Full-Body Illusion of Avatars with Different Transparency

Abstract

This study examined the effects of avatar transparency and visual feedback representing contact with an external object on the full-body illusion. Twenty-two participants performed physical exercise for three minutes while observing 12 different visual stimuli on a head-mounted display. The visual stimuli consisted of a combination of two factors: the presence/absence of tiles whose luminosity changed on contact with the avatar and six conditions in which the avatar’s transparency was in 20% intervals from 0% to 100%. The measures were the onset and duration of the full-body illusion reported during each trial and the subjective intensity of the sense of body ownership and sense of agency reported after each trial. As a result, the onset time of the full-body illusion was shorter, the duration was longer, and the sense of agency was stronger in the condition with tiles than in the condition without tiles when the avatar transparency was 100% (invisible avatar). The full-body illusion did not show the effect of avatar transparency on the full-body illusion at transparency levels of 0%, 20%, 40%, 60%, or 80%. These results suggest that the full-body illusion may occur even when the avatar is visually invisible or less visible.