Why do some of us get sick while riding a bus?

Was it something you ate? Or maybe you drank too much soda before the ride? Well… It’s not your stomach or your bowels, it’s The Idiot Brain!

There is some funny stuff going on in your brain while you’re on a cruise ship or sitting on a bus that causes you to feel sick. Such a phenomenon is called motion sickness and it can be caused by a variety of motion environments (e.g., buses, boats, planes, or even virtual reality).


Humans are equipped with highly sophisticated sensory systems and neurological mechanisms from which proprioception emerged ‒ the ability to feel the current position of our body in space. Then, there is the vestibular system located in each of our inner ears. Roughly said, it acts as a “bubble level,” telling us if we’re tilted or hanging upside down.

Don’t forget the vision! Different types of movement send different eye-to-brain signals. For example, if you pay close attention when you’re walking (on two legs), this type of movement produces a bouncing-like image in front of you. Plus, the bubble level is also sending characteristic signals to the brain. That way our brain knows exactly how its body is moving ‒ everything is OK (for now)!

Now, imagine you are sitting on a bus with your eyes open constantly — minus the time you spend blinking — and the environment is moving around you, but you know you’re sitting straight. It is absolutely logical for you because you took a bus in order to spare your legs from walking long distances. Although, your brain is getting mixed signals. The proprioceptive system and the eyes are telling to your brain: “we are not moving,” however, your vestibular system is detecting a high-speed movement. Your brain, then, gets confused and the only reasonable explanation for such signal mixture is — you guessed it — poisoning!

The only thing in nature that can deeply disrupt the normal functioning of our inner biological systems is poisoning. So if the brain thinks that some kind of poison has got inside our body, it will do anything in its power to get rid of it, including the activation of the vomiting reflex.


The reptilian brain — the oldest of the three — controls the vital functions of our body such as heart rate, breathing, body temperature, and balance. Our reptilian brain includes the main structures found in a reptile’s brain: the brainstem and the cerebellum. The reptilian brain is reliable but tends to be somewhat rigid and compulsive.

Evolutionarily advanced regions in the brain plausibly know if we are sitting on a bus, but the reptile brain won’t just let his younger companion overwrite the ancient pathways related to such movement experience. In such situations, our brain is eager to trigger the vomiting reflex in order to get the imaginary poison out of the system.

Now, some people don’t even get sick during a bus ride. Moreover, some of them are totally fine with reading a book while commuting, but not me. If I spend more than five minutes staring at small letters, or a shiny little screen I start to feel nausea, and … you figured the final outcome of the story by now.

Lazar Kulasevic

Founder of Spiderest.

View all posts by Lazar Kulasevic →

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