| MadSci Network: Other |
The answer we've come up with is that your head would recoil backwards from the force of the sneeze, but the muscles in your neck contract sufficiently to overcome the recoil and push your head forward. Some of this is just body reflexes - your brain likes for your head to stay on a level plane, so any action to move it otherwise is countered. Physiologically sneezing acts to clear dust and other particles from your nose and upper respiratory tract. Keeping your head straight or bending it forward would keep the trachea straight and open to the pulse of fast moving air. Then on a conscious level, it's generally considered more polite to bow one's head when sneezing, than to lean your head back and sneeze into the open.