Flashing a quick smile may be a quick cure for stress.
Researchers from the University of Kansas have learned people who smile have lower heart rates and reduced stress responses compared to those who are more straight faced.
Researchers had college students hold chopsticks in their mouths to simulate either a smile or a neutral expression, and then induced a stressful situation.
They believe that activating certain facial muscles (like those used to smile) sends calming messages to the brain.
Researchers also learned that you don't have to actually be happy to reap the benefits of smiling.