We've covered theories on why we yawn previously. Today, I came across a video compiling a series of yawns that represents a kind of implied test. Can you watch a 90-second video of yawns without yawning yourself? For me, the answer is, yawn, NO. More interesting, perhaps: can watching another species of animal make you yawn?
The most forceful yawn for me was at 0:58, when two cats perform a synchronized yawn. Also keep your eyes peeled for the yawning baby hedgehog.