Why do people get headaches when reading in a moving vehicle?

Wendell

Did you mean why do people get nauseated? I think that's much more common than headaches. The human body has 3 main systems that govern balance: the optical (what you see), the kinesthetic (feedback from your muscles and nerves) and the vestibular (based on fluid flow in a small organ in the inner ear.) When these 3 systems receive different signals, it causes nausea. For example, when you're looking down and reading in a car (especially if it's turning corners,) your optical system doesn't see anything moving. Your vestibular system, on the other hand, feels the motion of the car and sends signals to the brain that you are moving. The discrepancy between these signals causes the brain (for whatever reason) to give you a sense of nausea. This is why stationary amusement park rides (like Star Tours, in which the car moves somewhat while the screen gives a different picture and really confuses your brain) cause nausea more than just about any other type of ride. Movies on a curved panoramic screen (like certain IMAX theatres) can cause you very similar nausea because your vestibular system knows you're not moving, while the action on the screen tells your optical system that it's moving. In all of these cases, it's because your brain is getting mixed signals. Neither stimulus would cause you nausea normally. Closing your eyes helps. Reading in a car that's on a straight, open highway doesn't usually make you sick. Sep 18 02, 11:25 AM

Gnomon

Reading in a car that is moving along a straight road gives you headaches because the page is vibrating slightly. Your eyes and brain have to compensate for this vibration, and the strain of it gives you a headache. You don't get headaches while looking at other things in the car because you don't look at them in the same sort of detail. If you try doing find needlepoint/cross-stitch in the car, you'll get headaches too! Sep 18 02, 12:04 PM

Son of The Household Cavalry

Possibly from hitting the windscreen when they hit the car in front. Reading while driving is not advisable. Sep 18 02, 10:49 PM