Load-dependent depth selectivity: How perceptual load modulates attentional distribution across three-dimensional space

Although vision is inherently three-dimensional, depth has often been overlooked in the literature on selective attention. The present study examined whether attention can be voluntarily focused on a specific depth plane and how perceptual load modulates the efficiency of this focus. Fifty participants took part in the study, which was conducted in virtual reality, a recently emerging technique offering precise experimental control of depth. The target always appeared in the middle plane, and the distractor could appear either in the same plane as the target, in front of it, or behind it. The perceptual load was manipulated by defining Go/No-go cues on the basis of either a single feature (low load) or a conjunction of features (high load). The results revealed that under low load, distractors in the front and same planes interfered with performance, whereas distractors in the back plane did not, which is consistent with a viewer-centered attentional gradient. Under high load, distractor interference was eliminated across all depth planes. These findings indicate that depth can guide attentional selection, but selectivity depends on task demands. Specifically, increased perceptual load promotes more efficient filtering of irrelevant depth planes. Overall, these results extend Perceptual Load Theory to three-dimensional contexts, highlighting the importance of considering depth in models of selective attention.