Visuo-Gravitational Conflicts in Virtual Reality

Virtual Reality (VR) has gained significant popularity since the release of commercial Head-Mounted Displays, with applications ranging from recreation and gaming to training and rehabilitation. Despite advancements in VR technology, implications of VR on cognition and perception have not been fully explored. One outstanding issue which may hamper VR uptake and impair the user experience is Cybersickness, symptoms of motion sickness induced by VR exposure. Cybersickness is believed to arise from conflicts between sensory modalities signalling self-motion (Gallagher & Ferrè, 2018; Rebenitsch & Owen, 2016). For example, when viewing a VR rollercoaster, vision signals that the user is moving in a certain direction with a certain acceleration, while the vestibular system signals that the user is stationary. These visuo-vestibular self-motion conflicts may also cause aftereffects following VR exposure, such as altered vestibular perception and reflexes, and disrupted proprioceptive coordination (Di Girolamo & Pic, 2001; Gallagher et al., 2019, 2020; Harm et al., 2008). While visuo-vestibular self-motion conflicts have been given some attention in the literature, far less attention has been given to conflicts between other senses which signal self-motion, for example proprioception and somatosensation. Moreover, the sensory modalities implicated in self-motion perception are also crucial for the perception of gravity (Jörges & López-Moliner, 2017; Lacquaniti et al., 2015), and it is unclear whether conflicts relating to gravity (such as vision signalling an altered orientation or reduced strength of gravity with respect to true gravity) may also cause cybersickness and VR aftereffects. The aim of our research is to investigate whether reducing visuo-gravitational conflicts can reduce cybersickness and VR aftereffects, as well as improve the overall VR experience. Participants will play an off-the-shelf VR application which visually signals that they are in a Zero-Gravity environment. In the experimental condition (Low-G), visuo-gravitational conflicts will be reduced by supporting the participants’ bodyweight on an Anti-gravity Treadmill (Alter-G) such that the participant feels almost weightless. Accordingly, visual, proprioceptive and somatosensory signals will all indicate that the participant is in a reduced-gravity environment, reducing visuo-gravitational conflicts. In the control condition (Normal-G), participants will stand on the treadmill but they will remain at 100% body weight, creating gravitational conflicts between visual and proprioceptive/somatosensory systems. In both conditions, we will take objective (heart rate, blood pressure, Dennison et al., 2016) and subjective (Kennedy et al., 1993; Keshavarz & Hecht, 2011) measures of cybersickness, while VR aftereffects will be assessed through a psychophysical verticality detection task (Arshad et al., 2023). The user experience will be assessed through measuring immersion (the feeling of engagement by the virtual environment, Jennett et al., 2008) and presence (the feeling of being located within the virtual environment, Witmer & Singer, 1994).