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Why are we smiling?

    Animal grin or smile?

    Long before the advent of spoken language, our ancestors communicated using gestures. And now much of what we communicate to each other is non-verbal gestures. But why do we bare our teeth when we want to express friendliness? Why are we laughing?

    Our emotional expressions are innate, part of our evolutionary heritage. The brain monitors the safety zone around the body and controls bending, squirming, squinting and other actions that protect us from the effects of the outside world. These areas of the brain immediately process the space around the body, use sensory information and convert it into movement.

    The monkeys’ defensive actions are terribly similar to standard human social cues. Why is it that when you blow on a monkey’s face, its expression looks so strangely like a human smile? Why, while laughing, do we seem to use some elements of a protective stance? As it turned out, there is a relationship between defensive movements and social behavior.

    In the 1960s, the American psychologist Edward Hall adapted this idea to human behavior. Hall found that each person has a protective zone 60–90 cm wide, widening towards the head and narrowing towards the feet. The zone does not have a fixed size: if you are nervous, it grows, if you are relaxed, it shrinks. It also depends on cultural upbringing. Personal space is less in Japan and more in Australia. Put a Japanese and an Australian in the same room and a strange dance will follow: the Japanese will step forward, the Australian will step back, and so they will follow one after the other. Maybe even without paying attention to what is happening.

    Hall led us to an important discovery. The mechanism we use to protect also forms the basis of our social engagement. In the end, he organizes a kind of network within the social space. Smiling is one of the main tools of social interaction. Upper lip lifted to show teeth. Cheeks spread out to the sides. The skin around the eyes is wrinkled. Duchenne de Boulogne, a neurologist who lived in the 19th century, noticed that a cold and fake smile is often limited to the mouth, while a genuine, friendly smile always involves the eyes. A sincere smile is now named Duchenovskaya in his honor.

    Дюшеновская улыбка

    A smile can also indicate submission. Employees who are subject to someone smile much more when they are among influential people. It only adds to the mystery. Why showing teeth is a sign of friendliness? Why do it as a sign of humility? Aren’t teeth needed to testify to aggression?

    Most ethologists agree that the smile is evolutionarily ancient and that variants of it are found in many primates. If you are watching a group of monkeys, you will notice that they sometimes give each other what looks like a grimace. They communicate without aggression – ethologists call this “silent display of teeth.” Some theorists argue that this gesture originated from more or less the opposite – preparation for an attack.

    Imagine two monkeys – A and B. Monkey B crosses the personal space of monkey A, causing him to react defensively. Monkey A squints, protecting his eyes. Her upper lip tightens. She bares her teeth – the meaning of a tightened lip is not so much to prepare for an attack, but to tighten the skin on her face, slightly covering her eyes with skin folds. The ears “pull back” to protect themselves from damage. The head retracts and the shoulders rise to cover the vulnerable throat and neck. The head turns away from the approaching object. The torso leans forward to protect the abdomen. Depending on the location of the threat, the arms may be crossed in front of the torso or in front of the face. Monkeys most often adopt a conventional defensive stance that protects fragile and vulnerable parts of the body.

    Защитная реакция

    Monkey B can learn a lot by watching monkey A’s reaction. If monkey A defends himself, as if in full response to monkey B’s actions, then this is a good sign that monkey A is scared. She is uncomfortable. Her personal space is invaded. She perceives monkey B as an enemy, as someone socially superior to her. On the other hand, monkey A may respond “indistinctly” by narrowing his eyes slightly and turning his head back. This means that monkey A is not particularly frightened – he does not perceive monkey B as socially superior or as an enemy.

    Such information is very useful to the members of the social group. Monkey B can learn where to stand in order to show respect to monkey A. Thus, a social signal develops – natural selection will prefer monkeys that can read the submission reactions in their group and adjust their behavior in accordance with them. By the way, this is perhaps the most important part of this story: the most evolutionary pressure is on those who receive the signal, not on those who send it. This story is about how we started responding to a smile.

    Nature is an arms race!

    If monkey B can gather useful information by watching monkey A, then it is useful for monkey A to manipulate this information to influence monkey B. That is, evolution prefers monkeys that can, under the right circumstances, kind of play a defensive reaction. It is useful to convince others that you are not threatening them.

    The origin of the smile is a briefly flashed imitation of a defensive stance. In humans, there is only a stripped-down version of it, in which the facial muscles are involved: the upper lip is pulled up, the cheeks diverge to the sides and up, the eyes squint. Today we use it to communicate from a position of friendly aggression rather than from a position of complete submission and assistance.

    And yet we can still observe the “monkey” gestures in ourselves. Sometimes we smile to show total submission, and this servile smile can come along with an echo of the defensive stance throughout the body: head down, shoulders up, torso up, hands in front of the chest. Like monkeys, we respond to these signals automatically. We can’t help but feel warm towards those who radiate a Duchenne smile. We cannot help but feel contempt for a person who outwardly shows obedience, just as we cannot help but be suspicious of those who imitate warmth with a soulless smile with cold eyes.

    It is incredible that so much could come from such a simple root. An ancient defense mechanism that analyzes the space around the body and organizes defensive movements suddenly finds itself in the hypersocial world of primates, surrounded by smiles, laughter, crying and fawning. Each of these behaviors is then subdivided into several others, growing into a whole codebook of cues for use in different social settings.

    Not all human expressions can be explained through this, but very many. Duchenne smile, cold smile, laughter at a joke, laughter of appreciation for a clever witticism, cruel laughter, a grovel designed to show reverence for someone or a straight back showing confidence, crossed arms showing suspicion, open arms, a sad grimace with which we show sympathy for someone’s sad story – this whole set of expressions could come from one sensory-motor defense mechanism that has nothing to do with communication.

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