Contrast polarity, chromaticity, and stereoscopic depth modulate contextual interactions in vernier acuity

Abstract

Vernier alignment thresholds are strongly compromised when the vernier is embedded in an array of equal-length flanking lines. Here, we show that these contextual interactions can be diminished by giving the flanks the opposite contrast polarity, e.g., white flanks surrounding a black vernier. Similar results are obtained for red verniers and equiluminant green flanks and when vernier and flanks have different binocular disparity. Using special flank configurations, we can eliminate location uncertainty as an important factor for this kind of contextual interactions. We interpret these results as evidence that perceptual grouping of the vernier and the flanks plays an important role in the vernier threshold elevation caused by contextual flanks.

Nonspecific competition underlies transient attention

“…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).…”

“…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).…”

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

“…1A). Based on previous studies (Kooi et al, 1994;Manassi et al, 2012;Sayim et al, 2008), we expected flankers, which are identical in color to the vernier (same-color flankers), to crowd more strongly than different-color flankers. We presented the stimuli in a two-by-three factorial design with the factors Vernier Color (red or green) and Flankers (no flankers, same-color flankers, or different-color flankers).…”

Contextual effects in human visual cortex depend on surface structure

“…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.…”