Effect of distance cue and walking speed on matching and discrimination of visually simulated walking speed in treadmill-based locomotor VR

Abstract

For synchronized treadmill-based virtual reality locomotor systems, the simulated walking speed (SWSof), which is based on optic flow information in the virtual environment, should be perceived as fast as the true walking speed (TWS), which is based on the treadmill. However, previous research has indicated that people often underestimate the SWSof physically equivalent to the TWS in such systems, and the underestimation varies among conditions. Thus, in this study, we focused on factors that influence (1) the difference between the SWSof and the TWS when the two speeds are perceived equivalently and (2) the minimum SWSof that can be perceptually discriminated from the TWS. The two values were obtained by the method of constant stimuli. With a constant TWS (1, 2, or 4 km/h), participants judged if the speed of presented SWSof was perceived faster than their perceived TWS, for various SWSof, in the two different types of virtual environment (with rich distance cues or with poor distance cues). The results showed that the difference between the TWS and the perceptually matched SWSof (level of underestimation) was affected by both the distance cue and TWS. The virtual environment with rich distance cues and a low TWS resulted in a larger underestimation. In addition, for the discrimination threshold, the results showed that a high TWS resulted in a larger discrimination threshold.