Smile

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Smile

A smile is a facial expression

Facial expression

A facial expression results from one or more motions or positions of the muscles of the face. These movements convey the emotional state of the individual to observers....
formed by flexing those muscle

MUSCLE

MUSCLE is public domain, multiple sequence alignment software for protein and nucleotide sequences.MUSCLE is integrated into UGENE bioinformatics tool as a plugin....
s most notably near both ends of the mouth

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 smile can also be found around the eyes (See 'Duchenne smile' below). Among human

Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s, it is customarily an expression denoting pleasure

Pleasure

Pleasure is commonly conceptualized as a positive experience, happiness, entertainment, enjoyment, ecstasy , and Euphoria . However, it is a difficult concept to define as the experience of pleasure differs from individual to individual....
, happiness, or amusement

Amusement

Amusement is the state of experience humour and usually entertainment events or situations, and is associated with enjoyment, happiness, laughter and pleasure....
, but can also be an involuntary expression of anxiety

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

Grimace

Grimace may refer to:*A character in McDonaldland*A type of facial expression*A Grimace active in the mid-to-late 14th century...
. Cross-cultural studies have shown that smiling is used as a means of communicating emotions throughout the world.

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Encyclopedia

A smile is a facial expression

Facial expression

MUSCLE

Mouth

Human

Pleasure

Amusement

Anxiety

Grimace

Animal

Animals are a major group of 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....
s, the exposure of teeth, which may bear a resemblance to a smile, is often used as a threat or warning display

Threat display

Threat display is a type of display behaviour aiming at intimidation of a potential enemy. It may be directed at a rival of the same species , or at a potential threat from a different species....
- known as a snarl

Snarl

A snarl is a facial expression, where the upper lip is raised, and the nostrils widen, generally indicating hate, anger or pain. In addition to humans, other mammals including monkeys and dogs snarl, often to warn others of their potential bite....
- or a sign of submission

Submission

Submission may refer to:*Submission , an Islamic religion practiced by the United Submitters International*Submission , a film directed by Theo van Gogh and written by Ayaan Hirsi Ali...
. In chimpanzees, it can also be a sign of fear

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....
. The study of smiles is a part of gelotology

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....
, psychology, and linguistics, comprising various theories of affect, humor, and laughter.

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

Kinesics

Kinesics is the interpretation of body language such as facial expressions and gestures ? or, more formally, non-verbal behavior related to movement, either of any part of the body or the body as a whole....
view the smile as an affect display

Affect display

In psychology, affect display or affective display is a subject's externally displayed Affect . The display can be by facial, vocal, or gestural means ....
. It can communicate feelings such as: love, happiness, pride, contempt, and embarrassment.

Duchenne smile

Although many different types of smiles have been identified and studied, researchers have paid particular attention to an anatomical distinction first recognized by French physician Guillaume Duchenne. While conducting research on the physiology

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....
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

Zygomaticus major muscle

The Zygomatic major is a muscle of the human body. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly....
(which raises the corners of the mouth) and the orbicularis oculi muscle

Orbicularis oculi muscle

The 'orbicularis oculi' is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament....
(which raises the cheeks and forms crow's feet around the eyes). A non-Duchenne smile involves only the zygomatic major muscle. Many researchers believe that Duchenne smiles indicate genuine spontaneous emotions since most people cannot voluntarily contract the outer portion of the orbicularis oculi muscle.

Smile

Historical background

Duchenne smile

Gallery

See also

Further reading

External links