Uncovering foveal crowding?

Lev, Maria; Yehezkel, Oren; Polat, Uri

doi:10.1038/srep04067

Cited by 47 publications

(95 citation statements)

References 38 publications

(102 reference statements)

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“…Crowding refers to our inability to identify an object (primarily in the peripheral visual field) because it is presented with nearby objects [1][2][3][4][5][6] . Crowding is considered to be an impediment to reading 7 , face recognition 8 , eye saccade and hand movement, visual search 2 as well as deficits like macular degeneration 9 , amblyopia 10 and dyslexia 11 .…”

Section: Introductionmentioning

confidence: 99%

Mixture model investigation of the inner-outer asymmetry in visual crowding reveals a heavier weight towards the visual periphery

Shechter

Yashar

2020

Preprint

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Crowding, the failure to identify a peripheral item in clutter, is an essential bottleneck in visual information processing. A hallmark characteristic of crowding is the innerouter asymmetry in which the outer flanker (more eccentric) produces stronger interference than the inner one (closer to the fovea). We tested the contribution of the inner-outer asymmetry to the pattern of crowding errors in a typical radial crowding display in which both flankers are presented simultaneously on the horizontal meridian.In two experiments observers were asked to estimate the orientation of a Gabor target. Instead of the target, observers reported the outer flanker much more frequently than the inner one. When the target was the outer Gabor, crowding was reduced. These findings suggest that orientation crowding reflects source confusion (substitution) between the target and the outer flanker, but not vice versa. Furthermore, when there were four flankers, two on each side of the target, observers misreported the outer flanker adjacent to the target, not the outermost flanker. This finding postulates the role of spatial selection in crowding. Our findings reveal a counterintuitive phenomenon: in a radial arrangement of orientation crowding, within a region of selection, the outer item dominates appearance more than the inner one.

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Section: Introductionmentioning

confidence: 99%

Mixture model investigation of the inner-outer asymmetry in visual crowding reveals a heavier weight towards the visual periphery

Shechter

Yashar

2020

Preprint

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“…The extent of this window, the critical distance, scales with eccentricity (Bouma, 1970; Chung et al, 2001). The crowding strength and the critical distance depend on temporal properties of the stimuli (Chung & Patel, 2011; Chung, 2016; Lev, Yehezkel, & Polat, 2014). Many other factors, such as attention (Freeman & Pelli, 2007; Grubb et al, 2013; Yeshurun & Rashal, 2010) and perceptual grouping (Manassi, Sayim, & Herzog, 2012, 2013) also affect crowding.…”

Section: Introductionmentioning

confidence: 99%

Unmasking saccadic uncrowding

2016

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Stimuli that are briefly presented around the time of saccades are often perceived with spatiotemporal distortions. These distortions do not always have deleterious effects on the visibility and identification of a stimulus. Recent studies reported that when a stimulus is the target of an intended saccade, it is released from both masking (De Pisapia, Kaunitz, & Melcher, 2010) and crowding (Harrison, Mattingley, & Remington, 2013). Here, we investigated pre-saccadic changes in single and crowded letter recognition performance in the absence (Experiment 1) and the presence (Experiment 2) of backward masks to determine the extent to which saccadic “uncrowding” and “unmasking” mechanisms are similar. Our results show that pre-saccadic improvements in letter recognition performance are mostly due to the presence of masks and/or stimulus transients which occur after the target is presented. More importantly, we did not find any decrease in crowding strength before impending saccades. A simplified version of a dual-channel neural model, originally proposed to explain masking phenomena, with several saccadic add-on mechanisms, could account for our results in Experiment 1. However, this model falls short in explaining how saccades drastically reduced the effect of backward masking (Experiment 2). The addition of a remapping mechanism that alters the relative spatial positions of stimuli was needed to fully account for the improvements observed when backward masks followed the letter stimuli. Taken together, our results (i) are inconsistent with saccadic uncrowding, (ii) strongly support saccadic unmasking, and (iii) suggest that pre-saccadic letter recognition is modulated by multiple perisaccadic mechanisms with different time courses.

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“…It is generally agreed to occur across the entire visual field8, although it is markedly more difficult to measure at the fovea9. As discussed in a review by Pelli and Tillman4, crowding affects all basic object recognition tasks, predicts reading speed and dyslexia, and is diagnostic of foveal deficits present in amblyopia10.…”

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confidence: 99%

Visual crowding is a combination of an increase of positional uncertainty, source confusion, and featural averaging

Harrison

Bex

2017

Sci Rep

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Although we perceive a richly detailed visual world, our ability to identify individual objects is severely limited in clutter, particularly in peripheral vision. Models of such “crowding” have generally been driven by the phenomenological misidentifications of crowded targets: using stimuli that do not easily combine to form a unique symbol (e.g. letters or objects), observers typically confuse the source of objects and report either the target or a distractor, but when continuous features are used (e.g. orientated gratings or line positions) observers report a feature somewhere between the target and distractor. To reconcile these accounts, we develop a hybrid method of adjustment that allows detailed analysis of these multiple error categories. Observers reported the orientation of a target, under several distractor conditions, by adjusting an identical foveal target. We apply new modelling to quantify whether perceptual reports show evidence of positional uncertainty, source confusion, and featural averaging on a trial-by-trial basis. Our results show that observers make a large proportion of source-confusion errors. However, our study also reveals the distribution of perceptual reports that underlie performance in this crowding task more generally: aggregate errors cannot be neatly labelled because they are heterogeneous and their structure depends on target-distractor distance.

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Uncovering foveal crowding?

Cited by 47 publications

References 38 publications

Mixture model investigation of the inner-outer asymmetry in visual crowding reveals a heavier weight towards the visual periphery

Mixture model investigation of the inner-outer asymmetry in visual crowding reveals a heavier weight towards the visual periphery

Unmasking saccadic uncrowding

Visual crowding is a combination of an increase of positional uncertainty, source confusion, and featural averaging

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