Why do people get car sick?

SDStaff Hawk replies:

Had an eventful trip, did you?

Car sickness falls under the general category of motion sickness, to which sea sickness and air sickness also belong. Generally speaking, motion sickness is what happens when the brain gets conflicting signals from the eyes and the ears. Yes, the ears.

The outer ear is responsible for hearing, but the inner ear is responsible for equilibrium. Perhaps you know this. What you may not know is that there are two types of equilibrium: static (orientation of the head/body relative to the ground) and dynamic (orientation of the head/body in response to sudden movements). Both play a crucial role in keeping your lunch down.

When you’re in a car or boat, the eyes may tell the brain that the body is not in motion — you’re just sitting there. One of the mechanisms of the inner ear, the one that monitors static equilibrium, may corroborate the visual information, since the head/body relative to its immediate surroundings (that is, the vehicle) is, in fact, fixed.

On the other hand, the other mechanism of the inner ear, the one that monitors dynamic equilibrium, is screaming. It’s telling the brain that the head/body is in motion.

Now, the brain, which is getting mixed signals, decides it’s going to do something. Usually, this involves the revisualization of a past meal, i.e., “tummy confetti,” “technicolor yawn,” or “offers to the porcelain god.” Personally, I’ve found the best remedy is to remove one of the signals to the brain by closing my eyes.

Having taken the time to give you the straight dope on this, you now have the basis for understanding why ear infections produce dizziness. The infection messes with the inner ear, which again sends the brain conflicting messages against the eyes.

SDStaff Hawk, Straight Dope Science Advisory Board

Send questions to Cecil via cecil@straightdope.com.

STAFF REPORTS ARE WRITTEN BY THE STRAIGHT DOPE SCIENCE ADVISORY BOARD, CECIL’S ONLINE AUXILIARY. THOUGH THE SDSAB DOES ITS BEST, THESE COLUMNS ARE EDITED BY ED ZOTTI, NOT CECIL, SO ACCURACYWISE YOU’D BETTER KEEP YOUR FINGERS CROSSED.