Evidence for the beneficial effect of perceptual grouping on visual working memory: an empirical study on illusory contour and a meta-analytic study

Li, Jiaofeng; Qian, Jiehui; Liang, Fan · 2018 · DOAJ

DOI: 10.1038/s41598-018-32039-4

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Summary

This study investigates the impact of perceptual grouping on visual working memory (VWM), addressing controversies regarding the robustness of this effect and the influence of experimental moderators. While previous research suggests that Gestalt principles facilitate VWM, it remains unclear whether this benefit extends to features irrelevant to the grouping mechanism and how factors like stimulus type or task design affect the magnitude of the effect. The authors conducted an empirical study using illusory contours and a meta-analysis of existing literature to resolve these inconsistencies. The empirical component comprised three experiments using change detection tasks with colored circular sectors. Experiment 1 compared memory performance across conditions involving physical connectedness, solid occlusion, illusory contours (Kanizsa figures), and random orientations. Experiment 2 introduced a competitive resource allocation paradigm by testing grouped and ungrouped items within the same trial. Experiment 3 controlled for spatial proximity to fixation to isolate the grouping effect from attentional biases. The meta-analysis systematically reviewed 43 eligible studies published between 1997 and 2017, extracting effect sizes and analyzing moderators such as grouping method, display duration, and feature characteristics. The empirical results demonstrated that perceptual grouping by illusory contour significantly improved memory performance for grouped items compared to ungrouped items, even when the tested feature (color) was irrelevant to the formation of the illusory figure. This benefit was comparable in magnitude to grouping by physical connectedness or solid occlusion. Experiment 3 confirmed that the grouping effect persisted after controlling for spatial proximity, although items near fixation still showed superior performance. The meta-analysis revealed a robust beneficial effect of perceptual grouping on VWM overall. However, moderator analyses indicated that the effect size varied based on the type of grouping method, the duration and layout of the memory display, and the characteristics of the tested feature. Conversely, the use of cues or verbal suppression tasks did not significantly moderate the effect. The findings suggest that the mechanism underlying the grouping benefit differs depending on whether the stored feature is relevant to the grouping process. For grouping-relevant features, the benefit may be independent of attention, whereas for grouping-irrelevant features, it likely relies on attentional prioritization of grouped items. This study clarifies that perceptual grouping generally enhances VWM capacity but highlights that the extent of this enhancement is contingent on specific experimental parameters and the nature of the visual features being encoded.

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• working memory