bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Representations of Objects: Invariance over a Shape-Distorting Transformation
Authors: Hilton H J , Cooper L A
Published: December 2015

Object perception seems robust over changes in properties such as rotation, reflection, and size. Such changes, however, are shape preserving. To investigate the effect of changes that disrupt overall shape yet keep the global relations among the parts intact, a set of objects was scaled by 50% along just the x-axis. Compression or expansion along a single axis markedly affects the overall shape of an object but leaves the global relations among the parts intact. In an initial encoding phase, subjects viewed images of symmetric and asymmetric three-dimensional nonsense objects and determined whether each faced principally to the left or right. We have previously found that such judgments require subjects to process the objects as global three-dimensional forms. In a subsequent test phase, subjects judged whether a set of both studied and novel objects were symmetric or asymmetric. Half of the studied items were either compressed or expanded along the x-axis in the test presentation. The magnitude of priming was equivalent for the transformed and the untransformed objects. In a second experiment, subjects performed the same initial left/right encoding task followed by a recognition test that assessed explicit memory for the previously presented objects. Although subjects were instructed to disregard changes in scale, recognition performance was reliably better for the untransformed objects. These results support the role of a structural representation system that captures the global relations among the parts and the principal axis of an object and an episodic system which also encodes features of shape.
Depth and Motion in Object Completion
Authors: Kellman P J , Shipley T F
Published: December 2015

Models of illusory and occluded contour and surface completion have focused on static spatial relations in planar surfaces. We consider several findings indicating that depth and motion play important roles in object completion. In one set of studies, effects of depth separation were studied in a speeded classification paradigm in which surface pieces were oriented in parallel or convergent (intersecting) planes. Subjects' task was to respond “parallel” or “convergent” on each trial. It was hypothesised that object completion would facilitate performance, and that depth separation of the two visible areas would disrupt completion. Speed and accuracy were reliably reduced when object parts were separated in depth via stereoscopic information. In a second series of studies a speeded classification paradigm was used to test perception of illusory figures from edges specified solely by motion (accretion-deletion of texture). The aim of a third study was to test occluded object completion where the visible parts of the object were not simultaneously present, but revealed over time. Results showed reliable object completion effects when certain spatial and temporal relationships held among object parts.

We discuss three elements of a revised theoretical model suggested by these results: (1) edge inputs to boundary completion processes need not be luminance edges—they may also be motion-specified edges; (2) the criterion of relatability governing edge interpolation processes must include depth relations as well as planar ones; (3) the criterion of relatability must be reformulated in terms of spatiotemporal, rather than merely spatial, relationships. Particulars of a new model that meets these conditions are briefly described.
The Role of Attention on Viewpoint-Invariant Object Recognition
Authors: Stankiewicz B J , Hummel J E
Published: December 2015

Researchers in the field of visual perception have dedicated a great deal of effort to understanding how humans recognise known objects from novel viewpoints (often referred to as shape constancy). This research has produced a variety of theories—some that emphasise the use of invariant representations, others that emphasise alignment processes used in conjunction with viewpoint-specific representations. Although researchers disagree on the specifics of the representations and processes used during human object recognition, most agree that achieving shape constancy is computationally expensive—that is, it requires work. If it is assumed that attention provides the necessary resources for these computations, these theories suggest that recognition with attention should be qualitatively different from recognition without attention. Specifically, recognition with attention should be more invariant with viewpoint than recognition without attention. We recently reported a series of experiments, in which we used a response-time priming paradigm in which attention and viewpoint were manipulated, that showed attention is necessary for generating a representation of shape that is invariant with left-right reflection. We are now reporting new experiments showing that shape representation activated without attention is not completely view-specific. These experiments demonstrate that the automatic shape representation is invariant with the size and location of an image in the visual field. The results are reported in the context of a recent model proposed by Hummel and Stankiewicz ( Attention and Performance16 in press), as well as in the context of other models of human object recognition that make explicit predictions about the role of attention in generating a viewpoint-invariant representation of object shape.
How Acting Allows to Segregate Objects in a Visual Scene
Authors: Gaussier P , Joulain C , Revel A , Cocquerez J P
Published: December 2015

Our purpose is to allow an autonomous robot to find and to categorise objects in a visual scene according to the actions it performs. The robot information comes from a CCD gray-level camera. The edges are extracted and a simple DOG filter is used to find ‘corner’-like forms in the image. These positions are used as possible focus points. The robot eye performs saccadic movements on the whole visual scene. A log-polar transform of the image is performed in the neighbourhood of the focus points to mimic the projection of the retina on the primary cortical areas. It simplifies object recognition by allowing size and rotation invariance. Those local views are learned on a self-organised topological map according to a vigilance level. At the same time, the robot tries to associate them with a particular action. For instance, we want the robot to learn to turn left when it sees a ‘turn-left’ arrow in the image. The problem is that the robot cannot see only a single object in the visual scene. There are many distractors such as doors, holes, and other objects not significant for the robot behaviour. At the beginning, a probabilistic conditioning rule allows the robot to associate all the seen objects to the performed movement. The robot repeatedly removes or creates new synaptic links to take into account only salient associations. As a result, object categorisation is not performed at the visual level (pure recognition of visual shape), but at the motor level (the action the robot has to perform). Our experiments show that learning and recognition of an object can be greatly simplified if we take into account the sensory-motor loop of the robot in its environment.
Pixel-Based versus Correspondence-Based Representations of Human Faces: Implications for Sex Discrimination
Authors: Troje N F , Vetter T
Published: December 2015

In human perception, as well as in machine vision, a crucial step in solving any object recognition task is an appropriate description of the object class under consideration. We emphasise this issue when considering the object class ‘human faces’. We discuss different representations that can be characterised by the degree of alignment between the images they provide for. The representations used span the whole range between a purely pixel-based image representation and a sophisticated model-based representation derived from the pixel-to-pixel correspondence between the faces [Vetter and Troje, 1995, in Mustererkennung Eds G Sagerer, S Posch, F Kummert (Berlin: Springer)]. The usefulness of these representations for sex classification was compared. This was done by first applying a Karhunen — Loewe transformation on the representation to orthogonalise the data. A linear classifier was trained by means of a gradient-descent procedure. The classification error in a completely cross-validated simulation ranged from 15% in the simplest version of the pixel-based representation to 2.5% for the correspondence-based representation. However, even with intermediate representations very good performance was achieved.
Orientation Discrimination for Moving Isoluminant and Luminance Targets
Authors: Wuerger S M , Morgan M J
Published: December 2015

Last year we presented orientation discrimination thresholds for stationary isoluminant red — green and luminance-defined stimuli as a function of spatial frequency and contrast (Wuerger and Morgan, 1995 Perception24 Supplement, 16). The horizontal profile of the stimuli was a Gabor function with a carrier frequency of either 0, 2, or 4 cycles deg−1. Observers made a binary decision (clockwise versus anticlockwise from vertical) and thresholds were defined as the standard deviation of their psychometric function. One main finding was that for carrier frequencies of 2 and 4 cycles deg−1, when stimuli of equal cone contrast are compared, orientation discrimination thresholds for red — green isoluminant stimuli do not differ significantly from the thresholds for luminance-defined stimuli.

To further characterise the chromatic mechanisms involved in spatial vision, we assessed orientation discrimination thresholds for isoluminant red — green and luminance-defined Gabor stimuli as a function of the velocity of the moving target. When velocity is increased, orientation discrimination thresholds for isoluminant targets increase more rapidly than the thresholds for luminance targets of identical cone contrasts. We conclude that orientation discrimination is mediated by different chromatic mechanisms with different spatial and temporal sensitivities.
Long-Lasting Detection Facilitation Induced by Gabor Flankers
Authors: Tanaka Y , Sagi D
Published: December 2015

Contrast detection threshold of a Gabor signal (GS) is enhanced in the presence of high contrast GS flankers. Repetitive performance of the task induces contrast sensitivity changes on different time scales: minutes when using mental imagery, and weeks in the context of perceptual learning. We tested the time course of lateral enhancement within a single trial, using a forward masking technique. Contrast detection thresholds were measured (2AFC) for a foveal GS target presented briefly (32 ms) preceded by a presentation (80 ms) of two high-contrast GS flankers, with stimulus onset asynchrony (SOA) varying from 0 to 3600 ms. Using target-to-mask separation of 3\lambda and 12\lambda (\lambda =18°, GS wavelength), we found that the 3\lambda separation GS flankers decreased target threshold by 0.25 log units at SOA=0 and by 0.17 log units at 3600 ms. At 12\lambda separation, threshold decreased by 0.11 log units at SOA=0 and by 0.14 log units at 3600 ms. Long-term and short-term enhancements showed similar dependence on stimulus configuration (maximal for collinear target and masks) and local parameters (orientation and spatial frequency differences between target and flankers). The results imply that spatial filters in early vision retain an input trace for as long as a few seconds (up to 14.4 seconds tested). This trace may subserve the consolidation of filter activity into long-term memory.
Anisotropy in Oriented-Line-Target Detection at High and Low Luminance Contrast
Authors: Doherty L M , Foster D H
Published: December 2015

Observers can detect a uniquely oriented line segment (‘target’) in a background field of uniformly oriented line segments (‘nontargets’) even if viewing time is brief. When the lines have high luminance contrast, the variation of orientation increment threshold with nontarget orientation is periodic, generally with a period of about 90° although smaller periods have been found. Do the orientation-sensitive mechanisms giving rise to periodicities function only at high contrast?

This question was addressed in a line-target detection experiment. Twenty white line segments of length 1 deg visual angle were presented in a circular field of diameter 20 deg visual angle. Nontarget orientations were in the range 0°, 5°, …, 175°, and the difference between nontarget and target orientations was varied adaptively. Stimulus displays lasting 40 ms were followed by a blank interstimulus interval lasting 60 ms and then a random-line mask. A view-tunnel provided a grey background of luminance 35 cd m−2 and stimulus contrast was 0.1, 0.3, 0.5, 0.7, or 0.9 log unit above the observer's luminance detection threshold for one line segment. When contrast was 0.1 log unit above this threshold, performance was near chance level. As contrast increased from 0.3 to 0.9 log unit above luminance detection threshold, performance improved and orientation increment thresholds decreased, showing that early orientation-processing is most effective at high luminance contrast. Nonetheless, periodicities were found in all conditions where performance was better than chance which suggests that the orientation-sensitive mechanisms associated with periodicities operate at both high and low luminance contrast.
Efficient Cues for Discriminating Skewed Curved-Line Segments
Authors: Foster D H , Kukkonen H T
Published: December 2015

Visual discrimination of circular arcs differing in curvature reaches hyperacute levels of performance. What spatial attributes of curved contours provide the necessary visual cue? Statistical-efficiency theory has previously been applied to data on the discrimination of symmetric curved-line segments undergoing expansions and contractions perpendicular to their chords. The results have suggested that relative invariants with respect to these transformations are the best cues, since they accounted for the most variance in the data (a relative invariant is an attribute such that the ratio of its values is constant under transformation). Expansions and contractions are examples of affine transformations, which in general provide a good approximation to the effects of viewpoint change. If some attribute of a curved line is a relative invariant with respect to affine transformations, is it then a good cue? An experiment was performed in which observers discriminated curved-line segments that had been affine transformed by progressive amounts of shear along their chords as well as expansions and contractions along and perpendicular to their chords. Shear can be interpreted as a relative affine invariant, and, since shear destroys symmetry by skewing the curve, it should provide a good cue. In fact, although expansions and contractions proved to be good cues, shear did not. Candidate cues that were not relative affine invariants (eg Euclidean curvature, turning angle) were also poor cues. It appears that being a relative affine invariant is a necessary but not sufficient condition for a cue to be efficient in the discrimination of curved-line segments.
Edge Assignment in Cells of Monkey Area V2
Authors: Zhou H , Friedman H , von der Heydt R
Published: December 2015

One of the processes of visual perception is to organise 2-D images into figure and ground, assigning the borders to the figure. We have studied the neural basis of this phenomenon. We recorded from orientation-selective cells of areas V1 and V2 in the awake, fixating monkey. A square (typically 4 deg) of uniform colour or gray was displayed in a uniform surround field (11 deg) of different colour or gray. The square was much larger than the response fields of the cells studied. Its orientation and colour were optimised for each cell. In interleaved tests, we centred two opposite edges of the square in the RF, and also reversed the colours of square and surround, resulting in four different display combinations. Flipping edges and colours produced pairs of displays with an identical edge in the response field, but the figure on opposite sides. The display was static for each period of fixation, and mean spike numbers per second were measured.

Many cells were selective for the sign of local contrast. In V2 we found cells that were highly discriminative for the direction of the figure, eg responding 10 times more to the left edge of a gray square with white surround than to the right edge of a white square with gray surround. In some cells, this discrimination was nearly independent of the figure size. The response could either be independent of local contrast (general edge assignment), or conditional on figure colour (joint assignment of edge and colour). We have observed direction-of-figure preference also in V1, but with smaller discrimination ratios. We conclude that figural edge assignment is part of early cortical processing.
Components of Visual Information Specifying the Surface of a Picture: Their Relative Effectiveness in Decreasing Cross-Talk from the Depicted Scene
Authors: Sedgwick H A , Raul C , Flagg T
Published: December 2015

An observer viewing a pictorial representation of a three-dimensional (3-D) scene can attend either to the represented scene or to the flat surface of the picture itself. Although these two modes of perception are conceptually independent, we have shown that in practice there is substantial cross-talk between them (Sedgwick and Nicholls, 1993 Perception22 Supplement, 109). We have also shown that the strength of this cross-talk can be affected by the balance between the visual information specifying the 3-D scene and the visual information specifying the picture surface. In the present research we dissected surface information into several components and attempted to determine their relative effectiveness in decreasing cross-talk from the depicted 3-D scene. We used computer-generated displays both to create the depicted 3-D scene and to simulate the picture surface. Observers made magnitude estimates of the projected size on the picture surface of rectangular objects depicted as standing on a receding platform. We examined four components of surface information: (1) a realistic-looking frame surrounding the picture; (2) a visible surface texture (resembling woven fabric); (3) the pixel resolution of the image (512 versus 2048); (4) a background colour linking the frame to the image. We found that adding texture and adding framing each decreased cross-talk by about the same amount, but that the framing effect interacted with image resolution. Neither image resolution nor background, taken individually, significantly affected the strength of the cross-talk.
Two Stages for Depth Integration of Motion Parallax
Authors: Ujike H , Saida S
Published: December 2015

Motion parallax has been shown to be a principal cue for depth perception under monocular viewing. The simulated depth of stimuli in previous studies has been constant in both magnitude and direction. In the present study we addressed the question how the visual system detects parallactic depth change. To answer this we investigated the temporal characteristics of parallactic depth change and the effect of a motion signal on them. The stimulus consisted of four bands of 15-cycle sinusoidal gratings and parallactic depth was simulated between each band. In experiment 1, we measured the amount of perceived depth change with different frequencies (0.125 to 10 Hz) of simulated depth change and with different velocities (2.5 to 40 cm s−1) of head movements. The result showed the perceived depth change decreased with frequency of depth change, and it increased with head velocity when the frequency was constant. In experiment 2, we measured the motion threshold with different velocities of head movement. The result showed the threshold was constant across different head velocities. In experiment 3, we measured the amount of perceived depth using apparent motion stimuli with the head moving. The result showed depth decreased with SOA of apparent motion stimuli, but there was no effect of different head velocities. The results of these three experiments indicate that parallactic depth change is determined by the duration of simulated depth, which corresponds to the integration time of motion, as well as by the extent of head movement. We conclude that parallactic depth is integrated in two stages: first, integration of motion and, second, integration of motion parallax.
Vection with Real-World Stimuli
Authors: Ohmi M
Published: December 2015

Psychophysical studies have revealed that retinal and depth periphery play a dominant role in activating vection, or visually induced sensation of self-motion. But since abstract stimuli such as random-dot patterns and vertical stripes have been used in these studies, the results are not always applicable for designing more realistic visual displays in real-world applications. Indeed, it has been shown that for human orientation, a real-world display is more effective than an abstract one (Howard and Childerson, 1994 Perception23 753 – 762). We investigated how vection was controlled by the peripheral part of a stimulus consisting of a real-world display. Stereoscopic and nonstereoscopic video clips were taken through a windshield while driving on (i) a straight, (ii) a gradually curved, and (iii) a sharply curved road at slow and fast speeds. Vection was measured with these stimuli which were presented on a 63 deg wide and 38 deg high video projection monitor. The results showed that although the stereoscopic display generally activated more forward and sideways vection than the nonstereoscopic one, the difference was barely statistically significant. When only the central 18 deg diameter of the display was presented, similar vection was activated as with a full field display. When the central 40 deg diameter of the display was occluded, vection did not change significantly, though observers found difficulty in assessing the direction of self-motion. It is concluded that retinal and depth periphery of real-world stimuli do not play a significant role in activating vection.
Hand Action in a Radial Direction Captures Visual Motion in Depth
Authors: Ishimura G
Published: December 2015

Transversal hand action in the frontoparallel plane biases the perception of bistable visual motion. This has been called action capture. In daily behaviour, however, hand action in a ‘radial’ direction from the head might be more important, because we frequently reach our hand for an object in front of us while guiding the action with vision. The purpose of this study was to measure the strength of action capture in the radial direction.

Horizontal luminance gratings were placed above and below the fixation point. Binocular disparity, perspective contour, and spatial frequency gradient cues were attached to the gratings so that they simulated the ‘ceiling’ and the ‘floor’ of a long corridor. The display was reflected on a tilted mirror to face upward. The subject looked into the display and moved his/her dominant hand toward, or away from, the face behind the mirror. Just after the action onset, detected by the computer, one of the two gratings (the ceiling or the floor) flickered in short period to simulate bistable visual motion in depth (approaching or departing). The subject indicated the perceived motion direction in the frontoparallel plane using a 2AFC (upward or downward) method. The results showed that perceived motion was significantly biased to the ‘departing’ direction when the hand moved ‘away from’ the face, and it was biased to the ‘approaching’ direction when the hand moved ‘toward’ it. It is concluded that action capture occurs not only in transversal but also in radial movements.
Cooperative Interaction between Change in Disparity and Size for the Perception of Motion in Depth
Authors: Susami K , Kaneko H , Ashida H
Published: December 2015

While an object is moving in depth, its retinal disparity and size are cooperatively changing along the viewing distance. We examined the effect of a cooperative relation between the two cues for the perception of motion in depth—changes in disparity and size—with the Wheatstone stereoscopic display. In experiment 1, we used a stereoscopic stimulus whose disparity and size were independently modulated with sine-wave form, but at different frequencies (0.7 Hz vs 0.8 Hz, and vice versa). So, the cooperative and the uncooperative phases between the two cues repeatedly followed each other. The subjects continuously pushed a response key when the stimulus was clearly perceived to be moving in depth. In general, the impression of motion in depth was clear when the two cues were simultaneously modulated in similar phase, but not in different phase. In experiment 2, we measured the perceived distance of a stimulus that is moving in depth, when the two cues were moderated in the same phase and in counterphases. The perceived distance was increased when the two cues moved in the same phase. We found that not only the effect of each cue, but also the effect of the cooperative change of the two cues was affecting the perception of motion in depth. These results suggest that the cooperative interaction of two cues, that is their relative phase, is important for the perception of motion in depth.
Dynamic Structural Change of 3-D Illusory Surface Observed with Binocular Viewing
Authors: Idesawa M , Sakaguchi Y , Shimada Y
Published: December 2015

When adequate visual stimuli are suitably arranged, for example, partially along the surface boundary or beyond the covering illusory surface, an opaque or transparent illusory surface can be seen (Idesawa, 1991 Japanese Journal of Applied Physics30-4B L751 – 754; 30-7B L1289). By moving the visual stimuli of the occluding objects which were not physically depicted, several interesting phenomena have been observed.

Dynamic fusion and separation of illusory surfaces have been observed when the visual stimuli were changed continuously between two different conditions; only one illusory surface was perceived in the first condition and two separate illusory surfaces were perceived in the second condition. Hysteresis was recognised in the geometrical positions between fusion and separation of the surfaces.

In addition, elastically distorting illusory surfaces have been observed when the positions of two occluding objects, placed on opposite sides, were moved continuously in a sinusoidal way in opposite phase between two positions where the two illusory surfaces could not be bridged together when they were stationary. The phenomena have been observed both for opaque and for transparent illusory surfaces. They could be interpreted as reflections of the surface-perceiving process in our visual system. Probably our visual system tends to contain the previously perceived structure; then the transition from one structure to another is delayed until the geometrical conditions change sufficiently to break the previously perceived structure.
Fixation Disparity as a Function of Viewing Distance and Prism Load
Authors: Jaschinski W
Published: December 2015

In binocular vision, fixation disparity is present when a fixation point falls within Panum's area, but not on corresponding retinal points. To investigate the effect of vergence load, fixation disparity was measured at viewing distances of 20, 30, 40, 60, and 100 cm (while the test subtended a constant angular size) by the psychophysical method of dichoptically presented nonius lines with a central fusion stimulus. As the viewing distance was shortened from 100 to 20 cm, mean fixation disparity changed monotonically from 1 min arc esophoria (ie the eyes converged in front of the target) to 3 min arc exophoria. The average standard deviation of the psychometric function, which is a measure of the temporal variability of vergence, was smallest at 100 cm (when fixation disparity was esophoric) and increased at shorter distances.

Fixation disparity was also measured at a constant distance of 40 cm, but with prisms in front of the eyes that induced the same vergence angles as would be induced by viewing distances between 20 and 100 cm. The slope of these conventional ‘fixation disparity curves’ as a function of prism load correlated with the slope of fixation disparity as a function of viewing distance ( r=0.39, p=0.02, n=25). However, testing at different distances, as introduced here, has the advantage of preserving the natural interaction between vergence and accommodation. Since the change of fixation disparity with distance differed reliably among subjects (with a test — retest correlation of 0.65 in 34 subjects with good binocular vision) this measure may be useful for identifying subjects who are prone to near-vision complaints.
Interaction between Perspective Visual Cues and Monocular versus Binocular Vision in the Perception of Pitch Subjective Vertical
Authors: Poquin D , Goujon L , Ohlmann T , Zoppis B
Published: December 2015

In a pitch vertical adjustment, a rectangular and plane surface (rod) could be assessed as being upright when its lateral sides looks parallel. According to this hypothesis, geometrical analysis underscores that adjustment errors relative to the vertical are a function of the width of the rod, its gradient of perspective, and its distance from the observer's eyes. In order to verify this relationship, thirty-two subjects assessed pitch subjective vertical (PSV) in two visual conditions (monocular versus binocular) by rotating in darkness different luminous rods in the median plane. The trapezoid rods varied both in their width and in their angles of convergence measured from each lateral side. The rod-to-eyes distance was fixed at 60 cm and the length of the rod was 25 cm. The results showed that the data fitted in with the geometrical analysis in monocular and binocular conditions. However, in the binocular condition the weight of the shape visual cues decreased considerably. Moreover, a significant constant error remained even with the rectangular surface. It is concluded that rod adjustment to PSV is essentially a visual process similar to the perception of surface slant as Perrone's model develops it (1982 Perception11 641 – 654). Indeed, the visual cues involved in the vertical adjustment task are in accordance with this model. Also, the constant error observed in PSV could be explained by the deviation of the subjective eye level which Perrone supposes to account for the slant underestimation in his model.
Behavioural and Visual Evoked Potential Measures of the Role of Disparity in Stereo Detection and Discrimination
Authors: Selmes C M , Finlay D C , Fulham W R
Published: December 2015

The initial experiment in this research used psychophysical responses to dynamic random-dot stereograms (DRDS) to examine disparity detection and disparity or depth discrimination in stereopsis. Using identical crossed and uncrossed disparity stimuli across conditions at 150 ms exposure, we found that while disparity could be detected and form discriminated, observers were unable to discriminate depth direction. These results suggest that disparity detection is a faster process than disparity discrimination and that form can be discriminated prior to the assignment of depth direction. In a second experiment we examined disparity (correlation) and noncorrelation in stereopsis and used visual evoked potentials (VEPs) in response to three DRDS displays: (a) a target containing disparity on a correlated background, (b) an uncorrelated target on a correlated background, and (c) a target containing disparity on an uncorrelated background. At 200 ms stimulus exposures, VEPs to regions of disparity and regions of noncorrelation on correlated backgrounds were largely undifferentiated. There was not, however, any discernible VEP to stimuli incorporating disparity on an uncorrelated background. These findings imply that while form may be discriminated on the basis of a region of disparity (correlation) in stereopsis, the uncorrelated background condition suggests this is a slow process, since there was no apparent response to form or depth in the recording epoch. Early processes may regard the entire DRDS as a region of noncorrelation with both target and background being mismatched, and hence initially undifferentiated. A faster process may discriminate form on the basis of a region of noncorrelation, as suggested by the correlated background conditions.
Is Binocular Rivalry a Summative Effect of Random Events?
Authors: Snoeren P R
Published: December 2015

Some decades ago, it was noticed that the distribution function of waiting times in binocular rivalry looked similar to the gamma distribution function. The best fit of experimental data with a gamma distribution function was obtained with an argument very close to 4, for all stimuli and all subjects. The Poisson distribution function is conceptually related to the gamma distribution, ie the distribution function of waiting times for n random events is the gamma distribution with the integer n as argument. The fact that the best fitted parameter is an integer suggests that the process underlying binocular rivalry is a Poisson process. More precisely, it suggests that a percept under binocular rivalry alternates after four successive random events. Without passing judgment about the nature of these events, the above suggestion is currently investigated. One can think of many mechanisms that cause similar distribution functions of waiting times, but distinguishing them is only possible by using dynamic stimuli. The easiest dynamic stimulus, from both experimental and computational viewpoints, is the so-called step function. With a step function, one rivalrous static stimulus is instantaneously replaced by another. Because this operation changes the mean event rate, the time behaviour directly after the step is different from the time behaviour of both stimuli viewed in static conditions separately. When the mean event rates of the two separate static stimuli are known, statistical predictions about the time behaviour directly after the step can be tested.
Intermodal Compensatory Effects in a Visual Search Task with Congenitally Deaf Adults
Authors: Stivalet P , Moreno Y , Cian C , Richard J , Barraud P-A
Published: December 2015

In a visual search paradigm we measured the stimulus onset asynchrony (SOA) between a stimulus and a mask that was required to reach 90% correct responses. This procedure has the advantage of taking into account the real processing time and excluding the time for the generation of the motor response. Twelve congenitally deaf adult subjects and twelve normal subjects were given a visual search task for a target letter O among a varying number of distractor letters Q and vice-versa.

In both groups we found the asymmetrical visual search pattern classically observed with parallel processing for the search for the target Q and with serial processing for the search for the target O (Treisman, 1985 Computer Vision, Graphics, and Image Processing31 156 – 177). The difference between the mean search slopes for an O target was not statistically significant between the groups; this might be due to the variability within the groups. The visual search amidst the congenitally deaf does not seem to benefit from a compensatory effect in relation to the acoustic deprivation. Our results seem to confirm data reported by Neville (1990 Annals of the New York Academy of Science 71 – 91) obtained by an electrophysiological technique based on event-related potentials. Nevertheless, the deaf subjects were 2.5 times faster at the visual search task.
Interstimulus Interference Effect with Stroop-Type Stimuli
Authors: Ignatov M
Published: December 2015

The interstimulus interference in reacting to Stroop-type stimuli was investigated. Two aspects of the interstimulus organisation were analysed: the serial structure of the items in the test sheets and the spatial structure of the items on different test sheet types. More difficult serial structures were expected in cases where the correct colour-naming response to an incongruous combination was the suppressed word-naming response of either the previous or the next incongruous stimulus. Variation in the spatial organisation of the items was aimed at causing different opportunities for perceiving several adjacent items at once. As a third factor the study included not a characteristic of the test material, but a related cognitive style variable—the field dependence/independence, measured by a version of the Gottschaldt embedded figures. Every test condition (printed words in incongruous colours) was matched with a control condition (patches of colour) in a double-mirror design. A factorial design of 2 × 3 × 3 was applied and the data were processed with the aid of a three-way ANOVA. The results confirmed the importance of the interstimulus organisation of multiple Stroop-type stimuli. It is inferred that the extent to which perceptual and, in particular, selective-attention processes affect Stroop colour naming performance might be only a fraction of the whole interstimulus and intrastimulus interference effect.
Attention Switching vs Attention Sharing in Searching Dual RSVP Streams
Authors: Prins N , Juola J F
Published: December 2015

Ideas about how visual attention is distributed over space include spotlight, zoom lens, and various resource allocation models. Spotlight and serial allocation models assume that attention is narrowly focused and switches from one object to another in visual search. Zoom lens and parallel allocation models, on the other hand, describe a flexible gradient within which attention can be shared among several items simultaneously. We report two experiments in which simultaneous rapid serial visual presentations (RSVPs) of two streams of digits were used, one above and one below a fixation point. In experiment 1, subjects were told to report the digit immediately following a uniquely coloured signal digit. In some trial blocks the coloured signal digit always appeared in either the top or bottom stream, and in other blocks the signal digit could occur in either stream. Stream location probabilities were varied between blocks in order to induce strategic variations in attentional allocation. In experiment 2, subjects were told to report the first two digits visible when the fixation point changed colour. Subjects were instructed to report one digit from the top stream and one from the bottom, with report order counterbalanced between blocks. The lag between the response signal and the actual digit reported was shown to vary strongly with signal location probability (experiment 1), and the lag between items reported from the top and bottom streams depended heavily on the order of report (experiment 2). The results were more consistent with an attention-switching model than with an attention-sharing model of visual attention.
Visual Recognition as Controlled Search of Complicated Fragments
Authors: Krol V M
Published: December 2015

We tested the hypothesis that object recognition is an active search of complicated fragments in the visual image. This search is performed in accordance with criteria based on invariant descriptions of an object's perceptual class. The basic strategy is to activate these descriptions during parallel search. ‘Upper’ segments search for appropriate fragments of the picture. ‘Subordinate’ segments are included by request of the ‘upper’ segments. Description segments include three types of records: integral (whole) characteristics of some fragment; characteristics of fragments which are members of this fragment; and characteristics of relations between the fragments.

This structure of perceptual description permits parallel analysis of the visual scene by different segments by the ‘autonomy’ principle and permits the use of incomplete sets of segments for recognition by the ‘quorum’ principle. Different ways of forming connections between segment records may be considered as ‘thinking’ components of visual perception.

The main points of our model follow from results of our tachistoscopic experiments. We measured thresholds for the recognition of test figures. Different levels of figure complexity were used: parallel lines and strips, geometric figures, schematic faces, textures, etc. It was found that the stages of the recognition process are connected with types of operations described in our model. These results give rise to the possibility that the properties of the neurons involved in visual search might be identified.
Observations of energy transport and rate of spreads from low-intensity fires in longleaf pine habitat – RxCADRE 2012
Authors: Butler B. , Teske C. , Jimenez D. , O'Brien J. , Sopko P. , Wold C. , Vosburgh M. , Hornsby B. , Loudermilk E.
Published: December 2015

Wildland fire rate of spread (ROS) and intensity are determined by the mode and magnitude of energy transport from the flames to the unburned fuels. Measurements of radiant and convective heating and cooling from experimental fires are reported here. Sensors were located nominally 0.5 m above ground level. Flame heights varied from 0.3 to 1.8 m and flaming zone depth varied from 0.3 to 3.0 m. Fire ROS derived from observations of fire transit time between sensors was 0.10 to 0.48 m s–1. ROS derived from ocular estimates reached 0.51 m s–1 for heading fire and 0.25 m s–1 for backing fire. Measurements of peak radiant and total energy incident on the sensors during flame presence reached 18.8 and 36.7 kW m–2 respectively. Peak air temperatures reached 1159°C. Calculated fire radiative energy varied from 7 to 162 kJ m–2 and fire total energy varied from 3 to 261 kJ m–2. Measurements of flame emissive power peaked at 95 kW m–2. Average horizontal air flow in the direction of flame spread immediately before, during, and shortly after the flame arrival reached 8.8 m s–1, with reverse drafts of 1.5 m s–1; vertical velocities varied from 9.9 m s–1 upward flow to 4.5 m s–1 downward flow. The observations from these fires contribute to the overall understanding of energy transport in wildland fires.
INFERRING PLANET MASS FROM SPIRAL STRUCTURES IN PROTOPLANETARY DISKS
Authors: Fung (馮澤之) Jeffrey , Dong (董若冰) Ruobing
Published: December 2015

Recent observations of protoplanetary disk have reported spiral structures that are potential signatures of embedded planets, and modeling efforts have shown that a single planet can excite multiple spiral arms, in contrast to conventional disk–planet interaction theory. Using two and three-dimensional hydrodynamics simulations to perform a systematic parameter survey, we confirm the existence of multiple spiral arms in disks with a single planet, and discover a scaling relation between the azimuthal separation of the primary and secondary arm,

and the planet-to-star mass ratio q:

for companions between Neptune mass and 16 Jupiter masses around a 1 solar mass star, and

for brown dwarf mass companions. This relation is independent of the disk’s temperature, and can be used to infer a planet’s mass to within an accuracy of about 30% given only the morphology of a face-on disk. Combining hydrodynamics and Monte-Carlo radiative transfer calculations, we verify that our numerical measurements of

are accurate representations of what would be measured in near-infrared scattered light images, such as those expected to be taken by Gemini/GPI, Very Large Telescope/SPHERE, or Subaru/SCExAO in the future. Finally, we are able to infer, using our scaling relation, that the planet responsible for the spiral structure in SAO 206462 has a mass of about 6 Jupiter masses.
Evolution of Compatibility Range in the Rice−Magnaporthe oryzae System: An Uneven Distribution of R Genes Between Rice Subspecies
Authors: Gallet Romain , Fontaine Colin , Bonnot François , Milazzo Joëlle , Tertois Christophe , Adreit Henri , Ravigné Virginie , Fournier Elisabeth , Tharreau Didier
Published: December 2015

Efficient strategies for limiting the impact of pathogens on crops require a good understanding of the factors underlying the evolution of compatibility range for the pathogens and host plants, i.e., the set of host genotypes that a particular pathogen genotype can infect and the set of pathogen genotypes that can infect a particular host genotype. Until now, little is known about the evolutionary and ecological factors driving compatibility ranges in systems implicating crop plants. We studied the evolution of host and pathogen compatibility ranges for rice blast disease, which is caused by the ascomycete Magnaporthe oryzae. We challenged 61 rice varieties from three rice subspecies with 31 strains of M. oryzae collected worldwide from all major known genetic groups. We determined the compatibility range of each plant variety and pathogen genotype and the severity of each plant−pathogen interaction. Compatibility ranges differed between rice subspecies, with the most resistant subspecies selecting for pathogens with broader compatibility ranges and the least resistant subspecies selecting for pathogens with narrower compatibility ranges. These results are consistent with a nested distribution of R genes between rice subspecies.
Embryonal Tumor With Abundant Neuropil and True Rosettes: A Distinct Immunohistochemical Pattern
Authors: Al-Salam Suhail , Al Alashari Mouied
Published: December 2015

Embryonal tumors with abundant neuropil and true rosettes (ETANTR) are rare pediatric embryonal neoplasms that combine features of neuroblastoma and ependymoblastoma. We report a distinct immunohistochemical-staining pattern of ETANTR in a 12-month-old baby who presented with a supratentorial mass. The tumor exhibited a characteristic biphasic pattern of neuropil-rich areas and patchy cellular neuropil-poor areas. The neoplastic cells in neuropil-rich areas are diffusely immunoreactive to chromogranin A, synaptophysin, neurofilament, and CD56, but show no immunoreactivity to nestin, SOX2, WT-1, β-catenin, and vimentin. While the cells in neuropil-poor areas, including ependymoblastic and Flexner-Wintersteiner rosettes, are diffusely immunoreactive to nestin, SOX2, WT-1, β-catenin, and vimentin but show no immunoreactivity to chromogranin A, synaptophysin, neurofilament, and CD56. Ependymoblastic rosettes show luminal membranous immunoreactivity to EMA. We believe that ETANTR has a distinct histologic and immunohistochemical pattern supporting the embryonal origin of this tumor with divergent neuroblastic and primitive glial differentiation.