Why Some People Get Motion Sick and Others Almost Never Do

On the same flight, one passenger reads a paperback through turbulence without looking up. Two rows back, someone else has their eyes shut, a hand pressed to their forehead, wishing the plane would just land. Same aircraft, same bumps in the air. Two completely different afternoons.

That split is common enough to be almost universal. About one in three people are highly susceptible to motion sickness, while others barely notice the conditions that send their seatmates reaching for a bag. The gap isn't about willpower or a delicate stomach. It traces back to how tightly, and how differently, each person's brain reconciles what their eyes, inner ears and joints are telling it at the same moment.

Why Do Some People Get Motion Sick and Others Don't?

Every moving vehicle asks the brain to combine three separate reports. The eyes register what's visible. The vestibular organs, tiny fluid-filled structures in each inner ear, register acceleration and tilt. Joints and muscles add a third layer: proprioception, the sense of where the body is in space, even with eyes closed.

"The brain takes different sensory bits of information from all three and then combines those together, integrating them, if you will, into one cohesive message," Dr. Kristen K. Steenerson, a clinical associate professor at Stanford University School of Medicine who specializes in inner ear and balance disorders, told Popular Science.

Read below deck on a rocking boat, and the eyes report a stationary book and cabin wall while the inner ear reports rolling and pitching. The two accounts don't match. That's the sensory conflict, or neural mismatch, researchers point to as the trigger.

"Everyone is capable of motion sickness. It's just that everyone has different thresholds for how much motion exposure is stimulating enough to make them sick."

Dr. Kristen K. Steenerson, Stanford University School of Medicine

One long-standing theory for why the body reacts so violently to a sensory disagreement: it may be a leftover alarm from before anyone traveled by car or ship. Steenerson described it to Popular Science as a poison-detection system gone slightly overzealous. The brain gets confused and says, you know, let's try and get rid of everything just in case. A stumbling, disoriented gait was, for most of human history, a symptom of having eaten something toxic. The nervous system still treats a mismatched signal the same way, even when the actual cause is a choppy ferry crossing.

The organs of balance themselves matter too. Jelte Bos, who studies motion perception at the Dutch Organization for Applied Scientific Research and Vrije Universiteit Amsterdam, has found that people whose vestibular organs don't function at all are effectively immune to the visually driven version of the condition, a finding documented by The Scientist. No working balance organ means no conflicting signal, and no sickness. It's one of the odder facts in the field: people can lose part of the system that causes the problem and, in a narrow sense, come out ahead.

Is Motion Sickness Genetic?

Largely, yes. Twin studies and genome-wide research both point to a strong inherited component. Some estimates put it as high as 70% of the variation in who gets sick and who doesn't.

The clearest evidence came from a genome-wide association study of more than 80,000 23andMe customers, which turned up 35 genetic variants linked to motion sickness at a statistically significant level. Several sit in or near genes tied to inner-ear development, eye and cranial formation, and balance function, among them PVRL3, TSHZ1, MUTED, HOXB3 and HOXD3. Others appear to act through the nervous system or glucose regulation, which may help explain why some people feel steadier after eating something small during a rough crossing.

That same research found something that echoes a companion piece on this site about why mosquitoes seem to target some people and ignore others: a handful of these genetic variants had markedly different effects by sex, with some showing up to three times the impact in women. The study also confirmed links between motion sickness and migraine, vertigo, morning sickness during pregnancy, and postoperative nausea. Conditions that, on the surface, look unrelated but appear to share underlying biology.

Why Am I More Prone to Motion Sickness Than Everyone Else in the Car?

Genetics sets the baseline. A handful of named factors then push individual risk up or down from there.

Migraine history. People who get migraines are more likely to also be highly susceptible to motion sickness, and the two conditions appear to share some genetic overlap rather than being simple coincidence.

Anxiety. People prone to high anxiety carry elevated risk too, though researchers are still untangling how much of that is a direct physiological link versus anxiety amplifying the perception of symptoms once they start.

Age. Susceptibility isn't flat across a lifetime. It climbs through early childhood, peaks somewhere around age seven to 12, and then declines through the teenage years and adulthood, only to creep back up later in life as the inner ear's motion sensors gradually lose sharpness.

Sex. Women are more prone than men overall, and susceptibility shifts further with hormonal fluctuations during the premenstrual phase, pregnancy, and the transition through perimenopause. Researchers tie this to changing estrogen levels rather than to anything psychological.

There's also a quieter factor that has nothing to do with biology: who's driving. The person steering a car braces for each turn before it happens, because they're the one initiating it. Passengers get no such warning. Bos's research on anticipation and unpredictable motion helps explain why the driver's seat is, for many people, the one seat in the car that rarely makes anyone sick.

None of this is a verdict on anyone's constitution. A brain that reacts hard to sensory mismatch isn't a weak one. By some accounts it's arguably doing exactly what motion sickness evolved to do, just in circumstances evolution never anticipated. Which is small comfort, admittedly, to the person in seat 14C with their eyes closed. But it might explain why the guy next to them, headphones in, never even looks up.