Motion sickness occurs when there is a conflict between visual and vestibular sensory inputs, leading the autonomic nervous system to trigger symptoms like nausea and cold sweats. Intense perceived motion, like that experienced in the central or close-up seats in a 3-D movie, aggravates this sensation due to more pronounced visual stimuli.
Many people experience motion sickness while traveling in a car because of conflicting sensory inputs from the visual and vestibular systems. The visual system provides information about what we see, while the vestibular system, located in the inner ear, senses motion and balance. When these two systems send contradictory messages to the brain - for instance, when the eyes see motion that is not felt by the vestibular system, or vice versa - the brain may respond with symptoms like nausea, cold sweats, and vomiting. This is because the autonomic nervous system, which controls involuntary bodily functions, is affected by the discordant sensory information.
Sitting close to the screen or in the middle of the theater during a 3-D movie can exacerbate motion sickness because the perceived motion is much more intense in these positions, reducing the visual connection to a stable horizon and amplifying the conflict between the visual and vestibular inputs.