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There's another reason for putting on a happy face: It influences your brain in a positive way. In one study, subjects who were asked to hold a pen in their mouth (causing them to inadvertently make the facial muscle movements characteristic of a smile) rated cartoons to be funnier than did other subjects, even though they were unaware that it was the smile that was boosting their reaction. There's an interesting biological reason for this effect: When you feel down, your brain tells your face you're sad and your facial muscles respond by putting on a depressed expression—and convey back to the brain that, yes, you're feeling blue. Consciously changing the facial muscles so they don't correspond to what you're feeling is a way of sending a different message: "Hey, it's not so bad down here after all." The brain will respond by beginning to change your mood accordingly.