Human Systems Integration Division @ NASA Ames

A previous investigation in our laboratory showed that virtual environment users rely on image velocity errors rather than image displacement errors to sense head-tracking latency. In that study, the effect of image displacement error may have been suppressed because its peak amplitudes were associated with higher head velocity, which is thought to suppress visual motion sensitivity. To determine whether diminished motion sensitivity could play a role in user discrimination of latency, we investigated whether subjective perception of image motion comparable to that caused by latency is impaired by concurrent horizontal or vertical head movement. Eight participants monocularly viewed a checkerboard pattern in a head-mounted display that was oscillated from side-to-side with half peak-to-peak amplitudes from 0� to 5.64�. Perceptual sensitivity to image motion amplitude was reduced by almost half, during 30� repetitive horizontal head movements at 0.4 Hz. Accordingly, the reduced sensitivity to motion during head
movement appears to be a phenomenon that modulates users� tolerance of erroneous image motion caused by virtual environment latency.