smile

A woman smiling.

The presence of cheek dimples is controlled by a single gene.

A smile is a facial expression formed by flexing those muscles most notably near both ends of the mouth. The smile can also be found around the eyes (See 'Duchenne smile' below). Among humans, it is customarily an expression denoting pleasure, happiness, or amusement, but can also be an involuntary expression of anxiety, 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, the exposure of teeth, 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, it can also be a sign of fear. The study of smiles is a part of gelotology, 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. Humans smile differently. Some show their teeth when they smile, some don't.

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

A laughing smile with teeth showing and mouth open.

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 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 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

The painting Mona Lisa by Leonardo da Vinci.	Girl with closed mouth smile.	An exaggerated open-mouthed smile	Politicians are often shown smiling as this is considered a sign of hospitality and confidence.
Artwork on this ball is a common abstract representation of a smiling face.	A section of Mars that looks like a smile	Some people can smile at inappropriate times	A child smiling

See also

Wikimedia Commons has media related to: Smile

• Laughter
• Emotion
• Emoticon
• Facial Action Coding System
• Frown
• Facial expression
• Smiley
• Social psychology

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. ^ Ekman, 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 2003 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