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Monocular signals in human lateral geniculate nucleus reflect the Craik–Cornsweet–O'Brien effectEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The human visual system has a remarkable ability to accurately estimate the relative brightness of adjacent objects despite large variations in illumination. However, the lightness of two identical equiluminant gray regions can appear quite different when a light–dark luminance transition falls between them. This illusory brightness “filling-in” phenomenon, the Craik–Cornsweet–O'Brien (CCOB) illusion, exposes fundamental assumptions made by the visual system in estimating lightness, but its neural basis remains unclear. While the responses of high-level visual cortex can be correlated with perception of the CCOB,...
Source: Journal of Vision Articles - November 20, 2009 Category: Opthalmology Source Type: journals

A summary-statistic representation in peripheral vision explains visual crowdingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Peripheral vision provides a less faithful representation of the visual input than foveal vision. Nonetheless, we can gain a lot of information about the world from our peripheral vision, for example in order to plan eye movements. The phenomenon of crowding shows that the reduction of information available in the periphery is not merely the result of reduced resolution. Crowding refers to visual phenomena in which identification of a target stimulus is significantly impaired by the presence of nearby stimuli, or flankers. What information is available in the periphery? We propose that the visual system locally represents ...
Source: Journal of Vision Articles - November 19, 2009 Category: Opthalmology Source Type: journals

The fate of task-irrelevant visual motion: Perceptual load versus feature-based attentionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We tested contrasting predictions derived from perceptual load theory and from recent feature-based selection accounts. Observers viewed moving, colored stimuli and performed low or high load tasks associated with one stimulus feature, either color or motion. The resultant motion aftereffect (MAE) was used to evaluate attentional allocation. We found that task-irrelevant visual features received less attention than co-localized task-relevant features of the same objects. Moreover, when color and motion features were co-localized yet perceived to belong to two distinct surfaces, feature-based selection was further increased...
Source: Journal of Vision Articles - November 18, 2009 Category: Opthalmology Source Type: journals

Faces and text attract gaze independent of the task: Experimental data and computer modelEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Previous studies of eye gaze have shown that when looking at images containing human faces, observers tend to rapidly focus on the facial regions. But is this true of other high-level image features as well? We here investigate the extent to which natural scenes containing faces, text elements, and cell phones—as a suitable control—attract attention by tracking the eye movements of subjects in two types of tasks—free viewing and search. We observed that subjects in free-viewing conditions look at faces and text 16.6 and 11.1 times more than similar regions normalized for size and position of the face and text. In ter...
Source: Journal of Vision Articles - November 18, 2009 Category: Opthalmology Source Type: journals

The role of vertical mirror symmetry in visual shape detectionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The goal of our study is a better understanding of the role of vertical mirror symmetry in perceptual grouping. With a simple psychophysical task and a set of controlled stimuli, we investigated whether vertical mirror symmetry acts as a cue in figure-ground segregation. We asked participants to indicate which of two sequentially presented Gabor arrays contained a visual shape. The shape was defined by a subset of Gabor elements positioned along the outline of an unfamiliar shape. By adding orientation noise to these Gabor elements, the shape percept became less salient. Across the different noise levels, symmetric shapes ...
Source: Journal of Vision Articles - November 18, 2009 Category: Opthalmology Source Type: journals

Origin of the fast negative ERG component from isolated aspartate-treated mouse retinaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The leading edge of the a-wave of the ERG is generally believed to accurately reflect the changes in the circulating current through the cGMP-gated channels in the outer segment plasma membrane of rods and cones. The aspartate-isolated mammalian electroretinogram (ERG) to a rod-saturating flash contains a fast “nose”-like wave temporally overlapping with the a-wave. We characterize the nature of this nose, investigate the membrane current mechanisms involved in the nose mechanism, and propose a model that can explain the generation of the nose component in the rod inner segment. On the basis of pharmacological treatmen...
Source: Journal of Vision Articles - November 17, 2009 Category: Opthalmology Source Type: journals

Stereoscopic discrimination of the layout of ground surfacesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Safe and effective locomotion depends critically on judgements of the surface properties of the ground to be traversed. Little is known about the role of binocular vision in surface perception at distances relevant to visually guided locomotion in humans. Programmable arrays of illuminated targets were used to present sparsely textured surfaces with real depth at distances of 4.5 and 9.0 m. Psychophysical measurements of discrimination thresholds demonstrated a clear superiority for stereoscopic over monocular judgments of relative and absolute surface slant. Judgements of surface roughness in particular demonstrated a sub...
Source: Journal of Vision Articles - November 17, 2009 Category: Opthalmology Source Type: journals

Recalibration of multisensory simultaneity: Cross-modal transfer coincides with a change in perceptual latencyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
After exposure to asynchronous sound and light stimuli, perceived audio-visual synchrony changes to compensate for the asynchrony. Here we investigate to what extent this audio-visual recalibration effect transfers to visual-tactile and audio-tactile simultaneity perception in order to infer the mechanisms responsible for temporal recalibration. Results indicate that audio-visual recalibration of simultaneity can transfer to audio-tactile and visual-tactile stimuli depending on the way in which the multisensory stimuli are presented. With presentation of co-located multisensory stimuli, we found a change in the perceptual ...
Source: Journal of Vision Articles - November 13, 2009 Category: Opthalmology Source Type: journals

Categorical color constancy for simulated surfacesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Color constancy is the ability to perceive constant surface colors under varying lighting conditions. Color constancy has traditionally been investigated with asymmetric matching, where stimuli are matched over two different contexts, or with achromatic settings, where a stimulus is made to appear gray. These methods deliver accurate information on the transformations of single points of color space under illuminant changes, but can be cumbersome and unintuitive for observers. Color naming is a fast and intuitive alternative to matching, allowing data collection from a large portion of color space. We asked observers to na...
Source: Journal of Vision Articles - November 12, 2009 Category: Opthalmology Source Type: journals

Latency characteristics of the short-wavelength-sensitive cones and their associated pathwaysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
There are many distinct types of retinal ganglion and LGN cells that have opponent cone inputs and which may carry chromatic information. Of interest are the asymmetries in those LGN cells that carry S-cone signals: in S-ON cells, S+ signals are opposed by (L + M) whereas, in many S-OFF cells, L+ signals are opposed by (S + M), giving −S + L − M (C. Tailby, S. G. Solomon, & P. Lennie, 2008). However, the S-opponent pathway is traditionally modeled as ±[S − (L + M)]. A phase lag of the S-cone signal has been inferred from psychophysical thresholds for discriminating combinations of simultaneous sinusoidal modulations...
Source: Journal of Vision Articles - November 12, 2009 Category: Opthalmology Source Type: journals

Orientation tuning of curvature adaptation reveals both curvature-polarity-selective and non-selective mechanismsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We have used a curvature after-effect, or CAE, to explore whether curvature detectors are tuned for the overall orientation of a curve. CAEs were measured for half-cycle cosine-shaped contours as a function of adaptor contour orientation for a fixed test contour orientation. CAEs (i) were greatest when the adaptor and test contours had the same orientation, (ii) decreased rapidly as the orientation of the adapting contours rotated away from the test, the data being well fit by a Gaussian function with a standard deviation of 16°, (iii) increased again to a secondary peak when the adapting contours were rotated 180° relat...
Source: Journal of Vision Articles - November 11, 2009 Category: Opthalmology Source Type: journals

The initial torsional Ocular Following Response (tOFR) in humans: A response to the total motion energy in the stimulus?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We recorded the initial torsional ocular following responses (tOFRs) elicited at short latency by visual images that occupied the frontal plane and rotated about the lines of sight. Using 1-D radial gratings, the local spatio-temporal characteristics of these tOFRs closely resembled those we previously reported for the hOFRs to horizontal motion with 1-D vertical gratings. When the 1-D radial grating was subdivided into a number of concentric annuli, each with the same radial thickness, tOFRs were less than predicted from the sum of the responses to the individual annuli: spatial normalization. However, the normalization w...
Source: Journal of Vision Articles - November 10, 2009 Category: Opthalmology Source Type: journals

The sliding window of audio–visual simultaneityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Humans exist in an environment wherein many unrelated events occur in close spatial and temporal proximity. Audio–visual timing experiments, however, have often examined only isolated pairs of sensory events. We therefore decided to assess how audio–visual timing perception would be shaped by the presence of an additional audio or visual event. We found that the point of subjective synchrony for a sensory event can be shifted away from the presence of other temporally proximate events. These interactions made audio–visual pairs seem unrelated, or asynchronous, at timings at which they had seemed synchronous when pres...
Source: Journal of Vision Articles - November 10, 2009 Category: Opthalmology Source Type: journals

Nonlinear characterization of a simple process in human visionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Perceptual processes are often modeled as linear filters followed by a decisional rule. This simple model is central to the understanding of visual processing in humans. Its scope may be extended to capture a wider range of behaviors by the addition of nonlinear operators or kernels, but there is no evidence in human sensory processing that these operators are able to enhance the linear description. We focused on a simple process in human vision, the perception of brightness in a center-surround annular stimulus. We used psychophysical reverse correlation to fully characterize this process up to its second-order nonlineari...
Source: Journal of Vision Articles - November 6, 2009 Category: Opthalmology Source Type: journals

Dissociable effects of attention and crowding on orientation averagingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We examined this idea in the context of an orientation averaging task, having subjects judge the mean orientation of a set of oriented signal elements either in isolation, or “crowded” by nearby randomly oriented elements. In some conditions, subjects also had to perform an attentionally demanding secondary task. By measuring performance at different levels of signal orientation variability, we show that crowding increases subjects' local uncertainty (about the orientation of individual elements) but that diverting attention reduces their global efficiency (the effective number of elements they can average over). Furth...
Source: Journal of Vision Articles - October 29, 2009 Category: Opthalmology Source Type: journals

Separate motion-detecting mechanisms for first- and second-order patterns revealed by rapid forms of visual motion priming and motion aftereffectEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Fast adaptation biases the perceived motion direction of a subsequently presented ambiguous test pattern (R. Kanai & F. A. Verstraten, 2005). Depending on both the duration of the adapting stimulus (ranging from tens to hundreds of milliseconds) and the duration of the adaptation-test blank interval, the perceived direction of an ambiguous test pattern can be biased towards the same or the opposite direction of the adaptation pattern, resulting in rapid forms of motion priming or motion aftereffect respectively. These findings were obtained employing drifting luminance gratings. Many studies have shown that first-order mot...
Source: Journal of Vision Articles - October 28, 2009 Category: Opthalmology Source Type: journals

Different cue weights at the same placeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The visual system uses multiple cues to estimate properties of interest. Since the errors in the estimates from different cues for the same property are generally different, a weighted average of the cues provides a better overall estimate. The most precise estimate is found when each cue's weight is proportional to its reliability. We here show that the weights given to cues for surface slant can differ between two transparent surfaces that are at the same location at the same time. Thus the weights must be assigned separately for each structure, rather than for each location. (Source: Journal of Vision Articles)
Source: Journal of Vision Articles - October 28, 2009 Category: Opthalmology Source Type: journals

Everyone knows what is interesting: Salient locations which should be fixatedEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Most natural scenes are too complex to be perceived instantaneously in their entirety. Observers therefore have to select parts of them and process these parts sequentially. We study how this selection and prioritization process is performed by humans at two different levels. One is the overt attention mechanism of saccadic eye movements in a free-viewing paradigm. The second is a conscious decision process in which we asked observers which points in a scene they considered the most interesting. We find in a very large participant population (more than one thousand) that observers largely agree on which points they conside...
Source: Journal of Vision Articles - October 27, 2009 Category: Opthalmology Source Type: journals

A new theory of structure-from-motion perceptionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Humans can recover 3-D structure from the projected 2D motion field of a rotating object, a phenomenon called structure from motion (SFM). Current models of SFM perception are limited to the case in which objects rotate about a frontoparallel axis. However, as our recent psychophysical studies showed, frontoparallel axes of rotation are not representative of the general case. Here we present the first model to address the problem of SFM perception for the general case of rotations around an arbitrary axis. The SFM computation is cast as a two-stage process. The first stage computes the structure perpendicular to the axis o...
Source: Journal of Vision Articles - October 27, 2009 Category: Opthalmology Source Type: journals

Mechanisms underlying perceptual learning of contrast detection in adults with anisometropic amblyopiaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
What underlies contrast sensitivity improvements in adults with anisometropic amblyopia following perceptual learning in grating contrast detection? In this paper, we adopted the external noise approach (Z.-L. Lu & B. A. Dosher, 1998) to identify the mechanisms underlying perceptual learning in adults with anisometropic amblyopia. By measuring contrast thresholds in a range of external noise conditions at two performance levels (79.3% and 70.7%), we found that a mixture of internal additive noise reduction and external noise exclusion underlay training induced contrast sensitivity improvements in adults with anisometropic ...
Source: Journal of Vision Articles - October 27, 2009 Category: Opthalmology Source Type: journals

The roles of mask luminance and perceptual grouping in visual backward maskingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Visual backward masking is a commonly used technique in vision research and psychology. There are two distinct types of masking. Either masking is strongest for a simultaneous presentation of the target and the mask (A-type masking) or masking is strongest when the mask trails the target (B-type masking). To account for the two types of masking, a variety of explanations have been put forward that often rely on low-level features such as the target-mask energy ratio. However, recent studies have demonstrated that the global spatial layout of the mask is an equally important factor. Here, we investigated both factors jointl...
Source: Journal of Vision Articles - October 22, 2009 Category: Opthalmology Source Type: journals

Tactile force perception depends on the visual speed of the collision objectEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Previous research on the interaction between vision and touch has employed static visual and continuous tactile stimuli, and has shown that two kinds of multimodal interaction effect exist: the averaging effect and the contrast effect. The averaging effect has been used to explain several kinds of stimuli interaction while the contrast effect is associated only with the size-weight illusion (A. Charpentier, 1891). Here, we describe a novel visuotactile interaction using visual motion information that can be explained with the contrast effect. We show that the magnitude of tactile force perception (MTFP) from an impact on t...
Source: Journal of Vision Articles - October 21, 2009 Category: Opthalmology Source Type: journals

Relative contributions of 2D and 3D cues in a texture segmentation task, implications for the roles of striate and extrastriate cortex in attentional selectionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we investigate whether and how 3D depth perception, believed to be processed mostly beyond V1 and starting in V2 (J. S. Bakin, K. Nakayama, & C. D. Gilbert, 2000; B. G. Cumming & A. J. Parker, 2000; F. T. Qiu & R. von der Heydt, 2005; R. von der Heydt, H. Zhou, & H. S. Friedman, 2000), contribute additionally to direct attention. We measured the reduction of the interference or the RT when the position of the texture grid for Iir was offset horizontally from that for Irel, forming an offset, 2D, stimulus. This reduction was compared with that when this positional offset was only present in the input image to...
Source: Journal of Vision Articles - October 21, 2009 Category: Opthalmology Source Type: journals

Size tuning and contextual modulation of backward contrast maskingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The strength of contrast masking depends not only on spatial but also on temporal parameters. In a previous study (T. P. Saarela & M. H. Herzog, 2008), we showed that the detection of a briefly presented Gabor patch is most strongly impaired when an iso-oriented grating mask immediately follows the Gabor and that this masking effect is relieved when a surround is added to the mask. Here, we studied the spatial characteristics of this backward masking effect. Gradually changing the size of the iso-oriented masking grating changes contrast detection thresholds in a non-monotonic way that can be explained in terms of contrast...
Source: Journal of Vision Articles - October 21, 2009 Category: Opthalmology Source Type: journals

Attentive and pre-attentive aspects of figural processingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Here we use the steady-state visual evoked potential (SSVEP) to study attentive versus non-attentive processing of simple texture-defined shapes. By “tagging” the figure and background regions with different temporal frequencies, the method isolates response components associated with the figure region, the background region, and with non-linear spatio-temporal interactions between regions. Each of these response classes has a distinct scalp topography that is preserved under differing attentional task demands. In one task, attention was directed to discrimination of shape changes in the figure region. In the other tas...
Source: Journal of Vision Articles - October 19, 2009 Category: Opthalmology Source Type: journals

Orientation-tuned suppression in binocular rivalry reveals general and specific components of rivalry suppressionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
During binocular rivalry (BR), conflicting monocular images are alternately suppressed from awareness. During suppression of an image, contrast sensitivity for probes is reduced by ~0.3–0.5 log units relative to when the image is in perceptual dominance. Previous studies on rivalry suppression have led to controversies concerning the nature and extent of suppression during BR. We tested for feature-specific suppression using orthogonal rivaling gratings and measuring contrast sensitivity to small grating probes at a range of orientations in a 2AFC orientation discrimination task. Results indicate that suppression is not ...
Source: Journal of Vision Articles - October 15, 2009 Category: Opthalmology Source Type: journals

Involuntary cueing effects on accuracy measures: Stimulus and task dependenceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Observers reported the orientation of a tilted grating that was presented together with a vertical distractor grating. In the main experiments, target contrast was low. There was location uncertainty because target location varied randomly and differences between target and distractor were small. In contrast to a previous report (T. Liu, F. Pestilli, & M. Carrasco, 2005), our results showed that non-informative peripheral cues do not improve perceptual performance at the cued location. However, informative peripheral or central cues improved perceptual performance. When we changed the task from an unspeeded perceptual task...
Source: Journal of Vision Articles - October 14, 2009 Category: Opthalmology Source Type: journals

Experience-dependent changes in the topography of visual crowdingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The present work examined discrimination accuracy for targets that were presented either alone in the visual field (clean displays) or embedded within a dense array of letter distractors (crowded displays). The strength of visual crowding varied strongly across the four quadrants of the visual field. Furthermore, this spatial bias in crowding was strongly influenced by the observers' prior experience with specific distractor stimuli. Observers who were monolingual readers of English experienced amplified crowding in the upper-left quadrant, while subjects with primary reading skills in Korean, Chinese, or Japanese tended t...
Source: Journal of Vision Articles - October 14, 2009 Category: Opthalmology Source Type: journals

Portraits made to measure: Manipulating social judgments about individuals with a statistical face modelEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The social judgments people make on the basis of the facial appearance of strangers strongly affect their behavior in different contexts. However, almost nothing is known about the physical information underlying these judgments. In this article, we present a new technology (a) to quantify the information in faces that is used for social judgments and (b) to manipulate the image of a human face in a way which is almost imperceptible but changes the personality traits ascribed to the depicted person. This method was developed in a high-dimensional face space by identifying vectors that capture maximum variability in judgmen...
Source: Journal of Vision Articles - October 13, 2009 Category: Opthalmology Source Type: journals

The effect of crowding on orientation-selective adaptation in human early visual cortexEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we combined psychophysical and fMRI adaptation techniques to search for the cortical locus of crowding. In the psychophysical experiment, when subjects' attention was controlled, we found that the threshold elevation aftereffect (TEAE) was not affected by crowding, regardless of the contrast level of adapting stimulus. In the fMRI experiment, the orientation-selective fMRI adaptation in V1 was not affected by crowding either. However, downstream from V1, we found that crowding weakened the adaptation effect in V2 and V3. Our results demonstrate that crowding occurs beyond V1 and provide one of the first piec...
Source: Journal of Vision Articles - October 13, 2009 Category: Opthalmology Source Type: journals

What is binocular vision for? A birds' eye viewEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
It is proposed that with the possible exception of owls, binocularity in birds does not have a higher order function that results in the perception of solidity and relative depth. Rather, binocularity is a consequence of the requirement of having a portion of the visual field that looks in the direction of travel; hence, each eye must have a contralateral projection that gives rise to binocularity. This contralateral projection is necessary to gain a symmetrically expanding optic flow-field about the bill. This specifies direction of travel and time to contact a target during feeding or when provisioning chicks. In birds t...
Source: Journal of Vision Articles - October 13, 2009 Category: Opthalmology Source Type: journals

Motion-aftereffect-induced blindnessEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Motion-induced blindness (MIB) describes the occasional disappearance of salient visual objects in the presence of moving features (Y. S. Bonneh, A. Cooperman, & D. Sagi, 2001). Here we test whether motion adaptation and the ensuing motion aftereffect (MAE) are sufficient to trigger disappearance of salient targets. In three experiments, observers adapted to either rotating or static stimuli. Immediately afterwards, a static test pattern was presented consisting of a mask with texture elements and three superimposed target dots in a triangular arrangement. Observers reported dot disappearance and reappearance. The results ...
Source: Journal of Vision Articles - October 12, 2009 Category: Opthalmology Source Type: journals

Image statistics do not explain the perception of gloss and lightnessEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A fundamental problem in image analysis is to understand the nature of the computations and mechanisms that provide information about the material properties of surfaces. Information about a surface's 3D shape, optics, illumination field, and atmospheric conditions are conflated in the image, which must somehow be disentangled to derive the properties of surfaces. It was recently suggested that the visual system exploits some simple image statistics—histogram or sub-band skew—to infer the lightness and gloss of surfaces (I. Motoyoshi, S. Nishida, L. Sharan, & E. H. Adelson, 2007). Here, we show that the correlations Mo...
Source: Journal of Vision Articles - October 9, 2009 Category: Opthalmology Source Type: journals

Visual search without attentional displacementEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The time needed to search for an object in a complex environment increases with the number of distracting stimuli, a phenomenon known as the “set-size effect.” This observation has led to the view that, during visual search, several attentional shifts are performed, suggesting that visual information is processed serially. In an attempt to find direct evidence for such attentional shifts, we implemented several dual tasks combining a covert visual search (CVS) task or a cued target detection task with a character reporting task which allowed us to determine, a posteriori, the attentional allocation. We found that, in t...
Source: Journal of Vision Articles - October 7, 2009 Category: Opthalmology Source Type: journals

The effects of target template specificity on visual search in real-world scenes: Evidence from eye movementsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We can locate an object more quickly in a real-world scene when a specific target template is held in visual working memory, but it is not known exactly how a target template's specificity affects real-world search. In the present study, we compared word and picture cues in real-world scene search. Using an eye-tracker, we segmented search time into three behaviorally defined epochs: search initiation time, scanning time, and verification time. Results from three experiments indicated that target template specificity affects scanning and verification time. Within the scanning epoch, target template specificity affected the...
Source: Journal of Vision Articles - October 6, 2009 Category: Opthalmology Source Type: journals

Downhill slopes look shallower from the edgeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A dramatic failure of orientation constancy is documented in the perception of downhill slopes. Contrary to naïve expectation, steep downhill slopes look shallower from the edge than they do from back from the edge. Three experiments document and quantify this failure of constancy for real and virtual surfaces using a variety of dependent measures. Two additional studies document overestimation of both non-visually perceived head pitch and perceived gaze declination. A model of orientation constancy failure is fit to the data that combine exaggerations in perceived gaze declination with exaggerated scaling of perceived op...
Source: Journal of Vision Articles - October 5, 2009 Category: Opthalmology Source Type: journals

Smooth pursuit performance during target blanking does not influence the triggering of predictive saccadesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Visually guided catch-up saccades during the pursuit of a moving target are highly influenced by smooth pursuit performance. For example, the decision to execute a saccade and its amplitude is driven by the difference in velocity between the eye and the target. In previous studies, we have demonstrated that the predictive saccades that occur during the blanking of the moving target compensate for the variability of the smooth pursuit response. Therefore, we wondered whether the predictive smooth pursuit response during target blanking influenced the occurrence of predictive saccades, which is the case for visually guided c...
Source: Journal of Vision Articles - October 5, 2009 Category: Opthalmology Source Type: journals

An object-color spaceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Putting aside metaphorical meanings of the term, color space is understood as a vector space, where lights having the same color (i.e., subjectively indistinguishable) are represented as a point. The CIE 1931 color space, empirically based on trichromatic color measurements, is a classical example. Its derivatives, such as CIELAB and sRGB, have been successfully used in many applications (e.g., in color management). However, having been designed for presenting the color of self-luminous objects, these spaces are less suitable for presenting color of reflecting objects. Specifically, they can be used to represent color of o...
Source: Journal of Vision Articles - October 5, 2009 Category: Opthalmology Source Type: journals

No capacity limit in attentional tracking: Evidence for probabilistic inference under a resource constraintEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Human ability to simultaneously track multiple items declines with set size. This effect is commonly attributed to a fixed limit on the number of items that can be attended to, a notion that is formalized in limited-capacity and slot models. Instead, we propose that observers are constrained by stimulus uncertainty that increases with the number of items but use Bayesian inference to achieve optimal performance. We model five data sets from published deviation discrimination experiments that varied set size, number of deviations, and magnitude of deviation. A constrained Bayesian observer better explains each data set than...
Source: Journal of Vision Articles - October 4, 2009 Category: Opthalmology Source Type: journals

Accommodative and vergence responses to conflicting blur and disparity stimuli during developmentEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Accommodative and vergence responses of the typically developing visual system are generated using a combination of cues, including retinal blur and disparity. The developmental importance of blur and disparity cues in generating these motor responses was assessed by placing the two cues in conflict with each other. Cue-conflicts were induced by placing either −2 D lenses or 2 MA base-out prisms before both eyes of 140 subjects (2.0 months to 40.8 years) while they watched a cartoon movie binocularly at 80 cm. The frequency and amplitude of accommodation to lenses and vergence to prisms increased with age (both p < 0.001...
Source: Journal of Vision Articles - October 4, 2009 Category: Opthalmology Source Type: journals

The spatial tuning of adaptation-based time compressionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Temporal processing is traditionally dissociated from spatial vision. Recent evidence, however, has shown that adaptation to high temporal frequency (D. Burr, A.Tozzi, & M. C. Morrone, 2007; A. Johnston, D. H. Arnold, & S. Nishida, 2006; A. Johnston et al., 2008) induces spatially specific reductions in the apparent duration of subsecond intervals containing medium frequency drift or flicker. Here we examine the spatial tuning of these temporal adaptation effects. Our results show that duration compression is tightly tuned to the spatial location of the adaptor and can be induced by very narrow adaptors. We also demonstrat...
Source: Journal of Vision Articles - October 1, 2009 Category: Opthalmology Source Type: journals

The spatial tuning of adaption-based time compressionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Temporal processing is traditionally dissociated from spatial vision. Recent evidence, however, has shown that adaptation to high temporal frequency (D. Burr, A.Tozzi, & M. C. Morrone, 2007; A. Johnston, D. H. Arnold, & S. Nishida, 2006; A. Johnston et al., 2008) induces spatially specific reductions in the apparent duration of subsecond intervals containing medium frequency drift or flicker. Here we examine the spatial tuning of these temporal adaptation effects. Our results show that duration compression is tightly tuned to the spatial location of the adaptor and can be induced by very narrow adaptors. We also demonstrat...
Source: Journal of Vision Articles - October 1, 2009 Category: Opthalmology Source Type: journals

Averaging facial expression over timeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The visual system groups similar features, objects, and motion (e.g., Gestalt grouping). Recent work suggests that the computation underlying perceptual grouping may be one of summary statistical representation. Summary representation occurs for low-level features, such as size, motion, and position, and even for high level stimuli, including faces; for example, observers accurately perceive the average expression in a group of faces (J. Haberman & D. Whitney, 2007, 2009). The purpose of the present experiments was to characterize the time-course of this facial integration mechanism. In a series of three experiments, we me...
Source: Journal of Vision Articles - October 1, 2009 Category: Opthalmology Source Type: journals

Occlusion-related lateral connections stabilize kinetic depth stimuli through perceptual couplingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Local sensory information is often ambiguous forcing the brain to integrate spatiotemporally separated information for stable conscious perception. Lateral connections between clusters of similarly tuned neurons in the visual cortex are a potential neural substrate for the coupling of spatially separated visual information. Ecological optics suggests that perceptual coupling of visual information is particularly beneficial in occlusion situations. Here we present a novel neural network model and a series of human psychophysical experiments that can together explain the perceptual coupling of kinetic depth stimuli with acti...
Source: Journal of Vision Articles - October 1, 2009 Category: Opthalmology Source Type: journals

Effects of gestational length, gender, postnatal age, and birth order on visual contrast sensitivity in infantsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To investigate effects of visual experience versus preprogrammed mechanisms on visual development, we used multiple regression analysis to determine the extent to which a variety of variables (that differ in the extent to which they are tied to visual experience) predict luminance and chromatic (red/green) contrast sensitivity (CS), which are mediated by the magnocellular (M) and parvocellular (P) subcortical pathways, respectively. Our variables included gestational length (GL), birth weight (BW), gender, postnatal age (PNA), and birth order (BO). Two-month-olds (n = 60) and 6-month-olds (n = 122) were tested. Results rev...
Source: Journal of Vision Articles - September 29, 2009 Category: Opthalmology Source Type: journals

Sensitivity and perceptual awareness increase with practice in metacontrast maskingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Can practice effects on unconscious stimuli lead to awareness? Can we “learn to see”? Recent evidence suggests that blindsight patients trained for an extensive period of time can learn to discriminate and consciously perceive stimuli that they were previously unaware of. So far, it is unknown whether these effects generalize to normal observers. Here we investigated practice effects in metacontrast masking. Subjects were trained for five consecutive days on the stimulus onset asynchrony (SOA) that resulted in chance performance. Our results show a linear increase in sensitivity (d′) but no change in bias (c) for the...
Source: Journal of Vision Articles - September 24, 2009 Category: Opthalmology Source Type: journals

Improved classification images with sparse priors in a smooth basisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Classification images provide compelling insight into the strategies used by observers in psychophysical tasks. However, because of the high-dimensional nature of classification images and the limited quantity of trials that can practically be performed, classification images are often too noisy to be useful unless denoising strategies are adopted. Here we propose a method of estimating classification images by the use of sparse priors in smooth bases and generalized linear models (GLMs). Sparse priors in a smooth basis are used to impose assumptions about the simplicity of observers' internal templates, and they naturally...
Source: Journal of Vision Articles - September 22, 2009 Category: Opthalmology Source Type: journals

Intermittent occlusion enhances the smoothness of sampled motionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We present evidence showing that a target in sampled motion is perceived as smoother when structure in the background appears and disappears synchronously with the target. Specifically, we found that target flicker is turned into permanent target visibility at short interstimulus intervals and jerkiness is replaced by smoothly accelerating and decelerating motion at longer ones. We argue that this “smoothening” effect is essentially a form of amodal completion in space–time being evoked by spatiotemporal cues to occlusion. The effect highlights the importance of amodal representations in perception. (Source: Journal of Vision Articles)
Source: Journal of Vision Articles - September 21, 2009 Category: Opthalmology Source Type: journals

The role of orientation and position in shape perceptionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study investigates the contributions of position versus orientation information in shape perception by putting the two in conflict. Sampling the orientation of, e.g., a rounded pentagon and positioning the samples on a circle creates a stimulus in which element positions are consistent with a circle but element orientations with a pentagon.Whether orientation or position dominates the percept depends on a number of factors. First, perceived shape shows a band-pass relationship with respect to number of samples. Element orientation captures element position unless elements are widely separated or very closely spaced. T...
Source: Journal of Vision Articles - September 20, 2009 Category: Opthalmology Source Type: journals