The two-frequency-response hypothesis on vection : an extended study using an immersive VR environment
Tak Wa Wong · 2018
Viewers of Virtual Reality (VR) simulations often feel like they are moving even though they are actually stationary. This phenomenon is called vection or illusions of self-motion. The effects of oscillation frequency on vection along different axes have been studied with fixed velocity and fixed amplitude by Chen et al. (2016) and Fu (2017). Results suggest that in contrast to the literature, there were two different types of frequency response curves instead of one, depending on either velocity or amplitude held constant. This has been referred to as the “two-frequency-response (2FR)” hypothesis. This hypothesis can explain inconsistent frequency responses associated with vection in the literature, but it has only been tested with screen-based projected images. This study examines the 2FR hypothesis in an immersive VR environment. In Experiment 1, viewers were exposed to an immersive VR disco light environment presented on an HTC VIVE headset. Dotted disco lights were moving according to selected combinations of five levels of frequency, rms velocity, and amplitude. Results show that the 2FR hypothesis is applicable, but the shape of the response curve under constant amplitude was different from the findings of Fu (2017). One possible reason for the difference in results might be the differences in scene complexity. Experiment 1 used oscillating patterns in two dimensions while Fu used contrasted stripes of one dimension. As such, the vertical spatial complexity in this study was found to be significantly higher than that in Fu. In Experiment 2, the contrasted stripe patterns used in Fu were adopted and presented in the HTC VR environment. Results indicate that the findings of Experiment 1 still hold. This suggests that the addition or removal of vertical spatial complexity did not affect the frequency response of vection. Future work to identify the cause of different frequency response shapes is required. The current work demonstrates that the 2FR hypotheses holds for vection generated using a VR headset. Studying the frequency responses of vection with changing amplitude and velocity of scene movement should be avoided.