Spatial updating in real and virtual environments: contribution and interaction of visual and vestibular cues

INTRODUCTION: When we move through the environment, the self-to-surround relations constantly change. Nevertheless, we perceive the world as stable. A process that is critical to this perceived stability is "spatial updating", which automatically updates our egocentric mental spatial representation of the surround according to our current self-motion. According to the prevailing opinion, vestibular and proprioceptive cues are absolutely required for spatial updating. Here, we challenge this notion by varying visual and vestibular contributions independently in a high-fidelity VR setup. METHODS: In a learning phase, participants learned the positions of twelve targets attached to the walls of a 5x5m room. In the testing phase, participants saw either the real room or a photo-realistic copy presented via a head-mounted display (HMD). Vestibular cues were applied using a motion platform. Participants' task was to point "as accurately and quickly as possible" to four targets announced consecutively via headphones after rotations around the vertical axis into different positions. RESULTS: Automatic spatial updating was observed whenever useful visual information was available: Paticipants had no problem mentally updating their orientation in space, irrespective of turning angle. Performance, quantified as response time, configuration error, and pointing error, was best in the real world condition. However, when the field of view was limited via cardboard blinders to match that of the HMD (40 × 30°), performance decreased and was comparable to the HMD condition. Presenting turning information only visually (through the HMD) hardly altered those results. In both the real world and HMD conditions, spatial updating was obligatory in the sense that it was significantly more difficult to ignore ego-turns (i.e., "point as if not having turned") than to update them as usual. CONCLUSION: The rapid pointing paradigm proved to be a useful tool for quantifying spatial updating. We conclude that, at least for the limited turning angles used (