Comparison between Lateral Head Movement and To-and-Fro Head Movement on Depth Perception from Motion Parallax

Depth perception from motion parallax has been investigated with right-and-left head movement. From ecological point of view, humans move forward more frequently than sideways. The aim of this study was to determine the influence of the head movement direction on depth perception from motion parallax. We investigated depth perception at and above threshold level with lateral head movement and to-and-fro movement. Stimuli were vertical half cylinders, which was concave or convex, depicted with random dots that move synchronously with head. The viewing distance was 78.5 cm on average. The size of each display was 6.6 × 6.6 deg. The dot density in the entire display was always maintained constant for prevention of depth impression from difference in dot density. Four subjects participated the experiments. Mean threshold for lateral and to-and-fro motion were about 0.1 cm and 5 cm respectively. Mean gains of apparent depth for lateral and to-and-fro motion were about 1 and 0.2, respectively.