Why does the way one person drives affect passengers with sickness but not themselves?
Being a passenger and watching the road move past can make you sick, especially if you are prone to motion sickness [1]. Being a driver can also make you less likely to experience motion sickness, since you are able to anticipate the movement [2]. Another factor that makes passengers more likely to experience motion sickness is the lack of control they have over the vehicle. As a driver, you are able to focus on the road ahead and anticipate the twists and turns, stops and starts, which helps to keep your brain from predicting the movement [3, 4]. While passengers can focus on the road ahead as well, it is still difficult for their brains to accurately predict the movement since they have no control over the vehicle [4].
Motion sickness is thought to be caused by conflicting signals in the inner ear, eyes, and sensory receptors [2]. Motion is sensed by the brain through different pathways of the nervous system including the inner ear, the eyes, and the tissues of the body surface [2]. When the body is moved intentionally, for example when walking, the input from all of the pathways are coordinated by our brain [2]. The symptoms of motion sickness appear when the central nervous system receives conflicting messages from the sensory systems: the inner ear, eyes, skin pressure receptors, and the muscle and joint sensory receptors [2]. As an example, if someone is sat on a boat or in a car (not looking out of a window), their inner ears sense movement up and down, left and right, but their eyes see a static view, as if they are not moving at all [2]. It is hypothesized that the conflict among the inputs is responsible for motion sickness [2].