Facial Feedback Hypothesis

A sign behind the cash register at my local McDonalds promises a smile with every order. If the customer does not receive a smile, he or she is entitled to a complementary order of hashbrowns. The young woman who took my order displayed her impressive set of braces all the way back to the rubberbands. And yet, I felt there was something lacking. How could I be sure I had received the smile I was entitled to as a valued customer? Something about her smile made me wonder if she really was happy to take my order. I asked to speak to the manager. Does McDonald’s have graphs or guidelines as to what constitutes a smile? What, after all, is a smile? “A smile,” the manager replied, with an expert grin, “is what makes a customer feel happy.”

While this response did not yield the secret recipe of the McSmile, it did point to the unusual ability of the smile to reproduce itself. Smiles are infectious. Smiles are also innate. We are born with the ability to smile, and smiles are recognized across cultures. “Smile and the world smiles with you,” as my Granny used to say.

It is the ability of smiles to make others smile that is transforming a facial expression into a global industry.

A great deal of research is now being done to determine how exactly smiles work and why. The reason for most of this research has less to do with the woman behind the cash register as it does with the cash register itself. Researchers are incorporating smiles and other facial expressions into new interfaces. As a result, smiles are being subjected to rather humorless examination. A recent conference on the facial expressions in Seoul South Korea included a paper titled, “Multimodal Coordination of Facial Action, Head Rotation, and Eye Motion during Spontaneous Smiles.”

One of the pioneers of the study of smiles was a graphic artist named Harvey Ball. It was Ball’s belief that the power of the smile was so great that even a symbolic representation was enough to cheer people up. In the early 60s, Ball was assigned to promote the State Mutual Life Assurance Company’s friendship campaign. Ball first drew a curved line on a yellow circle. Afraid that disgruntled employees would attempt to subvert his creation by turning the smile upside down, Ball added two dots to represent eyes. In less than ten minutes, the phenomenon of the “smiley face” was born. If Ball himself can be taken as an example, the smiley face had its desired effect. Even though Ball never saw any of the profits from his creation, according to his son, he left the world with no regrets, happy to have this as his legacy.

The representation of smiles has come a long way since then. At the artificial intelligence lab at MIT, researchers are engaged in understanding the relationship between facial expressions and emotional states for the purpose of creating advanced robot interfaces. One robot, called “Kismet”, is able to reproduce a wide range of emotions using an interface that includes synthetic eyes, mouth and ears. Studies have shown that when spoken words are combined with the appropriate facial expressions, people are twice as likely to understand what is being said and far more likely to remember it (Massaro 2000). According to Dr. Cynthia Breazeal of MIT, in order for robots to interact effectively with people, scientists and designers will need to figure out how machines display and react to emotion, in addition to how they display and react to other types of input. The researchers at MIT foresee a time when robots will perform tasks ranging from cleaning your apartment to taking your order at a restaurant to babysitting your toddler. And you can bet that they will do it with a smile.

Once they get the hang of it, there is good reason to believe that robots will surpass their human counterparts in their ability to smile. Ironically, the fact that computers do not have to feel the emotions they display gives them a big advantage. Smiles are not all created equal. A “true” or zygomatic smile requires the contraction of special zygomaticus muscles in the face that are directly linked to the cerebral cortex. The close connection between these muscles and emotion means that a zygomatic smile is very difficult to fake. Humans are also very adept at detecting false smiles. We can tell from a young age when people are “faking it.” If the woman at McDonald’s smile struck me as insincere, it probably was. She couldn’t help it if giving me my Big Mac didn’t make her day.

The perfect gleam of a robotic smile may raise the bar for all of us. We will become used to seeing perfect zygomatic smiles on the faces of robots and come to expect the same from our human interfaces. Our friends at McDonalds will be expected to smile more and more sincerely even as they are inevitably replaced. What effect will this happy contest have on us?

In the late 1990’s Safeway, the country’s second largest supermarket chain, began to require employees to smile and greet customers with direct eye contact. A year later, an article in USA Today titled “Safeway's Mandatory Smiles Pose Danger, Workers Say" reported that 12 female employees had filed grievances over the mandatory smile policy. Apparently, their smiles were taken at face value. The women reported being repeatedly sexually propositioned by their male customers.

According to the “facial feedback hypothesis,” while we may get some extra attention from our own species, we do not need to fear the dangers of over-smiling. Smiling itself produces feelings of happiness. The hypothesis states, “Involuntary facial movements provide sufficient peripheral information to drive emotional experience.” (Bernstein 2000) The research to prove this hypothesis seems appropriately comical. In one study participants were instructed watch cartoons holding a pencil in their mouths, either between their lips or between their teeth. People with the pencils in their lips were therefore prevented from smiling. It turned out that the people with the pencils in their teeth, who could smile, rated cartoons funnier than those who could not (David and Palladino 2000).

Thinking about McDonalds, however, made me wonder if happiness is really what smiling is all about. My suspicions were confirmed when I learned that the human smile is believed to have evolved from the grimaces of primates. These grimaces were not evidence of pleasure, but rather of fear. The submissive grin of the primate sends the message, “I am afraid and therefore friendly.” The main message I received from the woman behind the counter at McDonalds was not “Gee, this is a fun place to work,” but rather, “Gee, I don’t want to get fired so I’ll try to make you happy.” And, frankly, I was less interested in whether or not she was having a good day than whether or not she was going to hold the pickles. What I want from my burger interface—whether human or robot—is not contentment, but a sense of control. It turns out that the best way to communicate this complex relationship may be to smile-like-you’re-faking-it. So, until robots master the subtle art of deception, perhaps we humans can continue to save face. But can I still have my hashbrowns, please :)

Bernstein, D. A., Clarke-Stewart, A., Penner, L. A., Roy, E. J., & Wickens, C. D. (2000). Psychology (5th ed.). Boston, MA: Houghton Mifflin Company.
Davis, S. F., & Palladino, J. J. (2000). Psychology (3rd ed.). Upper Saddle River, NJ: Prentice-Hall, Inc.
B. Massaro, D.W. (2000). Perceptual interfaces in human computer interaction. In Proceedings of the IEEE International Conference on Multimedia and Expo (ICME’00)(Vol.1, pp.563-566). New York, NY.