Peripersonal Space: An Index of Multisensory Body–Environment Interactions in Real, Virtual, and Mixed Realities

Abstract

Human-environment interactions normally occur in the physical milieu and thus by medium of the body and within the space immediately adjacent to and surrounding the body, the peripersonal space (PPS). However, human interactions increasingly occur with or within virtual environments, and hence novel approaches and metrics must be developed to index human-environment interactions in virtual reality (VR). Here, we present a multisensory task that measures the spatial extent of human PPS in real, virtual, and augmented realities. We validated it in a mixed reality (MR) ecosystem in which real environment and virtual objects are blended together in order to administer and control visual, auditory, and tactile stimuli in ecologically valid conditions. Within this mixed-reality environment, participants are asked to respond as fast as possible to tactile stimuli on their body, while task-irrelevant visual or audiovisual stimuli approach their body. Results demonstrate that, in analogy with observations derived from monkey electrophysiology and in real environmental surroundings, tactile detection is enhanced when visual or auditory stimuli are close to the body, and not when far from it. We then calculate the location where this multisensory facilitation occurs as a proxy of the boundary of PPS. We observe that mapping of PPS via audiovisual, as opposed to visual alone, looming stimuli results in sigmoidal fits-allowing for the bifurcation between near and far space-with greater goodness of fit. In sum, our approach is able to capture the boundaries of PPS on a spatial continuum, at the individual-subject level, and within a fully controlled and previously laboratory-validated setup, while maintaining the richness and ecological validity of real-life events. The task can therefore be applied to study the properties of PPS in humans and to index the features governing human-environment interactions in virtual or MR. We propose PPS as an ecologically valid and neurophysiologically established metric in the study of the impact of VR and related technologies on society and individuals.

From multisensory integration in peripersonal space to bodily self‐consciousness: from statistical regularities to statistical inference

“…Results demonstrate a multisensory facilitation effect (i.e., reaction times to audio‐tactile or visuo‐tactile stimuli being faster than to tactile stimulation alone) that is spatially dependent; when audio–tactile/visuo‐tactile stimuli are in proximity, but not when they are far away. In other words, PPS seemingly obeys the spatial principle of multisensory integration (see Serino et al . for review).…”

Observing the Transformation of Bodily Self-consciousness in the Squeeze-machine Experiment

“…Moreover, different methods have been developed to measure the boundaries of the PPS, using its properties and a cross-modal task. 15,20,21,22,23 Here, we adopted a dynamic audio-tactile interaction task, 15 which has revealed the interaction between our body and environment (see reference 24 ), and can be easily incorporated into the squeeze-machine experiment. This, could form part of a series of methods in which the effectiveness of the squeeze-machine experiment as self-consciousness research could be determined.…”

Audiovisual integration in depth: multisensory binding and gain as a function of distance

“…In their study, Noel and colleagues investigated how the TBW changed as a function of whether audiovisual events occurred within or beyond peripersonal space—the space immediately adjacent to and surrounding your body (Serino et al 2015, 2017). The results suggested that TBWs were larger when stimuli were presented within peripersonal as opposed to extrapersonal space.…”