as the monocular elements, raising the possibility that quantitative depth as a function of separation could be attributable to Panum's limiting case (double fusion) rather than to a new form of stereopsis. We compared the depth performance of monocular objects fusible with the edge of the surface in the contralateral eye (lines) and non-fusible objects (disks) and found that, although the fusible objects showed highly quantitative depth, the disks did not, appearing behind the surface to the same degree at all separations from it. These findings indicate that, although there is a crude sense of depth for discrete monocular objects placed in a valid position for uniocular occlusion, depth is not quantitative. They also indicate that Panum's limiting case is not, as has sometimes been claimed, itself a case of da Vinci stereopsis since fusibility is a critical factor for seeing quantitative depth in discrete monocular objects relative to a binocular surface.
Dodge-Ing the Issue: Dodge, Javal, Hering, and the Measurement of Saccades in Eye-Movement Research
Authors: Wade Nicholas J , Tatler Benjamin W , Heller Dieter
Published: March 2004

Dodge, in 1916, suggested that the French term ‘saccade’ should be used for describing the rapid movements of the eyes that occur while reading. Previously he had referred to these as type I movements. Javal had used the term ‘saccade’ in 1879, when describing experiments conducted in his laboratory by Lamare. Accordingly, Javal has been rightly credited with assigning the term to rapid eye movements. In English these rapid rotations had been called jerks, and they had been observed and measured before Lamare's studies of reading. Rapid sweeps of the eyes occur as one phase of nystagmus; they were observed by Wells in 1792 who used an afterimage technique, and they were illustrated by Crum Brown in 1878. Afterimages were used in nineteenth-century research on eye movements and eye position; they were also employed by Hering in 1879, to ascertain how the eyes moved during reading. In the previous year, Javal had employed afterimages in his investigations of reading, but this was to demonstrate that the eyes moved horizontally rather than vertically. Hering's and Lamare's auditory method established the discontinuous nature of eye movements during reading, and the photographic methods introduced by Dodge and others in the early twentieth century enabled their characteristics to be determined with greater accuracy.
Configuration-Specific Attentional Modulation of Flanker – Target Lateral Interactions
Authors: Freeman Elliot , Sagi Dov , Driver Jon
Published: March 2004

Elements of a contour are often easier to detect when they possess collinearity, with their local orientations matching the global orientation of the contour. We recently reported attentional modulation of such lateral interactions between a central near-threshold target Gabor patch and flanking high-contrast patches (Freeman et al, 2001 Nature Neuroscience4 1032–1036). Here, we examined whether such attentional effects reflect specific modulation of mechanisms sensitive to collinear configurations, or instead more general modulation of sensitivity to either the global or local orientation-components of the stimulus. Thresholds for detecting a central Gabor target were measured, while observers also judged the Vernier alignment between one pair of flankers and ignored a second flanker pair (when present). Target contrast-thresholds were facilitated only when attending collinear flankers. There was no facilitation when attending flankers that shared only local orientation with the target, or flankers that fell on a global axis aligned with target orientation but having orthogonal local orientation. Ignored collinear flankers had no effect on target thresholds. These results demonstrate strong and specific attentional modulation of contour-integration mechanisms in early vision sensitive to collinear configurations.
The Role of Pictorial Convention in Haptic Picture Perception
Authors: Thompson Leanne J , Chronicle Edward P , Collins Alan F
Published: March 2004

An investigation of tactile picture perception is reported. Blindfolded sighted subjects explored either ‘line drawings’ or ‘textured’ tactile pictures produced on Zytex swell paper. All pictures were ‘two-dimensional’, that is they depicted only one object face and so did not represent a third dimension. Both picture sets represented the same objects. Results revealed that the textured pictures, in which solid surfaces of depicted objects were uniformly textured, were recognised more often than tactile line drawings, in which surfaces of objects were simply bounded by lines. There were no significant correlations between imagery ability (visual, cutaneous, or kinaesthetic) and picture recognition success. Texture may be a form of ‘uniform connectedness’ (Palmer and Rock 1994 Psychonomic Bulletin & Review1 29–55) or ‘common region’ (Palmer 1992 Cognitive Psychology24 436–447), highlighting the global characteristics of stimuli. We argue that textured pictures may encourage the haptic system to take a more globally oriented approach to tactile picture perception, benefiting recognition.
Meet The Simpsons: Top—down Effects in Face Learning
Authors: Bonner Lesley , Burton A Mike , Jenkins Rob , McNeill Allan , Bruce Vicki
Published: March 2004

We examined whether prior knowledge of a person affects the visual processes involved in learning a face. In two experiments, subjects were taught to associate human faces with characters they knew (from the TV show The Simpsons) or characters they did not (novel names). In each experiment, knowledge of the character predicted performance in a recognition memory test, relying only on old/new confidence ratings. In experiment 1, we established the technique and showed that there is a face-learning advantage for known people, even when face items are counterbalanced for familiarity across the experiment. In experiment 2 we replicated the effect in a setting which discouraged subjects from attending more to known than unknown people, and eliminated any visual association between face stimuli and a character from The Simpsons. We conclude that prior knowledge about a person can enhance learning of a new face.
Visual Discrimination of Number without Counting
Authors: Ross John
Published: March 2004

Observers in this study judged which of two fields contained the greater number of spots. Spots had difference-of-Gaussian luminance profiles and could differ in contrast polarity or were of uniform luminance and could differ in size. Weber fractions for all observers except one varied little except when spots varied in size. It is suggested that the results of this and previous studies might be explained by the existence of neurons tuned for number.
Cross-Modal and Non-Sensory Influences on Auditory Streaming
Authors: Carlyon Robert P , Plack Christopher J , Fantini Deborah A , Cusack Rhodri
Published: March 2004

Carlyon et al (2001 Journal of Experimental Psychology: Human Perception and Performance27 115–127) have reported that the buildup of auditory streaming is reduced when attention is diverted to a competing auditory stimulus. Here, we demonstrate that a reduction in streaming can also be obtained by attention to a visual task or by the requirement to count backwards in threes. In all conditions participants heard a 13 s sequence of tones, and, during the first 10 s saw a sequence of visual stimuli containing three, four, or five targets. The tone sequence consisted of twenty repeating triplets in an ABA–ABA … order, where A and B represent tones of two different frequencies. In each sequence, three, four, or five tones were amplitude modulated. During the first 10 s of the sequence, participants either counted the number of visual targets, counted the number of (modulated) auditory targets, or counted backwards in threes from a specified number. They then made an auditory-streaming judgment about the last 3 s of the tone sequence: whether one or two streams were heard. The results showed more streaming when participants counted the auditory targets (and hence were attending to the tones throughout) than in either the ‘visual’ or ‘counting-backwards’ conditions.
Reproduction of Seen Actions: Stimulus-Selective Learning
Authors: Sekuler Robert , Siddiqui Aafia , Goyal Nikhil , Rajan Rohin
Published: March 2004

Subjects observed and reproduced abstract, irregular stimulus models generated by the steady movement of a disk across two-dimensional paths. The paths comprised 3 to 7 randomly oriented linear segments linked head-to-foot. Reproductions were expressed by moving a stylus over the surface of a graphics tablet while the disk was tracing its trajectory (concurrent reproduction), or soon after the disk had finished (delayed reproduction). For both concurrent and delayed conditions, fidelity of reproduction fell with increasing number of segments in the model. Overall quality of reproduction did not differ between the two conditions. When a few models were repeated, interspersed among non-repeated ones, performance improved but only when reproduction was delayed. This improvement was stimulus-selective, not a general improvement with practice. Two additional experiments showed that (i) memory for a seen model is well preserved for at least 6 s, with relatively modest need for rehearsal, and (ii) successful reproduction is possible with remarkably little information having been extracted from key points in the model's trajectory.
Normal Recognition of Emotion in a Prosopagnosic
Authors: Duchaine Bradley C , Parker Holly , Nakayama Ken
Published: March 2004

In the leading model of face perception, facial identity and facial expressions of emotion are recognized by separate mechanisms. In this report, we provide evidence supporting the independence of these processes by documenting an individual with severely impaired recognition of facial identity yet normal recognition of facial expressions of emotion. NM, a 40-year-old prosopagnosic, showed severely impaired performance on five of six tests of facial identity recognition. In contrast, she performed in the normal range on four different tests of emotion recognition. Because the tests of identity recognition and emotion recognition assessed her abilities in a variety of ways, these results provide solid support for models in which identity recognition and emotion recognition are performed by separate processes.
Efficient Extrapolation of the View with a Dynamic and Predictive Stimulus
Authors: Mitsumatsu Hidemichi , Yokosawa Kazuhiko
Published: March 2004

In the real-world, the retinal projection of an object changes as we move, or as a moving object passes in front of us. We have to recognise objects, despite such retinal-projection changes. Many studies have shown that the time required to identify objects after a change in the retinal projection is longer than when there is no retinal-projection change. This recognition cost is referred to as the view-dependent effect. Previous researchers have studied the view-dependent effect while disregarding the predictability of retinal-projection changes. Here, we demonstrate that there is no view-dependent effect when the predictability is introduced, in the case where participants track moving objects by head-turning or eye-movement in a virtual environment. Violation of the predictability, such as an unpredictable retinal-projection change or a movement of the first stimulus that was inconsistent with a subsequent retinal-projection change, caused a view-dependent effect. Moreover, we found that extraretinal information such as head-turning or eye-movement was unnecessary for view-independent recognition. These results indicate that humans can extrapolate to the tested view from the studied view in a view-independent way when retinal-projection change is predictable from the visual stimulus.
Perception of Surface Reflectance of 3-D Geometrical Shapes: Influence of the Lighting Mode
Authors: Khang Byung-Geun , Koenderink Jan J , Kappers Astrid M L
Published: March 2004

We examined in three experiments whether the perception of surface reflectance in 3-D geometrical shapes is influenced by the mode of lighting, the level of surface reflectance, the number of polyhedral faces, and the regularity of polyhedral shape. As stimuli, we used simulations of regular polyhedra in a 2AFC constant-stimuli procedure to measure how large variations in the reflectance needed to be for observers to be able to tell whether the whole surfaces were uniform or non-uniform. In almost all the cases observers were more successful in discriminating non-uniform polyhedra in the hemispherical diffuse lighting conditions than in the collimated lighting conditions. The different levels of reflectance had no effect on the discrimination of non-uniformity. Second, as the number of faces of the shape increased, discrimination thresholds became lower, indicating that the interpretation of reflectance variations was better when a shape had many faces. Finally, the regularity of the shape, such as the central symmetry, was not an important factor. These results suggest that the interpretation of surface reflectance is more precise when surfaces have less variance in relative strengths between the face luminance values; these surfaces were the ones obtained under hemispherical diffuse lighting.
Orientation-Selective Adaptation to Crowded Illusory Lines
Authors: Rajimehr Reza , Montaser-Kouhsari Leila , Afraz Seyed-Reza
Published: March 2004

Visual adaptation has been successfully used as a psychophysical tool for studying the functional organisation of visual awareness. It has been shown that orientation-selective adaptation to a grating pattern occurs in crowded conditions. In such conditions, simultaneous presentation of flanking distractors pushes the target stimulus out of conscious perception and severely impairs orientation discrimination in the periphery of the visual field. In the present study, orientation-selective adaptation to illusory lines induced by two line gratings abutting each other with a phase shift was examined in crowded and non-crowded conditions. To rule out the effects of lower level adaptations we used an animation paradigm in which the orientations of the two line gratings were altered repeatedly during adaptation phase without any change in the orientation of the resulting illusory line. Although performance of subjects in reporting the orientation of crowded illusory lines was at chance level, orientation-selective adaptation was preserved for crowded as well as non-crowded adapting targets. Two control experiments demonstrated that adaptation to endpoints of real lines at the location of abutting grating lines had minimal effect on the adaptation to illusory lines; and changes in the configuration of endpoints could not be responsible for better performance when adapting and test stimuli were different. We conclude that a crowding effect occurs after illusory lines have been processed in the visual stream. Since illusory lines seem to be represented at relatively early stages of visual processing (eg area V2), adaptation to crowded illusory stimuli suggests that neuronal activation in those early stages is not necessarily correlated with conscious perception.
First-Order and Second-Order Spectral ‘Motion’ Mechanisms in the Human Auditory System
Authors: Huddleston Wendy E , DeYoe Edgar A
Published: March 2004

Light energy displaced along the retinal photoreceptor array leads to a perception of visual motion. In audition, displacement of mechanical energy along the cochlear hair cell array is conceptually similar but leads to a perception of ‘movement’ in frequency space (spectral motion)—a rising or falling pitch. In vision there are other types of stimuli that also evoke a percept of motion but do not involve a displacement of energy across the photoreceptors (second-order stimuli). In this study, we used psychophysical methods to determine if such second-order stimuli also exist in audition, and if the resulting percept would rival that of first-order spectral motion. First-order auditory stimuli consisted of a frequency sweep of sixteen non-harmonic tones between 297 and 12123 Hz. Second-order stimuli consisted of the same tones, but with a random subset turned on at the beginning of a trial. During the trial, each tone in sequence randomly changed state (ON-to-OFF, or OFF-to-ON). Thus, state transitions created a ‘sweep’ having no net energy displacement correlated to the sweep direction. At relatively slow sweep speeds, subjects readily identified the sweep direction for both first-order and second-order stimuli, though accuracy decreased for second-order stimuli as the sweep speed increased. This latter characteristic is also true of some second-order visual stimuli. These results suggest a stronger parallelism between auditory and visual processing than previously appreciated.
Pulling Faces: An Investigation of the Face-Distortion Aftereffect
Authors: Watson Tamara L , Clifford Colin W G
Published: March 2004

After adaptation to a face distorted to look unnaturally thin or fat, a normal face appears distorted in the opposite direction (Webster and MacLin 1999 Psychonomic Bulletin & Review6 647–653). When the adapting face is oriented 45° from vertically upright and the test face 45° in the opposite direction, the axis of perceived distortion changes with the orientation of the face. The magnitude of this aftereffect shows a reduction of approximately 40% from that found when both adapting and test faces are tilted identically. This finding suggests that to a large degree the aftereffect is mediated not by low-level retinotopic (image-based) visual mechanisms but at a higher level of object-based processing. Aftereffects of a similar magnitude are obtained when adapting and test images are both either upright or inverted, or for an upright adapter and an inverted test; but aftereffects are smaller when the adapter is inverted and the test upright. This pattern of results suggests that the face-distortion aftereffect is mediated by object-processing mechanisms including, but not restricted to, configurational face-processing mechanisms.
“Seeing Things in My Head”: A Synesthete's Images for Music and Notes
Authors: Mills Carol Bergfeld , Boteler Edith Howell , Larcombe Glenda K
Published: March 2004

We explored synesthetic experiences (photisms) elicited by music and notes for GS, a 22-year-old female college student, who is a genuine digit synesthete (Mills et al 1999 Cognitive Neuropsychology16 181–191). After extensive interviews, we conducted five studies using synthesizer notes in different octaves and in different instrument sounds. GS described, drew, or selected her photisms from alternatives. The results were: (a) her photisms had shape, color, movement, and texture; (b) different instruments had photisms with different shapes and families of instruments had similar shapes; (c) low-pitched notes were darker and larger than high notes; (d) instrument and pitch affected each other; (e) a given note was perceived as darker after a high note than after a low note; and (f) GS's drawings of notes became more consistent with repeated trials. Theoretical observations are discussed on the basis of these results.
Sex, Beauty, and the Relative Luminance of Facial Features
Authors: Russell Richard
Published: March 2004

It has been suggested that the consistent luminance difference between the darker regions of the eyes and mouth and the lighter regions that surround them forms a pattern unique to faces. One of the more consistent uses of cosmetics to make the female face more attractive is to darken the eyes and mouth relative to the surrounding skin. The hypothesis that the size of the luminance difference between the eyes and mouth and the rest of the face affects the attractiveness of male and female faces differently was tested in four experiments in which attractiveness ratings were obtained for images of faces in which the luminance difference between the eyes and mouth and the rest of the face had been manipulated. Female faces were found to be more attractive when this luminance difference was increased than when it was decreased, and the opposite was found for male faces. An interpretation consistent with these results is that the luminance difference between the eyes and mouth and the rest of the face is naturally greater in women than men. In this case increasing or decreasing the luminance difference will make a face more feminine or masculine, respectively, and hence, more or less attractive depending on the sex of the face. Implications for the causes of cosmetics usage are discussed.
Spatial Integration in Glass Patterns
Authors: Kurki Ilmari , Laurinen Pentti , Peromaa Tarja , Saarinen Jukka
Published: March 2004

The extraction of a global orientation structure presumably has a different neural mechanism from that of the analysis of its local features. We investigated spatial integration within these two mechanisms using stimulus patterns composed of dot pairs (dipoles). The stimuli targeted local feature detection, contained no global configuration, but rather contained randomly oriented dipoles of a fixed length (the distance between the dots in a pair). For the detection of a global orientation structure, local dipole orientations were arranged in a concentric Glass pattern. Thresholds as a function of a stimulus area were determined by measuring the minimum proportion of dipoles among random-dot noise (signal-to-noise ratio) required for the detection of dipoles (features), as well as for the detection of an orientation structure. Thresholds for feature detection were significantly higher than those for the detection of the global structure—regardless of the stimulus size. Spatial integration, however, did not differ between the two tasks: the exponents of the power functions fitted to data for six observers were −0.48 ± 0.07 for random dipole orientations and −0.62 ± 0.1 for Glass patterns.
Illusory Illusions: The Significance of Fixation on the Perception of Geometrical Illusions
Authors: Fischer Burkhart , da Pos Osvaldo , Stürzel Frank
Published: March 2004

Some well-known geometrical illusions disappear when the eyes are fixating and saccades are suppressed for a period of time. This disappearance is not accompanied by fading due to stabilisation of the retinal image. Any saccade made on purpose restores the illusion immediately. The fixation time after which some illusions disappeared was measured for four illusions and four subjects each. Effects of practice have been observed after measurements were repeated on successive days. Present theories of vision cannot readily explain the effect.
Demonstrating the Acquired Familiarity of Faces by Using a Gender-Decision Task
Authors: Clutterbuck Ruth , Johnston Robert A
Published: March 2004

We report an experiment in which participants made gender judgments (male or female) to faces. There were three groups of faces: unfamiliar, familiar (celebrities), and a set which had been learned earlier by the participants during the experimental session. The principal purpose of this study was to establish an indirect measure of assessing whether faces have become familiar through learning that does not require overt recognition. Bruce and Young's (1986 British Journal of Psychology77 305–327) model of face recognition suggests face-processing tasks are independent of one another and so familiarity should have no impact on the time taken to perform gender decisions. However, recent studies have suggested that some face processes are not completely independent. A gender judgment is a simple task which would be useful in face-learning experiments. We examined whether exposure to previously novel faces facilitates a later gender decision to those faces. During a learning stage, participants viewed a set of unfamiliar faces. At test, participants were able to assign gender faster to previously familiar (famous) faces and learned faces than they were to unfamiliar faces. Therefore familiarity can influence the speed at which gender is analysed. We explain our findings with reference to the Burton et al (1990 British Journal of Psychology81 361–380) interactive activation and competition (IAC) model of face recognition and discuss how the gender judgment might be employed as a means of tracking the acquisition of familiarity in face-learning studies.
The Effect of Text Orientation, Visual Meridian, and Inter-Character Spacing on Word Identification in the Retinal Periphery
Authors: Chaparro Alex , Liao Corrina
Published: March 2004

Previous research has demonstrated that the masking effects of flankers about a target in the peripheral retina are not isotropic. Rather, regions of lateral interaction are ellipsoid in shape with the major axis oriented radially along a meridian through the fovea. This finding leads to the counterintuitive prediction that horizontal text positioned to the right of fixation might be read more slowly than similarly positioned text oriented diagonally or vertically. Similarly, vertically oriented text above fixation might be read more slowly than horizontally or diagonally oriented text above fixation. We investigated the effect of text orientation and inter-character spacing on word identification in the retinal periphery. Text was presented by rapid serial visual presentation. Words were centered 3° from fixation along four visual field meridians (VM) (right horizontal, upper-right diagonal, vertical, and upper-left diagonal). Regardless of VM identification, performance was best for horizontal text, declining slightly for orientations between +60° and −60° and declining more quickly for acute orientations. A weak effect of VM was observed for text with normal inter-character spacing. Performance was best for text centered along the horizontal meridian and declined slightly along the other VM. Finally, identification rates increased by ∼33 words min−1 with the addition of one character space between adjacent letters. The word-recognition processes are very tolerant of text orientation, exhibiting a modest decline for orientations within ±60° of horizontal regardless of VM.
Motion Induction from Biological Motion
Authors: Fujimoto Kiyoshi
Published: March 2004

A new type of motion illusion is described in which ambiguous motion becomes unidirectional on superimposition of a human figure walking on a treadmill. A point-light walker in profile was superimposed on a vertical counterphase grating backdrop. Eleven naïve observers judged the apparent direction of motion against the grating as left or right in a two-alternative forced-choice task and found that the grating appeared to drift in a direction opposite to the walking. The illusion disappeared when the point lights moved in scrambled configurations. This indicates that the illusion is caused by biological motion that provides recognition of gaits. A human figure walking backwards produced no illusion because of the difficulty in identifying the gait. This indicates that the illusion is determined by translational motion rather than form represented from biological motion.
Does Previewing One Stimulus Feature Help Conjunction Search?
Authors: Olds Elizabeth S , Fockler K Amanda
Published: March 2004

We examined the effects of previewing one aspect of a search display, in order to determine what subset of display information is most useful as a prelude to a search task. Observers were asked to indicate the presence or absence of a known target, in a conjunction search where the target was defined by the combination of colour and orientation (a yellow horizontal line presented among yellow vertical and pink horizontal distractors). In the colour preview condition of experiment 1, observers were first shown a 1 s preview of the locations and colours of the search items before the actual search set was presented. That is, search items first appeared as yellow and pink squares for 1 s, which each then turned into yellow and pink oriented lines (in the same locations) which comprised the display to be searched. In the orientation preview condition, observers were first shown a 1 s preview of the locations and orientations of the search items before the actual search display was presented. These two conditions were compared to a control condition consisting of standard conjunction search without any preview display. There was no effect of colour preview; there was a marginal effect of orientation preview, but in the opposite direction from what was expected—reaction time increased for orientation preview searches. In experiment 2 these previews were compared to two spatial cueing conditions; in this experiment the colour preview did provide a small amount of help. Finally, in experiment 3 both previews were presented in succession, and increased facilitation was found, in particular when the colour preview preceded the orientation preview. These findings are discussed in relation to the literature, in particular the Guided Search model (Wolfe et al 1989 Journal of Experimental Psychology: Human Perception and Performance15 419–433; Wolfe 1994 Psychonomic Bulletin & Review1 202–238).