Cyberkinetosis, or virtual reality headset sickness

It's a fact. We all experience difficulties when we put a virtual reality (VR) headset on our heads. Discomfort, sweating, drowsiness, headaches, even nausea if worn for long periods - we're all pretty much the same, and we all have a hard time of it.
Benoit Bardy, University of Montpellier

The inter-ocular distance of the headset, the fixed distance between the eye and the screen, the long image refresh time, the limited resolution and the rough overlap between the left and right visual fields create numerous distortions, resulting in an incorrect geometry of the spatio-temporal structure of the virtual scene. These inconsistencies are not simply intra-sensory or inter-sensory, they are also sensory-motor - we should say moto-sensory. Indeed, it is our movements that reveal these inconsistencies, bringing into play an unrealistic action-perception loop, destabilizing and generating kinetosis.
These limitations are important, but not essential. Technology is progressing. New headsets on the market have already corrected the errors of their predecessors, with new functionalities such as eye-movement tracking, enabling image rotation to be slaved to that of the eyes. Latencies and resolutions have evolved considerably, providing a realistic sensory-motor loop to limit our nausea reactions.

Conflict between the senses

The second category of reasons is more fundamental: it concerns the relationships between our senses, a cherished theme of cognitive science and neuroscience sometimes referred to as multisensory integration. The classic theory of the onset of kinetosis is based on the rarely challenged postulate of a conflict between our senses.
But the idea that our senses are in conflict, and can therefore deceive us, is not easy to accept. How can we walk, run, grasp the objects around us, play sports, dance, drive our car - in short, perform hundreds of daily motor acts, sometimes with extreme precision, in an often-changing physical environment, in a car or on a train for example, and still have to distrust these self-created sensory flows that are supposed to help us move efficiently? Something doesn't add up.
Are we sick when we drive our car on the freeway? When we take the elevator? When we walk on a treadmill or on the beach against the wind? As a general rule, the answer is no.

Yet, for example, walking on a treadmill implies that the optic flow at eye level results not only from the horizontal forces generated to move forward, but also from the speed of the treadmill; visual feedback is therefore quite discordant with proprioceptive and vestibular feedback. Basically, our eyes give us the impression that we're moving twice as fast as our feet! And half as fast when walking on the beach against the wind.
These examples suggest that non-redundancy between our senses is not abnormal: we could even say that it is more the rule than the exception, that any physical situation introduces multiple covariations (rather than conflicts) between our perceptual modalities. In fact, the subtle division of labor between our senses, with their different detection thresholds and sensitivity to complementary physical quantities, is precisely there to cover the whole range of situations we might encounter, and with rare exceptions, to inform us precisely about the reality of our interaction with the world.

Our movements are relative

Advocates of a conflict-theory explanation of kinetosis often forget the physics of the world we live in! It is possible to be both vertically displaced in relation to the earth and stationary in relation to the visual world. This visuo-proprioceptive configuration reveals that we are, for example, in an elevator. The reason, of course, is that our movements are relative, depending on the frame of reference (terrestrial, gravitational, inertial) in which they are observed, and it is quite common to be stationary in relation to one frame of reference and moving in relation to another. Our senses, in their complementarity, detect these relative persistence and change very well.
So why are we ill? Because the situations we encounter are unusual, because they call for new sensory covariations, and because the sensory-motor couplings involving this new relationship have to be built up, requiring slow adaptation.
Acquiring the sea legs needed to become a true sea dog follows this path. On the deck of a boat, we have to learn to control our balance on the basis of these new sensory relationships, anticipate deck movements and the disruptive effects of the swell, and build this new sensorimotor loop better adapted to the moving support. This process takes time, is a source of great destabilization, and it is this loss of stability that creates kinetosis.
A new postural theory of kinetosis has gradually developed over the past 25 years, pinpointing the causes of motion sickness in the loss of stability of the sensorimotor loop. This theory predicts the onset of postural instabilities before that of kinetosis. Indeed, it's not, or not only, because we're ill that we're unstable; it's also, and above all, because we're unstable that we're ill. This theory simply explains why women are often more sensitive than men, due to a different distribution of body mass, or why children are more sensitive than adults, due to the fact that their height continually alters their equilibrium.
This theory simply explains why we're more likely to get car sickness as a passenger than as a driver (the sensory-motor loop is absent in the first case, not in the second), and why staring at the horizon on the deck of a boat helps reduce seasickness. The horizon is in fact a stationary singularity in the optical flow, providing a reference to stabilize our postural oscillations.

Control your posture

Applied to VR headset use, a postural theory of cyberkinetosis is currently being developed, based on experimental data and the subjective experiences of gamers and VR software manufacturers. Technological tricks - a virtual nose between the two hemi-fields, a fixed landmark offering a reference point - as well as scenarios limiting jerky head and eye movements, and favoring situations of active postural control, appear intuitively. These tricks and scenarios, combined with the rapidly evolving technical specifications of headsets, improve motor control and thus reduce cyberkinetosis.
A multisensory simulator unique in France - iMose - was recently installed at the EuroMov center in Montpellier.

Thanks to its unusual dimensions (a VR gondola at the end of a 7 m-high robotic arm) and 6 degrees of freedom, it can artificially create and manipulate all kinds of sensory relationships. Research programs are underway on cyberkinetosis, but also more broadly on multisensory control of movement, loss of orientation in pilots, the dynamics of adaptation to these unusual situations, individual and cultural differences, and the role that virtual reality can play in learning and rehabilitation. This technological platform is open to researchers and manufacturers in the sector who wish to explore these scientific questions and test their virtual reality equipment.
Benoit BardyProfessor of Movement Sciences, Director of the EuroMov Center, senior member of the Institut Universitaire de France (IUF), University of Montpellier
Visit original version of this article was published on The Conversation.