I would like to talk to the person who spread wrong information about smiles. Who said we use only one muscle. I have noticed in my recent photographs, I have wrinkles at the temples on both sides when I smile. May be I smile too wide, The additional pressure gets transmitted to skin and muscle and shows up at the temples. I don’t know.
Looks like a lot of muscle to me. They actually look like tiny horns that come up with a big smile. I think they got it the other way round. When I frown I have nothing to speak of.