Because your eyes and inner ear are disagreeing: reading, your eyes report "stationary" while your inner ear's motion sensors report every bump and turn - and the brain answers unresolved sensory conflict with nausea, its poison alarm.
Hence the patterns: drivers almost never get sick (they see and anticipate every move), and looking out the window fixes most cases by re-syncing the channels. One footnote: frequent reading-induced car sickness predicts vestibular migraine in a 2024 study - worth mentioning if headaches run in your story. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Why do I get motion sickness reading in cars?
Because your brain is receiving a contradiction it cannot resolve - and nausea is its alarm. Neuro-otologists explain it as sensory conflict: your brain merges sight, inner-ear motion sensors, and expectation to figure out whether you are moving. Reading in a car splits the vote: your eyes, locked on a page with only the car's still interior in peripheral vision, report "stationary," while your inner ear's semicircular canals and otoliths honestly report every bump, turn, and acceleration. The brain reads unresolved sensory conflict as possible poisoning - hence the nausea reflex. It also explains the patterns everyone notices: drivers almost never get sick (they see the road and anticipate every move, so all channels agree), front passengers do better than back-seat readers, and looking out the window fixes most cases instantly because it re-syncs the eyes with the ears. The fixes in order of power: eyes on the horizon or the road ahead, front seat, fresh air, and - one interesting footnote - if reading-induced car sickness hits you hard and often, one 2024 study found it strongly predicts vestibular migraine, worth mentioning to a clinician if headaches run in your story.