The effect of distance on audiovisual temporal integration in an outdoor virtual environment

In this study, we explore the influence of stimulus distance on human tolerance for (physical) asynchronies in virtual reality (VR). A repeated audiovisual (AV) stimulus with sound and light bursts was presented to the participants in an outdoor virtual environment (VE) using a head-mounted display (HMD). The investigation focused on quantifying the point of subjective simultaneity (PSS) for both visual and auditory stimuli. A synchrony judgment method (SJ-3) was used for 11 stimulus onset asynchronies (SOA) and five egocentric distances from 10 m up to 50 m with 10 m increments. The data analysis showed negative PSS values that decreased with distance, resulting in a negative slope (-3 ms/m) of the regression line between PSS values and simulated distances. In contrast to the recent study conducted in the indoor VE, we conclude that the presented study in the outdoor VE does not incorporate a distance compensation mechanism and refutes the hypothesis of an 'implicit estimation' of sound-arrival time. The reasons behind the observed contrast are discussed in this paper. Moreover, the negative slope of the regression line (-3 ms/m) is similar to previous research, concluding that there is a temporal integration of auditory-visual information within human neural processes without distance compensation.