Increasing perceptual separateness affects working memory for depth – re-allocation of attention from boundaries to the fixated center

Abstract

For decades, working memory (WM) has been a heated research topic in the field of cognitive psychology. However, most studies on WM presented visual stimuli on a two-dimensional plane, rarely involving depth perception. Several previous studies have investigated how depth information is stored in WM, and found that WM for depth is even more limited in capacity and the memory performance is poor compared to visual WM. In the present study, we used a change detection task to investigate whether dissociating memory items by different visual features, thereby to increase their perceptual separateness, can improve WM performance for depth. Memory items presented at various depth planes were bound with different colors (Experiments 1 and 3) or sizes (Experiment 2). The memory performance for depth locations of visual stimuli with homogeneous and heterogeneous appearances were tested and compared. The results showed a consistent pattern that although separating items with various feature values did not affect the overall memory performance, the manipulation significantly improved memory performance for the middle depth locations but impaired the performance for the boundary locations when observers fixated at the center of the whole depth volume. The memory benefits of feature separation can be attributed to enhanced individuation of memory items, therefore facilitating a more balanced allocation of attention and memory resources.

Distribution of Attention in Three-Dimensional Space

“…This finding may reflect a more implicit effect of selection history that could be different if an explicit (top-down) instruction was given to participants prior to the single-or multiple-difficulty experiments 88 . Third, in addition to the target location relative to the viewer, the effect of the plane of fixation across depth can also be studied 38,89 . Such studies could determine whether there are dissociations between contributions of target distance relative to the observer and relative to the observer's point of fixation.…”

The Short-Term Retention of Depth

“…Qian and colleagues [5,[41][42][43] tested whether VWM stores depth information using CDT. In [5], from one to six blue squares were presented for 800 ms, each in a different stereoscopically-defined depth plane, and probed 900 ms later.…”

“…Wang et al [42] employed the same CDT method as [5] but also varied fixation depth. All the items were equally visable at every depth.…”

The role of ensemble average differs in working memory for depth and planar information

“…a 6-month-old infant can see the depth of a “visual cliff” to avoid a fatal fall; Gibson & Walk, 1960 ), recent studies show that our ability of memorizing depth information for only a few seconds is poor ( Qian, Li, Zhang, & Lei, 2020 ; Qian & Zhang, 2019 ; Reeves & Lei, 2017 ). Working memory for depth (WMd) is found to be inaccurate when a single depth position is required to be remembered (with a change detection accuracy of 78%), and even worse for multiple depth positions (with an accuracy below 70% for 4 items or more; see Qian & Zhang, 2019 & Wang, Jiang, Huang, & Qian, 2021 ). The inadequacy in working memory seems to be unique for depth information, because working memory for multiple planar visual features is fairly accurate ( Luck & Vogel, 1997 ) and unbiased ( Wilken & Ma, 2004 ).…”