Taking a break from weighty stuff like finding a cure for cancer and the like, scientists have discovered that dogs, jus tlike humans, find yawns contagious:
A team from Birkbeck College at the University of London wanted to know whether canines - known to be highly skilled at reading human social cues - could read the human yawn signal, reports the BBC.
The team found that 21 out of 29 dogs yawned when the stranger in front of them had first. By contrast, no dogs yawned during the test where the person did not yawn.
Chris
That makes sense to me.
But when you're looking at contagious yawning, wouldn't everyone be in the same room? And therefore affected by the same oxygen levels? It's not that I don't think contagious yawning exists, I'm just not sure I trust experiements where they heven't made mention of oxygen levels, and/or monitored the breathing rates of all involved.
Of course, I could be totally wrong :)
http://www.theaustralian.news.com.au/story/0,25197,24144138-2703,00.html
they did a control group to show that when the human did not yawn, none of the dogs yawned
Perhaps humans did it for the same reason once, long ago, and the visceral memory remains.