A smile is a facial expression formed by flexing those muscles Muscle is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause most notably near both ends of the mouth The mouth, buccal cavity, or oral cavity is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and mixing them with saliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth. The smile can also be found around the eyes Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain[citation needed]. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, molluscs, (See 'Duchenne smile' below). Among humans A human is a member of a species of bipedal primates in the family Hominidae . DNA and fossil evidence indicates that modern humans originated in east Africa about 200,000 years ago. When compared to other animals and primates, humans have a highly developed brain, capable of abstract reasoning, language, introspection and problem solving. This, it is customarily A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom an expression denoting pleasure Pleasure, a "state of mind", is commonly conceptualized as a positive experience, happiness, entertainment, enjoyment, ecstasy, and euphoria. Experience of pleasure is subjective, varying among individuals and typically stimulated by eating, exercise, sexuality, music, usage of drugs. The term analogously connotes a positive mental state, happiness Happiness is a state of mind or feeling such as contentment, satisfaction, pleasure, or joy. A variety of philosophical, religious, psychological and biological approaches have been taken to defining happiness and identifying its sources, or amusement Amusement is the state of experiencing humorous and usually entertaining events or situations, and is associated with enjoyment, happiness, laughter and pleasure. The word "Amuse" is so named from the opposite of "Muse"-to learn or to think, but can also be an involuntary expression of anxiety Anxiety is a psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create an unpleasant feeling that is typically associated with uneasiness, fear, or worry, in which case it is known as a grimace. Cross-cultural studies have shown that smiling is used as a means of communicating emotions throughout the world.^[1] Happiness is most often the motivating cause of a smile. Among animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. Most animals are also, the exposure of teeth Teeth are small whitish structures found in the jaws (or mouths) of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of tissues of varying density and hardness, which may bear a resemblance to a smile, is often used as a threat or warning display - known as a snarl - or a sign of submission. In chimpanzees Chimpanzees are members of the Hominidae family, along with gorillas, humans, and orangutans. Chimpanzee are thought to have split from human evolution about 6 million years ago and thus the two chimpanzee species are the closest living relatives to humans; all being members of the Hominini tribe . Chimpanzees are the only known members of the, it can also be a sign of fear Fear is an emotional response to threats and danger. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of pain. Psychologists John B. Watson, Robert Plutchik, and Paul Ekman have suggested that fear is one of a small set of basic or innate emotions. This set also includes such emotions as joy,. The study of smiles is a part of gelotology Gelotology is the study of humor and laughter, its effects on the human body, and of medical abnormalities of laughing. It is also the psychological and physiological study of laughter. The word is from the Greek gelos, geloto meaning laugh, laughter, laughing . The word gelotology is often misspelled as gelatology, psychology, and linguistics, comprising various theories of affect, humor, and laughter.^[2]

Historical background

Many biologists think the smile originated as a sign of fear. Primalogist Signe Preuschoft traces the smile back over 30 million years of evolution to a "fear grin" stemming from monkeys and apes who often used barely clenched teeth to portray to predators that they were harmless. Biologists believe the smile has evolved differently among species and especially among humans.

Biology is not the only academic discipline that interprets the smile. Those who study kinesics view the smile as an affect display. It can communicate feelings such as love, happiness, pride, contempt, and embarrassment.^[2]

Duchenne smile

Although many different types of smiles have been identified and studied, researchers have devoted particular attention to an anatomical distinction first recognized by French physician Guillaume Duchenne. While conducting research on the physiology Physiology is the study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided between plant physiology and animal and all living things physiology but the principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about of facial expressions in the mid-nineteenth century, Duchenne identified two distinct types of smiles. A Duchenne smile involves contraction of both the zygomatic major muscle (which raises the corners of the mouth) and the orbicularis oculi muscle (which raises the cheeks and forms crow's feet A wrinkle is a fold, ridge or crease in the skin. Skin wrinkles typically appear as a result of aging processes such as glycation or, temporarily, as the result of prolonged immersion in water. Wrinkling in the skin is caused by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors. With prolonged water around the eyes). A non-Duchenne smile involves only the zygomatic major muscle.^[3] Many researchers believe that Duchenne smiles indicate genuine spontaneous emotions since most people cannot voluntarily contract the outer portion of the orbicularis oculi muscle.^[4]

Gallery

See also

• Laughter Laughter is an audible expression or appearance of happiness, or an inward feeling of joy . It may ensue (as a physiological reaction) from jokes, tickling, and other stimuli. Inhaling nitrous oxide can also induce laughter; other drugs, such as cannabis, can also induce episodes of strong laughter. Strong laughter can sometimes bring an onset of
• Emotion An emotion is a mental and physiological state associated with a wide variety of feelings, thoughts, and behavior. Emotions are subjective experiences, or experienced from an individual point of view. Emotion is often associated with mood, temperament, personality, and disposition. The English word 'emotion' is derived from the French word é
• Emoticon An emoticon is a textual portrayal of a writer's mood or facial expression. They are often used to alert a responder to the tenor or temper of a statement, and can change and improve interpretation of plain text. The word is a portmanteau of the English words emotion and icon. In web forums, instant messengers and online games, text emoticons are
• Facial Action Coding System
• Frown
• Facial expression
• Smiley A smiley, or happy face , is a stylized representation of a smiling human face, commonly represented as a yellow (many other colors are also used) circle (or sphere) with two dots representing eyes and a half circle representing the mouth. “Smiley” is also sometimes used as a generic term for any emoticon
• Social psychology Social psychology is the study of how people and groups interact. Scholars in this interdisciplinary area are typically either psychologists or sociologists, though all social psychologists employ both the individual and the group as their units of analysis

References

1. ^ Carroll E. Izard (1971). The Face of Emotion, New York: Appleton-Century-Croft.
2. ^ ^{a b} Freitas-Magalhães, A. (2006). The Psychology of Human Smile. Oporto: University Fernando Pessoa Press.
3. ^ Duchenne, Guillaume (1990). The Mechanism of Human Facial Expression. New York: Cambridge University Press. (Original work published 1862).
4. ^ Elkman, P., Friesen, W. V., and O'Sullivan, M. (1988). "Smiles when lying". Journal of Personality and Social Psychology, 54, pp. 414–420.

Further reading

• Conniff, R. (2007). What's behind a smile? Smithsonian Magazine, 38,46-53.
• Miller, Professor George A., et al. Overview for "smile." Retrieved 12 December December 12 is the 346th day of the year in the Gregorian calendar. There are 19 days remaining until the end of the year 2003 2003 was a common year starting on Wednesday of the Gregorian calendar from this page.
• Ottenheimer, H.J. (2006). The anthropology of language: An introduction to linguistic anthropology. Belmont, CA: Thomson Wadsworh.
• Ekman, P., Davidson, R.J., & Friesen, W.V. (1990). The Duchenne smile: Emotional expression and brain psysiology II. Journal of Personality and Social Psychology, 58, 342-353. Cited in: Russell and Fernandez-Dols, eds. (1997).
• Russell and Fernandez-Dols, eds. (1997). The Psychology of Facial Expression. Cambridge. ISBN 0521587964.

External links

• Facial Emotion Expression Lab
• See examples of genuine, false, and contempt smiles
• Spot The Fake Smile on BBC Science & Nature
• BBC News: Scanner shows unborn babies smile

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