Why Do Some People Feel Motion Sickness While Others Don’t?

Most people who have taken road trips are familiar with the feeling of a lurching stomach and spinning head, counting the minutes until the car ride ends. While one passenger may be fighting the symptoms of motion sickness, the person next to them may be perfectly fine, nonchalantly scrolling on their phone or listening to music.

About one-third of people are highly susceptible to motion sickness—which is triggered by discrepancies between anticipated and sensed motion—while others may experience it under extreme conditions.¹ Aspects such as the neurological system’s ability to handle conflicting signals, genetics, and habituation to various types of motion dictate how likely one is to feel motion sickness.² People who have sensitive inner ears due to past infections are also more prone to feeling motion sickness.³

Why Do People Feel Motion Sickness?

The first accounts of motion sickness date back to thousands of years ago when the Greek physician Hippocrates wrote, “Sailing on the sea proves that motion disorders the body.” In fact, the word “nausea” is derived from the Greek root word naus, meaning ship.⁴

In the 19^th century, scientists observed that people with complete hearing loss were insensitive to motion sickness, highlighting the role of the inner ear in this phenomenon.⁵ Eventually, researchers found that the organs of balance, or vestibular organs, within the inner ear play a key role in motion sickness

Humans have one vestibular organ within each ear. “There are five nerves coming from [each] organ of balance,” explained Jelte Bos, who researches motion perception at the Dutch Organization for Applied Scientific Research and Vrije Universiteit Amsterdam.

These neurons carry information to the brainstem, which also receives input from the visual systems. “If that is congruent with what the organs of balance feel about self-motion, then the brain has optimal information,” said Bos.

Any mismatch between the actual and expected patterns of these inputs initiates motion sickness symptoms.

Motion Sickness Differences Among People

By surveying more than 80,000 people and following up with a genome-wide association study, scientists found a link between certain genetic variants and individual car sickness susceptibility.⁷ These genes were involved in balance function, eye and ear development, and neurological processes, among others.

The vestibular organs also influence how prone one is to feeling motion sickness. “If these organs of balance are not functioning, those people even do not suffer from this visually induced motion sickness,” said Bos. “Even when sitting still, normal people can get sick from that.”

Scientists such as Bos also use motion simulators to study motion sickness in people.⁸ “You are making people sick. You have to clean up the mess after throwing up,” said Bos. “But it's part of the game.”

Using such methods, Bos and his team identified that unpredictable motion results in more severe motion sickness.⁹ In combination with real car drives, this also helped the researchers validate that anticipating the motion can reduce car sickness. “The driver in a car has the optimal information because he knows ‘I am going to turn the wheel’,” which is one of the reasons that the driver is less likely to feel car sickness compared to the passengers, Bos noted.

In addition to this, researchers have also noted that certain characteristics are associated with motion sickness. These include sex, with women being more prone than men, and age, with children around nine years of age being the most susceptible. Hormonal fluctuations during pregnancy and the menstrual cycle may also increase susceptibility.

So, the next time someone reaches out for a sick bag during a road trip while everyone else seems fine, remember that motion sickness is not due to a weak stomach, but a combination of factors.