Visual capture and the experience of having two bodies: Direct comparison of two virtual reality techniques

The experience of singularity of the conscious self may break down in heautoscopy. In heautoscopy patients see a double or doppelganger of themselves. Moreover, the self may be experienced as reduplicated—existing at two or even more locations simultaneously (Blanke et al, 2004 Brain 127 243-258). Using head-mounted video display, self-location (where participants experience their self to be localized) and self-identification (identifying with a fake body) can be manipulated by applying conflicting visuotactile information (Lenggenhager et al, 2007 Science 317 1096). Yet the experienced singularity of the self was not affected, ie participants did not experience having multiple bodies. Here we investigated self-location and self-identification while participants (N=19) saw two fake bodies that were stroked either synchronously or asynchronously with their own body. We report that self-identification with two fake bodies was stronger during synchronous stroking and that self-location—measured by anterior posterior drift—was significantly shifted towards the two bodies in the synchronous condition only. Furthermore, synchronous stroking led to the feeling of having multiple bodies. We conclude that participants self-identify even with more than one fake body during congruent visuotactile stimulation and experience having more than one body, as seen in heautoscopy of neurological origin