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Nador J, Reeves A. Crowding expands and is less sensitive to target-flanker differences during a shift of visual attention. Vision Res 2023; 212:108305. [PMID: 37515890 DOI: 10.1016/j.visres.2023.108305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 06/02/2023] [Accepted: 07/20/2023] [Indexed: 07/31/2023]
Abstract
Target-flanker similarity and critical spacing control visual crowding when attention is pre-allocated, but these have not been studied when attention shifts. Flanked target Gabors appeared 8° left and right of central fixation throughout each 1.5 s trial. Subjects reported target Gabor tilt. In Expt. 1, target blinks increased accuracy, and flanker blinks decreased it, but only when attention shifted left or right from a central RSVP cue, hardly before it, indicating an exogenous/endogenous synergy. Whether parallel or orthogonal, flankers of the same wavelength as the target crowded substantially. Parallel half-wavelength flankers also crowded, but orthogonal half-wavelength ones did not. In Expt. 2, crowding when attention shifts was the same for targets and flankers within Bouma's bound (2.5° apart) as outside it (5.0° apart.) In Expt. 3, Bouma's bound was restored when attention was focused continuously on the target. We conclude that crowding temporarily expands and becomes less discriminative when attention shifts.
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Affiliation(s)
- Jeff Nador
- Dept. of Psychology, Northeastern University, 360 Huntingdon Ave., Boston, MA 02115, USA; Dept. of Psychology, Université de Fribourg, Faucigny 2, 1700 Fribourg, Switzerland.
| | - Adam Reeves
- Dept. of Psychology, Northeastern University, 360 Huntingdon Ave., Boston, MA 02115, USA.
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2
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Silva AE, Lehmann R, Perikleous N, Thompson B. The temporal dynamics of visual crowding in letter recognition: Modulating crowding with alternating flicker presentations. J Vis 2023; 23:18. [PMID: 37768277 PMCID: PMC10540873 DOI: 10.1167/jov.23.10.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 08/31/2023] [Indexed: 09/29/2023] Open
Abstract
Visual crowding reduces the visibility of a peripherally presented group of stimuli. This is especially challenging for peripheral reading because adjacent letters or characters perceptually crowd one another. We investigated the temporal course of spatial visual crowding by sequentially alternating the visibility of the target and flanking letters within a trigram letter stimulus presented 9° below fixation. We found that alternation rates of roughly 3 Hz released half of the total effect of crowding, whereas 10 Hz alternation rates elicited near-crowded performance. Furthermore, we found a robust performance asymmetry whereby presenting the target first elicited better performance than presenting the flankers first, an effect resembling forward masking. These results held for conditions of high, medium, and low spatial crowding. Future work will determine whether the alternation rates found in the current study can improve peripheral reading.
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Affiliation(s)
- Andrew E Silva
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Rebecca Lehmann
- Aalen University, Optics and Mechatronics, Aalen, Baden-Wuerttemberg, Germany
| | - Niki Perikleous
- Aalen University, Optics and Mechatronics, Aalen, Baden-Wuerttemberg, Germany
| | - Benjamin Thompson
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
- Centre for Eye and Vision Research, Hong Kong, SAR China
- Liggins Institute, University of Auckland, Auckland, New Zealand
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3
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Prahalad KS, Coates DR. Microsaccadic correlates of covert attention and crowding. J Vis 2022; 22:15. [PMID: 36121661 PMCID: PMC9503213 DOI: 10.1167/jov.22.10.15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Spatial crowding occurs when an object is cluttered among other objects in space and is a ubiquitous factor affecting object recognition in the peripheral visual field. Crowding is typically tested by presenting crowded stimuli at an eccentric location while having observers fixate at a point in space. However, even during fixation, our eyes are not perfectly steady but instead make small-scale eye movements (microsaccades) that have recently been suggested to be affected by shifts in attentional allocation. In the current study, we monitored microsaccadic behavior (a possible attentional correlate) to understand naturally occurring shifts in attention that occur following the presentation of a crowded stimulus. A tracking scanning laser ophthalmoscope (TSLO) was used to image the right eye of each observer during a psychophysical task. The stimuli consisted of Sloan numbers (0-9) presented briefly, either unflanked or surrounded by Sloan numbers at one of four nominal spacings. The extent of crowding was found to decrease by 26% on trials with the presence of incongruent microsaccades (proposed to suggest attentional capture). These findings complement the existing body of literature on the beneficial impact of explicit shifts of spatial attention to the location of a crowded stimulus.
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Affiliation(s)
| | - Daniel R Coates
- College of Optometry, University of Houston, Houston, TX, USA.,
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4
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Reuther J, Chakravarthi R, Martinovic J. Masking, crowding, and grouping: Connecting low and mid-level vision. J Vis 2022; 22:7. [PMID: 35147663 PMCID: PMC8842520 DOI: 10.1167/jov.22.2.7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
An important task for vision science is to build a unitary framework of low- and mid-level vision. As a step on this way, our study examined differences and commonalities between masking, crowding and grouping—three processes that occur through spatial interactions between neighbouring elements. We measured contrast thresholds as functions of inter-element spacing and eccentricity for Gabor detection, discrimination and contour integration, using a common stimulus grid consisting of nine Gabor elements. From these thresholds, we derived a) the baseline contrast necessary to perform each task and b) the spatial extent over which task performance was stable. This spatial window can be taken as an indicator of field size, where elements that fall within a putative field are readily combined. We found that contrast thresholds were universally modulated by inter-element distance, with a shallower and inverted effect for grouping compared with masking and crowding. Baseline contrasts for detecting stimuli and discriminating their properties were positively linked across the tested retinal locations (parafovea and near periphery), whereas those for integrating elements and discriminating their properties were negatively linked. Meanwhile, masking and crowding spatial windows remained uncorrelated across eccentricity, although they were correlated across participants. This suggests that the computation performed by each type of visual field operates over different distances that co-varies across observers, but not across retinal locations. Contrast-processing units may thus lie at the core of the shared idiosyncrasies across tasks reported in many previous studies, despite the fundamental differences in the extent of their spatial windows.
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Affiliation(s)
| | | | - Jasna Martinovic
- School of Psychology, University of Aberdeen, UK.,Department of Psychology, School of Philosophy, Psychology and Language Sciences, University of Edinburgh, UK.,
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5
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Chung STL, Patel SS. Spatial and temporal proximity of objects for maximal crowding. Vision Res 2022; 194:108012. [PMID: 35042087 DOI: 10.1016/j.visres.2022.108012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/14/2021] [Accepted: 01/06/2022] [Indexed: 11/16/2022]
Abstract
Crowding refers to the deleterious visual interaction among nearby objects. Does maximal crowding occur when objects are closest to one another in space and time? We examined how crowding depends on the spatial and temporal proximity, retinally and perceptually, between a target and flankers. Our target was a briefly flashed T-stimulus presented at 10° right of fixation (3-o'clock position). It appeared at different target-onset-to-flanker asynchronies with respect to the instant when a pair of flanking Ts, revolving around the fixation target, reached the 3-o'clock position. Observers judged the orientation of the target-T (the crowding task), or its position relative to the revolving flankers (the flash-lag task). Performance was also measured in the absence of flanker motion: target and flankers were either presented simultaneously (closest retinal temporal proximity) with different angular spatial offsets, or were presented collinearly (closest retinal spatial proximity) with different temporal onset asynchronies. We found that neither retinal nor perceptual spatial or temporal proximity could account for when maximal crowding occurred. Simulations using a model based on feed-forward interactions between sustained and transient channels in static and motion pathways, taking into account the differential response latencies, can explain the crowding functions observed under various spatio-temporal conditions between the target and flankers.
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Affiliation(s)
- Susana T L Chung
- School of Optometry, University of California, Berkeley, Berkeley, CA, USA.
| | - Saumil S Patel
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
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Coates DR, Ludowici CJH, Chung STL. The generality of the critical spacing for crowded optotypes: From Bouma to the 21st century. J Vis 2021; 21:18. [PMID: 34694326 PMCID: PMC8556556 DOI: 10.1167/jov.21.11.18] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 09/22/2021] [Indexed: 11/24/2022] Open
Abstract
It is rare to find a crowding manuscript that fails to mention "Bouma's law," the rule of thumb stating that flankers within a distance of about one half of the target eccentricity will induce crowding. Here we investigate the generality of this rule (even for just optotypes), the factors that modulate the critical spacing, and the evidence for the rule in Bouma's own data. We explore these questions by reanalyzing a variety of studies from the literature, running several new control experiments, and by utilizing a model that unifies flanked identification measurements between psychophysical paradigms. Specifically, with minimal assumptions (equivalent psychometric slopes across conditions, for example), crowded acuity can be predicted for arbitrary target sizes and flanker spacings, revealing a performance "landscape" that delineates the critical spacing. Last, we present a compact quantitative summary of the effects of different types of stimulus manipulations on optotype crowding.
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Affiliation(s)
- Daniel R Coates
- College of Optometry, University of Houston, Houston, TX, USA
| | | | - Susana T L Chung
- School of Optometry, Vision Science Graduate Group, University of California, Berkeley, Berkeley, CA, USA
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7
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Chakravarthi R, Bertamini M. Clustering leads to underestimation of numerosity, but crowding is not the cause. Cognition 2020; 198:104195. [DOI: 10.1016/j.cognition.2020.104195] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 01/13/2020] [Accepted: 01/16/2020] [Indexed: 10/25/2022]
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