Visual short-term memory is modulated by 3D depth in stereopsis.

Visual short-term memory (VSTM) is a memory mechanism temporarily holding visual information for later use. In the real world, objects are located in spatial depth and such depth information may be processed when objects are remembered. The present study investigated how VSTM is modulated by three-dimensional (3D) depth. Previous work used the color of objects to measure memory and provided mixed results, and the impact of separability in depth on memory is unclear. In Experiment 1a, we employed color feature and examined the effect of 3D depth across Stereo (stereoscopic vs. monoscopic) and Plane (one plane vs. multiple planes). VSTM was not found to be influenced by depth information. In Experiments 1b and 1c, the color was respectively replaced with two distinct spatial features, orientation and direction-of-rotation. We found similar results that the performance on VSTM was superior in the stereoscopic multi-plane condition compared to the monoscopic multi-plane condition or stereoscopic single-plane condition. These findings confirm, also via Bayesian statistical analyses, that the VSTM can benefit from 3D depth information in stereopsis, while the benefit is severely limited when the task is non-spatial.