The “facial feedback” hypothesis holds that physically expressing an emotion sends a biochemical signal from the facial muscles that “loops” back to the brain. It’s much the same as sound coming from a speaker that’s picked up by a microphone and sent back through the speaker as amplified feedback. A 1988 study by German researchers involved telling participants to hold a pen in their mouths in one of two ways – in the “lips” position, which activated the muscles used in frowning, or in the “teeth” position, which employed the muscles used for smiling. A control group simply held the pen in their hands. Then the three groups were shown a cartoon, and told to evaluate how funny they found it. Members of the “teeth” group reported finding the cartoon significantly more amusing than did those in the “lips” or control groups.

In other words, people who smiled – even though they didn’t realize there were smiling – found the world a jollier place. Remember: expressing emotion is a key component offeeling emotion. If you are a habitual half-smiler and fake laugher, make it a point to try opening up and letting go the next time you feel the urge. Repeat as necessary. You may well find yourself happier for having done so.