VR Sickness: WHAT & WHY
WHAT is it and WHY do we get it
Virtual Reality (VR) Sickness, as proposed by Jason Jerald in The VR Book, is an all encompassing term for motion, cyber- and simulation sicknesses caused by experiencing VR. If you ask yourself, why one would need an extra term, it’s quite simple. It entails all the three above listed terms and describes everything we know (and yet don’t know) about health problems potentially induced by this “new” medium.
There is currently no generally accepted term that covers all sickness resulting from VR usage, and most users don’t know or care about the specific terminology. A general term is needed that is not restricted by specific causes. Thus, this book tends to stay away from the terms cybersickness and simulator sickness, and instead uses the term VR sickness or simply “sickness” when discussing any sickness caused by using VR, irrespective of the specific cause of that sickness.
— Jason Jerald, The VR Book, 2016
Yet VR sickness is one of the few adverse health problems of VR. The other most prominent issues are: eye strain, fatigue (e.x. gorilla arm), physical injuries (e.x. muscle strain from repeated movement) or, known by everyone that ever showed VR to more than 5 people in the row — hygiene.
But let’s focus on, what it is usually referred to as Motion Sickness! First a quick symptoms summary:
- oculomotor: eyestrain, difficulty focusing, blurred vision and headache
- disorientation: dizziness, vertigo
- nausea: stomach awareness, increased salivation and burping
When reading on motion sickness and VR, often other similar phenomenons pop up: cybersickness & simulator sickness. But what is the difference?
- motion sickness — adverse symptoms and readily observable signs associated with exposure to real (physical or visual) and/or apparent motion (Lawson, 2014)
- cybersickness — visually induced motion sickness resulting from immersion in a computer-generated virtual world
- simulator sickness — sickness that results from shortcomings of the simulation, but not from the actual situation that is being simulated (Pausch et al., 1992)
Why do I #needBucket — theories
Now that the distinction between what we are talking about is a bit clearer, it is time to look for the causes of motion sickness. And there are multiple theories with different predictive and explanatory power. Let’s look at most promising ones:
Sensory conflict theory
Motion sickness may result when the environment is altered in such a way that incoming information across sensory moralities (primarily visual and vestibular) are not compatible with each other and do not match our mental model of expectations (Reason and Brand 1975).
Evolutionary / poison theory
If we get conflicting information from our senses, it means something is not right with our perceptual and motor systems. Our bodies have evolved to protect us by minimizing physiological disturbances produced by absorbed toxins.
Postural instability theory
Predicts that sickness results when an animal lacks or has not yet learned strategies for maintaining postural stability (Riccio and Stoffregen 1991). They suggest people need to learn new patterns in novel situations to control their postural stability. Until this learning is completed, sickness may result.
Rest frame hypothesis
Motion sickness does not arise from conflicting orientation and motion cues directly, but rather from conflicting stationary frames of reference implied by those cues (Prothero and Parker 2003).
Eye movement theory
Motion sickness occurs due to the unnatural eye motion required to keep the scene’s image stable on the retina. If the image moves differently than expected, such as often occurs in VR, then a conflict occurs between what the eyes expect and what actually occurs. The eyes then must move differently than they do in the real world in order to stabilize the image on the retina. As a result of this discrepancy, motion sickness results.
To be continued…
But why is this all important? Why would I bother with all this heavy theory?As a developer I don’t care much about academic approach to VR, right?
Well, wrong. Plane wrong. We can either experiment on our own by method of trial-and-error, or strive for higher efficiency and make educated guesses based on theory and academic accomplishments. However, the pragmatic use of this information is a huge topic on its own, so … see you in the next article!
Read = no? Listen = YES!
If you don’t want or don’t have time to read, or possibly you are an audio learning kind, I encourage you to check out our podcast ResearchVR. More on Motion Sickness in ResearchVR 005 — Motion Sickness in VR: Adverse Health Problems in VR part I.
Lawson, B. D. (2014). Motion Sickness Symptomatology and Origins. In K. Hale and K. Stanney (Eds.), Handbook of Virtual Environments (2nd ed., pp. 531–600). Boca Raton, FL: CRC Press.
Pausch, R., Crea, T., and Conway, M. J. (1992). A Literature Survey for Virtual Environments: Military Flight Simulator Visual Systems and Simulator Sickness. PRESENCE: Teleoperators and Virtual Environments, 1(3), 344–363. 205
Reason, J. T., and Brand, J. J. (1975). Motion Sickness. London: Academic Press. Riccio, G. E., and Stoffregen, T. A. (1991). An Ecological Theory of Motion Sickness and Postural Instability. Ecological Psychology. DOI: 10.1207/s15326969eco0303_2
Prothero, J. D., and Parker, D. E. (2003). A Unified Approach to Presence and Motion Sickness. In L. J. Hettinger and M. Haas (Eds.), Virtual and Adaptive Environments (pp. 47–66).