bluuebunny/crossref_metadata_2025_split huggingface dataset:
Visual Direction behind and near an Occluder
Authors: Banks M S , van Ee R , Backus B T 
Published: December 2015

Hering's laws imply that the visual direction assigned to a binocularly visible object is based on the oculocentric positions of the object in both eyes; the direction assigned to a monocularly visible object is based on its oculocentric position in that eye. It is interesting to consider how these laws apply near an occluder. Near the vertical edge of an opaque occluder, some regions of a far surface are visible to one eye only and other regions are visible to both eyes; the demarcation is created by the edge of the occluder and depends on the distance to the occluder and the far surface. If Hering's laws applied in this situation, we would expect spatial discontinuities in perceived visual directions near the edge of the occluder: in the monocular zone, the assignment of direction would be made by one eye's image and in the binocular zone, right next to the monocular zone, the assignment would be made by both eyes' images. Because of this switch in the eyes controlling the assignment, spatial discontinuities in perceived direction are expected. We measured perceived visual direction near an occluding edge and found spatial distortions, but no discontinuities. We measured the horizontal and vertical spatial extents of the distortions and inferred how the inputs to the two eyes are weighted when one eye's view is occluded, nearly occluded, and not nearly occluded. In conclusion, the visual system seems to avoid spatial discontinuities in perceived visual direction that could otherwise occur near an occluder by varying the weights attached to each eye's input depending on target position relative to the occluding edge.
Orientation Discrimination at Isoluminance
Authors: Reisbeck T E , Gegenfurtner K R 
Published: December 2015

Colour and form are important attributes of the objects in our visual environment. We tested the hypothesis that colour and orientation are processed independently in the visual system. Orientation perception for stimuli defined by luminance is characterised by a decrease in thresholds with increasing stimulus contrast, and by a strong oblique effect: stimuli along the horizontal or vertical axes are discriminated more easily. We determined orientation discrimination thresholds for stationary, slow (1 Hz) or fast (8 Hz) moving sine-wave gratings (1 cycle deg−1) defined by luminance or isoluminant (red — green) contrast. In a 4AFC paradigm, three of four stimulus patches were identical and the fourth differed in orientation, contrast, or in both. When we measured orientation discrimination thresholds as a function of stimulus contrast, thresholds decreased for all stimuli with increasing contrast. At all temporal frequencies the functions relating orientation thresholds to stimulus contrast had similar shapes for luminance and isoluminant gratings. On a cone-contrast metric, thresholds for stationary and slowly moving stimuli were consistently lower for isoluminant compared to luminance stimuli. For fast-moving stimuli orientation thresholds were similar for both kinds of gratings. For both types of stimuli a marked oblique effect was observed. To characterise processing of contrast and orientation completely, we measured simultaneous thresholds for contrast and orientation. The shapes of the resulting two-dimensional threshold contours were similar for luminance and isoluminant gratings, indicating similar rules for combining differences in contrast and orientation. We conclude that processing of isoluminant and luminance stimuli undergoes the same neural processing at least for the low spatial frequencies used here.
The Self-Organising Map, a Possible Model of Brain Maps
Authors: Kohonen T 
Published: December 2015

We stipulate that the following three categories of dynamic phenomena must be present in a realistic neural-network model: (i) activation; (ii) adaptation; (iii) plasticity control. In most neural models only activation and adaptation are present. The self-organising map (SOM) algorithm is the only neural-network model that includes all the three phenomena. Its modelling laws include the following partial functions: (1) Some parallel computing mechanism for the specification of a cell in a piece of cell mass whose parametric representation matches or responds best to the afferent input. This cell is called the ‘winner’. (2) Control of some learning factor in the cells in the neighbourhood of the ‘winner’ so that only this neighbourhood is adapted to the current input. By virtue of the ‘neighbourhood learning,’ the SOM forms spatially ordered maps of sensory experiences, which resemble the maps observed in the brain. The newest version of the SOM is the ASSOM (adaptive-subspace SOM). The adaptive processing units of ASSOM are able to represent signal subspaces, not just templates of the original patterns. A signal subspace is an invariance group; therefore the processing units of ASSOM are able to respond invariantly, eg to moving and transforming patterns, in a similar fashion as the complex cells in the cortex.
Synaesthesia and External ‘Projection’ of Kinesthetic Sensations in Phantom Limb Patients and Normal Individuals
Authors: Ramachandran V S 
Published: December 2015

By combining brain imaging (MEG) studies with psychophysical experiments we have shown that, very soon after amputation of an arm in humans, the sensory input from the face begins to activate the original ‘hand area’ of the cortex. Many patients with a phantom arm are unable to ‘move’ their phantom arm. We used a mirror to allow the patient to see the reflection of his normal hand superimposed on the phantom. If he now moved the real arm he not only saw the phantom moving but also experienced vivid kinesthetic sensations in the phantom—a remarkable example of synaesthesia. Finally, we had a normal subject look at his own reflection superimposed on a Halloween mask seen through a half-silvered mirror. If he now made vigorous lip and tongue movements he felt his kinesthetic sensations ‘projected’ on the mask; and his ‘free will’ controlling the dummy's face (it is as though the subject regards it as highly unlikely that his own lip sensations and motor commands should be so perfectly synchronised with the movements of the mask, simply by chance). If the mask was now punched in the eye, the subject registered a strong GSR (galvanic response) demonstrating that his ‘self’ had now temporarily cast off its mortal coil to inhabit the mask. In our last experiment we had a blindfolded subject repeatedly tapping and stroking the nose of an accomplice who was sitting in front of him. If the experimenter then taps and strokes the subject's nose in perfect synchrony, the subject starts experiencing an absurd lengthening of his nose (the phantom nose). This simple experiment demonstrates the single most important fact about the mechanisms of perception—that they can discern statistical regularities in the world with astonishing rapidity.
Reading with Visual Field Defects
Authors: Trauzettel-Klosinski S 
Published: December 2015

The influence of different visual field defects on the reading performance was examined with potential adaptive strategies to improve the reading process in mind. By means of an SLO, the retinal fixation locus (RFL) was determined with the use of single targets and text, and eye movements scanning the text were recorded on video tape. Additionally, eye movements were monitored by an Infrared Limbus Tracker. Visual fields were assessed by the Tübingen Manual and/or automatic perimetry. Normal subjects, and patients with central scotomata, ring scotomata, and hemianopic field defects (HFD) were examined. The main pathological reading parameters were an increase of saccade frequency and regressions per line, and a decrease of reading speed. In patients with field defects involving the visual field centre, fixation behaviour is significant for regaining reading ability. In absolute central scotoma, the lost foveal function promotes eccentric fixation. The remaining problem is insufficient resolution of the RFL, which can be compensated for by magnification of the text. In patients with insufficient size of their reading visual field, due to HFD and ring scotoma, it is crucial that they learn to use a new RFL despite intact foveolar function. Preconditions for reading have been found to be: (1) sufficient resolution of the RFL, (2) a reading visual field of a minimum extent, and (3) intact basic oculomotor function. In patients with visual field defects involving the centre, a sensory-motor adaptation process is required: the use of a new RFL as the new centre of the visual field and as the new zero point for eye-movement coordinates.
Why Do Some People Take a Long Time to See Complex Random-Dot Stereograms?
Authors: Buckley D , Frisby J P , Aranaz V J , Lipson M M 
Published: December 2015

Some observers take a long time to see the appropriate surface shapes depicted in complex random-dot stereograms (RDSs) whereas others report seeing them quickly. We have hypothesised that this may be due in part to some observers being more affected than others by the cue conflicts that are typically present in RDSs, for which disparity is often at odds with accommodation, texture, and outline shape cues. We report two experiments in which we investigated whether a measure of dominance of texture/outline cues over disparity cues in stereograms of ridges could predict latencies to see RDSs of ‘wedding cakes’ viewed from above. Latencies were measured for correctly reporting the number of layers in the wedding cakes. The ridge cue dominance index was obtained by using amplitude judgements of convex parabolic vertical and horizontal ridge stereograms embodying texture/outline vs disparity cue conflicts (Buckley and Frisby, 1993 Vision Research33 919 – 934). In the first experiment ( N=38) disparity cues in the wedding cakes were depicted with inconsistent dot texture elements, ie the dots signalled flatness as there were no density differences between the cake layers. Observers giving greater weight to texture/outline in the vertical-ridge amplitude task showed significantly longer latencies to the wedding cakes. In a second experiment with different observers ( N=35), 18 were shown wedding cakes with textures consistent with disparity (diamonds drawn with correct perspective and density) and 17 saw the same disparity cues carried by inconsistent textures (diamonds signalling flatness). Large and significant correlations were found between the cue dominance index from vertical ridges and the latencies to wedding cakes depicted with inconsistent textures: observers with higher texture/outline cue dominance showed longer latencies. This result was remarkable given the lack of any readily apparent differences between the consistent and inconsistent textures in the wedding-cake stimuli. Equivalent correlations for wedding cakes depicted with consistent textures were small and nonsignificant. We conclude that individual differences in latencies to complex RDSs can be partly explained by differences in observers' susceptibility to texture/disparity cue conflicts embodied in those RDSs.
The Preparation of Goal-Directed Movements Requires Selective Visual Attention: Evidence from the Line-Motion Illusion
Authors: Deubel H , Shimojo S , Paprotta I 
Published: December 2015

Previous research has demonstrated that visual attention is focused on the movement target, both before saccadic eye movements and before manual reaching, allowing for spatially selective object recognition (Deubel and Schneider, 1996 Vision Research36 1827 – 1837; Deubel, Schneider, and Paprotta, 1996 Perception Supplement, 13 – 19). Here we study the illusory line motion effect (Hikosaka et al, 1993 Vision Research33 1219 – 1240) in a dual-task paradigm to further investigate the coupling of attention and movement target selection. Subjects were presented a display with two potential movement targets (small circles). When one of the circles flashed, they performed a reaching movement with the unseen hand to the other stimulus; movements were registered with a Polhemus FastTrack system. At a SOA that was varied between 0 and 1000 ms after the movement cue, a line appeared and connected both stimuli. After the reaching movement, subjects indicated the perceived direction of line motion. In a second experiment, saccadic eye movements instead of reaching movements were studied. The data show that for short SOAs the subjects reported illusory line motion away from the cue location indicating that attention is automatically drawn to the cue. For longer SOAs but well before movement onset the illusory motion effect inverted—evidence for an attention shift to the movement target. The findings were very similar for manual reaching and for saccadic eye movements. The results confirm the hypothesis that the preparation of a goal-directed movement requires the attentional selection of the movement target. We discuss the assumption of a unitary attention mechanism which selects an object for visual processing, and simultaneously provides the information necessary for goal-directed motor action such as saccades, pointing, and grasping.
Advance in Attention Allocation in Visual Search
Authors: Fischer M H , Pollatsek A , Rayner K 
Published: December 2015

We investigated the allocation of visuo-spatial attention during dynamic viewing with a dual task. The primary search task (K, H, O, or V among Xs) required sequential left-to-right eye movements. An additional manual detection response was made to a visual probe that appeared early or late after the onset of one critical eye fixation (25 or 170 ms probe delay). The probe appeared either to the left, or directly above, or to the right of the currently fixated character (−10, −5, 0, +5, or +10 characters probe eccentricity). As predicted from research with single-eye movement tasks, probe detection became faster near the location of the forthcoming eye fixation, indicating an attention shift to that location. Fixation times increased as a consequence of probing, but less so when the probe appeared in the right compared to the left hemifield. Saccade lengths decreased as a result of probing, but remained largest when the probe appeared at +10 characters. These data support the notion of goal-directed attention shifts prior to eye movements in natural viewing.
Categorical Effects in the Perception of Familiar Faces
Authors: Angeli A , Gerbino W 
Published: December 2015

Photographs of morphed faces were shown to close friends of portrayed individuals. Three tasks were used: localisation of a morphed target on the continuum between the two original faces, simultaneous same - different discrimination of face pairs separated by a 20% morphing step (AB task), and sequential classification of the same pairs (ABX task). Localisation data were plotted against morph coefficients. Evidence of categorical processing was provided by steeper functions for upright vs upside-down faces. In the AB task, intermediate faces were discriminated better than faces separated by the same morphing step but closer to one original. This was confirmed in a control experiment where the participants were unfamiliar with portrayed individuals and were unlikely to process our stimuli categorically. The superiority of intermediate faces in the AB task was attributed to a nonlinearity of continua generated by the morphing procedure, and used as a baseline to evaluate ABX classification data. Also in the ABX task, intermediate faces, those straddling the categorical boundary, were classified more accurately than faces located on the same side of the boundary. However, the superiority in classification accuracy was larger than the superiority in discrimination accuracy operationalised by the AB task, as predicted by the categorical perception hypothesis.
Effect of Ambient Illuminant on Surface Colour Constancy
Authors: Kuriki I , Uchikawa K 
Published: December 2015

Generally, we are completely enclosed in a real environment, which may act as an entire view-field or adapting field. But in most studies on colour constancy experiments have been made with spatially restricted stimuli. We built a room with gray (N5) walls inside to measure the effect of ambient illuminant on colour constancy. The room illuminant could change its colour from white (D65) to either blue, orange, green, or purple. The observer sat in this main room and adapted to the illuminant for 5 min before the start of the experiment. The observer was shown a smaller room, which had the same variable-colour illuminant, through an aperture (11 deg × 8 deg) in the left side wall. We set the illuminant for each room independently, but in asymmetric illuminant-colour conditions either was set to white. The observer viewed the central part of a colour CRT monitor, placed behind a small aperture (5 deg × 5 deg) in the front wall, and matched its colour appearance to four OSA colour chips in the smaller room. Under symmetric illuminant conditions, eg blue vs blue, the observers' settings showed a complete match with the physical chromaticities of the colour chips. In asymmetric illuminant conditions, eg white vs blue, matched colours showed systematic deviations from both physical chromaticities and colour constancy. This implies that taking the ambient illuminant as adapting field did not yield perfect colour constancy. We introduce a simple model based on incomplete adaptation to the ambient illuminant and a spatial-interaction mechanism, which accounts for our results.
Spatiotemporal Dynamics of Attention-Induced Distortions and Illusions
Authors: Yoo M H , Schelchshorn J , Chung C S , Sireteanu R 
Published: December 2015

Selective attention induces perceptual distortions, ranging from repulsion of objects located near the attended area (Suzuki and Cavanagh, 1994 Investigative Ophthalmology and Visual Science35 2081) to magnification of inattended objects (Tsal and Shalev, 1996 Journal of Experimental Psychology: Human Perception and Performance22 233 – 243). Two hypothetical mechanisms have been postulated: a shift of receptive field positions away from the locus of attention (receptive-field shift hypothesis) or the enlargement of perceived space around the attended location (spatial-enlargement hypothesis). The aim of the present study was to distinguish between these two hypotheses, by investigating the spatial and temporal properties of attention-induced distortions. Perceptual judgments on Vernier alignment, line tilt, line length, and size of outlined figures were used to measure attention-induced changes in perception. Attention was induced exogenously (by blinking a specific set of dots around the test stimuli) or endogenously (by instructing the subject to selectively attend the dots). After inducing attention, the test stimuli were briefly flashed. A staircase method was used to measure the attentional effect. The experiment was performed with 3 Korean and 3 German subjects. A vertical line was perceived as repelled from the locus of attention, and a line segment appeared longer when attention was given to its vicinity. In addition, several well-known illusions (eg the Ponzo and the Gibson illusions) were produced by having the subjects merely attend a set of inducing dots. The effects decreased as the distance between the locus of attention or the time between the onset of attention and the stimulus presentation increased. The results imply that the space-enlargement hypothesis provides a better explanation for the attention-induced changes in perception than the receptive-field-shift hypothesis.
Brightness Illusion Induced by Consistency Constraints
Authors: Feher A 
Published: December 2015

We present a novel brightness illusion (the ‘Brick Illusion’) that is determined by perceptual interpretation. The image is ambiguous in terms of depth layering, and the strength of the illusion depends on the chosen interpretation. When a certain interpretation is enforced by stereo disparity, and the layering is disambiguated, the strength of the illusion changes according to constraints on the consistency between depth layering, transparency relationships, and surface brightness. We applied a 2AFC brightness comparison procedure to quantify the strength of the illusion. This procedure allowed us to measure the uncertainty of judgements on relative surface brightness in illusory conditions. The increased uncertainty of our observers among these conditions reflects the multidimensional nature of these judgements. This paper is linked to the following World Wide Web page: http://zeus.rutgers.edu/∼feher/brick.html . With a Java-enabled browser the reader can change the gray levels of the backgrounds and the disks, the disparity of the disks, and other parameters.
Temporal Correlations in Presentation Order during Learning Affects Human Object Recognition
Authors: Wallis G M , Bülthoff H H 
Published: December 2015

The view-based approach to object recognition supposes that objects are stored as a series of associated views. Although representation of these views as combinations of 2-D features allows generalisation to similar views, it remains unclear how very different views might be associated together to allow recognition from any viewpoint. One cue present in the real world other than spatial similarity, is that we usually experience different objects in temporally constrained, coherent order, and not as randomly ordered snapshots. In a series of recent neural-network simulations, Wallis and Baddeley (1997 Neural Computation9 883 – 894) describe how the association of views on the basis of temporal as well as spatial correlations is both theoretically advantageous and biologically plausible. We describe an experiment aimed at testing their hypothesis in human object-recognition learning. We investigated recognition performance of faces previously presented in sequences. These sequences consisted of five views of five different people's faces, presented in orderly sequence from left to right profile in 45° steps. According to the temporal-association hypothesis, the visual system should associate the images together and represent them as different views of the same person's face, although in truth they are images of different people's faces. In a same/different task, subjects were asked to say whether two faces seen from different viewpoints were views of the same person or not. In accordance with theory, discrimination errors increased for those faces seen earlier in the same sequence as compared with those faces which were not ( p<0.05).
Texture Segmentation and the Familiarity Effect
Authors: Meinecke C 
Published: December 2015

Texture segmentation performance is usually defined as being data-driven and bottom - up: visual features of the stimulus—like orientation differences between target and background texture elements—are then evaluated automatically. The question investigated in the experiments reported here is: Are there some hints that not only ‘pure visual features’ determine segmentation performance, but other factors like the familiarity of the stimulus material already exert an influence at these early stages of information processing? The familiarity effect is revealed by better performance when detecting an unfamiliar element embedded in familiar elements (eg an inverted letter ‘N’ among correct ‘N's) compared with the familiar element embedded in unfamiliar elements (see, eg, Frith, 1974 Perception & Psychophysics16 113 – 116). In a series of experiments, spatial and temporal factors of the stimulus conditions (eg density, jitter, display size, presentation time) have been varied, so as to determine the constraints under which the familiarity effect influences texture-segmentation performance. Results showed that the familiarity of texture elements had a rather strong influence on early visual processes. This influence disappeared only under very restricted display conditions (very short presentation time, very high density). This provides further information on which framing conditions are typical for data-driven early vision processes.