How big an issue is the nausea problem for Virtual Reality products? originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights.
I've been working with helmet mounted displays in military flight simulation for several decades - I am an expert in the field.
IMHO - these devices should be banned - but that may not be necessary because after the first wave of early adopters I think it'll go the way of 3D televisions. But that's just my opinion. Let me explain why.
Everyone thinks these things are new and revolutionary...but they really aren't. All that's happened is that they dropped in price from $80,000 to $500...and many corners have been cut along the way.
There are several claims that the nausea problem has either been fixed, or will soon be fixed, or that application design can be used to work-around the problem.
The claims that it's been fixed are based on the theory that the nausea is caused by latency/lag in the system, or by low resolution displays or by inaccurate head motion tracking...all of which can (and are) being fixed by obvious improvements to the system. Sadly, the $80,000 googles we made for the US military had less latency, higher resolution displays, and more accurate head tracking than any of the current round of civilian VR goggles...and they definitely made people sick - so this seems unlikely.
The problem is that the people who make those claims are either ignorant (or are deliberately ignoring) the evidence collected over 20 years of flight simulation experience with VR goggles (only we called them "Helmet Mounted Displays" - HMD's - and what we did was called "simulation" and not "virtual reality").
Worse still, there is strong research evidence that the harm they cause extends for as much as 8 hours AFTER you stop using the goggles.
I believe that the most major problem is with depth perception.
For objects closer than a few meters, you have to refocus the lens in your eye using the ciliary muscles. The amount of force that those muscles have to produce in order to achieve that focus is a direct measure of the distance to the object. There are no designs for displays that can produce light that's focussed at a wide range of distances - so without some very new technology - we can't fool the brain.
Other depth-perception mechanisms (which is the primary ones that VR displays employ) are stereopsis and convergence. In this case, the images seen in our two eyes are from slightly different vantage points and we 'fuse' those into a single image by making our eyes point inwards slightly so that the image is more or less the same in both eyes. This is done by applying tension to the inter-ocular muscles.
So we're continually estimating range using the tensions in two sets of muscles - one for focus, the other for convergence. When the brain gets the right signals, these two mechanisms agree perfectly.
But in a VR display, they don't agree. The focussing system says "This image is all at the same range" - the convergence system says "This image is at a variety of different ranges". That's not a problem beyond a few meters because the focussing system is only accurate for close-up objects - and the brain knows this.
So what happens when the convergence system says "It's 2 meters away" and the focusing system says "It's more than 3 meters away"?
In the real world, this simply cannot happen...so what have our caveman-evolved brains been wired to do under those circumstances? Well, some people simply reject the focus information and rely on other cues. But other people's brains say "This is an impossibility - we must be hallucinating"...and if you're hallucinating, and you're a caveman, then you've probably eaten something poisonous - a "magic mushroom" maybe? And when that happens, your brain goes into panic mode and tries to empty this substance from your stomach...and you feel very, very nauseous.
And THAT problem can't be fixed by any known technological means....we need entirely new research into optical systems that can dynamically refocus light on a pixel-by-pixel basis and which costs about $20 per eye.
So for that reason alone - people will always get sick with VR displays UNLESS the content is kept further than around 3 meters from them.
Sadly - that excludes ANY kind of application that happens inside a building - and ANY kind of application where you can interact with objects naturally at arm's length.
This is why these displays were moderately successful in flight simulation! We'd sit people in a physical cockpit mockup and use translucent displays that let you see the real, physical cockpit - and simulated only the stuff outside the airplane...which is conveniently more than a few meters away! Hence these head mounted displays worked reasonably well most of the time. One exception to that was for in-flight refuelling - where the drogue and probe gizmo was just a meter or so from the pilot's head...and that's why many pilots hated training for inflight refuelling in a simulator. Until very recently - they did that training in a physical rig without graphics.
When we move around in the real world, our bodies have to obey the laws of conservation of momentum. When you're walking along, and suddenly stop, the mass of your body wants to continue to move forwards - and you have to apply muscular force to preventing your arms from swinging forwards and your head from tipping. This momentum has to be absorbed when you're stopping in a car or even turning a corner.
Those forces are entirely absent in a VR rig...and your brain notices that.
With a TV or in a cinema - that's generally not a problem - we seem to be able to understand that the distant flat screen isn't "Real" - so we accept that there is no momentum compensation needed. But when we approach a more real display, we fall into that "uncanny valley" and suddenly we're subconsciously very bothered by the lack of momentum on our bodies.
Caveman brain again - "My eyes say we're accelerating - my muscles and balance organs say we're not - we're hallucinating - so vomit".
We get seasick for the exact opposite reason. Our view of the inside of a ship looks like it's a large, stationary room - but our motion systems say "No - we're obviously moving because of momentum transfer"...and we're hallucinating again...so vomit.
The Google Cardboard VR folks seem to know this and basically suggest that applications make it seem like we're basically standing still and just turning our heads around (which we really are - so no nausea). That'll work - but it's not going to get you an immersive 1st person shooter game...or a car racing game...or...well, pretty much anything immersive.
This was also a problem in flight simulation - but not all people get seasick or motion-sick - and pilots are amongst that lucky group.
But this problem simply cannot be fixed by any means. The laws of physics don't allow it.
SO WHERE ARE WE NOW?
So now, we can't be in a confined space because of focus-induced nausea - and we can't be accelerating and decelerating through the world because of momentum.
This locks out 99% of all of the really cool uses of VR. Hardly any videogames can get away without some acceleration of the viewpoint. No really fun, immersive, games can keep you more than 3 meters from every objects (in part because you're less than 3 meters tall - and you can look down and see the floor!)
Sure, we can probably find some genres of "experiences" for which we can stand still and watch the action from a distance - but that's absolutely NOT why people will want to buy these gadgets.
WHY DO PEOPLE LIKE VR THEN?
I've been working with these displays - both the $80,000 kind and the $500 kind - for years. Almost everyone can tolerate wearing them for several minutes before getting sick. About half of people feel sick after a few minutes - and (maybe) half of them get so sick that they have to take off the goggles ASAP. Anecdotal evidence - sadly.
Most of the demo's that are given at trade shows and other industry events are just a few minutes long. I don't know whether that' s intentional or not...but it explains why so many people THINK that they're going to love VR - sadly, they won't realize the problem until AFTER they've splurged $500 on one of these gizmos.
When you've spent an hour in one of these contraptions - it can get very bad indeed.
When I worked on a team of a dozen people developing applications for the Oculus display - we each had a headset and a foam dummy head to put it on when not in use. We were developing both software and content - and we knew what we were doing because we were a highly experienced team. If you stood in that lab you'd notice something significant...nobody was wearing their Oculus. Sometimes - rarely - they'd put it on to check something - then take it off again within 30 seconds. We would mostly look at the side-by-side displays on a regular monitor. Most of us were very glad when that project wound down.
There is a name for this..."Simulator Sickness" ("SimSickness" for short).
IT GETS WORSE EVEN THAN THAT.
The killing blow for me comes from a series of US Navy studies on sim sickness.
What they found was that even without nausea - there was a measurable degree of confusion and disorientation after prolonged exposure to VR experiences. This disorientation is the reason why the US Military advises against flying a plane or even driving a car for 24 hours after being inside a simulator.
The conclusions of the second paper are damning:
"One question still not answered is the actual time course of the symptoms experienced by the aviators in the simulator and the recurrence of delayed effects. Anecdotal data continues to be received indicating there is a part of the aviation population that experiences delayed problems beyond the simulator exposure and for periods that exceed 6 to 8 hours for approximately 8 percent of the population and l-to-2 days for an even smaller population. Studies be conducted to determine which scenarios are linked with simulator sickness and methods to prepare aviators to deal with those scenarios. A correlation of simulator sickness with actual flight experience under similar conditions should be determined in side-by-side studies conducted in the simulator and in the aircraft."
"Studies be conducted to ascertain the period of time that an aviator should wait postflight before piloting an actual aircraft or even driving a car."
Yeah - the US Navy believes that some people shouldn't drive a car within one to two DAYS of being inside a VR environment!
CONCLUSIONS: Sadly (because I want a "holodeck" as much as the next red-blooded geek) - I don't think it's possible to make a VR system that both delivers the experience that everyone wants - and doesn't make a sizeable proportion of the population so sick that they'll never want to do it again.
For the people who can stomach the display - my major concern is that the US Navy studies show that there is some disorientation that might persist long after finishing your game...so driving a car while "under the influence" of post-VR disorientation is probably as dangerous as drunk-driving.
If these devices are in pretty much every home - then there are huge problems in store for the industry in terms of product liability. There have been plenty of warnings from the flight simulation industry - there are no excuses for not reading the Wikipedia article on the subject. If people are driving "under the influence" and the VR companies didn't warn them about that - then they're in deep trouble.
IMHO, these consumer-grade VR devices should be carefully studied and if they do cause possible driving impairment, they should be banned until such time as the problems can be fixed...which may very well be "never".
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