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A facial expression is one or more motions or positions of the
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...

muscle
s beneath the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biolo ...

skin
of the face. According to one set of controversial theories, these movements convey the
emotion Emotions are mental state, psychological states brought on by neurophysiology, neurophysiological changes, variously associated with thoughts, feelings, behavioural responses, and a degree of pleasure or suffering, displeasure. There is currentl ...

emotion
al state of an individual to observers. Facial expressions are a form of
nonverbal communication Nonverbal communication (NVC) is the transmission of messages or signals through a nonverbal platform such as eye contact, facial expressions, gestures, Posture (psychology), posture, and body language. It includes the use of social cues, kinesic ...
. They are a primary means of conveying social information between
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...

human
s, but they also occur in most other
mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
and some other animal
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
. (For a discussion of the controversies on these claims, see Fridlund and Russell & Fernandez Dols.) Humans can adopt a facial expression voluntarily or involuntarily, and the neural mechanisms responsible for controlling the expression differ in each case. Voluntary facial expressions are often socially conditioned and follow a cortical route in the brain. Conversely, involuntary facial expressions are believed to be innate and follow a subcortical route in the brain. Facial recognition is often an emotional experience for the brain and the
amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek language, Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nucleus (neuroanatomy), nuclei located deep and lateral and medial, medially within the ...

amygdala
is highly involved in the recognition process. The eyes are often viewed as important features of facial expressions. Aspects such as blinking rate can possibly be used to indicate whether a person is nervous or whether he or she is lying. Also,
eye contact Eye contact occurs when two people look at each other's eyes at the same time. In human beings Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification ...

eye contact
is considered an important aspect of interpersonal communication. However, there are cultural differences regarding the social propriety of maintaining eye contact or not. Beyond the accessory nature of facial expressions in spoken communication between people, they play a significant role in communication with
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with #Non-manual elements, non-manual elements. Sign lan ...

sign language
. Many phrases in sign language include facial expressions in the display. There is controversy surrounding the question of whether facial expressions are a worldwide and universal display among humans. Supporters of the Universality Hypothesis claim that many facial expressions are innate and have roots in evolutionary ancestors. Opponents of this view question the accuracy of the studies used to test this claim and instead believe that facial expressions are conditioned and that people view and understand facial expressions in large part from the social situations around them. Moreover, facial expressions have a strong connection with personal psychology. Some psychologists have the ability to discern hidden meaning from a person's facial expression. A 2020 study on "emotion residue" found that even when study participants attempted to make neutral facial expressions, their faces still retained emotion residue from prior expressions, and these prior expressions were able to be detected by observers. One experiment investigated the influence of gaze direction and facial expression on face memory. Participants were shown a set of unfamiliar faces with either happy or angry facial expressions, which were either gazing straight ahead or had their gaze averted to one side. Memory for faces that were initially shown with angry expressions was found to be poorer when these faces had averted as opposed to direct gaze, whereas memory for individuals shown with happy faces was unaffected by gaze direction. It is suggested that memory for another individual's face partly depends on an evaluation of the behavioural intention of that individual.


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 A fascia (; plural fasciae ; adjective fascial; from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as ...
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 The pharyngeal arches, also known as visceral arches'','' are structures seen in the Animal embryonic development, embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the br ...
in the embryo. The
temporalis In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any indi ...
,
masseter In human anatomy, the masseter is one of the muscles of mastication There are four classical muscles of mastication. During mastication, three muscles of mastication (''musculi masticatorii'') are responsible for adduction of the jaw, and one (t ...
, and
internal Internal may refer to: *InternalityAn internality is the long-term benefit or cost to an individual that they do not consider when making the decision to consume a good or service. One way this is related to behavioral economics is by means of the c ...
and
external pterygoid muscle The lateral pterygoid or external pterygoid is a muscle of mastication with two heads. It lies superiorly to the medial pterygoid muscle, medial pterygoid. Origin and insertion The upper/superior head originates on the infratemporal surface and inf ...
s, which are mainly used for chewing, have a minor effect on expression as well. These muscles develop from the first pharyngeal arch.


Neuronal pathways

There are two brain pathways associated with facial expression; the first is voluntary expression. Voluntary expression travels from the
primary motor cortex The primary motor cortex (Brodmann area 4) is a Human brain, brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary cortex, primary region of the motor system and works in association with other motor a ...
through the
pyramidal tract The pyramidal tracts include both the corticobulbar tract The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the medullary pyramids, which are part of the ...
, specifically the
corticobulbar projections
corticobulbar projections
. The cortex is associated with display rules in emotion, which are social
precepts A precept (from the la, præcipere, to teach) is a wikt:commandment, commandment, instruction, or order intended as an authority, authoritative rule of action. Religious law In religion, precepts are usually commands respecting morality, moral con ...
that influence and modify expressions. Cortically related expressions are made consciously. The second type of expression is emotional. These expressions originate from the
extrapyramidal motor system In anatomy, the extrapyramidal system is a part of the motor system large scale brain networks, network causing involuntary actions. The system is called ''extrapyramidal'' to distinguish it from the tracts of the motor cortex that reach their targ ...
, which involves subcortical nuclei. For this reason, genuine emotions are not associated with the cortex and are often displayed unconsciously. This is demonstrated in infants before the age of two; they display distress, disgust, interest, anger, contempt, surprise, and fear. Infants' displays of these emotions indicate that they are not cortically related. Similarly, blind children also display emotions, proving that they are subconscious rather than learned. Other subcortical facial expressions include the "knit brow" during concentration, raised eyebrows when listening attentively, and short "punctuation" expressions to add emphasis during speech. People can be unaware that they are producing these expressions.


Asymmetries

The lower portions of the face are controlled by the opposite
cerebral hemisphere The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
, causing asymmetric facial expression. Because the
right hemisphere The lateralization of brain function is the tendency for some neural functions or cognitive process Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". ...
is more specialised for
emotional expression An emotional expression is a behavior that communicates an emotional state or attitude. It can be verbal or non-verbal, and can occur with or without self-awareness. Emotional expressions include facial movements like smiling or scowling, simple beh ...
, emotions are more strongly expressed on the left side of the face., particularly for negative emotions. Asymmetries in expression can be seen in chimeric faces (facial portraits made by combining the left and right halves of faces with different expressions) and also in
portraits A portrait is a painting Painting is the practice of applying paint, pigment, color or other medium to a solid surface (called the "matrix" or "support"). The medium is commonly applied to the base with a brush, but other implements, such ...

portraits
which more often show the left, more emotional side of the face than the right.


Neural mechanisms in face perception

The amygdala plays an important role in facial recognition. Functional imaging studies have found that when shown pictures of faces, there is a large increase in the activity of the amygdala. The amygdala receives visual information from the thalamus via the subcortical pathways. The amygdala may also have a significant role in the recognition of fear and negative emotions. It is believed that the emotion disgust is recognized through activation of the insula and basal ganglia. The recognition of emotion may also utilize the occipitotemporal neocortex, orbitofrontal cortex and right frontoparietal cortices.


Gender and facial cues

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.


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 Interpersonal communication is an exchange of information between two or more people but has been expanded to include machine actors such as robots and AI. It is also an area of research that seeks to understand how Human communication, humans use ...
. A person's eyes reveal much about how they are feeling, or what they are thinking. Blink rate can reveal how nervous or at ease a person may be. Research by
Boston College Boston College (BC) is a private university, private research university in Chestnut Hill, Massachusetts. Founded in 1863 as a Society of Jesus, Jesuit school, the university has more than 9,300 full-time undergraduates and nearly 5,000 gradua ...
professor Joe Tecce suggests that stress levels are revealed by blink rates. He supports his data with statistics on the relation between the blink rates of presidential candidates and their success in their races. Tecce claims that the faster blinker in the presidential debates has lost every election since 1980. Though Tecce's data is interesting, it is important to recognize that
non-verbal communication Nonverbal communication (NVC) is the transmission of messages or signals through a nonverbal platform such as eye contact, facial expressions, gestures, Posture (psychology), posture, and body language. It includes the use of social cues, kinesic ...
is multi-channeled, and focusing on only one aspect is reckless. Nervousness can also be measured by examining each candidates' perspiration,
eye contact Eye contact occurs when two people look at each other's eyes at the same time. In human beings Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification ...

eye contact
and stiffness.Rothwell, J. Dan. In the Company of Others: An Introduction to Communication. United States: McGraw-Hill, 2004. Within their first year, Infants learn rapidly that the looking behaviors of others convey significant information. Infants prefer to look at faces that engage them in mutual gaze and that, from an early age, healthy babies show enhanced neural processing of direct gaze.Eye Contact Detection in Humans From Birth
PNAS Vol 99 N.14 2002.
Eye contact is another major aspect of facial communication. Some have hypothesized that this is due to infancy, as humans are one of the few mammals who maintain regular eye contact with their mother while nursing. Eye contact serves a variety of purposes. It regulates conversations, shows interest or involvement, and establishes a connection with others. But different cultures have different rules for eye contact. Certain Asian cultures can perceive direct eye contact as a way to signal competitiveness, which in many situations may prove to be inappropriate. Others lower their eyes to signal respect, and similarly, eye contact is avoided in Nigeria; however, in
western culture Western culture, also known as Western civilization, Occidental culture, or Western society, is the heritage Heritage may refer to: History and society * In history History (from Greek , ''historia'', meaning "inquiry; knowledge acquired b ...
s this could be misinterpreted as lacking
self-confidence Confidence is a state of being clear-headed either that a hypothesis or prediction is correct or that a chosen course of action is the best or most effective. Confidence comes from a Latin word 'fidere' which means "to trust"; therefore, having ...
. Even beyond the idea of eye contact, eyes communicate more data than a person even consciously expresses.
Pupil dilation Pupillary response is a physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, includin ...
is a significant cue to a level of excitement, pleasure, or attraction. Dilated pupils indicate greater affection or attraction, while constricted pupils send a colder signal.


Sign languages

Facial expression is used in
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with #Non-manual elements, non-manual elements. Sign lan ...

sign language
s to convey specific meanings. In
American Sign Language American Sign Language (ASL) is a natural language In neuropsychology Neuropsychology is a branch of psychology. It is concerned with how a person's cognition and behavior are related to the brain and the rest of the nervous system. Pr ...

American Sign Language
(ASL), for instance, raised eyebrows combined with a slightly forward head tilt to indicate that what is being signed is a
yes–no question In linguistics Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying and modeling them. The traditional areas of linguistic analysis include p ...
. Lowered eyebrows are used for wh-word questions. Facial expression is also used in sign languages to show adverbs and adjectives such as distance or size: an open mouth, squinted eyes and tilted back head indicate something far while the mouth pulled to one side and the cheek held toward the shoulder indicate something close, and puffed cheeks mean very large. It can also show the manner in which something is done, such as carelessly or routinely. Some of these expressions, also called non-manual signs, are used similarly in different sign languages while others are different from one language to another. For example, the expression used for 'carelessly' in ASL means 'boring or unpleasant' in
British Sign Language British Sign Language (BSL) is a sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination wit ...
.


Universality hypothesis

The universality hypothesis is the assumption that certain facial expressions and face-related acts or events are signals of specific emotions (happiness with laughter and smiling, sadness with tears, anger with a clenched jaw, fear with a grimace, (or
gurn A gurn or chuck, in British English, is an extremely distorted and particular facial expression and a verb to describe the action. A typical gurn involves projecting the Human mandible, lower jaw as far forward and up as possible and covering the ...
) surprise with raised eyebrows and wide eyes along with a slight retraction of the ears, and disgust with a wrinkled nose and squinted eyes—emotions which frequently lack the social component of those like shame, pride, jealousy, envy, deference, etc.) and are recognized by people regardless of culture, language, or time. The belief in the evolutionary basis of these kinds of facial expressions can be traced back to
Darwin Darwin most often refers to: * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a capital city in Australia * Darwin ( ...

Darwin
's ''
The Expression of the Emotions in Man and Animals ''The Expression of the Emotions in Man and Animals'' is Charles Darwin Charles Robert Darwin (; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organisms, includi ...
.'' Reviews of the universality hypothesis have been both supportive and critical. Work in 2013 by Nelson and Russell and Jack et al. has been especially critical.


Support

's work on facial expressions had its starting point in the work of psychologist
Silvan Tomkins Silvan Solomon Tomkins (June 4, 1911 – June 10, 1991) was a psychologist A psychologist is a person who studies normal and abnormal mental states, perceptual, cognitive, emotional, and social processes and behavior by experimenting with, and ...
. Ekman showed that facial expressions of emotion are not culturally determined, but universal across human cultures. To demonstrate his universality hypothesis, Ekman ran a test on a group of the South
Fore people The Fore people live in the Okapa District of the Eastern Highlands Province, Papua New Guinea. There are approximately 20,000 Fore who are separated by the Wanevinti Mountains into the North Fore and South Fore regions. Their main form of sub ...
of
New Guinea New Guinea (; : ''Niu Gini''; id, Papua, historically ) is the , and with an area of , the largest island in the . Located in in the southwestern , it is separated by the wide from . Numerous smaller islands are located to the west and east ...

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.


Criticism

Both sides of this debate agree that the face expresses emotion. The controversy surrounds the uncertainty about what specific emotional information is read from a facial expression. Opponents of the universality hypothesis believe that more general information is pieced together with other contextual information in order to determine how a person feels. One argument against the evidence presented in support of the universality hypothesis is that the method typically used to demonstrate universality inflates recognition scores. Although each factor may contribute only a small amount to the inflation, combined, they can produce exaggerated scores. The three main factors are the following: * The universality hypothesis focuses on people's abilities to recognize spontaneous facial expressions as they occur naturally. However, the facial expressions used to test this hypothesis are posed. Studies of spontaneous facial expressions are rare and find that participants' recognition of the expressions is lower than that of the corresponding posed expressions. * In most studies, participants are shown more than one facial expression (Ekman recommends six of each expression). However, people judge facial expressions relative to others that they have seen, and participants who judge more than one facial expression have higher recognition rates than those who judge only one. * The response format that is most commonly used in
emotion recognitionEmotion recognition is the process of identifying human emotion. People vary widely in their accuracy at recognizing the emotions of others. Use of technology to help people with emotion recognition is a relatively nascent research area. Generally ...
studies is forced choice. In forced choice, for each facial expression, participants are asked to select their response from a short list of emotion labels. The forced choice method determines the emotion attributed to the facial expressions via the labels that are presented. That is, participants will select the best match to the facial expression even if it is not the emotion label they would have provided spontaneously and even if they would not have labeled the expression as an emotion at all.


Evolutionary significance of universality

Darwin argued that the expression of emotions has evolved in humans from animal ancestors, who would have used similar methods of expression. Darwin believed that expressions were unlearned and innate in human nature and were therefore evolutionarily significant for survival. He compiled supporting evidence from his research on different cultures, on infants, and in other animal species. Ekman found that people from different cultures recognized certain facial expressions despite vast cultural differences, and his findings tended to confirm Darwin's initial hypothesis. 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 Facial Action Coding System (FACS) is a system to taxonomize human facial movements by their appearance on the face, based on a system originally developed by a Swedish anatomist named Carl-Herman Hjortsjö. It was later adopted by Paul Ekman ...
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. Similarly, Darwin observed that infants' method of expression for certain emotions was instinctive, as they were able to display emotional expressions they had not themselves yet witnessed. Facial morphology impacts expression recognition in important ways, and therefore, infant facial morphology may also serve some specific communicative function. These similarities in morphology and movement are important for the correct interpretation of an emotion. Darwin was particularly interested in the functions of facial expression as evolutionarily important for survival. He looked at the functions of facial expression in terms of the utility of expression in the life of the animal and in terms of specific expressions within species. Darwin deduced that some animals communicated feelings of different emotional states with specific facial expressions. He further concluded that this communication was important for the survival of animals in group-dwelling species; the skill to effectively communicate or interpret another animal's feelings and behaviors would be a principal trait in naturally fit species. However, this suggests that solitary species such as
orang-utan Orangutans are great apes The Hominidae (), whose members are known as great apes or hominids (), are a taxonomic family In human society, family (from la, familia) is a group of people related either by consanguinity (by recogniz ...

orang-utan
s would not exhibit such expressions.


See also

*
Affect display Affect displays are the verbal and non-verbal displays of affect Affect may refer to: * Affect (education) * Affect (linguistics), attitude or emotion that a speaker brings to an utterance * Affect (philosophy) * Affect (psychology), the experien ...
* Bell's palsy *
Body language Body language is a type of nonverbal communication Nonverbal communication (NVC) is the transmission of messages or signals through a nonverbal platform such as eye contact, facial expression A facial expression is one or more motions or p ...

Body language
* Computer processing of body language ** Facial expression capture ** Facial expression databases ** Facial expression detection **
Facial recognition system A facial recognition system is a technology capable of matching a human face from a digital image or a Film frame, video frame against a database of faces, typically employed to authenticate users through ID verification services, works by pinpoi ...
*
Display rules Display rules are a social group or culture's informal norms that distinguish how one should express themselves. They can be described as culturally prescribed rules that people learn early on in their lives by interactions and socializations with ...
*
Emoticon An emoticon (, , rarely pronounced ), short for "emotion icon", also known simply as an emote, is a pictorial representation of a facial expression A facial expression is one or more motions or positions of the muscle Skeletal muscles ...

Emoticon
(Facial Expression Markup Language) *
Emotion classification Emotion classification, the means by which one may distinguish or contrast one emotion Emotions are biological states associated with all of the nerve systems brought on by neurophysiological changes variously associated with thoughts, feeling ...
*
Laughter Laughter is a pleasant physical reaction consisting usually of rhythmical, often audible contractions of the diaphragm Diaphragm may refer to: * Diaphragm (anatomy) or thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen ...

Laughter
*
Gelotology Gelotology (from the Greek ''gelos'' "laughter") is the study of laughter Laughter is a physical reaction in humans Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of ...
*
Metacommunicative competenceMeta-communication - (Etymology: Gk, meta + L, communicare, to inform), or metacommunication, is a secondary communication (including indirect cues) about About may refer to: * About (surname) * About.com, an online source for original informatio ...
* Thought Moments


References

*


External links


Facial Expressions Resources Page
contains links to research concerning facial expressions
Bell's Palsy information site
Information for sufferers of facial palsy/facial paralysis
The Umeå University Database of Facial Expressions
October 12, 2012. ''Journal of Medical Internet Research''


Facial expression analysis
David Matsumoto and
Paul Ekman Paul Ekman (born February 15, 1934) is an American psychologist A psychologist is a person who studies normal and abnormal mental states, perceptual, cognitive, emotional, and social processes and behavior by experimenting with, and observin ...

Paul Ekman
Scholarpedia ''Scholarpedia'' is an English-language wiki-based online encyclopedia An online encyclopedia, also called an Internet encyclopedia, or a digital encyclopedia, is an encyclopedia An encyclopedia or encyclopaedia (British English) is a re ...
, 3(5):4237. doi:10.4249/scholarpedia.4237 {{Nonverbal communication Anatomical simulation
Emotion Emotions are subjective experiences, often associated with Mood (psychology), mood, temperament, Personality psychology, personality, and disposition. Articles about specific emotional states should be placed in :Emotions or one of its subcategorie ...