Not just colds and swine flu, but...
This is MOST contagious. Amazing how one yawns and immediately, the next person too does. I have asked some folks including doctors why this is so, but no real answers seem available. Even whilst talking on the phone, if I yawn, the person at the other end miles and miles away, also yawns!
Guess this is for the 'weepier' souls, but usually, if someone cries -- really heartfelt and reasonable tears, I automatically feel MY water tap opening up. Very embarrassing and really, not of any help or use. But, there it is.
Snap at someone and see them snap back. Usually. Except for the highly calm folks (know very few myself and these are people who merely clam up as opposed to handling it maturely...which is WHAT I don't know!).
Whether they are contagious or not, they ought to be returned and therefore termed contagious. Else...how rude!
Giggles are not really contagious. In fact, I do know that they can really bug some people. You, know, the non-gigglers who in fact, can unknowingly cause more giggling. When I as a giggler come across an extremely straight face whilst in the middle of a big giggle session, things just get more giggle-worthy! Anyway, I can feel at least a smile coming on if I chance upon gigglers (unless of course, they are giggling at ME. Then, 'Hmph' to them).