Desperately Seeking Symmetry: emotion is expressed on left side of face

40:47 And almost like a contour map, you could actually look at the amount of change, amount of muscle movement that had occurred. Which you will see if you measure the muscle movement in millimeters on each side of the face, you'll see that the smile curves a few extra millimeters on the left side of the face. He says this is nearly always the case, always on the left side. What it's really telling you is that when somebody smiles or when they frown, they're doing it slightly more strongly on the left side of their face.

Now, if this is the case that our left side is saying more emotionally than our right side, then if you think about the mirror, it's a discombobulating thing, because it's taking your left, which is sort of broadcasting emotion, flipping it to your right, you're seeing yourself, you're all mixed up. You don't know which part of you is where. So, you're saying because I tend to address you with my attention on your left side, unbeknownst to me, and your left side is actually flipped over to your right, so it's a "Where are we?" sort of question.

https://radiolab.org/podcast/122382-desperately-seeking-symmetry