Humans sense motion through three nervous system inputs: visual, vestibular and proprioceptive. According to Mayo Clinic neurologist Scott Eggers, motion sickness is a discrepancy between "what your eyes see, what your inner ear vestibular system (which controls your sense of balance) senses, and what your body's sensory system tells you about where you are and the speed and direction of your movement."
A driver's three sources of motion detection agree, while a passenger's conflict. When a passenger focuses on stationary objects inside the car, such as a map, the brain registers stasis visually but feels movement. According to the dmv.org, the brain responds to the mixed messages with nausea.
When riding in a car, the driver's position aligns with the car's movement, protecting against motion sickness. In a right turn, the driver's body naturally leans right. A passenger often unconsciously resists the right-hand motion, moving against gravity. Uspharmacist.com reports drivers control and anticipate changes in direction while passengers incur rougher, unpredictable motion.
According to the University of Pittsburgh Medical Center, symptoms of car sickness include dizziness, upset stomach, nausea, vomiting, tiredness, sleepiness, sweating, faintness, headache and loss of facial color.
The Centers for Disease Control and Prevention state, "All individuals, given sufficient stimulus, will develop motion sickness." The best treatment is prevention. The Mayo Clinic advises passengers to focus on the horizon, sit in the front seat facing forward and minimize head movement.
