question: What makes people smile/frown or do any facial expressions connected to how they feel the same way everywhere? is it biological or just years of people doing that with their faces?
comment: Both. Biologically, the human brain is well-adapted to notice, understand, and use these physical cues. The human body is well adapted to actually displaying a smile/frown (and other common expressions). With that said, our instinct to do this is reinforced by other people we’re around— this is actually a method of communication and using body language in a way that feels “natural” and is easy for other people to understand takes practice, just like spoken language does.
passages: The muscles of the face play a prominent role in the expression of emotion, and vary among different individuals, giving rise to additional diversity in expression and facial features.
   Section::::Universality hypothesis.:Support.
  
  Ekman's work on facial expressions had its starting point in the work of psychologist Silvan Tomkins. Ekman showed that facial expressions of emotion are not culturally determined, but universal across human cultures.
   Section::::Universality hypothesis.
   Section::::Communication.
  
  Section::::Communication.:Eye contact.
  
  A person's face, especially their eyes, creates the most obvious and immediate cues that lead to the formation of impressions. This article discusses eyes and facial expressions and the effect they have on interpersonal communication.
   To demonstrate his universality hypothesis, Ekman ran a test on a group of the South Fore people of New Guinea, a pre-industrial culture that was isolated from the West. The experiment participants were told brief stories about emotional events (happiness, sadness, anger, fear, surprise, and disgust). After each story, they were asked to select the matching facial expression from an array of three faces. The Fore selected the "correct face" on 64–90% of trials but had difficulty distinguishing the fear face from the surprise face. Children selected from an array of only two faces, and their results were similar to the adults'. Subsequent cross-cultural studies found similar results.
   Despite the Darwin’s theory, in 1950 the prevailing belief was that facial expressions were determined by cultural background and learning process.
  
  In 1960s, Paul Ekman an American psychologist, set out to visit people from different nations (including an isolated indigenous tribe in Papua New Guinea) to study non-verbal behavior across cultures. His research showed that Darwin was right and that facial expressions and emotions are universal as people from diverse cultural background interpreted expressions in photos in similar way. Ekman’s work indicated existence of 7 basic emotions that are universally present: happiness, surprise, fear, anger, disgust, sadness and neutral.
   Section::::Creation.
  
  Section::::Creation.:Facial muscles.
  
  Facial expressions are vital to social communication between humans. They are caused by the movement of muscles that connect to the skin and fascia in the face. These muscles move the skin, creating lines and folds and causing the movement of facial features, such as the mouth and eyebrows. These muscles develop from the second pharyngeal arch in the embryo. The temporalis, masseter, and internal and external pterygoid muscles, which are mainly used for chewing, have a minor effect on expression as well. These muscles develop from the first pharyngeal arch.
  
  Section::::Creation.:Neuronal pathways.
   Facial expressions are produced to express a reaction to a situation or event or to evoke a response from another individual or individuals. They are signals of emotion and social intent. People make faces in response to "direct audience effects" when they are watching sports, discussing politics, eating or smelling, in pain, and see or hear something humorous. While one may have the same emotional reaction to a particular situation, he or she is more likely to express this emotion via a facial expression if they are in a social situation. Smiles, in particular, are "evolved signaling displays [that] are the result of selective pressures for conspicuous, stereotyped, and redundant communication". Smiling is a visual signal that requires eye contact from the recipient to the one smiling and is intended to communicate a feeling of happiness and joy. In an experiment by Alan Fridlund, smiling occurred least when one was watching a video alone, then more often when a person was alone watching the video but believed a friend was performing another task, even more often when that person believed a friend was simultaneously watching the video somewhere else, and most often when one was watching a movie with a friend physically present. This evidence shows that even if someone has the same internal reaction to a stimulus (like a movie), they are more likely to externalize these feelings when surrounded by peers or under the assumption that peers are engaged in the same activity.
   Developmental differences in solitary facial expressions
  
  Facial expressions are used to communicate emotions. They can also occur solitarily, without other people being present. People often imagine themselves in social situations when alone, resulting in solitary facial expressions. Toddlers and children in early childhood use social cues and contexts to discriminate and recognize facial expressions. They develop at this early stage facial expressions in order to provoke reactions from their caregivers and receive nurturance and support. Children reflect their peers' emotions in their own expressions for social interaction.
   The production of facial expressions, however, is not solely limited to interpersonal situations. Since humans are inherently social beings, they often imagine themselves in social situations even when they are alone. This phenomenon occurs in a variety of different contexts: treating oneself as a social interactant (talking to oneself), imagining others are present (either who are currently existent or have died), envisioning future social interactions, and personifying animals or inanimate objects (talking to pets). Solitary facial expressions are generated for an imagined other. According to role and impression- management theories, a perceived audience, whether real or imaginary, causes one to assume a role that is consistent with their audience. For example, a young girl may smile to herself in the mirror while imagining herself talking to a boy from class, but may grimace while imagining herself responding to her mother's scolding. Thus, "solitary faces occur for the same reasons as public ones, if only because when we are alone we create social interactions in our imaginations. They suggest the possibility that sociality may play a major role in the mediation of solitary faces". There are developmental differences in solitary facial expression, beginning with instinctive expressions in infancy and developing into more complex ones as a child's concept of sociality and emotion matures.
   There are two brain pathways associated with facial expression; the first is voluntary expression. Voluntary expression travels from the primary motor cortex through the pyramidal tract, specifically the corticobulbar projections. The cortex is associated with display rules in emotion, which are social precepts that influence and modify expressions. Cortically related expressions are made consciously.
   Section::::Discrimination and expression.
   Section::::Development of solitary facial expressions in middle childhood through adolescence.
   Research studies have indicated that voluntary facial expressions, such as smiling, can produce effects on the body that are similar to those that result from the actual emotion, such as happiness. Paul Ekman and his colleagues have studied facial expressions of emotions and have linked specific emotions to the movement of specific facial muscles. Each basic emotion is associated with a distinctive facial expression. Sensory feedback from the expression contributes to the emotional feeling. Example: Smiling if you want to feel happy. Facial expressions have a large effect on self-reported anger and happiness which then affects your mood. Ekman has found that these expressions of emotion are universal and recognizable across widely divergent cultures.
   People are also relatively good at determining if a smile is real or fake. A recent study looked at individuals judging forced and genuine smiles. While young and elderly participants equally could tell the difference for smiling young people, the "older adult participants outperformed young adult participants in distinguishing between posed and spontaneous smiles". This suggests that with experience and age, we become more accurate at perceiving true emotions across various age groups.
  
  Section::::Function.:Perception and recognition of faces.
   Masking also differs between cultures. Some studies state that certain cultures tend to moderate their expressions of emotion while others show a greater amount of positive emotions and expressions.
  
  Section::::Signs and symptoms.
   More than anything though, what shapes a child's cognitive ability to detect facial expression is being exposed to it from the time of birth. The more an infant is exposed to different faces and expressions, the more able they are to recognize these emotions and then mimic them for themselves. Infants are exposed to an array of emotional expressions from birth, and evidence indicates that they imitate some facial expressions and gestures (e.g., tongue protrusion) as early as the first few days of life. In addition, gender affects the tendency to express, perceive, remember, and forget specific emotions. For instance, angry male faces and happy female faces are more recognizable, compared to happy male faces and angry female faces.
   Section::::Function.:Perception and recognition of faces.:Biological perspective.
   The pioneer F-M Facial Action Coding System 3.0 (F-M FACS 3.0) was created in 2018 by Dr. Freitas-Magalhães, and presents 4,000 segments in 4K, using 3D technology and automatic and real-time face recognition (FaceReader 7.1). The F-M FACS 3.0 features 8 pioneering action units (AUs) and 22 pioneering tongue movements (TMs), in addition to functional and structural nomenclature.
  
  Since 2003, F-M Group International (F-MGI) has had a FACS certification program for professionals who wish to become FACS (F-M Group International FACS certified coders, F-MGIFCC).
  
  Section::::Universality hypothesis.:Criticism.
   BULLET::::- The eyes, sitting in the orbit and protected by eyelids and eyelashes
  
  BULLET::::- The distinctive human nose shape, nostrils, and nasal septum
  
  BULLET::::- The cheeks, covering the maxilla and mandibula (or jaw), the extremity of which is the chin
  
  BULLET::::- The mouth, with the upper lip divided by the philtrum, sometimes revealing the teeth
  
  Facial appearance is vital for human recognition and communication. Facial muscles in humans allow expression of emotions.
   Action units (AUs) can be examined frame by frame, since these micro-expressions are often rapid. Paul Ekman’s research in facial deception has found several constants in certain expressions, with the action units relating to lip-corner pulling (AU12) and cheek-raising (AU6) qualifiers for happiness in most people. Brow-lowering (AU4) and lip-stretching (AU20) are disqualifiers for happiness. Emotional leakage appears in these fleeting expressions.
   Facial expression is integral when expressing emotions through the body. Combinations of eyes, eyebrow, lips, nose, and cheek movements help form different moods of an individual (example happy, sad, depressed, angry, etc.).
  
  A few studies show that facial expression and bodily expression (body language) are congruent when interpreting emotions. Behavioural experiments have also shown that recognition of facial expression is influenced by perceived bodily expression. This means that the brain processes the other's facial and bodily expressions simultaneously.
   The fusiform face area, part of the fusiform gyrus is an area some believe to specialize in the identification and processing of human faces, although others suspect it is responsible for distinguishing between well known objects such as cars and animals. Neuroimaging studies have found activation in this area in response to participants viewing images of prototypical faces, but not scrambled or inverted faces, suggesting that this region is specialized for processing human faces but not other material. This area has been an area of increasing debate and while some psychologists may approach the fusiform face area in a simplistic manner, in that it specializes in the processing of human faces, more likely this area is implicated in the visual processing of many objects, particularly those familiar and prevalent in the environment. Impairments in the ability to recognize subtle differences in faces would greatly inhibit emotion perception and processing and have significant implications involving social interactions and appropriate biological responses to emotional information.
   The face is itself a highly sensitive region of the human body and its expression may change when the brain is stimulated by any of the many human senses, such as touch, temperature, smell, taste, hearing, movement, hunger, or visual stimuli.
  
  Section::::Structure.:Shape.
   Cross-cultural studies had shown that there are similarities in the way emotions are expressed across diverse cultures, but studies have even shown that there are similarities between species in how emotions are expressed. Research has shown that chimpanzees are able to communicate many of the same facial expressions as humans through the complex movements of the facial muscles. In fact, the facial cues were so similar that Ekman's Facial Action Coding System could be applied to the chimps in evaluating their expressions. Of course, differences between the species' physical facial properties, such as white sclera and everted lips in chimps, would mean that some expressions could not be compared.
  