Visually perceived depth from single-dot circular trajectories.

This study investigates the perception of three-dimensional depth elicited by a single dot traversing an oblique projection of circular motion within the frontal plane. We show that this minimal motion stimulus evokes vivid depth experiences comparable to those from two-dot relative motion, demonstrating that speed variations of a single element alone enable 3D space perception. In addition, perspective projection which is an important depth-cue for other stimuli, for example resulting in linear perspective and texture gradients in stills, do not contribute much compared to parallel projection for our stimuli. The results also demonstrate a robust view-from-above perceptual bias, indicating that ecological priors influence depth disambiguation. These effects are discussed using Gestalt principles of simplicity and Bayesian models of perception. Together, these findings enrich our understanding of motion-based depth perception and highlight novel mechanisms by which the visual system reconstructs depth from minimal cues.