To avoid a potentially nasty cleanup, students are deprived of food for four hours before entering the experimental chamber. Inside, they step onto a force-sensing platform and stare at a paper map of the U.S. The walls begin sliding back and forth on a track a mere 1.8 centimeters with each cycle. At the right frequencies, this movement triggers a tugging sensation that begins somewhere in the brain and mysteriously travels to the belly. But before the full effects of motion sickness set in, the subjects will typically turn away and beg for mercy.
At that point, the students may be thinking that the course credit they will receive for participating in Thomas Stoffregen's sensory funhouse may not be worth it. But for the University of Minnesota psychologist, every student he lures inside is another data point that he believes will overturn the dogma about the cause of motion sickness. If he is right, the findings could lead to new ways of identifying people susceptible to motion sickness before they get sick and may provide designers of simulators and video games with ways to keep controllers in the hands of potentially woozy players.
For the past century, scientists have believed that motion sickness derives from a conflict among our senses. Our inner ears contain sensors for both angular motion (the semicircular canals) and linear motion (the otoliths). When these sensors disagree with the information we expect to receive from our eyes and muscles, motion sickness manifests itself. And yet, Stoffregen says, our senses constantly provide different channels of information: redundancy is an essential part of the sensory system, and our brains do not compare our senses in any direct manner. Moreover, because it is impossible to determine which of the conflicting senses is interpreted as being "wrong" by an individual's brain, Stoffregen has branded the conflict theory with the highest-order insult a scientist can muster: unfalsifiable.
Indeed, researchers have long wondered why some individuals and certain classes of people children and pregnant women are more susceptible to motion sickness than others. What is more, experiments conducted since the dawn of the Space Age, when NASA wanted to prevent its astronauts from falling ill, can predict who will succumb to motion sickness with only about 30 percent accuracy. Finally, Stoffregen notes the puzzling observation that, whereas people may feel sick on the deck of boat, they rarely get the urge to vomit when fully immersed in water.
Stoffregen instead argues that motion sickness comes from the brain's persistent inability to modulate the body's movements in a challenging environment. Postural instability the inability to maintain balance was considered a symptom of motion sickness. Not so, Stoffregen says. Although postural control relies on sensory feedback, motion sickness is really a sign that the motor-control system is going haywire.
His alternative theory, first published in 1991, landed with a dull thud, and his papers garner just a handful of citations each year. But experts have been muttering privately about Stoffregen ever since and lately some have grudgingly begun to accept him. "It was a very, very different theory," says Larry Hettinger, a longtime motion sickness researcher now at defense contractor Northrop Grumman. "I clearly remember people thinking, 'This is nonsense, this is crazy foolishness.'"
The growing acceptance of Stoffregen's view has much to do with experiments conducted over the past two decades. Inside the moving room, he has found that volunteers can significantly reduce motion sickness simply by widening their stance an observation, he says, not predicted by sensory conflict theory. Students standing with their feet five centimeters apart tend to get motion sickness about 60 percent of the time. Spreading their legs to 30 centimeters increases the stability of the head and torso and decreases the incidence of motion sickness to about 20 percent. Stoffregen says that by monitoring body sway, he can predict the onset of motion sickness with 60 percent accuracy. If swaying is just a symptom of motion sickness, it would be detectable only after participants reported feeling sick.
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8 Comments
Add CommentAs an ocean sailor, I find his theory interesting. In my observations there may be an anxiety component to seasickness as well. On long voyages, I experience mild seasickness within 12 hours of leaving port, but it abates within the next 12 hours.
Reply | Report Abuse | Link to this"Floating in water, the human body becomes passively stable, and postural control is no longer an issue. If Stoffregen is right, then under such a condition, motion sickness would be impossible..."
Interesting, but I have known scuba divers who get seasick upon surfacing in ocean swells.
While onboard an icebreaker crossing the Drake Passage (known to produce some of the roughest seas in the world), I discovered that lying in my bunk with a headset on that played music with a distinct beat, my brain was able to focus on the musical rhythm and block the sensations of seasickness. Maybe the astronauts can also avoid seasickness by simply listening to some good rock and roll!
Reply | Report Abuse | Link to thisThere is a rare underwater condition that you can encounter in SCUBA diving called a surge. This is an odd underwater current that will cause motion sickness while completely submerged, it will subside after surfacing if the water is calm. I have never experienced it myself, but my brother has while diving the the Bahamas the day after a hurricane.
Reply | Report Abuse | Link to thisI often get seasick while swimming and/or snorkeling in waves that are not breaking.
Reply | Report Abuse | Link to thisAs long as I'm talking about me...I do not get sick while watching video of motion, or on amusement park rides with consistent circular motion (like the Enterprise as described on wikipedia). I only get ill when my acceleration is constantly changing, like in waves, windy roads, or rides like the Pirate ship (as described on wikipedia).
I just finished the article "Finding Balance" by Brendan Borrell that appeared in the April 2009 edition of Scientific American I think I've seen the experiment he proposes actually performed, many times. He wrote.
Reply | Report Abuse | Link to this"...the ultimate test of his theory is still in the works, Floating in water, the human body becomes passively stable and postural control is no longer an issue. If Stoffregen is right, then under such condition, motion sickness would be impossible."
I have quire a bit of experience with people who have gotten sea sick while floating in water. I'm a frequent scuba diver and while I don't tend to get seasick I've dove with many who do. It is common for them to get sick while floating on the surface in rough seas, By "rough" I mean waves or steep swells up to about four feet tall. It' s very common that some divers start to become sick if forced to stay on the surface in these conditions. Less common but still still frequent is that some people will get sea sick while under water in mostly shallow depths of around 25 feet when there is "surge" This is a back and forth (perpendicular to shore) water movement that can cycle as far as about 5 to 6 feet with 10 to 15 second period.
It is slightly more serious when a diver gets seasick underwater than above. He has to manage both vomiting and breathing through a regulator. The danger is that a new, or in-frequent diver cannot manage that level of task loading and panics. This is a common enough problem that it is covered by most scuba training agencies on the basic open water classes.
From my experience, I'd estimate the fraction of divers who get sick while floating in (or under) rough water is about the same as those who would get sick on a boat in similar conditions.
I don't know that I disagree with the new theory so much as the idea that postural control is no longer an issue when a person is submerged in water. In other words I don't think floating in water is a good test of the theory.
Great replies! I get so sick of reading uneducated responses on news websites. It's refreshing to see responses that are intelligent and thoughtful (is that redundant?).
Reply | Report Abuse | Link to thisSurely the body becomes passively stable in microgravity conditions too.
Reply | Report Abuse | Link to thisI think I have cracked motion sickness with an iPhone/iPad app. It does sensory conflict resolution by using 3 forms of bio-feedback. Not good for this theory for it confirms the traditional idea of sensory conflict. I need more beta testers though. People that suffers from motion sickness and owns and iPad/iPhone. Please guys, help out. You can register here: http://www.nomotion.info/testflight-50-beta-testers-wanted/
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