Here's What a Rat Looks Like When It's Happy

Now we know what facial expression the rodents make when they're feeling good. The best way to tell if a rat's happy, according to a new study, is to look at its ears. A happy rat's ears hang relaxed to the sides (right), instead of perked up (left). It can be hard to tell, since they can't exactly greet us with a grin. But now, for the first time, scientists have spotted the rat equivalent of a smile--and it's all in the ears. They found that happy laboratory rats not only can be literally tickled pink, but they relax their ears so that they hang loosely to the side.