Virtual Reality Alters Perceived Functional Body Size

2025-10-01

AI Summary

This study investigates how immersive virtual reality (VR) via head-mounted displays (HMDs) alters perception of one’s functional body size. Using a passable aperture paradigm, motion capture, and a dual-task design, we demonstrate that VR induces depth compression, leading participants to systematically overestimate the spatial clearance required for bodily passage—a bias persisting post-VR as an aftereffect. Mechanistic analysis identifies vergence–accommodation conflict (VAC) as the primary driver. Geometric modeling to correct VAC restores alignment between perceptual and action-based aperture thresholds, revealing a plastic, functional perceptual adaptation mechanism. This work provides the first quantitative characterization of VR-induced systematic shifts in functional body-size perception and their neuroadaptive basis, offering critical empirical evidence for VR human factors design and embodied cognition theory.

Technology Category

• Humans and AI: Game Design — Virtual Humans, NPCs and Autonomous Characters
• Cognitive Modeling & Cognitive Systems: Adaptive Behavior
• Computer Vision: Motion & Tracking

Application Category

• User Modeling, Personalization and Recommendation: Practical large-scale studies of user experience
• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Virtualization and resource management in Web systems and infrastructures

Abstract

Virtual reality (VR) introduces sensory perturbations that may impact perception and action. The current study was designed to investigate how immersive VR presented through a head-mounted display (HMD) affects perceived functional body size using a passable aperture paradigm. Participants (n=60) performed an action task (sidle through apertures) and a perception task (adjust aperture width until passable without contact) in both physical, unmediated reality (UR) and VR. Results revealed significantly higher action and perceptual thresholds in VR compared to UR. Affordance ratios (perceptual threshold over action threshold) were also higher in VR, indicating that the increase in perceptual thresholds in VR was driven partly by sensorimotor uncertainty, as reflected in the increase in the action thresholds, and partly by perceptual distortions imposed by VR. This perceptual overestimation in VR also persisted as an aftereffect in UR following VR exposure. Geometrical modelling attributed the disproportionate increase in the perceptual threshold in VR primarily to depth compression. This compression, stemming from the vergence-accommodation conflict (VAC), caused the virtual aperture to be perceived as narrower than depicted, thus requiring a wider adjusted aperture. Critically, after mathematically correcting for the VAC's impact on perceived aperture width, the affordance ratios in VR became equivalent to those in UR. These outcomes demonstrate a recovered invariant geometrical scaling, suggesting that perception remained functionally attuned to action capabilities once VAC-induced distortions were accounted for. These findings highlight that VR-induced depth compression systematically alters perceived body-environment relationships, leading to an altered sense of one's functional body size.

Problem

• VR alters perceived functional body size through sensory perturbations
• Depth compression in VR distorts body-environment relationship perception
• Vergence-accommodation conflict causes systematic perceptual overestimation in VR

Innovation

• Mathematical correction of vergence-accommodation conflict
• Depth compression modeling to explain perceptual distortions
• Recovery of invariant geometrical scaling after VAC correction