Human Systems Integration Division @ NASA Ames

Previous studies have shown that self-motion has an inhibiting effect on concurrent 3D motion perception. To investigate whether self-motion similarly impairs concurrent image motion perception, we examined human perception of head - referenced horizontal image motion during head movement. The displayed stimulus was composed of a checkerboard image in a head mounted display oscillating from side to side at four frequencies (0.25, 0.5, 1 and 2 Hz) with half peak-to-peak amplitudes ranging from 0� to 5.64. Eight observers rated the magnitude of the checkerboard motion while either rotating their head about a vertical axis (yaw), about a horizontal axis (pitch), or holding it still. For all image oscillation frequencies, perceptual sensitivity to image motion amplitude was reduced during both horizontal and vertical head movements (mean reduction:
0.44 and 0.17, respectively). In contrast, perceptual bias was affected only at 2 Hz (mean shift: �9.9% and �12.2% of the full image motion amplitude for horizontal and vertical head movements, respectively). The results indicate that head movement causes gain reductions in motion magnitude estimation at image oscillation frequencies ?1 Hz. At an oscillation frequency of 2 Hz, head movement produces both a gain reduction and a bias shift. Virtual environment developers could take advantage of such effects by relaxing requirements for image stability as well as motion fidelity during head movement.