People smile for different reasons. We smile when we feel nervous, or embarrassed by a bad joke, or as a mask when we don’t wish to show others the entire truth about our feelings, and of course sometimes we smile out of genuine happiness and joy.

In 1967, a young man from San Francisco named Paul Ekman traveled to the end of the world to a tribe that lived far away from “known civilization” to explore the secret of smiling. After getting back to civilization, the young researcher invented an entire system for translating expression of feeling into numbers and tables. It takes forty-two muscles in the human face to create facial expressions. Ekman gave a number to each. “Nine,” for example, meant wrinkling the nose, “fifteen,” pressing the lips together. With this tool, Ekman discovered nineteen different ways of smiling. Of these, eighteen are not genuine, though they are very useful in terms of making human interaction possible. The examination of feelings unfolding inside people, seemingly hidden from sight, was left to philosophers and poets. But Ekman removed any doubts about the accessibility of private experience to science*.

A Duchenne smile (in honor of the French physiologist Guillaume-Bemjamin Duchenne) involves contraction of both the zygomatic major muscle (which raises the corners of the mouth) and the orbicularis oculi muscle (which raises the cheeks and forms crow’s feet around the eyes). With the help of his facial numbering system, Ekman could show that only this smile expresses a true sense of contentment. More recent research suggests that only the Duchenne smile is uniquely associated with positive emotion. The Pan-Am smile, also known as the “Botox smile”, is the name given to a “fake smile”, in which only the zygomatic major muscle is voluntarily contracted to show politeness as demonstrated in the Pan American World Airways commercials in which the pretty flight attendants would always flash every jet-setter the same perfunctory smile.

Yesterday I did my own study by examining the pictures my husband Joe took of me on Christmas Eve and then a couple of weeks later to be used for the cover of LET GO. The smile in the after Christmas pictures is definitely not Duchenne. Then I thought about the circumstances in which these pictures were taken. On Christmas Eve, I was posing for the camera in my family room next to a glittering Christmas tree and surrounded by family as well as Joe’s brother and his wife who drove all the way from New Jersey to spend Christmas with us. Smiling was effortless because deep down I was happy, content and grateful. But circumstances were different a couple of weeks a later. Of course our guests had long gone and our oldest daughter had returned to college earlier that day. On that particular Sunday afternoon, my household helper didn’t show up as she was in the hospital with severe stomach flu. So every time Joe needed to adjust the lighting, I ran back to the kitchen to check on dinner. On top of that Jake was grumpy. Mommy wasn’t giving him enough attention because he wanted to make the last day of the winter break special (meaning he wanted me to take him to Toys R Us just to look) and I kept telling him that I didn’t think we could make it. So in all the shots taken that afternoon, even though my hair looked more perfect and the lighting was improved, I couldn’t pull a Duchenne smile.

When trained psychologists look through collections of photos, they can at a glance separate out the Duchenne from the non-Duchenne smilers. Dacher Keltner and LeeAnne Harker of the University of California at Berkley studied 141 senior-class photos from the 1960 yearbook of Mills College. With the exception of three women who weren’t smiling, half of the smilers were Duchenne smilers. All the women were contacted at ages twenty-seven, forty-three and fifty-two and asked about their marriages and life satisfaction. Astonishingly, Duchenne women, on average, were more likely to be married, to stay married, and to experience more personal well-being over the next thirty years. Questioning their results, Harker and Keltner considered whether the Duchenne women were prettier, and their good looks rather than the genuineness of their smile predicted more life satisfaction. They found that looks had nothing to do with good marriages or life satisfaction**.

It is estimated that only 10% of the population can produce a Duchenne smile on demand without special training. For the rest of us, we can either practice to get the orbicularis oculi muscle to contract more readily or we can learn ways to generate more positive emotion so that our smile will mirror our inner state instead of just orchestrated muscle movements.

Image credit: Wikimedia Commons
* The Science of Happiness by Stefan Klein
** Authentic Happiness by Martin Seligman