Comprehensive article, well done! I've made some grammar changes to bring the reading level down a bit. A few other points:
- "Ethologists agree that almost all vertebrates yawn" - A reference would be helpful
- Is it possible to go into slightly more detail about SSRIs and other drugs as a potential cause of excessive yawning?
- Might it be worth a line suggesting why yawning is interpeted as being so rude socially?
- A section refuting other causes (e.g. lack of oxygen) would round out the article nicely.
All the best
--PaulWicks 12:41, 27 May 2008 (EDT)