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2D location biases depth-from-disparity judgments but not vice versa
Abstract
Visual cognition in our 3D world requires understanding how we accurately localize objects in 2D and depth, and what influence both types of location information have on visual processing. Spatial location is known to play a special role in visual processing, but most of these findings have focused on the special role of 2D location. One such phenomena is the spatial congruency bias, where 2D location biases judgments of object features but features do not bias location judgments. This paradigm has recently been used to compare different types of location information in terms of how much they bias different types of features. Here we used this paradigm to ask a related question: whether 2D and depth-from-disparity location bias localization judgments for each other. We found that presenting two objects in the same 2D location biased position-in-depth judgments, but presenting two objects at the same depth (disparity) did not bias 2D location judgments. We conclude that an object’s 2D location may be automatically incorporated into perception of its depth location, but not vice versa, which is consistent with a fundamentally special role for 2D location in visual processing.
... So far, the SCB has been investigated by manipulating location in same-different judgement tasks using stimuli such as shapes (e.g., Boduroglu & Shah, 2009;Finlayson & Golomb, 2016;Golomb et al., 2014;Shafer-Skelton, Kupitz, & Golomb, 2017), faces (e.g., Paradiso, Shafer-Skelton, Martinez, & Golomb, 2016;Shafer-Skelton et al., 2017), gabor patches (e.g., Shafer-Skelton et al., 2017), letters (e.g., Cave & Chen, 2017), and random dot stereograms (Finlayson & Golomb, 2017). Key findings to date suggest that the SCB is a perceptual effect rather than a response effect, as the magnitude of the bias scales with perceptual similarity (e.g., Cave & Chen, 2017;Golomb et al., 2014;Paradiso et al., 2016) but not with changes in response code (e.g., Cave & Chen, 2017). ...
... Interestingly, the privileged status of location appears to apply only to 2D location, but not to 3D location. Finlayson and Golomb (2017) used the spatial congruency paradigm to investigate the effect of 2D location on depth-from-disparity/3D judgements and vice versa. The results show that 2D location biases 3D judgements but not the other way round. ...
Four experiments explore the generalizability of two different types of bias in visual comparison. The first type is a spatial congruency bias, in which two target stimuli are more likely to be classified as matching (‘same’) if they appear successively at the same location. The second type is an analytic bias, which varies depending on the overall similarity of the displays and the need to select specific parts from each object. Both types of bias had previously been demonstrated in comparisons based on shape and other visual features. The current tasks move beyond feature comparisons, requiring the comparison of the local positions of visual elements (dots or letters) that appear within each pattern. Given the privileged role of location in visual representations and attentional selection, it is important to test how visual comparisons of location differ from comparisons of shape and other features. The spatial congruency bias is replicated in the comparison of local positions and, as in previous experiments, its strength diminishes when the displays being compared are less similar to one another. Also, as demonstrated previously with letter comparisons, there is an analytic bias shifting responses toward ‘different’ when the displays being compared are less similar to one another. Responses are also shifted more toward ‘same’ in location comparisons relative to feature comparisons. The general pattern of results suggests that as more attentional selection is required in a comparison task, there is a stronger overall bias to respond ‘different’.
... However, the depth estimates were fairly accurate for all set sizes in the whole-display condition, indicating the cost of memory load may be compensated by the benefit of configuration information. Research showed that manipulating the 2-D spatial locations (Finlayson & Golomb, 2017) or the depth positions of non-target items (Klinghammer et al., 2016) could bias the judgment of stored depth position. Since the consistent 2-D spatial configuration and relational depth information were provided in the whole display, both could contribute to the improvement of DWM. ...
Depth perception is essential for effective interaction with the environment. Although the accuracy of depth perception has been studied extensively, it is unclear how accurate the depth information is stored in working memory. In this study, we investigated the accuracy and systematic biases of depth representation by a delayed estimation task. The memory array consisted of items presented at various stereoscopic depth positions, and the participants were instructed to estimate the depth position of one target item after a retention interval. We examined the effect of spatial configuration by comparing the memory performance in the whole‐display condition where non‐target memory items were present during retrieval with that in the single‐display condition where non‐target memory items were absent. In the single‐display condition, we found an overestimation bias that the depth estimates were farther than the corresponding depth positions defined by disparity, and a contraction bias that the stored depth positions near the observer were overestimated and those far from the observer were underestimated. The magnitude of these biases increased with the number of to‐be‐stored items. However, in the whole‐display condition, the overestimation bias was corrected and the contraction bias did not increase with the number of to‐be‐stored items. Our findings suggested that the number of to‐be‐stored items could affect the accuracy of depth working memory, and its effect depended crucially on whether the information of spatial configuration of memory display was available at the retrieval stage.
A basic function of human visual perception is the ability to recognize and locate objects in the environment. It has been shown that two-dimensional (2D) location can reliably bias judgments on object identity (spatial congruency bias; Golomb et al., 2014), suggesting that 2D location information is automatically bound with object features to induce such a bias. Although the binding problem of feature and location has been vigorously studied under various 2D settings, it remains unclear how depth location can be bound with object features in a three-dimensional (3D) setting. Here we conducted five experiments in various 3D contexts using the congruency bias paradigm, and found that changes of object’s depth location could influence perceptual judgments on object features differently depending on whether its relative depth order with respect to others changed or not. Experiments 1 and 2 showed that the judgments on an object’s color could be affected by changes in its ordinal depth, but not by changes in its absolute metric depth. Experiment 3 showed that the bias was asymmetric—changes in an object’s color did bias the judgments on metric-depth location, but not if its depth order had changed. Experiments 4 and 5 investigated whether these findings could be generalized to a peripersonal near space and a large-scale far space, respectively, using more ecological virtual environments. Our findings suggest that ordinal depth plays a special role in feature-location binding: an object may be automatically bound with its relative depth relation, but not with its absolute metric-depth location.
A fundamental aspect of human visual perception is the ability to recognize and locate objects in the environment. Importantly, our environment is predominantly three-dimensional (3D), but while there is considerable research exploring the binding of object features and location, it is unknown how depth information interacts with features in the object binding process. A recent paradigm called the spatial congruency bias demonstrated that 2D location is fundamentally bound to object features, such that irrelevant location information biases judgments of object features, but irrelevant feature information does not bias judgments of location or other features. Here, using the spatial congruency bias paradigm, we asked whether depth is processed as another type of location, or more like other features. We initially found that depth cued by binocular disparity biased judgments of object color. However, this result seemed to be driven more by the disparity differences than the depth percept: Depth cued by occlusion and size did not bias color judgments, whereas vertical disparity information (with no depth percept) did bias color judgments. Our results suggest that despite the 3D nature of our visual environment, only 2D location information - not position-in-depth - seems to be automatically bound to object features, with depth information processed more similarly to other features than to 2D location.
M. B. Miller and G. L. Wolford (1999) argued that the high false-alarm rate associated with critical lures in the Roediger–McDermott (H. L. Roediger & K. B. McDermott, 1995) paradigm results from a criterion shift and therefore does not reflect false memory. This conclusion, which is based on new data reported by Miller and Wolford, overlooks the fact that Roediger and McDermott's false-memory account is as compatible with the new findings as the criterion-shift account is. Furthermore, a consideration of prior work concerned with investigating the conditions under which participants are and are not inclined to adjust the decision criterion suggests that the criterion-shift account of false memory is unlikely to be correct.
Binocular vision is obviously useful for depth perception, but it might also enhance other components of visual processing, such as image segmentation. We used naturalistic images to determine whether giving an object a stereoscopic offset of 15-120 arcmin of crossed disparity relative to its background would make the object easier to recognize in briefly presented (33-133 ms), temporally masked displays. Disparity had a beneficial effect across a wide range of disparities and display durations. Most of this benefit occurred whether or not the stereoscopic contour agreed with the object's luminance contour. We attribute this benefit to an orienting of spatial attention that selected the object and its local background for enhanced 2D pattern processing. At longer display durations, contour agreement provided an additional benefit, and a separate experiment using random-dot stimuli confirmed that stereoscopic contours plausibly contributed to recognition at the longer display durations in our experiment. We conclude that in real-world situations binocular vision confers an advantage not only for depth perception, but also for recognizing objects from their luminance patterns and bounding contours.
We experience our visual world as seen from a single viewpoint, even though our two eyes receive slightly different images. One role of the visual system is to combine the two retinal images into a single representation of the visual field, sometimes called the cyclopean image [1]. Conventional terminology, i.e. retinotopy, implies that the topographic organization of visual areas is maintained throughout visual cortex [2]. However, following the hypothesis that a transformation occurs from a representation of the two retinal images (retinotopy) to a representation of a single cyclopean image (cyclopotopy), we set out to identify the stage in visual processing at which this transformation occurs in the human brain. Using binocular stimuli, population receptive field mapping (pRF), and ultra-high-field (7 T) fMRI, we find that responses in striate cortex (V1) best reflect stimulus position in the two retinal images. In extrastriate cortex (from V2 to LO), on the other hand, responses better reflect stimulus position in the cyclopean image. These results pinpoint the location of the transformation from a retinal to a cyclopean representation and contribute to an understanding of the transition from sensory to perceptual stimulus space in the human brain.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Is depth perception from binocular disparities-stereopsis-slow or fast? Many of the temporal properties of stereopsis are known. For example, rapidly changing disparities are perceptually difficult to track, which suggests that stereopsis is generally slow. But, remarkably, this basic question has not yet been addressed. We compared speed-accuracy trade-off functions between 2 forced-choice discriminations: 1 based on stereoscopic depth and 1 based on luminance. Unexpectedly, both speed-accuracy trade-off functions deviated from chance levels of accuracy at the same response time-approximately 200 ms-with stereo accuracy increasing, on average, more slowly than luminance accuracy after this initial delay. Thus, the initial processing of disparity for perceived depth took no longer than the initial processing of luminance for perceived brightness. This finding, that binocular disparities are available early during visual processing, means that depth is perceived quickly, and, intriguingly, that disparities may be more important for everyday visual function than previously thought. (PsycINFO Database Record
(c) 2015 APA, all rights reserved).
A common conceptualization of signal detection theory (SDT) holds that if the effect of an experimental manipulation is truly perceptual, then it will necessarily be reflected in a change in d′ rather than a change in the measure of response bias. Thus, if an experimental manipulation affects the measure of bias, but not d′, then it is safe to conclude that the manipulation in question did not affect perception but instead affected the placement of the internal decision criterion. However, the opposite may be true: an effect on perception may affect measured bias while having no effect on d′. To illustrate this point, we expound how signal detection measures are calculated and show how all biases—including perceptual biases—can exert their effects on the criterion measure rather than on d′. While d′ can provide evidence for a perceptual effect, an effect solely on the criterion measure can also arise from a perceptual effect. We further support this conclusion using simulations to demonstrate that the Müller-Lyer illusion, which is a classic visual illusion that creates a powerful perceptual effect on the apparent length of a line, influences the criterion measure without influencing d′. For discrimination experiments, SDT is effective at discriminating between sensitivity and bias but cannot by itself determine the underlying source of the bias, be it perceptual or response based.
Many activities necessitate the deployment of attention to specific distances and directions in our three-dimensional (3D) environment. However, most research on how attention is deployed is conducted with two dimensional (2D) computer displays, leaving a large gap in our understanding about the deployment of attention in 3D space. We report how each of four parameters of 3D visual space influence visual search: 3D display volume, distance in depth, number of depth planes, and relative target position in depth. Using a search task, we find that visual search performance depends on 3D volume, relative target position in depth, and number of depth planes. Our results demonstrate an asymmetrical preference for targets in the front of a display unique to 3D search and show that arranging items into more depth planes reduces search efficiency. Consistent with research using 2D displays, we found slower response times to find targets in displays with larger 3D volumes compared with smaller 3D volumes. Finally, in contrast to the importance of target depth relative to other distractors, target depth relative to the fixation point did not affect response times or search efficiency.
Models of depth perception typically omit the orientation and height of the observer despite the potential usefulness of the height above the ground plane and the need to know about head position to interpret retinal disparity information. To assess the contribution of orientation to perceived distance, we used the York University Tumbled and Tumbling Room facilities to modulate both perceived and actual body orientation. These facilities are realistically decorated rooms that can be systematically arranged to vary the relative orientation of visual, gravity, and body cues to upright. To assess perceived depth we exploited size/distance constancy. Observers judged the perceived length of a visual line (controlled by a QUEST adaptive procedure) projected on to the wall of the facilities, relative to the length of an unseen iron rod held in their hands. In the Tumbled Room (viewing distance 337 cm) the line was set about 10% longer when participants were supine compared to when they were upright. In the Tumbling Room (viewing distance 114 cm), the line was set about 11% longer when participants were either supine or made to feel that they were supine by the orientation of the room. Matching a longer visual line to the reference rod is compatible with the opposite wall being perceived as closer. The effect was modulated by whether viewing was monocular or binocular at a viewing distance of 114 cm but not at 337 cm suggesting that reliable binocular cues can override the effect.
Objects can be characterized by a number of properties (e.g., shape, color, size, and location). How do our visual systems combine this information, and what allows us to recognize when 2 objects are the same? Previous work has pointed to a special role for location in the binding process, suggesting that location may be automatically encoded even when irrelevant to the task. Here we show that location is not only automatically attended but fundamentally bound to identity representations, influencing object perception in a far more profound way than simply speeding reaction times. Subjects viewed 2 sequentially presented novel objects and performed a same/different identity comparison. Object location was irrelevant to the identity task, but when the 2 objects shared the same location, subjects were more likely to judge them as the same identity. This "congruency bias" reflected an increase in both hits and false alarms when the objects shared the same location, indicating that subjects were unable to suppress the influence of object location-even when maladaptive to the task. Importantly, this bias was driven exclusively by location: Object location robustly and reliably biased identity judgments across 6 experimental scenarios, but the reverse was not true: Object identity did not exert any bias on location judgments. Furthermore, while location biased both shape and color judgments, neither shape nor color biased each other when irrelevant. The results suggest that location provides a unique, automatic, and insuppressible cue for object sameness. (PsycINFO Database Record (c) 2014 APA, all rights reserved).
The extraction of the distance between an object and an observer is fast when angular declination is informative, as it is with targets placed on the ground. To what extent does angular declination drive performance when viewing time is limited? Participants judged target distances in a real-world environment with viewing durations ranging from 36-220 ms. An important role for angular declination was supported by experiments showing that the cue provides information about egocentric distance even on the very first glimpse, and that it supports a sensitive response to distance in the absence of other useful cues. Performance was better at 220-ms viewing durations than for briefer glimpses, suggesting that the perception of distance is dynamic even within the time frame of a typical eye fixation. Critically, performance in limited viewing trials was better when preceded by a 15-s preview of the room without a designated target. The results indicate that the perception of distance is powerfully shaped by memory from prior visual experience with the scene. A theoretical framework for the dynamic perception of distance is presented. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
In visual search, target detection times are relatively insensitive to set size when targets and distractors differ on a single feature dimension. Search can be confined to only those elements sharing a single feature, such as color (Egeth, Virzi, & Garbart, 1984). These findings have been taken as evidence that elementary feature dimensions support a parallel segmentation of a scene into discrete sets of items. Here we explored if relative depth (signaled by binocular disparity) could support a similar parallel segmentation by examining the effects of distributing distracting elements across two depth planes. Three important empirical findings emerged. First, when the target was a feature singleton on the target depth plane, but a conjunction search among distractors on the nontarget plane, search efficiency increased compared to a single depth plane. Second, benefits of segmentation in depth were only observed when the target depth plane was known in advance. Third, no benefit of segmentation in depth was observed when both planes required a conjunction search, even with prior knowledge of the target depth plane. Overall, the benefit of distributing the elements of a search set across two depth planes was observed only when the two planes differed both in binocular disparity and in the elementary feature composition of individual elements. We conclude that segmentation of the search array into two depth planes can facilitate visual search, but unlike color or other elementary properties, does not provide an automatic, preattentive segmentation.
Are objects moving in depth searched for efficiently? Previous studies have reported conflicting results, with some finding efficient search for only approaching motion (Franconeri & Simons, 2003), and others reporting that both approaching and receding motion are found more efficiently than static targets (Skarratt, Cole, & Gellatly, 2009). This may be due to presentation protocol differences and a confounding variable. We systematically tested the effect of the motion-in-depth presentation method and the effect of a confounding unique depth singleton on search performance. Simulating motion in depth using size scaling, changing binocular disparity, or a calibrated combination of these two depth cues, we found that search performance was affected by presentation method and that a combination of size scaling and changing disparity gives rise to the most compelling motion-in-depth perception. Exploiting this finding in Experiment 2, we found that removing the depth singleton does not affect motion-in-depth search performance. Overall, we found that search is more efficient for targets moving in depth than static targets. Approaching and receding motion had an equal advantage over static targets in target selection, shown through shallower search slopes. However, approaching motion had lower intercepts, consistent with an advantage over receding motion in later stages of processing associated with target identification and response.
Two experiments were conducted to explore whether attentional selection occurs in depth, or whether attentional focus is “depth
blind,” as suggested by Ghiradelli and Folk (1996). In Experiment 1, observers viewed stereoscopic displays in which one of
four spatial locations was cued. Two of the locations were at a near-depth location and two were at a far-depth location,
and a single target was presented along with three distractors. The results indicated a larger cost in reaction time for switching
attention inx,y and depth than inx,y alone, supporting a “depth-aware” attentional spotlight. In Experiment 2, no distractors were present, similar to the displays
used by Ghiradelli and Folk. In this experiment, no effect for switching attention in depth was found, indicating that the
selectivity of attention in depth depends on the perceptual load imposed on observers by the tasks and displays.
Subjects were presented with circular arrays of letters and were instructed to report first a given target (or targets) and
then any other letters they could identify. The targets) was (were) a letter of a given color (Experiment 1) or a given shape
(Experiment 2), or two letters of a given shape (Experiment 3). In all three experiments, the additional letters reported
tended to be adjacent to the first reported target(s). The results suggest that the selective processing of targets specified
by color or by shape is accomplished by attending to the targets’ locations.
In these experiments, each stimulus consists of a series of frames, each containing a target digit of one color and a distractor
digit of another color. The task is to name the highest digit of the target color. Subjects make fewer errors when successive
targets appear at the same location than when they appear at different locations, apparently because they select target objects
by using a mechanism that is based on location. When successive targets appear at the same location, there is no need to “move”
the selection mechanism to a new location, leaving more time to identify the stimuli. These experiments show that location-based
selection is used even though selection by color would be more direct. They also demonstrate a method of measuring location-based
selection that can be applied to a variety of visual tasks. Further experiments reveal that although location-based selection
is used to identify a digit in the presence of a digit distractor, it is not used to identify a digit in the presence of a
letter distractor, suggesting that this selection mechanism is not used in this situation to prevent interference among the
basic features making up letters and digits, but to inhibit responses associated with the distractors.
Humans exploit a range of visual depth cues to estimate three-dimensional structure. For example, the slant of a nearby tabletop can be judged by combining information from binocular disparity, texture and perspective. Behavioral tests show humans combine cues near-optimally, a feat that could depend on discriminating the outputs from cue-specific mechanisms or on fusing signals into a common representation. Although fusion is computationally attractive, it poses a substantial challenge, requiring the integration of quantitatively different signals. We used functional magnetic resonance imaging (fMRI) to provide evidence that dorsal visual area V3B/KO meets this challenge. Specifically, we found that fMRI responses are more discriminable when two cues (binocular disparity and relative motion) concurrently signal depth, and that information provided by one cue is diagnostic of depth indicated by the other. This suggests a cortical node important when perceiving depth, and highlights computations based on fusion in the dorsal stream.
The crux of vision is to identify objects and determine their locations in the environment. Although initial visual representations are necessarily retinotopic (eye centered), interaction with the real world requires spatiotopic (absolute) location information. We asked whether higher level human visual cortex-important for stable object recognition and action-contains information about retinotopic and/or spatiotopic object position. Using functional magnetic resonance imaging multivariate pattern analysis techniques, we found information about both object category and object location in each of the ventral, dorsal, and early visual regions tested, replicating previous reports. By manipulating fixation position and stimulus position, we then tested whether these location representations were retinotopic or spatiotopic. Crucially, all location information was purely retinotopic. This pattern persisted when location information was irrelevant to the task, and even when spatiotopic (not retinotopic) stimulus position was explicitly emphasized. We also conducted a "searchlight" analysis across our entire scanned volume to explore additional cortex but again found predominantly retinotopic representations. The lack of explicit spatiotopic representations suggests that spatiotopic object position may instead be computed indirectly and continually reconstructed with each eye movement. Thus, despite our subjective impression that visual information is spatiotopic, even in higher level visual cortex, object location continues to be represented in retinotopic coordinates.
The theoretical framework of General Recognition Theory (GRT; Ashby & Townsend, Psychological Review, 93, 154-179, 1986) coupled with the empirical analysis tools of Multidimensional Signal Detection Analysis (MSDA; Kadlec & Townsend, Multidimensional models of perception and recognition, pp. 181-228, 1992) have become one important method for assessing dimensional interactions in perceptual decision-making. In this article, we critically examine MSDA and characterize cases where it is unable to discriminate two kinds of dimensional interactions: perceptual separability and decisional separability. We performed simulations with known instances of violations of perceptual or decisional separability, applied MSDA to the data generated by these simulations, and evaluated MSDA on its ability to accurately characterize the perceptual versus decisional source of these simulated dimensional interactions. Critical cases of violations of perceptual separability are often mischaracterized by MSDA as violations of decisional separability.
Much research concerning attention has focused on changes in the perceptual qualities of objects while attentional states were varied. Here, we address a complementary question--namely, how perceived location can be altered by the distribution of sustained attention over the visual field. We also present a new way to assess the effects of distributing spatial attention across the visual field. We measured magnitude judgments relative to an aperture edge to test perceived location across a large range of eccentricities (30°), and manipulated spatial uncertainty in target locations to examine perceived location under three different distributions of spatial attention. Across three experiments, the results showed that changing the distribution of sustained attention significantly alters known foveal biases in peripheral localization.
We measured binocular and monocular depth thresholds for objects presented in a real environment. Observers judged the depth separating a pair of metal rods presented either in relative isolation, or surrounded by other objects, including a textured surface. In the isolated setting, binocular thresholds were greatly superior to the monocular thresholds by as much as a factor of 18. The presence of adjacent objects and textures improved the monocular thresholds somewhat, but the superiority of binocular viewing remained substantial (roughly a factor of 10). To determine whether motion parallax would improve monocular sensitivity for the textured setting, we asked observers to move their heads laterally, so that the viewing eye was displaced by 8-10 cm; this motion produced little improvement in the monocular thresholds. We also compared disparity thresholds measured with the real rods to thresholds measured with virtual images in a standard mirror stereoscope. Surprisingly, for the two naive observers, the stereoscope thresholds were far worse than the thresholds for the real rods-a finding that indicates that stereoscope measurements for unpracticed observers should be treated with caution. With practice, the stereoscope thresholds for one observer improved to almost the precision of the thresholds for the real rods.
Three experiments examined the time course of layout priming with photographic scenes varying in complexity (number of objects). Primes were presented for varying durations (800-50 ms) before a target scene with 2 spatial probes; observers indicated whether the left or right probe was closer to viewpoint. Reaction time was the main measure. Scene primes provided maximum benefits with 200 ms or less prime duration, indicating that scene priming is rapid enough to influence everyday distance perception. The time course of prime processing was similar for simple and complex scene primes and for upright and inverted primes, suggesting that the prime representation was intermediate level in nature.
The role of perceptual organization in the precision of attentional control was assessed in three experiments. Observers viewed circular arrays of disks that varied in density. One disk was cued, directing attention to that disk. A series of tones then indicated shifts of attention to the next disk that was of the same color (Experiments 1 and 2) or on the same depth plane (Experiment 3). In the homogeneous condition, all of the disks were the same color (Experiments 1 and 2) or on the same depth plane (Experiment 3). In the heterogeneous condition, the disks alternated in color (Experiments 1 and 2) or stereoscopically defined depth (Experiment 3). If the observers were able to limit attention to disks within a group, the effective density of the displays in the heterogeneous conditions should have been one half that in the homogeneous conditions. There was little evidence that the observers could do this, indicating a limited role of perceptual organization in the precision of attentional control.
Processing of binocular disparity is thought to be widespread throughout cortex, highlighting its importance for perception and action. Yet the computations and functional roles underlying this activity across areas remain largely unknown. Here, we trace the neural representations mediating depth perception across human brain areas using multivariate analysis methods and high-resolution imaging. Presenting disparity-defined planes, we determine functional magnetic resonance imaging (fMRI) selectivity to near versus far depth positions. First, we test the perceptual relevance of this selectivity, comparing the pattern-based decoding of fMRI responses evoked by random dot stereograms that support depth perception (correlated RDS) with the decoding of stimuli containing disparities to which the perceptual system is blind (anticorrelated RDS). Preferential disparity selectivity for correlated stimuli in dorsal (visual and parietal) areas and higher ventral area LO (lateral occipital area) suggests encoding of perceptually relevant information, in contrast to early (V1, V2) and intermediate ventral (V3v, V4) visual cortical areas that show similar selectivity for both correlated and anticorrelated stimuli. Second, manipulating disparity parametrically, we show that dorsal areas encode the metric disparity structure of the viewed stimuli (i.e., disparity magnitude), whereas ventral area LO appears to represent depth position in a categorical manner (i.e., disparity sign). Our findings suggest that activity in both visual streams is commensurate with the use of disparity for depth perception but the neural computations may differ. Intriguingly, perceptually relevant responses in the dorsal stream are tuned to disparity content and emerge at a comparatively earlier stage than categorical representations for depth position in the ventral stream.
Bartlett viewed thinking as a high level skill exhibiting ballistic properties that he called its “point of no return”. This paper explores one aspect of cognition through the use of a simple model task in which human subjects are asked to commit attention to a position in visual space other than fixation. This instruction is executed by orienting a covert (attentional) mechanism that seems sufficiently time locked to external events that its trajectory can be traced across the visual field in terms of momentary changes in the efficiency of detecting stimuli. A comparison of results obtained with alert monkeys, brain injured and normal human subjects shows the relationship of this covert system to saccadic eye movements and to various brain systems controlling perception and motion. In accordance with Bartlett's insight, the possibility is explored that similar principles apply to orienting of attention toward sensory input and orienting to the semantic structures used in thinking.
The borders of human visual areas V1, V2, VP, V3, and V4 were precisely and noninvasively determined. Functional magnetic
resonance images were recorded during phase-encoded retinal stimulation. This volume data set was then sampled with a cortical
surface reconstruction, making it possible to calculate the local visual field sign (mirror image versus non-mirror image
representation). This method automatically and objectively outlines area borders because adjacent areas often have the opposite
field sign. Cortical magnification factor curves for striate and extrastriate cortical areas were determined, which showed
that human visual areas have a greater emphasis on the center-of-gaze than their counterparts in monkeys. Retinotopically
organized visual areas in humans extend anteriorly to overlap several areas previously shown to be activated by written words.
One of the fundamental challenges of visual cognition is how our visual systems combine information about an object's features with its spatial location. A recent phenomenon related to object-location binding, the "spatial congruency bias," revealed that two objects are more likely to be perceived as having the same identity or features if they appear in the same spatial location, versus if the second object appears in a different location. The spatial congruency bias suggests that irrelevant location information is automatically encoded with and bound to other object properties, biasing perceptual judgments. Here we further explored this new phenomenon and its role in object-location binding by asking what happens when an object moves to a new location: Is the spatial congruency bias sensitive to spatiotemporal contiguity cues, or does it remain linked to the original object location? Across four experiments, we found that the spatial congruency bias remained strongly linked to the original object location. However, under certain circumstances-for instance, when the first object paused and remained visible for a brief time after the movement-the congruency bias was found at both the original location and the updated location. These data suggest that the spatial congruency bias is based more on low-level visual information than on spatiotemporal contiguity cues, and reflects a type of object-location binding that is primarily tied to the original object location and that may only update to the object's new location if there is time for the features to be re-encoded and rebound following the movement.
Despite frequent eye movements that rapidly shift the locations of objects on our retinas, our visual system creates a stable perception of the world. To do this, it must convert eye-centered (retinotopic) input to world-centered (spatiotopic) percepts. Moreover, for successful behavior we must also incorporate information about object features/identities during this updating – a fundamental challenge that remains to be understood. Here we adapted a recent behavioral paradigm, the “spatial congruency bias,” to investigate object-location binding across an eye movement. In two initial baseline experiments, we showed that the spatial congruency bias was present for both gabor and face stimuli in addition to the object stimuli used in the original paradigm. Then, across three main experiments, we found the bias was preserved across an eye movement, but only in retinotopic coordinates: Subjects were more likely to perceive two stimuli as having the same features/identity when they were presented in the same retinotopic location. Strikingly, there was no evidence of location binding in the more ecologically relevant spatiotopic (world-centered) coordinates; the reference frame did not update to spatiotopic even at longer post-saccade delays, nor did it transition to spatiotopic with more complex stimuli (gabors, shapes, and faces all showed a retinotopic congruency bias). Our results suggest that object-location binding may be tied to retinotopic coordinates, and that it may need to be re-established following each eye movement rather than being automatically updated to spatiotopic coordinates.
Visual information is initially represented as 2D images on the retina, but our brains are able to transform this input to perceive our rich 3D environment. While many studies have explored 2D spatial representations or depth perception in isolation, it remains unknown if or how these processes interact in human visual cortex. Here we used functional MRI and multi-voxel pattern analysis to investigate the relationship between 2D location and position-in-depth information. We stimulated different 3D locations in a blocked design: each location was defined by horizontal, vertical, and depth position. Participants remained fixated at the center of the screen while passively viewing the peripheral stimuli with red/green anaglyph glasses. Our results revealed a widespread, systematic transition throughout visual cortex. As expected, 2D location information (horizontal and vertical) could be strongly decoded in early visual areas, with reduced decoding higher along the visual hierarchy, consistent with known changes in receptive field sizes. Critically, we found that the decoding of position-in-depth information tracked inversely with the 2D location pattern, with the magnitude of depth decoding gradually increasing from intermediate to higher visual and category regions. Representations of 2D location information became increasingly location-tolerant in later areas, where depth information was also tolerant to changes in 2D location. We propose that spatial representations gradually transition from 2D-dominant to balanced 3D (2D and depth) along the visual hierarchy.
A fundamental aspect of human visual perception is the ability to recognize and locate objects in the environment. Importantly, our environment is predominantly three-dimensional (3D), but while there is considerable research exploring the binding of object features and location, it is unknown how depth information interacts with features in the object binding process. A recent paradigm called the spatial congruency bias demonstrated that 2D location is fundamentally bound to object features, such that irrelevant location information biases judgments of object features, but irrelevant feature information does not bias judgments of location or other features. Here, using the spatial congruency bias paradigm, we asked whether depth is processed as another type of location, or more like other features. We initially found that depth cued by binocular disparity biased judgments of object color. However, this result seemed to be driven more by the disparity differences than the depth percept: Depth cued by occlusion and size did not bias color judgments, whereas vertical disparity information (with no depth percept) did bias color judgments. Our results suggest that despite the 3D nature of our visual environment, only 2D location information - not position-in-depth - seems to be automatically bound to object features, with depth information processed more similarly to other features than to 2D location.
The angular declination of a target with respect to eye level is known to be an important cue to egocentric distance when objects are viewed or can be assumed to be resting on the ground. When targets are fixated, angular declination and the direction of the gaze with respect to eye level have the same objective value. However, any situation that limits the time available to shift gaze could leave to-be-localized objects outside the fovea, and, in these cases, the objective values would differ. Nevertheless, angular declination and gaze declination are often conflated, and the role for retinal eccentricity in egocentric distance judgments is unknown. We report two experiments demonstrating that gaze declination is sufficient to support judgments of distance, even when extraretinal signals are all that are provided by the stimulus and task environment. Additional experiments showed no accuracy costs for extrafoveally viewed targets and no systematic impact of foveal or peripheral biases, although a drop in precision was observed for the most retinally eccentric targets. The results demonstrate the remarkable utility of target direction, relative to eye level, for judging distance (signaled by angular declination and/or gaze declination) and are consonant with the idea that detection of the target is sufficient to capitalize on the angular declination of floor-level targets (regardless of the direction of gaze).
The purpose of this paper is to investigate the effect of irrelevant location information on performance of visual choice-reaction tasks. We review empirical findings and theoretical explanations from two domains, those of the Simon effect and the spatial Stroop effect, in which stimulus location has been shown to affect reaction time when irrelevant to the task. We then integrate the findings and explanations from the two domains to clarify how and why stimulus location influences performance even when it is uninformative to the correct response. Factors that influence the processing of irrelevant location information include response modality, relative timing with respect to the relevant information, spatial coding, and allocation of attention. The most promising accounts are offered by models in which response selection is a function of (1) strength of association of the irrelevant stimulus information with the response and (2) temporal overlap of the resulting response activation with that produced by the relevant stimulus information.
this chapter deals with [a] . . . type of compatibility, which might be classified as a variety of spatial comaptibility / we will describe a series of related experiments that demonstrated that the location of a stimulus provides an irrelevant directional cue that affects the time required to process the meaning of the stimulus / in other words, there seems to be a strong stereotypic tendency to respond initially to the directional component of a stimulus rather than to its symbolic content (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Thesis (Ph. D.)--George Peabody College for Teachers, 1933.
Retinotopic mapping of functional magnetic resonance (fMRI) responses evoked by visual stimuli has resulted in the identification of many areas in human visual cortex and a description of the organization of the visual field representation in each of these areas. These methods have recently been employed in conjunction with tasks that involve higher-order cognitive processes such as spatial attention, working memory, and planning and execution of saccadic eye movements. This approach has led to the discovery of multiple areas in human parietal and frontal areas, each containing a topographic map of visual space. In this review, we summarize the anatomical locations, visual field organization, and functional specialization of these new parietal and frontal topographic cortical areas. The study of higher-order topographic cortex promises to yield unprecedented insights into the neural mechanisms of cognitive processes and, in conjunction with parallel studies in non-human primates, into the evolution of cognition.
Previous research has shown spontaneous location processing when location is not a task relevant feature and when a target is presented together with distractors. The present study investigates whether such processing can occur in the absence of distractor inhibition, and whether there is a processing asymmetry between location and an object feature. The results show that not all features are created equal. Whereas attending to an object's color or texture led to the involuntary processing of that object's location, attending to an object's location did not necessarily result in the encoding of its color or texture when these nonspatial properties were not task relevant. These results add to the body of evidence demonstrating the special role of location in attentional selection. They also provide a clearer picture of the interactions among location, object features, and participants' behavioral goals.
The results of two experiments are reported in which the change over time in the perceived depth location of a monocular, luminous test object with respect to two binocular luminous stimuli located at different distances was measured. It was found that: 1) The test object receded perceptually in depth over time achieving a stable location in space after 4 min of viewing. 2) The initial perceived location in depth of the test object depended upon which of the two binocular objects was fixated. When the farther binocular object was fixated the test object appeared further away than when the nearer one was fixated. 3) The size of the further binocular object also affected the initial perceived location of the test object. When it was larger, the test object appeared further away than when it was smaller. 4) There was an interaction between the binocular object fixated upon and the lateral separation between it and the test object: the smaller the separation, the greater the fixation effect.
These results were accounted for in terms of the equidistance tendency, the depth adjacency principle, and a possible attentional factor. Taken together the results indicate that while reduced viewing conditions reduce the available stimulus information, they do not reduce the organizational options of the visual system.
A series of experiments explored a form of object-specific priming. In all experiments a preview field containing two or more letters is followed by a target letter that is to be named. The displays are designed to produce a perceptual interpretation of the target as a new state of an object that previously contained one of the primes. The link is produced in different experiments by a shared location, by a shared relative position in a moving pattern, or by successive appearance in the same moving frame. An object-specific advantage is consistently observed: naming is facilitated by a preview of the target, if (and in some cases only if) the two appearances are linked to the same object. The amount and the object specificity of the preview benefit are not affected by extending the preview duration to 1 s, or by extending the temporal gap between fields to 590 ms. The results are interpreted in terms of a reviewing process, which is triggered by the appearance of the target and retrieves just one of the previewed items. In the absence of an object link, the reviewing item is selected at random. We develop the concept of an object file as a temporary episodic representation, within which successive states of an object are linked and integrated.
In recent years, many new cortical areas have been identified in the macaque monkey. The number of identified connections between areas has increased even more dramatically. We report here on (1) a summary of the layout of cortical areas associated with vision and with other modalities, (2) a computerized database for storing and representing large amounts of information on connectivity patterns, and (3) the application of these data to the analysis of hierarchical organization of the cerebral cortex. Our analysis concentrates on the visual system, which includes 25 neocortical areas that are predominantly or exclusively visual in function, plus an additional 7 areas that we regard as visual-association areas on the basis of their extensive visual inputs. A total of 305 connections among these 32 visual and visual-association areas have been reported. This represents 31% of the possible number of pathways if each area were connected with all others. The actual degree of connectivity is likely to be closer to 40%. The great majority of pathways involve reciprocal connections between areas. There are also extensive connections with cortical areas outside the visual system proper, including the somatosensory cortex, as well as neocortical, transitional, and archicortical regions in the temporal and frontal lobes. In the somatosensory/motor system, there are 62 identified pathways linking 13 cortical areas, suggesting an overall connectivity of about 40%. Based on the laminar patterns of connections between areas, we propose a hierarchy of visual areas and of somatosensory/motor areas that is more comprehensive than those suggested in other recent studies. The current version of the visual hierarchy includes 10 levels of cortical processing. Altogether, it contains 14 levels if one includes the retina and lateral geniculate nucleus at the bottom as well as the entorhinal cortex and hippocampus at the top. Within this hierarchy, there are multiple, intertwined processing streams, which, at a low level, are related to the compartmental organization of areas V1 and V2 and, at a high level, are related to the distinction between processing centers in the temporal and parietal lobes. However, there are some pathways and relationships (about 10% of the total) whose descriptions do not fit cleanly into this hierarchical scheme for one reason or another. In most instances, though, it is unclear whether these represent genuine exceptions to a strict hierarchy rather than inaccuracies or uncertainities in the reported assignment.
Psychometric functions were collected to measure biases and sensitivities in certain classical illusory configurations, such as the Müller-Lyer. We found that sensitivities (thresholds or just noticeable differences) were generally not affected by the introduction of illusory biases, and the implications of this for theories of the illusions are discussed. Experiments on the Müller-Lyer figure showed that the effect depends upon mis-location of the ends of the figure, rather than upon a global expansion as demanded by the size-constancy theory. A new illusion is described in which the perceived position of a dot is displaced towards the centre of a surrounding cluster of dots, even though it is clearly discriminable from other members of the cluster by their colour. We argue that illusions illustrate powerful constraints upon visual processing: they arise when subjects are instructed to carry out a task to which the visual system is not adapted.
Treisman and others have reported that the visual search for a target distinguished along a single stimulus dimension (for example, colour or shape) is conducted in parallel, whereas the search for an item defined by the conjunction of two stimulus dimensions is conducted serially. For a single dimension the target 'pops out' and the search time is independent of the number of irrelevant items in the set. For conjunctions, the search time increases as the set becomes larger. Thus, it seems that the visual system is incapable of conducting a parallel search over two stimulus dimensions simultaneously. Here we extend this conclusion for the conjunction of motion and colour, showing that it requires a serial search. We also report two exceptions: if one of the dimensions in a conjunctive search is stereoscopic disparity, a second dimension of either colour or motion can be searched in parallel.
1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most cells can be categorized as simple, complex, or hypercomplex, with response properties very similar to those previously described in the cat. On the average, however, receptive fields are smaller, and there is a greater sensitivity to changes in stimulus orientation. A small proportion of the cells are colour coded.
2. Evidence is presented for at least two independent systems of columns extending vertically from surface to white matter. Columns of the first type contain cells with common receptive‐field orientations. They are similar to the orientation columns described in the cat, but are probably smaller in cross‐sectional area. In the second system cells are aggregated into columns according to eye preference. The ocular dominance columns are larger than the orientation columns, and the two sets of boundaries seem to be independent.
3. There is a tendency for cells to be grouped according to symmetry of responses to movement; in some regions the cells respond equally well to the two opposite directions of movement of a line, but other regions contain a mixture of cells favouring one direction and cells favouring the other.
4. A horizontal organization corresponding to the cortical layering can also be discerned. The upper layers (II and the upper two‐thirds of III) contain complex and hypercomplex cells, but simple cells are virtually absent. The cells are mostly binocularly driven. Simple cells are found deep in layer III, and in IV A and IV B. In layer IV B they form a large proportion of the population, whereas complex cells are rare. In layers IV A and IV B one finds units lacking orientation specificity; it is not clear whether these are cell bodies or axons of geniculate cells. In layer IV most cells are driven by one eye only; this layer consists of a mosaic with cells of some regions responding to one eye only, those of other regions responding to the other eye. Layers V and VI contain mostly complex and hypercomplex cells, binocularly driven.
5. The cortex is seen as a system organized vertically and horizontally in entirely different ways. In the vertical system (in which cells lying along a vertical line in the cortex have common features) stimulus dimensions such as retinal position, line orientation, ocular dominance, and perhaps directionality of movement, are mapped in sets of superimposed but independent mosaics. The horizontal system segregates cells in layers by hierarchical orders, the lowest orders (simple cells monocularly driven) located in and near layer IV, the higher orders in the upper and lower layers.
Random-dot stereoscopic patterns have been used to provide behavioural
evidence of stereoscopic vision in macaque monkeys. Cells sensitive to
binocular depth have been found in area 18 of the macaque monkey cortex.
A new hypothesis about the role of focused attention is proposed. The feature-integration theory of attention suggests that attention must be directed serially to each stimulus in a display whenever conjunctions of more than one separable feature are needed to characterize or distinguish the possible objects presented. A number of predictions were tested in a variety of paradigms including visual search, texture segregation, identification and localization, and using both separable dimensions (shape and color) and local elements or parts of figures (lines, curves, etc. in letters) as the features to be integrated into complex wholes. The results were in general consistent with the hypothesis. They offer a new set of criteria for distinguishing separable from integral features and a new rationale for predicting which tasks will show attention limits and which will not.
In these experiments, each stimulus consists of a series of frames, each containing a target digit of one color and a distractor digit of another color. The task is to name the highest digit of the target color. Subjects make fewer errors when successive targets appear at the same location than when they appear at different locations, apparently because they select target objects by using a mechanism that is based on location. When successive targets appear at the same location, there is no need to "move" the selection mechanism to a new location, leaving more time to identify the stimuli. These experiments show that location-based selection is used even though selection by color would be more direct. They also demonstrated a method of measuring location-based selection that can be applied to a variety of visual tasks. Further experiments reveal that although location-based selection is used to identify a digit in the presence of a digit distractor, it is not used to identify a digit in the presence of a letter distractor, suggesting that this selection mechanism is not used in this situation to prevent interference among the basic features making up letters and digits, but to inhibit responses associated with the distractors.
In this report we describe the results of an experiment in which we demonstrated that a powerful and compelling stereoscopic experience is elicited with very brief (< 1 msec) stimulus durations. The observers were highly successful in recognizing briefly flashed, stereoscopic, random-dot surfaces in the absence of monocular contours. The results are shown to be closely related to the range of depths for any stimulus form; however, the recognition thresholds were nonmonotonic as a function of disparity. Previous investigators have disagreed about the existence of a temporal threshold for stereopsis. We believe that prior findings suggesting that stereopsis cannot occur at short exposure durations are probably due to inadequate control of fixation disparity. Therefore, there is poor dichoptic image registration when a stereoscopic stimulus is presented. The present results also raise difficulties for any theory of stereopsis that requires eye movements.