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Emotions are often thought of as internal states, invisible to the outside world. Yet the human body can reflect these psychological states, becoming a powerful means of communication with the outside world. This is the case with smiling: happiness or joy is represented by the lips curved upward, often accompanied by crinkling around the eyes. It turns out that what seems like a simple facial expression is more complex and beneficial than it appears.
The science of smiling
Smiling engages 13 of the 43 facial muscles, with the most important being the zygomaticus major and the orbicularis oculi. The first one is located between the corners of the lips and the upper cheeks and controls the way we smile. The orbicularis oculi surrounds the eyes and is responsible for raising the cheeks.
In 1862 the anatomist Duchenne found that the difference between a genuine smile — called Duchenne smile — and a fake smile — called non-Duchenne smile —lies in the activation of the orbicularis oculi. A genuine smile is characterized by both eye constriction and cheek elevation, while a fake smile involves only cheek elevation.
Duchenne’s research paved the way for further studies on smiling, conducted by Paul Ekman, who devoted his career to the study of facial expressions and body movements. He is also well known for inspiring the development of the Facial Action Coding System (FACS), a universal tool for measuring facial movements and identifying underlying emotions. According to Ekman’s studies there are at least 18 different types of smiles, classified into:
- Non-enjoyment smiles: smiles expressing negative emotions such as feeling miserable.
- Emotional blends: smiles registering that more emotions are felt at once.
- Smiles with a gaze: smiles accompanied by a specific gaze, such as a flirtatious smile.
- Social smiles: smiles having different social functions, such as the coordination smile: an asymmetrical slight smile regulating interactions between people.
Finally, false smiles are intended to mislead others that positive emotions are being felt, and they are difficult to recognize because of a limited understanding of non-verbal communication. However, there are subtle cues that can indicate fake smiles: they are asymmetrical; the offset time of the false smile may appear noticeably inappropriate; and they will only partially cover the actions of the lower face.
Research on smiling
Psychology and biology have collaborated for years to explore the science of smiling, producing groundbreaking studies and surprising results.
The pen-in-mouth experiment by Strack, Martin, and Stepper (1988) demonstrated the facial feedback hypothesis, which states that facial expressions can influence emotional experiences. Participants rated cartoons for funniness while holding a pen either in their teeth – thus being induced to smile – or in their lips – being prevented from smiling. Consistent with the hypothesis, participants who held the pen with their teeth rated the cartoons as funnier than those who held the pen with their lips.
However, the facial feedback hypothesis is not universally accepted, as some studies support this theory while others have failed to replicate its findings. In 2022, Nicholas Coles brought together researchers from all sides of the debate in the Many Smiles Collaboration to test the facial feedback hypothesis using standardized methods. Participants were induced to smile using three techniques while doing other small tasks, and at the end rated how happy they were feeling. One third of participants used the pen-in-mouth method, one-third mimicked the facial expressions seen in photos of smiling actors, the final third was given instructions to move their facial muscles into a smile. The findings provided stronger evidence for the hypothesis —but showed that not all methods work equally well, as the pen-in-mouth method underperformed.
Harker and Keltner examined the link between positive emotions and well-being, finding that women who displayed more genuine, “warm” smiles in their college yearbook photos were more likely to:
- Score higher on self-reported personality traits of affiliation, competence, and low negative emotionality across adulthood.
- Be rated more positively by observers on several personality dimensions and perceived as more rewarding to interact with.
- Report greater personal well-being and higher marital satisfaction up to 30 years later.
The benefits of smiling
Research shows that smiling can really do wonders for your brain, body, and overall well-being. First, it triggers the release of mood-lifting chemicals such as neuropeptides which enable neural communication and fight off stress. Moreover, neurotransmitters help to lower heart rate and blood pressure, with endorphins acting as a natural pain killer and serotonin functioning as an antidepressant.
Smiling literally improves a person’s appearance in the eyes of others. Research shows that people who smile are seen as more attractive and likable. Additionally, seeing a smiling face has an uplifting effect as it activates the orbitofrontal cortex — the brain region processing sensory rewards.
Smiling is also contagious as the brain region responsible for facial expressions, known as the cingulate cortex, works as an unconscious automatic response area. When you smile at someone, their brain is wired to return the smile, and it takes conscious effort not to do so.
To conclude, smiling is not just the expression of happiness, but it is also a powerful ally for our brain, psychological well-being and physical health. The beneficial effect of smiling was celebrated by Harvey Ball, the artist who designed the famous yellow smiley face in 1963. He established the World Smile Day in 1999 to encourage acts of kindness around the world, with the slogan: “Do an act of kindness. Help one person smile.”
By Sofia Nelam Singh
singh.sofianelam@gmail.com
sofianelam.singh01@icatt.it
Sitography
https://news.stanford.edu/stories/2022/10/posing-smiles-can-brighten-mood
Nolen-Hoeksema, S., Fredrickson, B. L., Loftus, G. R., & Lutz, C. (2014). Atkinson & Hilgard’s introduction to psychology (16th ed.). Cengage Learning
https://www.psychologytoday.com/gb/blog/cutting-edge-leadership/201206/there-s-magic-in-your-smile
A.P.E. 
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