Abstract
We perceive illusory self-motion when a coherent motion is presented in a large visual field (vection), usually in the opposite direction to the visual motion (eg, Kitazaki & Sato, Perception 2003). Our body posture is influenced by the large-field visual motion to sway in the opposite direction to vection. However, an aftereffect of vection on a proprioceptive self-localization has not been investigated. Illusory body ownership such as the out-of-body experience drifts the proprioceptive self-localization toward the illusory body (Lenggenhager, Tadi, Metzinger & Blanke, Science 2007). If vection induces a shift of perceived self-body similarly to the out-of-body experience, we predict that the self-localization after vection would drift in the opposite direction to vection (negative aftereffect). In Experiment 1, twenty subjects observed a radially expanding or contracting flow of a cloud of 100 or 200 random dots on a head-mounted display. Latency and duration of vection were measured during 60s stimulus presentation. After the visual stimulus, they performed a self-localization task; the subjects were moved back at a random distance without sight, and asked to walk to the original location by themselves without sight. All conditions were repeated 10 times in random orders. We found that vection was stronger with more dots (p=.0083), and the self-localization drifted in the opposite direction to vection regardless of the number of dots (p=.0181). In Experiment 2, twenty subjects observed a jittering or non-jittering radially expansion or contraction of 230 dots, and performed identical tasks. We found that the self-localization drifted in the opposite direction to vection regardless of jitter (p=.0179), while we did not find a jitter effect on vection. To conclude, the proprioceptive self-localization drifted in the opposite direction to vection after the vection-stimulus presentation. It is suggested that vection would affect the perception of self-body location, and induce its aftereffect.
Meeting abstract presented at VSS 2017