日髙 聡太

For virtual reality systems, the enhancement of a sense of presence (a subjective experience of being in one place even when one is physically situated in another) has been the most important issue. Both theoretically and empirically, the sense of presence has been found to relate dominantly to background components contained in a scene. In contrast, the reality or virtuality which can be assumed to link essentially to foreground components in a scene has not been investigated in detail. The present study defined the latter type of sense as vraisemblance (verisimilitude), and made an exploratory investigation into spatio-temporal characteristics responsible for the higher vraisemblance by using a scene containing Shishi-odoshi (a traditional Japanese fountain made of bamboos) in a Japanese garden as audio-visual stimuli. In Experiment 1, the effects of the field size of view and the sound pressure level of the background were investigated. Higher vraisemblance was observed with the middle field size of view with the original sound pressure level of the background, whereas higher sense of presence was observed with the larger field size of view with the larger background sound. In Experiment 2, the effect of temporal asynchrony between the foreground audio-visual stimuli produced by Shishi-odoshi was investigated. The results show that the range of temporal-window for the audio-visual stimuli necessary for high vraisemblance was different from those for high presence. These findings suggest that the sense of vraisemblance can be distinguishable from the sense of presence, and deeply involved to the foreground-based aesthetic impression in a scene.

We used a questionnaire to investigate how non-researchers conceptualize sense of presence. Respondents were 108 students with no professional education related to engineering or virtual reality. More than 90% of the respondents knew of the term, but they tended to use sense of presence not only to refer to a subjective experience of being there in a mediated environment, but also to refer to an experience that makes them feel excited or as having an extraordinary experience in an actual environment. Factor analysis revealed four sense of presence components: evaluation, impact, activity, and mechanicalness. Events with high presence were likely to be evaluated as preferred, impressive, and dynamic. Furthermore, the participants estimated that distal and proprioceptive sensors such as vision, audition, equilibrium, and kinesthesis were closely related to a sense of presence. These results suggest that sense of presence is not a single and simple concept for non-researchers, but is instead an ambiguous and the multidimensional construct with modality-selectivity. These aspects of sense of presence must be considered in specifying physical factors for high presence and establishing objective measures of sense of presence.