Attention in depth: perceptual load modulates distractor interference in a three-dimensional space.

Although vision is inherently three-dimensional, depth has often been overlooked in the literature on selective attention. The present study examined how perceptual load modulates attentional selection in depth. 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 suggest that increased perceptual load is associated with reduced distractor interference regardless of the distractor's depth plane, although the mechanism underlying this effect remains to be clarified. Overall, these results provide initial evidence for extending Perceptual Load Theory to three-dimensional contexts and highlight the importance of considering depth in models of selective attention.