When you’re happy and you know it, aside from clapping your hands, you’re likely to smile. But the reverse process turns out to be true as well— when you smile, you can convince your brain not only that you’re happy, but that others around you are grinning right back.
Smiling stimulating sentiment
The physical act of smiling has been tied to people’s responses to a variety of experiences. Even something as unnatural as clenching a pen to force a pseudo-grin can make enough of a difference to make cartoons seem funnier. Neutral or frowning expressions then reverse the effect, leading to lower emotional responses for the former and negative reactions for the latter.
Perception of contagious contentment
These shifts in perception also extend to our perceptions of other people’s emotions. Test subjects were shown photos of other people’s faces displaying a variety of emotional states. Their brains were being monitored for activity related to emotionally-charged facial recognition in order to see what emotions the test subjects’ brains were registering in the photos.
Smiling test subjects showed strong recognition of smiling faces in the photos. But they also registered neutral expressions as smiling as well. The smiling participant’s perception was being colored by their own mechanical/emotional state. Hopefully there will be a follow-up looking to see how much seeing, or at least believing, everyone around you is smiling reinforces your own mood.
Source: Smiling Changes How You View the World by Christian Jarrett, Science of Us