While all of the body's sensory organs contribute to motion sickness, excess stimulation to the vestibular system within the inner ear (the body's balance center) has been shown to be one of the primary reasons for this condition.
Researchers at the Naval Medical Center in San Diego, California, reported in 2003 that 70 percent of research subjects with severe motion sickness had abnormalities of the vestibular system.
Audiometric techniques are also used when an individual has vertigo or dizziness, since many hearing and vestibular or balance problems are related.
The inner ear, also called the vestibular system, contains fluid that helps fine tune the information the brain receives from the eyes and the body.
A particularly intense vestibular disorder, Meniere's disease, interferes with the volume of fluid in the inner ear.