Editing Motion sickness (section)

=== Defense against poisoning ===
It has also been proposed that motion sickness could function as a defense mechanism against [[neurotoxin]]s.<ref name="Treisman1977" /> The [[area postrema]] in the [[human brain|brain]] is responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When feeling motion but not seeing it (for example, in the cabin of a ship with no portholes), the [[inner ear]] transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. As a result of the incongruity, the brain concludes that the individual is [[hallucination|hallucinating]] and further concludes that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin. Treisman's indirect argument has recently been questioned via an alternative direct evolutionary hypothesis, as well as modified and extended via a direct poison hypothesis.<ref name="Lawson 20142"/> The direct evolutionary hypothesis essentially argues that there are plausible means by which ancient real or apparent motion could have contributed directly to the evolution of aversive reactions, without the need for the co-opting of a poison response as posited by Treisman. Nevertheless, the direct poison hypothesis argues that there still are plausible ways in which the body's poison response system may have played a role in shaping the evolution of some of the signature symptoms that characterize motion sickness.{{citation needed|date=July 2021}}