A beautiful smile can lighten your mood and may even inspire you to have a conversation with a stranger. But, on the other hand, some smiles can repel you or make you feel disgusted.

One time I was checking into a hotel on vacation. Walking towards the receptionist, I said “Hello,” with a beautiful smile on my face. The lady smiled back, but it was immediately obvious that there was a thick layer of bitterness behind the smile. Nevertheless, she was able to sustain the smile while she was talking to me.

While checking me in, she needed to make a phone call to make a confirmation. The telephone was adjacent to her. Just as she turned away to make the call, I could see her facial expression turn from a smile into what I would describe as a combination of anger and disgust. When she finished with the call, she turned towards me, and again, I saw her face turn from the deadly combination into an unreal smile.

This type of smile is called the Pan Am smile. The smile is named after Pan American World Airways. Pan Am flight attendants were always required to smile, no matter the circumstance, or what a customer does. This pressure to put on a smile often resulted in a forced smile and a “fake smile.”

The Pan Am smile only engages the muscle around the mouth called the zygomatic major. However, a genuine smile, also called the Duchenne smile, engages both the zygomatic major and the muscles around the eyes called the orbicularis oculi.

Pan American World Airways is long dead and gone, but Pan Am smile lives on!