Sliding perspectives: dissociating ownership from self-location during full body illusions in virtual reality

Abstract

Bodily illusions have been used to study bodily self-consciousness and disentangle its various components, among other the sense of ownership and self-location. Congruent multimodal correlations between the real body and a fake humanoid body can in fact trigger the illusion that the fake body is one's own and/or disrupt the unity between the perceived self-location and the position of the physical body. However, the extent to which changes in self-location entail changes in ownership is still matter of debate. Here we address this problem with the support of immersive virtual reality. Congruent visuotactile stimulation was delivered on healthy participants to trigger full body illusions from different visual perspectives, each resulting in a different degree of overlap between real and virtual body. Changes in ownership and self-location were measured with novel self-posture assessment tasks and with an adapted version of the cross-modal congruency task. We found that, despite their strong coupling, self-location and ownership can be selectively altered: self-location was affected when having a third person perspective over the virtual body, while ownership toward the virtual body was experienced only in the conditions with total or partial overlap. Thus, when the virtual body is seen in the far extra-personal space, changes in self-location were not coupled with changes in ownership. If a partial spatial overlap is present, ownership was instead typically experienced with a boosted change in the perceived self-location. We discussed results in the context of the current knowledge of the multisensory integration mechanisms contributing to self-body perception. We argue that changes in the perceived self-location are associated to the dynamical representation of peripersonal space encoded by visuotactile neurons. On the other hand, our results speak in favor of visuo-proprioceptive neuronal populations being a driving trigger in full body ownership illusions.

Enhancing Our Lives with Immersive Virtual Reality

“…19 The difference between the results of Petkova and Ehrsson (2008) and Slater et al (2010b) was taken up by Maselli and Slater (2013). The vital importance of 1PP for body ownership was also emphasized by Petkova et al (2011) and considered further by Maselli and Slater (2014).…”

Visual appearance of a virtual upper limb modulates the temperature of the real hand: a thermal imaging study in Immersive Virtual Reality

“…Recent advances in computer science have allowed researchers to use Immersive Virtual Reality (IVR) to investigate the SoE over a virtual body by adapting the original version of the RHI paradigm. Data obtained regarding embodiment of virtual body parts (Slater et al ., , ; Sanchez‐Vives et al ., ) and full virtual bodies (Ehrsson, ; Lenggenhager et al ., ; Petkova & Ehrsson, ; Slater et al ., ; Maselli & Slater, , ) show that first‐person perspective (1PP) and visual appearance of the virtual body (Kilteni et al ., ; Perez‐Marcos et al ., ; Martini et al ., ; Tieri et al ., ,b) have crucial roles in eliciting SoE (Petkova & Ehrsson, ; Petkova et al ., ; Slater et al ., ; Maselli & Slater, ). Similarly, we recently reported that even the mere passive observation of a virtual limb from a 1PP (without any multisensory visuo‐tactile or visuo‐motor boosting) is sufficient to elicit FO at explicit (e.g., questionnaire answers; Tieri et al ., 2015a), implicit [e.g.…”

A Virtual Out-of-Body Experience Reduces Fear of Death

“…A further study [18] showed that a full body ownership illusion can also be achieved in virtual reality, where participants saw from 1PP a virtual body spatially coincident with and substituting their own, and also in a mirror, with visuotactile stimulation, and synchronous head movements. Since then a number of studies and experiments have reproduced the body ownership illusion in virtual reality—for example, investigating factors that lead to or break the illusion [19–21], and the implications of virtual body types for changes in attitudes and behaviours [22–24]. For a general review see [25, 26].…”