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The Science Behind Smiles

Sep 27, 20244 min read

Though taken for granted, smiling is a vital expression of emotion and means of communication that predates human life. Around 30 million years ago, monkeys and apes used their smiles as a display of fear and aggression towards predators. Yet, somehow, smiling has evolved into an “unambiguous expression of positive emotions” (Manstead, 2019) that is recognized across the world.



The fascinating interplay of muscle movements that creates a smile has captivated both psychologists and anthropologists, who are eager to explore its universality and the profound effects it has on our lives. Ancient monkeys, apes, and other primates used an open-mouthed, bare-fanged expression as a show of hostility towards their targets. A similar expression was also used to yield to a stronger opponent. The distinction lay in their teeth - an open-toothed grin was seen as a threat, while a close-toothed one showed their submission. Later, chimpanzees began to use a similar fang-flashing expression as a greeting.


Just as subtle physical changes in smiles signal different intentions in primates, different combinations of facial muscular action in humans connect to the intentions and reasoning behind a smile. The development of the Facial Action Coding System (FACS) by Paul Ekman and Wallace Friesen in 1978 allowed for the isolation and examination of these muscular components. The primary muscle associated with a smile is the zygomaticus major muscle, whose contraction results in an upturned mouth. The contraction of this muscle has been found in all of the at least 18 types of smiles identified using the FACS. When the zygomaticus major is activated alongside the orbicularis oculi muscle, this signals a genuine expression of enjoyment or pleasure. These two muscles working simultaneously are what create the upturned mouths and crinkled eyes of a true smile. 


The examination of the musculature of smiles has provided an enormous amount of evidence for the universality of the expression. Studies investigating smiling in blind individuals have shown that joyful smiling is present without the need for observational learning, rather it is an innate part of human existence. Similarly, studies of infants describe a marked difference between the smiles with which they greet their mother versus strangers, representing not only the automatic nature of the genuine smile but also the early development of the ‘social smile’ as a means of non-verbal communication. Additionally, studies that questioned whether smiles were recognized by different groups and cultures were conducted across both literate and preliterate, and Western and non-Western cultures, supporting the notion of its universal recognition as a signal of happiness. 


Despite this universality, the interpretation of a smile  varies across cultures. While in some countries smiling broadly as a greeting is seen as friendly in others, this practice could easily label you as stupid or  insane. Examples of this are abundant, such as the longstanding Russian proverb stating ‘Smiling with no reason is a sign of stupidity,’ (Krys et al., 2016, 103). Norwegian culture takes this a step further, describing those who smile at strangers as insane. Similarly, studies uphold that it is a sign of disrespect to smile in the presence of an authority figure in Japan, while older French artwork encapsulates the belief previously held by the French aristocracy that smiling is a sign of low intelligence. These cultural differences demonstrate an important limitation in the use of smiling in social situations. ‘Social smiling’ refers to a practiced smile used to convey sincerity, trustworthiness, friendliness, or politeness to others, and while it may be a useful tool in some cultures, this evidence shows that it may have unintended consequences on one's image. 


While smiling is a universal indication of happiness, the question remains as to why this expression exists in the first place. Internally, the muscle movements associated with smiling cause the release of endorphins, a type of feel-good hormone, while simultaneously lowering stress hormones like cortisol and adrenaline. Externally, smiling allows us to appear confident, friendly, and even more attractive. These broadly detailed benefits only scratch the surface of the many ways that smiling impacts our lives. 


Beyond this, we must also consider what our lives would be like if smiles simply did not exist. We would no longer get to experience someone lighting up a room simply by beaming at those within it, no longer smirk at our friends when we find something amusing, and no longer offer a kind grin to someone who looks upset. In this way, it can be easy to take smiling for granted in our everyday lives. In the future, research by biologists, anthropologists, psychologists, and cultural theorists will allow us to gain a greater understanding of this irreplaceable expression of joy, and the enormous impact that it will forever have on our lives.



 

Written by Anastasia DeCaires 

References


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11 okt 2024
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Fabulous article. A joy to read.

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