Virtual Reality Alters Perceived Functional Body Size

This paper looks at a practical VR problem: players do not judge their own body scale the same way in-headset as they do in the real world. Using a passable-aperture task, the authors compared 60 participants in physical reality and immersive HMD-based VR, measuring both action thresholds (sidling through) and perceptual thresholds (adjusting an opening until it felt passable).

In VR, both thresholds were significantly higher. In plain terms, people behaved as if their bodies needed more clearance, and they also reported that more clearance was needed. The study argues this is not just motor uncertainty: the headset also biases perception itself, especially through depth compression tied to vergence-accommodation conflict (VAC).

The useful part for developers is that the distortion was modeled mathematically. Once the VAC-related compression was corrected, affordance ratios in VR matched those in unmediated reality, suggesting the underlying action-perception relationship is still stable if you account for the optics. The paper also reports an aftereffect: the overestimation persisted back in physical reality after VR exposure.

For game teams, this is a reminder that VR interaction tuning is not just about controller input or comfort settings. Level geometry, doorway widths, crawl spaces, and any mechanic that depends on body-environment fit may need headset-specific validation. If your game relies on players judging whether they can fit, reach, or squeeze through something, the headset can systematically shift that judgment.