During unconscious facial mimicry, Schilbach discovered, several regions of the brain become active. One of those, the left precentral gyrus, becomes active when people get the urge to move their facial muscles (such as when a song makes them sad). Other regions (the right hippocampus and the posterior cingulate cortex) become active when we have emotional experiences, helping to retrieve emotional memories. Another part of the brain that becomes active during facial mimicry (the dorsal midbrain) relays emotional signals to the rest of the body, bringing on the physical feelings that go along with emotions, like a racing heartbeat.  
 
When humans mimic others’ faces, in other words, we don’t just go through the motions. We also go through the emotions.  
 
Recently Bernhard Haslinger at the Technical University of Munich realized that he could test the facial feedback theory in a new way. He could temporarily paralyze facial muscles and then scan people’s brains as they tried to make faces.