Grouping, pooling, and when bigger is better in visual crowding

Abstract

In crowding, perception of a target is strongly deteriorated by nearby elements. Crowding is often explained by pooling models predicting that adding flankers increases crowding. In contrast, the centroid hypothesis proposes that adding flankers decreases crowding--"bigger is better." In foveal vision, we have recently shown that adding flankers can increase or decrease crowding depending on whether the target groups or ungroups from the flankers. We have further shown how configural effects, such as good and global Gestalt, determine crowding. Foveal and peripheral crowding do not always reveal the same characteristics. Here, we show that the very same grouping and Gestalt results of foveal vision are also found in the periphery. These results can neither be explained by simple pooling nor by centroid models. We discuss when bigger is better and how grouping might shape crowding.

Contextual effects in human visual cortex depend on surface structure

“…Indeed, grouping also plays a critical role in crowding (Manassi et al 2012). Despite some similarity in the stimulus configurations, our results were not due to crowding.…”

“…However, a number of recent psychophysical findings have shown that high-level perceptual grouping can influence basic visual detection and discrimination performance in stimulus configurations that resemble those used in orientation-specific surround suppression experiments Joo et al 2012;Manassi et al 2012;Mareschal et al 2001;Sayim et al 2008). Thus we hypothesized that perceptual grouping would influence orientation-specific surround suppression such that it would occur only when the target and flankers were grouped into a single array.…”

Nonspecific competition underlies transient attention

“…Consistent with what has been found earlier in other paradigms (Baylis & Driver, 1992;Kooi et al, 1994;Manassi et al, 2012), target discrimination was impaired when the surrounding distractors were similar (i.e. had the same polarity).…”

“…First, greater similarity between the target and distractors in terms of polarity led to more competition and impaired performance, similar to what has been found in studies of crowding and visual search (Baylis & Driver, 1992;Kooi et al, 1994;Sayim et al, 2008). The impairment by similarity has been suggested to result from grouping between the elements that may take place not only when the target is similar with the distractors, but also when these form a configuration that does not allow for target pop-out (Malania et al, 2007;Manassi et al, 2012). While feature pop-out is long known to lead to faster RTs in visual search (Baylis & Driver, 1992;Treisman & Gelade, 1980), the current results show that it plays a role also in unspeeded discrimination, even under circumstances when attention is already cued to the target location.…”

“…At least three factors have been found to contribute to crowding, namely feature similarity, target-distractor compatibility, and spatial proximity. First, distractors that are similar to the target by features such as color, orientation, and size lead to impaired discrimination performance and thus more crowding (Kooi, Toet, Tripathy, & Levi, 1994;Manassi, Sayim, & Herzog, 2012), possibly due to grouping between similar elements (Manassi et al, 2012;Saarela, Sayim, Westheimer, & Herzog, 2009;Sayim, Westheimer, & Herzog, 2008). Competition by feature similarity has also been found to impair performance in other tasks, such as visual search (Baylis & Driver, 1992).…”