Broad attention uncovers benefits of stimulus uniformity in visual crowding

Abstract

Crowding is the interference by surrounding objects (flankers) with target perception. Low target-flanker similarity usually yields weaker crowding than high similarity (‘similarity rule’) with less interference, e.g., by opposite- than same-contrast polarity flankers. The advantage of low target-flanker similarity has typically been shown with attentional selection of a single target object. Here, we investigated the validity of the similarity rule when broadening attention to multiple objects. In three experiments, we measured identification for crowded letters (Experiment 1), tumbling Ts (Experiment 2), and tilted lines (Experiment 3). Stimuli consisted of three items that were uniform or alternating in contrast polarity and were briefly presented at ten degrees eccentricity. Observers reported all items (full report) or only the left, central, or right item (single-item report). In Experiments 1 and 2, consistent with the similarity rule, single central item performance was superior with opposite- compared to same-contrast polarity flankers. With full report, the similarity rule was inverted: performance was better for uniform compared to alternating stimuli. In Experiment 3, contrast polarity did not affect performance. We demonstrated a reversal of the similarity rule under broadened attention, suggesting that stimulus uniformity benefits crowded object recognition when intentionally directing attention towards all stimulus elements. We propose that key properties of crowding have only limited validity as they may require a-priori differentiation of target and context.

Multidimensional feature interactions in visual crowding: When configural cues eliminate the polarity advantage

“…Conventional crowding rules of spacing, similarity, and grouping have typically been shown using task-irrelevant flankers: observers were asked to report a single target, while processing of the flankers was not required. However, when the context was task-relevant, previous studies showed that conventional crowding rules did not readily apply ( Melnik, Coates, & Sayim, 2018 ; Rummens & Sayim, 2021 ). For instance, when all letters of a trigram had to be reported, the recognition of the central letter was only minimally better ( Chung & Mansfield, 2009 ) or similar ( Rummens & Sayim, 2021 ) when neighboring letters had opposite compared to identical contrast polarity.…”

“…However, when the context was task-relevant, previous studies showed that conventional crowding rules did not readily apply ( Melnik, Coates, & Sayim, 2018 ; Rummens & Sayim, 2021 ). For instance, when all letters of a trigram had to be reported, the recognition of the central letter was only minimally better ( Chung & Mansfield, 2009 ) or similar ( Rummens & Sayim, 2021 ) when neighboring letters had opposite compared to identical contrast polarity. These findings are consistent with high target-flanker similarity being less costly when all letters were targets instead of a single letter only ( Huckauf & Heller, 2002 ; Rummens & Sayim, 2021 ; Zhang, Zhang, Liu, & Yu, 2012 ).…”

“…Target identification is generally better when the similarity between the target and its surrounding flankers is low. For instance, it was shown that identifying a crowded letter was superior with opposite compared to same contrast polarity flankers ( Chung & Mansfield, 2009 ; Kooi, Toet, Tripathy, & Levi, 1994 ; Rosen & Pelli, 2015 ; Rummens & Sayim, 2019 ; Rummens & Sayim, 2021 ), a benefit referred to as the “polarity advantage” ( Chakravarthi & Cavanagh, 2007 ). Similarly, previous studies revealed that flanker tilts closer to the target orientation yielded stronger crowding than flanker tilts further away ( Andriessen & Bouma, 1976 ; Hariharan, Levi, & Klein, 2005 ; He, Wang, & Fang, 2019 ; Levi, Hariharan, & Klein, 2002 ; Solomon, Felisberti, & Morgan, 2004 ; Wilkinson, Wilson, & Ellemberg, 1997 ).…”

“…For instance, when all letters of a trigram had to be reported, the recognition of the central letter was only minimally better ( Chung & Mansfield, 2009 ) or similar ( Rummens & Sayim, 2021 ) when neighboring letters had opposite compared to identical contrast polarity. These findings are consistent with high target-flanker similarity being less costly when all letters were targets instead of a single letter only ( Huckauf & Heller, 2002 ; Rummens & Sayim, 2021 ; Zhang, Zhang, Liu, & Yu, 2012 ). Furthermore, word recognition, a task in which all letters are task-relevant, has been shown to benefit from strong (compared to weak) grouping between adjacent word parts.…”

Atypical visual field asymmetries in redundancy masking

“…RM is related to crowding ( Bouma, 1970 ; Bouma, 1973 ; Herzog, Sayim, Chicherov, & Manassi, 2015 ; Levi, 2008 ; Melnik, Coates, & Sayim, 2018 ; Melnik, Coates, & Sayim, 2020 ; Pelli, Palomares, & Majaj, 2004 ; Rummens & Sayim, 2019 ; Rummens & Sayim, 2021 ; Sayim & Cavanagh, 2013 ; Sayim, Greenwood, & Cavanagh, 2014 ; Strasburger, 2020 ; Strasburger, Harvey, & Rentschler, 1991 ; Whitney & Levi, 2011 ). A loss of information possibly related to RM, such as the omissions or truncations of elements ( Sayim & Wagemans, 2017 ), was shown in a number of recent crowding studies ( Coates, Bernard, & Chung, 2019 ; Coates, Wagemans, & Sayim, 2017 ; Sayim & Wagemans, 2017 ; see also Korte, 1923 ).…”