Can walking motions improve visually induced rotational self-motion illusions in virtual reality?

Illusions of self-motion (vection) can provide compelling sensations of moving through virtual environments without the need for complex motion simulators or large tracked physical walking spaces. Here we explore the interaction between biomechanical cues (stepping along a rotating circular treadmill) and visual cues (viewing simulated self-rotation) for providing stationary users a compelling sensation of rotational self-motion (circular vection). When tested individually, biomechanical and visual cues were similarly effective in eliciting self-motion illusions. However, in combination they yielded significantly more intense self-motion illusions. These findings provide the first compelling evidence that walking motions can be used to significantly enhance visually induced rotational self-motion perception in virtual environments (and vice versa) without having to provide for physical self-motion or motion platforms. This is noteworthy, as linear treadmills have been found to actually impair visually induced translational self-motion perception (Ash, Palmisano, Apthorp, & Allison, 2013). Given the predominant focus on linear walking interfaces for virtual-reality locomotion, our findings suggest that investigating circular and curvilinear walking interfaces offers a promising direction for future research and development and can help to enhance self-motion illusions, presence and immersion in virtual-reality systems.

More than just perception-action recalibration: walking through a virtual environment causes rescaling of perceived space.

Egocentric distances in virtual environments are commonly underperceived by up to 50 % of the intended distance. However, a brief period of interaction in which participants walk through the virtual environment while receiving visual feedback can dramatically improve distance judgments. Two experiments were designed to explore whether the increase in postinteraction distance judgments is due to perception-action recalibration or the rescaling of perceived space. Perception-action recalibration as a result of walking interaction should only affect action-specific distance judgments, whereas rescaling of perceived space should affect all distance judgments based on the rescaled percept. Participants made blind-walking distance judgments and verbal size judgments in response to objects in a virtual environment before and after interacting with the environment through either walking (Experiment 1) or reaching (Experiment 2). Size judgments were used to infer perceived distance under the assumption of size-distance invariance, and these served as an implicit measure of perceived distance. Preinteraction walking and size-based distance judgments indicated an underperception of egocentric distance, whereas postinteraction walking and size-based distance judgments both increased as a result of the walking interaction, indicating that walking through the virtual environment with continuous visual feedback caused rescaling of the perceived space. However, interaction with the virtual environment through reaching had no effect on either type of distance judgment, indicating that physical translation through the virtual environment may be necessary for a rescaling of perceived space. Furthermore, the size-based distance and walking distance judgments were highly correlated, even across changes in perceived distance, providing support for the size-distance invariance hypothesis.