Do you yawn when you see or hear someone yawn? I do. I even yawn when I hear the word "yawn." What does this mean? It means I'm tired.
I may be tired, but studies show contagious yawning is a function of empathy. You yawn because you relate to the emotional state of being tired, bored, or whatever. You are yawning vicariously though the other guy.
In poker, empathy helps to get you into the mind of your opponent. This is a beneficial place to be as long as you don't get too attached. I theorize that bad play, like yawning, is contagious.
In my own "studies" I have seen a maniac sit down among responsible, veteran players and slowly drive them insane. Before I know it, the whole table is playing every hand, chasing to the river, consistently over betting the pot...madness! I admit nothing changes a player's outlook like a bad beat, but even before the maniac draws out on someone, the maniac flu spreads. This is true live, and even more true in US Online Poker, but is there a strategy around it?
I know the strategies at play here: "you must become a maniac to beat a maniac" and all that, but these are BAD strategies. If you can't inoculate youself from maniac flu, the best strategy is to find a new table. Put emphasis on empathizing with the pros.