Crowding without visual awareness

Cham, Joey; Cheung, Sing‐Hang

doi:10.1167/9.8.991

Cited by 1 publication

(2 citation statements)

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“…Several studies have also investigated the effects of flanker awareness on crowding (Chakravarthi & Cavanagh, 2009 ; Cham & Cheung, 2009 ; Ho & Cheung, 2011 ; Veenemans, Cavanagh, & Chakravarthi, 2009 ; Wallis & Bex, 2011 ), with conflicting results. Wallis and Bex ( 2011 ) showed that flanker awareness was necessary to elicit crowding.…”

Section: Introductionmentioning

confidence: 99%

“…Other studies showed that flanker awareness is not necessary for crowding. Making flankers invisible with pre- and postmasks (Veenemans et al, 2009 ), interocular suppression (a.k.a., continuous flash suppression; Cham & Cheung, 2009 ; Ho & Cheung, 2011 ) or noise and metacontrast masking (Chakravarthi & Cavanagh, 2009 ) led to crowding. For example, Ho & Cheung ( 2011 ) showed that Gabor flankers rendered invisible by interocular suppression (IOS) interact with target Gabors.…”

Section: Introductionmentioning

confidence: 99%

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Crowding, visual awareness, and their respective neural loci

2017

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In peripheral vision, object identification can be impeded when a target object is flanked by other objects. This phenomenon of crowding has been attributed to basic processes associated with image encoding by the visual system, but the neural origin of crowding is not known. Determining whether crowding depends on subjective awareness of the flankers can provide information on the neural origin of crowding. However, recent studies that manipulated flanker awareness have yielded conflicting results. In the current study, we suppressed flanker awareness with two methods: interocular suppression (IOS) and adaptation-induced blindness (AIB). We tested two different types of stimuli: gratings and letters. With IOS, we found that the magnitude of crowding increased as the number of physical flankers increased, even when the observers did not report seeing any of the flankers. In contrast, when flanker awareness was manipulated with AIB, the magnitude of crowding increased with the number of perceived flankers. Our results show that whether crowding is contingent on awareness of the flankers depends on the method used to suppress awareness. In addition, our results imply that the locus of crowding is upstream from the neural locus of IOS and close to or downstream from that of AIB. Neurophysiology and neuroimaging studies jointly implicate mid-to-high level visual processing stages for IOS, while direct evidence regarding the neural locus of AIB is limited. The most consistent interpretation of our empirical findings is to place the neural locus of crowding at an early cortical site, such as V1 or V2.

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