Evidence for the effect of depth on visual working memory

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.

Saturation and brightness modulate the effect of depth on visual working memory

“…It may also rival with an incongruent disparity cue to deteriorate depth perception (p ¼ 0.094; control experiment) and further diminished the benefit for memorizing closer items. The results are consistent with our previous study, where we found a memory advantage for perceptually closer items with depth perception induced by the congruent relative size and disparity cues (Qian et al, 2017). Therefore, we conclude that disparity-defined depth does play a role in influencing the VWM performance.…”

“…Although neither of the above two studies found a beneficial effect of stereoscopic depth on VWM using simultaneous presentation of stimuli, our recent study suggests differently by using an adapted change detection paradigm (Qian, Li, Wang, Liu, & Lei, 2017). We found that presenting the items in stereoscopic depth alone hardly affected VWM performance, which is consistent with the previous studies.…”

“…By presenting these monocular depth cues either alone, or in conjunction with a congruent or incongruent binocular disparity cue, we are able to test whether and how these depth cues interact with each other and therefore affect the VWM performance. Similar to our previous study (Qian et al, 2017), we would expect that memory performance could be improved for perceptually closer items, as long as the depth cues create salient and stable depth perception. On the other hand, items differing in saturation and/or brightness may also differ in perceptual saliency.…”

“…This suggests that varying saturation alone may be insufficient, or difficult at least, to affect the VWM performance. Therefore, here we first hypothesized that saturation and brightness affect VWM through an underlying mechanism of depth perception, and employed a change detection paradigm similar to our previous study (Qian et al, 2017). Experiment 1 examined the joint effect of relative saturation and brightness, and Experiments 2 and 3 tested the individual effects of relative saturation and relative brightness, respectively.…”

“…In addition, disparity cue was applied in all experiments to provide stereoscopic depth, whose direction was either consistent or inconsistent with that implied by relative saturation/brightness. Since previous studies showed that the memory performance for two depth planes did not significantly differ from that for one plane (Reeves & Lei, 2014;Qian et al, 2017), we only focused on the effect of depth order-that is, the difference between the front and the back planes within a two-plane layout.…”