INVESTIGATING ILLUSORY MOTION PARALLAX VIA VISUAL CUE DECOUPLING AND FORWARD MODELS IN VR

Abstract

Under natural viewing, stereopsis and motion parallax provide consistent information about three-dimensional structure, but stereoscopic displays can decouple them: observers moving before a stereoscopic display that lacks viewpoint-contingent updates perceive illusory parallactic motion. This thesis investigates that illusion in head-mounted virtual reality and tests whether it arises from predictive mechanisms that use stereoscopic depth to generate expectations about motion parallax. Across five two-interval forced-choice experiments, the illusion required binocular disparity, and its perceived direction aligned with negative parallax, consistent with a signed prediction error rather than an unsigned cue conflict. Its magnitude was modulated by scene context, downward viewing angle, and observer distance. These findings support a forward-model account: binocular disparity specifies depth and predicts head-coupled motion parallax, and the absent expected parallax yields a prediction error experienced as scene motion. The results inform how the visual system integrates conflicting depth cues and the design of stereoscopic displays.