Step frequency and perceived self-motion

Abstract

There is a discrepancy between the ability to correctly match the gains of visual and motor speed in virtual reality (VR) when walking on solid ground and the failure of this ability when walking on a treadmill. Moreover, this discrepancy has been found to interact with effects of the structure of the visual environment. The authors used a high-fidelity treadmill VR system to reproduce the high interactivity of normal walking in wide-area VR. Under these conditions, it was found that gain matches in a richly structured near environment differ by only about 10% in treadmill VR from matches in wide-area VR and that trial-to-trial variations in step frequency predicted changes in perceived locomotor speed. Gait differences resulting from treadmill walking (which are shown not to be a product of wearing a head-mounted display), apparently lead to an overestimation of motor speed on treadmills. When the near visual environment represented an empty hallway, additional errors were present that could be accounted for by known illusions in the perception of visual speed during self-motion. A study of normal gait at different speeds measured by head-tracker is reported as evidence of other possible sources of perceptual estimates of locomotor speed in normal walking.