Latency Discrimination Mechanisms in Virtual Environments: Velocity and Displacement Error Factors

Abstract

Latency (time delay) in head-tracked virtual environments (VEs) is well known to disturb users' sense of presence as well as hinder performance in manipulation tasks. We have determined in previous studies that observers cannot rely solely on direct temporal detection of time delay. They, at least in part, perceive the consequent visual “slip” of the VE scene from its expected spatially stable location. By employing an occlusion technique, the present experiment enabled comparison of the influence of visual image displacement and velocity errors on observer discrimination of VE system latency when using head-mounted displays. The results show better latency sensitivity (i.e., lower Just Noticeable Differences, or JNDs) in situations where velocity error magnitude predominates over displacement error cues, even though the velocity errors were visible for shorter durations. Correlation analyses indicate that latency-induced velocity errors are most closely related to latency JND than displacement errors.