Tech evangelists predicted that 2016 would be the year of virtual reality. And in some ways they were right. Several virtual reality headsets finally hit the commercial market, and millions of people bought one. But as people begin immersing themselves in new realities, a growing number of worrisome reports have surfaced: VR systems can make some users sick.

Scientists are just beginning to confirm that these new headsets do indeed cause a form of motion sickness dubbed VR sickness. Headset makers and software developers have worked hard to combat it, but people are still getting sick. Many in the industry fear this will be a major obstacle to mass adoption of virtual reality.

A lot of VR, people today cannot tolerate, says Kay Stanney, a human factors engineer with a focus on VR at Design Interactive in Orlando, Fla. Search for VR sickness on Twitter, she says, and youll see that people are getting sick every day.

Around 25 to 40 percent of people suffer from motion sickness depending on the mode of transport, scientists have estimated, and more women are susceptible than men.

Count me among those women. Im highly prone to motion sickness. Cars, planes and boats can all make me feel woozy. It can take me a day or more to fully shake the nausea, headache and drowsiness. Certain that virtual reality would also make me sick, Ive purposefully avoided strapping on a headset. (Until this assignment came along.)

Women who got sick playing a VR horror game

Men who got sick playing the game

So far, avoiding VR hasnt been much of a loss for me. A lot of the VR industry is focused on video games, vying for a chunk of an estimated $100 billion market. And most of the early adopters who are willing to pay for one of the new premium headsets $400 for Sonys PlayStation VR or $800 for an Oculus Rift or HTC Vive are probably serious gamers or technophiles. I dont fit either category.

But, avoidance promises to become harder as VR moves beyond games. The technology has already begun creeping into other fields. Car companies, including Audi, General Motors Co.and used-car seller Vroom, are building VR showrooms where you can check out cars as if you were actually on the lot. Architects are using VR to walk clients through buildings that dont yet exist. Schools and learning labs are taking students on virtual field trips to both contemporary and historical sites.

Facebook CEO Mark Zuckerberg sees virtual reality as the next big social platform. In 2014, Facebook bought Oculus VR, maker of the Rift headset, for around $2 billion. This is really a new communication platform, Zuckerberg wrote in the Oculus announcement. Imagine sharing not just moments with your friends online, but entire experiences and adventures. New VR sites where people can socialize or play games together in virtual spaces, like AltspaceVR and Rec Room, are springing up. And some tech luminaries see a future in which VR is integrated into many more aspects of our daily lives, from movies and entertainment to work and health care.

Nobody knows if the broader public will embrace virtual reality. Sales of the expensive high-end headsets have been underwhelming the three premium systems combined sold an estimated 1.5 million headsets in 2016. But sales of cheaper mobile headsets were more impressive. For less than $100, Samsung Gear VR, Google Daydream View, Google Cardboard and others are powered by your mobile phone. But with smaller screens and less computer power, they are far less capable than the Rift or the Vive. Still, they are selling. In January, Samsung reported that it had sold 5 million of the $99 Gear VR headset since its release in November 2015.

But VR may never really catch on if it makes people sick. And while VR companies and developers are confident that theyll find solutions, many motion sickness experts are pessimistic. My hunch is that [the solutions] are extremely limited, says Steven Rauch, director of the Vestibular Division at Massachusetts Eye and Ear in Boston.

In some ways, the very premise of virtual reality makes it an ideal vehicle for motion sickness.

Motion sickness has probably been with us as long as weve had boats. References to seasickness date back to Greek mythology; the word nausea is derived from the Greek naus, meaning ship. J.A. Irwin introduced the term motion sickness in the scientific literature in 1881. Since then, an extensive body of research has accumulated.

The most widely accepted theory to emerge is that motion sickness is brought on by a mismatch between two or more of the senses that help you keep your balance. For example, when youre below deck on a ship at sea, your eyes see a stationary room. But your vestibular system the fluid-filled canals and specialized membranes in your inner ear senses the motion of the ship as it rolls over waves. Youre getting conflicting information on different sensory channels into the balance system, Rauch says. That is believed to be the primary cause of motion sickness.

In virtual reality, the mismatch is there as well, says visual neuroscientist Bas Rokers of the University of WisconsinMadison. But the sensory cues are reversed: Your eyes see that you are moving through the virtual world in a virtual car or a virtual spaceship, or strolling down a virtual path but your vestibular system knows youre not actually moving. That gives you a cue conflict, he says.

While most motion sickness experts think sensory mismatch is to blame, some disagree. Kinesiologist Thomas Stoffregen of the University of Minnesota in Minneapolis, whos been studying motion sickness for 25 years, thinks instability is the culprit. On a ship, the rolling motion puts you off balance, and that makes you sick, he says. Motion sickness situations are ones in which the control of your body is challenged somehow. If you dont rise to that challenge, then the contents of your stomach may rise.

This idea, known as the postural instability theory, can be applied to VR as well, Stoffregen says. If your eyes convince your brain that youre in the virtual world, your body will respond to it instead of the real world you are physically in, which can throw your balance off. Imagine sitting in a chair in the real world while riding in a car in the virtual world. As the car approaches a turn, youll want to lean into it, which could land you on the floor. The more convincing the virtual world is, the more likely you are to link the control of your body to what youre seeing, Stoffregen says. And in a virtual car, that is a mistake.

While the postural instability theory is outside the scientific mainstream, it offers an explanation for another mystery of motion sickness: why more women suffer than men.

Stoffregen and colleagues have shown repeatedly that its possible to predict who is likely to get motion sick in various circumstances by measuring postural sway the small, subconscious movements people make to stay balanced while standing still. By analyzing several aspects of sway, including the distance, direction and timing of the movements, the researchers have found that people who are susceptible to motion sickness sway differently than those who arent. And postural sway differs measurably between men and women. The difference, Stoffregen says, can be attributed to physical differences between the sexes, such as height and center of balance.

Stoffregens research suggests women are also more prone to VR sickness than men. In a study published in December in Experimental Brain Research, Stoffregen and colleagues measured the postural sway of 72 college students before they were asked to play one of two VR games for 15 minutes using an Oculus Rift DK2. The first game made two of 18 men and six of 18 women feel motion sick, not enough for a statistically significant difference.

But more than half of the students who played the horror game Affected, using a handheld controller to explore a dark, spooky building, reported feeling sick. Of the 18 women playing that game, 14 felt sick. Thats nearly 78 percent, compared with just over 33 percent of the men. When the scientists compared those results against the postural sway data, just as in their previous motion sickness studies, they found a measurable difference in sway between those who got sick and those who didnt (SN: 1/21/17, p. 7).

Rokers has another explanation for the gender difference that fits with the sensory mismatch theory. In a study published in January 2016 in Entertainment Computing, Rokers and colleagues looked at how visual acuity might affect susceptibility to VR sickness. Seventy-three people with either natural or corrected 20/20 vision completed a battery of visual tests and then spent up to 20 minutes in an Oculus Rift DK1 headset watching videos. The videos showed motion from different points of view, such as a drone flying around a bridge or a passenger in a car driving through mild traffic. Of the female participants, 75 percent felt sick enough to stop watching before the 20 minutes had passed, compared with 41 percent of the men.

People who were better at perceiving 3-D motion in the visual tests were more likely to feel sick. And on average, the women in the study performed better on the 3-D motion perception tests than the men.

Its not clear why women would have better visual acuity for 3-D motion, but the results suggest that the more sensitive you are to sensory cues, the more likely you are to detect a mismatch, Rokers says. If you can tell that your senses are providing you different information, then you are more likely to get motion sick.

Just being a woman doesnt necessarily mean youll be highly susceptible to motion sickness like I am. Lots of other factors are likely at play. Some research suggests Asians are more likely to suffer. People who get migraines are also unusually prone to motion sickness. Scientists at genetic-testing company 23andMe reported in Human Molecular Genetics in 2015 that they had found 35 genetic variants associated with car sickness. Age is also a factor: Infants are generally immune, susceptibility increases from age 2 to 15, and although it hasnt been my experience, the problem subsides for many people in adulthood.

Everybodys brain has a different capacity for processing motion, Rauch says. Just like some people are good with languages and some people are good with math, some people are good with motion processing, of doing this complex sensory-integration task. The people who are good at it become figure skaters and divers and gymnasts, he says. But there are other people who throw up if they ride backwards on the metro. That would be me.

Under the right circumstances, though, anyone with a functioning vestibular system can experience motion sickness nearly everyone stranded on a lifeboat in choppy seas will get sick.

Very little motion sickness research has been done on the latest VR headsets available to consumers. But Rauch says the very nature of VR, which is to trick your eyes into telling your brain youre in another world, is inviting a sensory conflict. Theres always going to be some sensory conflict, and so the VR is going to be more successful in people who can tolerate that, Rauch says. For me, he was clear: Its always going to be torture.

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Some games, like theBlu: Encounter(screenshot shown on first slide)and Job Simulator (middle slide), are unlikely to cause sickness because they require little movement around the virtual world. The dinosaur-hunting game Island 359 (last slide)has a teleport option for more susceptible players.

The U.S. military was the first to report, in 1957, that virtual environments could be problematic: Flight simulators were making some pilots motion sick. Since then, many studies have confirmed that simulator sickness is a real problem.

One of the biggest tech hurdles for VR has been the inherent delay between when you move your head and when the display updates to reflect that movement. If the lag is too great, you can end up with a potentially vomit-inducing sensory mismatch. Todays high-end systems have capitalized on advances in displays, video rendering, motion tracking and computing to cut down the lag to the neighborhood of 20 milliseconds low enough to avoid triggering motion sickness. Theyve beaten most of the pure hardware problems, says Steven LaValle, a computer scientist at the University of Illinois at Urbana-Champaign and a former head scientist at Oculus.

But even with the best virtual reality system, what you do in the virtual world matters. If youre sitting or standing in one place in both the real world and the virtual world, youre very unlikely to feel sick. And as long as a step in the real world results in an equivalent step in the virtual world, moving around is fine too. All three of the premium headsets use external lasers to track the motion of the headset within a limited space up to 3.5 meters by 3.5 meters with the HTC Vive. But to explore further, youll need to use handheld controllers with buttons, triggers and directional touch pads to move your virtual self around, just as in a regular 2-D video game. Thats where things can go wrong.

I like to joke that the controller is like a sickness generator, says LaValle, who worked on reducing motion sickness while at Oculus. Every time you grab onto a controller, youre creating motions that are not corresponding perfectly to the physical world. And when thats being fed into your eyes and ears, then you have trouble.

The people creating the content for VR systems are taking the problem seriously, says Steve Bowler, cofounder of VR game company CloudGate Studio, based outside of Chicago. Developers are really, really focused on zero tolerance for user motion sickness.

On its face, it makes no sense that exposure to motion should bring on disabling nausea and vomiting. But we share this seemingly odd connection between our sense of balance and the gastrointestinal tract with many nonhuman animals, including dogs, monkeys, sheep, birds and even fish. The most often cited explanation is an evolutionary theory put forward by cognitive psychologist Michel Treisman in Science in 1977. Ingesting a poison can also mess with your balance system. So the body interprets the motion reaction as a symptom of poisoning and responds as it would with poison, by vomiting to try to get rid of the harmful substance, he suggested. Although its just an idea and has never been tested, it has some intuitive appeal.

One of the most successful strategies developers have hit on is using teleportation to take short skips around the virtual world. Basically you aim the controller where you want to go and the screen fades to black for a split second, sort of like the blink of an eye. When it fades back in, youre at the new location. This, Bowler says, eliminates motion sickness even for the most susceptible people he knows. But that comfort comes at a cost: The whole point of VR is to convince you that youre physically in this other world; if youre magically teleporting here and there, its not going to feel as real, he says.

Bowler favors a technique known as sprint or dash that aims to reduce the effects of acceleration. Instead of gradually ramping your speed up and back down, a sprint bumps you up to speed almost instantaneously, maintains that speed until you reach your target and then drops you quickly back down to a standstill.

While sprinting doesnt approximate natural movement very well, it does let you see the motion, unlike teleportation. And Bowler says hes had about a thousand people at various events try sprinting in a dinosaur-hunting game his group built called Island 359 with almost no reports of motion sickness. Anyone who feels uncomfortable can switch to chasing dinosaurs using a teleportation option instead.

Oculus seems to have accepted that VR sickness cant be eliminated from all VR experiences at the moment, so most Oculus-approved games come with comfort ratings to let users know if a game or experience is more or less likely to make them sick. Those assessments might help people like me avoid the most nauseating games.

Bowler considers himself an ambassador for virtual reality. After almost an hour of very patiently and enthusiastically explaining how VR works, he somehow convinced me to try it. A few days later I was at UploadVR in San Francisco strapping on the HTC Vive with Bowler looking on via Skype from his office in the Chicago suburbs.

The headset was heavy and awkward, but I otherwise felt fine while creating a virtual 3-D painting or walking around on the deck of a shipwreck as an enormous blue whale swam by ogling me. I even shot at drones while dodging virtual bullets, with no hint of motion sickness. I decided I was ready to hunt dinosaurs.

First I tried teleportation mode in Bowlers game, and as he promised, no nausea. Though the splatters of blood and guts when I slashed some attacking mini dinosaurs was almost enough to make me gag, the strangeness of teleportation made me feel more like I was inside a 2-D video game than on a dinosaur-infested island. I decided to see if I could handle sprint mode. I wanted to know if it would feel more real.

That was a mistake. I could only manage about a half dozen sprints before I felt the first hints of nausea. I had to quit. Once the headset was off I felt better. But soon, a lingering nausea and drowsiness hit, like I sometimes experience after a turbulent flight. I didnt entirely recover until the following evening. Im glad Bowler convinced me to give it a try, and the parts I could handle were pretty fun. But I wont be going back for more anytime soon.

Virtual reality still has lots of room for improvement, but whether it will ever reach the point of being comfortable for everyone is an open question. The VR industry is moving at a pace science cant match, forging ahead with its own grand experiment as millions of users test its products. Much of what we learn about how VR affects people will show up first in living rooms and on Twitter rather than in scientific labs and journals. And though the results of those experiments are still coming in, tech luminaries havent hesitated to declare 2017 as the real year of virtual reality.

A slew of possible solutions for VR sickness most with very little research behind them have been suggested by scientists, developers, companies, entrepreneurs and users.

Here are just a few:

This article appears in the March 18, 2017, issue of Science News with the headline, "Real sick: The immersive experience of the virtual world is not for everyone."

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Virtual reality has a motion sickness problem - Science News