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Abstract The capacity of visual working memory (VWM) is found to be extremely limited. Past research shows that VWM can be facilitated by Gestalt principles of grouping, however, it remains controversial whether factors like the type of Gestalt principles, the characteristics of stimuli and the nature of experimental design could affect the beneficial effect of grouping. In particular, studies have shown that perceptual grouping could improve memory performance for a feature that is relevant for grouping, but it is unclear whether the same improvement exists for a feature that is irrelevant for grouping. In this article, an empirical study and a meta-analytic study were conducted to investigate the effect of perceptual grouping on VWM. In the empirical study, we examined the grouping effect by employing a Kanizsa illusion in which memory items were grouped by illusory contour. We found that the memory performance was improved for the grouped items even though the tested feature was grouping irrelevant, and the improvement was not significantly different from the effect of grouping by physical connectedness or by solid occlusion. In the meta-analytic study, we systematically and quantitatively examined the effect of perceptual grouping on VWM by pulling the results from all eligible studies, and found that the beneficial grouping effect was robust but the magnitude of the effect can be affected by several moderators. Factors like the types of grouping methods, the duration and the layout of the memory display, and the characteristics of the tested feature moderated the grouping effect, whereas whether employing a cue or a verbal suppression task did not. Our study suggests that the underlying mechanism of the grouping benefit may be distinct with regard to grouping relevancy of the to-be-stored feature. The grouping effect on VWM may be independent of attention for a grouping relevant feature, but may rely on attentional prioritization for a grouping irrelevant feature.

Abstract Visual working memory (VWM) is a cognitive memory buffer for temporarily holding, processing, and manipulating visual information. Previous studies have demonstrated mixed results of the effect of depth perception on VWM, with some showing a beneficial effect while others not. In this study, we employed an adapted change detection paradigm to investigate the effects of two depth cues, binocular disparity and relative size. The memory array consisted of a set of pseudo-randomly positioned colored items, and the task was to judge whether the test item was changed compared to the memory item after a retention interval. We found that presenting the items in stereoscopic depth alone hardly affected VWM performance. When combining the two coherent depth cues, a significant larger VWM capacity of the perceptually closer-in-depth items was observed than that of the farther items, but the capacity for the two-depth-planes condition was not significantly different from that for the one-plane condition. Conflicting the two depth cues resulted in cancelling the beneficial effect of presenting items at a closer depth plane. The results indicate that depth perception could affect VWM, and the visual system may have an advantage in maintaining closer-in-depth objects in working memory.