Interesting:
ScienceDaily (Sep. 15, 2010) — If someone near you yawns, do you yawn, too? About half of adults yawn after someone else does in a phenomenon called contagious yawning. Now a new study has found that most children aren't susceptible to contagious yawning until they're about 4 years old -- and that children with autism are less likely to yawn contagiously than others......
http://www.sciencedaily.com/releases...0915080427.htm