Crowding, grouping, and object recognition: A matter of appearance

Abstract

In crowding, the perception of a target strongly deteriorates when neighboring elements are presented. Crowding is usually assumed to have the following characteristics. (a) Crowding is determined only by nearby elements within a restricted region around the target (Bouma's law). (b) Increasing the number of flankers can only deteriorate performance. (c) Target-flanker interference is feature-specific. These characteristics are usually explained by pooling models, which are well in the spirit of classic models of object recognition. In this review, we summarize recent findings showing that crowding is not determined by the above characteristics, thus, challenging most models of crowding. We propose that the spatial configuration across the entire visual field determines crowding. Only when one understands how all elements of a visual scene group with each other, can one determine crowding strength. We put forward the hypothesis that appearance (i.e., how stimuli look) is a good predictor for crowding, because both crowding and appearance reflect the output of recurrent processing rather than interactions during the initial phase of visual processing.

Targets but not flankers are suppressed in crowding as revealed by EEG frequency tagging

“…Our results suggest that crowding occurs in a slow, recurrent process. Using EEG source localization techniques, we found that high-level visual areas reflected crowding better than V1 supporting, again, the idea that crowding is linked to grouping and appearance (Herzog et al, 2015).…”

“…Crowding depends on multiple grouping cues, including similarity and pattern completion as was shown in previous studies (Herzog et al, 2015;Manassi et al, 2012;Sayim et al, 2008). For example, a red vernier was flanked by red or green flankers.…”

“…When the target and the flankers do not group, crowding is weak. Only when elements group, can crowding be strong (Herzog et al, 2015).…”

“…Whereas superb resolution is desirable in certain situations, it is not when the human brain needs to process wholes rather than parts. For example, we have shown that strong crowding disappears when the flankers ungroup from the target, e.g., by becoming part of a larger whole (Herzog et al, 2015;Malania et al, 2007;Manassi et al, 2012Manassi et al, , 2013Saarela et al, 2009;Sayim et al, 2010).…”

Visual crowding involves delayed frontoparietal response and enhanced top‐down modulation

“…When a peripherally presented target, which is easily recognized on its own, is surrounded by nearby flankers, its recognition performance is often largely disrupted (Levi, ; Whitney & Levi, ). This phenomenon, referred to as crowding, is not only a well‐established effect in spatial vision which occurs under a wide range of conditions and tasks but also a basic property of peripheral vision that sets the limit for peripheral perception (Anderson, Dakin, Schwarzkopf, Rees, & Greenwood, ; Chen et al., ; Chicherov & Herzog, ; Chicherov, Plomp, & Herzog, ; Greenwood, Sayim, & Cavanagh, ; Herzog, Sayim, Chicherov, & Manassi, ; Levi, ; Manassi, Sayim, & Herzog, ; Ronconi, Bertoni, & Marotti, ; Shin, Chung, & Tjan, ; Whitney & Levi, ; Xiong, Yu, & Zhang, ; Zhang, Zhang, Liu, & Yu, ). It is of vital importance to study crowding and its underlying neural mechanism, as it would advance our understandings of conscious vision and object recognition.…”