Mixture model investigation of the inner\u2013outer asymmetry in visual crowding reveals a heavier weight towards the visual periphery

Adi Shechter,Amit Yashar

doi:10.1038/s41598-021-81533-9

Abstract

Crowding, the failure to identify a peripheral item in clutter, is an essential bottleneck in visual information processing. A hallmark characteristic of crowding is the inner–outer asymmetry in which the outer flanker (more eccentric) produces stronger interference than the inner one (closer to the fovea). We tested the contribution of the inner-outer asymmetry to the pattern of crowding errors in a typical radial crowding display in which both flankers are presented simultaneously on the horizontal meridian. In two experiments, observers were asked to estimate the orientation of a Gabor target. Instead of the target, observers reported the outer flanker much more frequently than the inner one. When the target was the outer Gabor, crowding was reduced. Furthermore, when there were four flankers, two on each side of the target, observers misreported the outer flanker adjacent to the target, not the outermost flanker. Model comparisons suggested that orientation crowding reflects sampling over a weighted sum of the represented features, in which the outer flanker is more heavily weighted compared to the inner one. Our findings reveal a counterintuitive phenomenon: in a radial arrangement of orientation crowding, within a region of selection, the outer item dominates appearance more than the inner one.

Highlights

Crowding, the failure to identify a peripheral item in clutter, is an essential bottleneck in visual information processing
A main effect on precision was observed, F(2,24) = 28.05, p < 0.001, partial η2 = 0.70, indicating higher precision in the uncrowded condition than in the two-flanker condition, t(12) = 5.30, p < 0.001, Cohen’s d = 1.93, and in the two-flanker condition compared to the four-flanker condition, t(12) = 2.18, p = 0.050, Cohen’s d = 0.56
One-way Analysis of Variance (ANOVA) analyses on precision and crowding condition as within subjects factor revealed a significant main effect of crowding conditions on precision, F(2,26) = 44.30, p = 0.000, partial η2 = 0.77, indicating higher precision in the uncrowded condition compared to the two-flanker condition, t(13) = 6.13, p = 0.000, Cohen’s d = 1.45, and in the two-flanker condition compared to the four-flanker condition, t(13) = 4.19, p = 0.001, Cohen’s d = 1.60

Summary

Introduction

The failure to identify a peripheral item in clutter, is an essential bottleneck in visual information processing. Several studies have proposed a population coding model that codes target and flanker features as a weighted sum within a receptive field and can explain both averaging and misreporting errors of o rientation[37,40,49], color and spatial frequency[49]. Investigations of these models often use estimation reports in which observers estimated the target feature in a continuous space; for example, reporting the orientation of the target by adjusting the orientation of a probe. Whether the relative contribution, and activation, of the outer flanker is different from the inner one is still unclear

Methods

Results

Discussion

Conclusion