The psychological study of the smile. (2023)

A smile begins in our sensory corridors. The ear catches a whispered word. On the platform, you see an old friend. His hand feels the pressure of another hand. These emotional data are sent to the brain, excite the left anterior temporal region in particular, and then slowly spread to the surface of the face, where two tense muscles come into action: the zygomaticus major, which sits on the cheek, pulls the lips turned up, and the orbicularis oculi, which surrounds the eye socket, compresses the outer corners in a crow's-foot fashion. The entire event is brief, typically lasting two-thirds to four seconds, and witnesses often respond by mirroring the action and smiling back.

Other muscles can simulate a smile, but only the peculiar tango of the zygomaticus major and orbicularis oculi creates a real expression of positive emotions. Psychologists call this the "Duchenne smile" and most consider it the only indicator of true pleasure. It is named after the French anatomist Guillaume Duchenne, who studied emotional expression by stimulating various facial muscles with electrical currents. (The technique is said to be so painful that Duchenne performed some of his tests on the severed heads of executed criminals.) In his 1862 book Mecanisme de la Physionomie Humaine, Duchenne wrote that the zygomaticus major can be compelled to act, but that only the "sweet sentiments of the soul" compel the orbicularis oculi to contract. "His laziness of his in smiling," Duchenne wrote, "exposes a false friend."

Headless villains are no longer studied by psychologists, mostly graduate students, but they have expanded our understanding of smiles since the Duchenne discoveries. We now know that real smiles can reflect a "sweet soul." The intensity of a genuine smile can predict marital happiness, personal well-being, and even longevity. We know that some smiles, Duchenne's false friends, do not reflect joy, but rather a wide range of emotions, including shame, deceit, and sadness. We know that variables (including age, gender, culture, and social background) affect the frequency and character of a smile, and the purpose a smile serves in the larger scheme of things. In short, scientists have learned that one of humanity's simplest expressions is wonderfully complex.

A true "sign of pleasure"

It took some time for Duchenne's observations to be accepted by behavioral scientists. In 1924, Carney Landis, then a psychology student at the University of Minnesota, published a classic—and ethically dubious by today's standards—study on human facial expressions. Landis photographed study participants engaging in a variety of activities ranging from the sacred to the profane: listening to jazz, reading the Bible, viewing pornography, and decapitating live mice. He analyzed the photographed reactions, but found no evidence that specific expressions identified specific emotions. As for the smile, Landis couldn't associate it with satisfaction; In fact, the smile was so ubiquitous that Landis considered it a constant response, "typical of any situation," he wrote in the Journal of Comparative Psychology.

Many psychologists have agreed for decades that smiles reflect a wide range of emotions rather than a universal expression of happiness. This belief persisted until the 1970s, when Paul Ekman and Wallace Friesen, psychologists at the University of California, San Francisco, recorded the exact muscle coordinates behind 3,000 facial expressions in their Facial Action Coding System, known as FACS. Ekman and Friesen used their system to revive Duchenne's then-forgotten distinction between genuine smiles of joy and other types of smiles.

In subsequent research conducted with Richard Davidson of the University of Wisconsin, Ekman and Friesen confirmed the unique connection between positive emotions and a genuine Duchenne smile. The researchers attached electrodes to the subjects' heads and then showed a series of short films. Two short films meant to evoke positive emotions featured animals at play; Two others that were intended to provoke negative reactions came from a nurse training video showing amputated legs and severe burns.

Using the FACS, the researchers cataloged viewer reactions and found that Duchenne smiles were correlated with entertaining movies. The neural data showed that Duchenne smiles elicited increased activity in the left anterior temporal region of the brain, an area with clear connections to positive affect. (They also recorded an increase in the left parietal region, which is usually stimulated by verbal activity.) In general, scientists erred in lumping smiles together as a "single class of behavior," the trio concluded in a 2000 issue of the Journal of Personality and Social Psychology 1990. "The Duchenne smile is clearly a better sign of happiness than the Duchenne smile." other types of smiles.

A renewed appreciation for Duchenne and his unique sign of joy emerged. Psychiatric researchers soon discovered that whenever positive emotions surfaced, they were followed by a Duchenne smile. Patients with depression exhibited more Duchenne smiles at their exit interviews than when they were admitted, and Duchenne smiles alone, not other types of smiles, were found to increase during the course of psychotherapy. Even the most superficial and inexperienced observer could identify Duchenne-style faces and, based solely on these appearances, attribute extremely positive characteristics to the personality behind them.

Some researchers now believe that real smiles are not fleeting sparks of emotion, but clear windows into a person's basic attitude. University of California, Berkeley psychologists LeeAnne Harker and Dacher Keltner used FACS to analyze photos of women in college yearbooks and then compared smile ratings to personality data collected during a 30-year longitudinal study. Women who displayed Duchenne-like expressions of true positive emotions in photographs of her at age 21 had higher levels of general well-being and marital satisfaction at age 52. "People photograph themselves with unrestrained ease and remarkable frequency, often without realizing that each snapshot can capture both the future and the fleeting emotions of the moment," Harker and Keltner write in a 2001 issue of the Journal of Personality and Social Psychology. A related study published in Motivation and Emotion in 2009 confirmed a correlation between poor smiles in adolescence and divorce later in life.

In a more recent study published this year in Psychological Science, Ernest Abel and Michael Kruger of Wayne State University expanded this line of research from emotional to biological outcomes: longevity. Abel and Kruger classified the smiles of professional baseball players recorded in a 1952 yearbook and determined each player's age at death (46 players were alive at the time of the study). The researchers found that smile intensity could explain 35% of the variability in survival; In fact, players with a Duchenne smile in their yearbook photo were only half as likely to die each year as those without.

A "vehicle for all ambiguities"

Landis was right about one thing about smiling: Not all smiles are a genuine expression of happiness. In addition to the Duchenne smile, Ekman described seventeen other types of smiles in his 1985 book Telling Lies. Herman Melville understood this and once called the smile "the medium of choice for all ambiguities." People smile when they are scared, flirty, surprised, or hurt. An embarrassed smile is indicated by an averted look, a touch to the face, and a tilt of the head down and to the left.

People also smile when they lie, a fact that Shakespeare does not miss: Hamlet marvels at "how one can smile and smile and be a villain." In the late 1960s, Ekman and Friesen theorized that a trained expert could tell a lying face from an honest face. To test this idea, the researchers asked a group of young nurses to watch a disturbing video and then tell an interviewer that they had indeed seen an entertaining video. Their facial expressions during this lie were captured on video and analyzed by FACS.

Compared with smiles reported in candid interviews, lying nurses showed fewer genuine Duchenne smiles, Ekman and Freisen reported in a 1988 article in the Journal of Personality and Social Psychology, co-authored with Maureen O'Sullivan of the University of San Francisco. written. The deceitful smile was betrayed by a raised upper lip, revealing a hint of disgust, or by the downturned corners of the mouth, showing a hint of sadness. Ekman's work with lies later inspired the television show Lie to Me, in which investigators solve crimes by interpreting facial expressions.

It is not uncommon for moments of sadness or even pain to bring about a smile. The world's most recognizable smile is fascinating precisely because it can display a variety of moods; Bob Dylan described the Mona Lisa as the "blues of the highway." (Harvard neurobiologist Margaret Livingstone argued in a 2000 Science article that La Gioconda's smile exists in your peripheral vision but disappears when you look directly into her mouth, see inset.)

However, it seems that smiling is good for the body in difficult times. Keltner and George Bonanno from Catholic University measured the facial expressions of people talking about a recently deceased spouse. In a 1997 issue of the Journal of Personality and Social Psychology, researchers reported less distress in those who displayed a genuine Duchenne laugh during arguments compared to those who did not.

The benefits of smiling during grief also appear to be biological. Barbara Fredrickson and Robert Levenson once observed the facial expressions of 72 people watching a funeral scene in the horror film Steel Magnolias. Not only did fifty of the participants smile at least once during the clip, the authors reported in a 1998 article in Cognition and Emotion, but those who did recovered to baseline cardiovascular values ​​faster than those who couldn't smile. .

A "contingent social ad"

Smiling certainly seems to be built into our nature. None other than Darwin, whose 1872 book The Expression of the Emotions in Man and Animals is considered a seminal work in the study of the smile, argued that facial expressions were universal products of human evolution rather than unique principles of one's culture. The zygomatic major has a long evolutionary history, says University of Pittsburgh expressionist Jeffrey Cohn, and the facial muscles used to smile are found in all humans. "There is good evidence that the motor routine associated with smiling is innate," says Cohn. "The hardware is there."

It is not surprising, then, that newborns are capable of making and interpreting facial expressions with great precision. With only 10 months z. For example, a small child gives a fake smile to an approaching stranger while reserving a genuine Duchenne smile for his mother. Decades ago, Cohn observed how 3-month-old babies responded to changes in their mother's expression. When mothers feigned depression, babies would pump up their tiny fists in despair and flinch after just 3 minutes without a smile.

As babies grow, their tendency to smile differs based on their gender. The ability to achieve a Duchenne smile is evenly distributed between the genders, but men say they smile less than women, and both genders believe this to be the case. So do behavioral scientists, who are almost unanimously convinced that women smile more than men. In general, this seems to be true. But the differences in smiling behavior between men and women depend on several key factors. A few years ago, a research team led by Yale psychologist Marianne LaFrance conducted an extensive meta-analysis of smiling research, analyzing data from 162 studies and a total of more than 100,000 participants, and isolating three variables that influence in the smile: Sexual inequalities in the smile.

One moderator is gender norms: when people know they're being watched, the gender gap in smiling is larger than when people think they're alone. The second is situational constraint: when men and women share a task or role that follows strict social rules, such as those that require flight attendants to smile and undertakers to remain somber, the gap in smile is reduced. A third moderator is the emotional climate: embarrassing or socially tense situations make women smile more than men, but happy or sad situations do not. Smiling, LaFrance and his collaborators concluded in a 2003 issue of Psychological Bulletin, "it's a highly contingent social display."

"If you ask the people who smile the most, they'll all say, 'Women, of course,'" says LaFrance, whose book on smile research, Lip Service, is co-authored by W.W. Norton next summer. "What people don't take as much into account, both inside and outside of the field of psychology, is how variable the smile is depending on the context of a social situation."

Part of this variability is the viewer's cultural background. A study published in the Journal of Experimental Social Psychology in 2007 highlights the different perceptions of smiles between Americans and Japanese. When viewing the emoticons, the Americans located the expression in the mouth and saw 🙂 as happy and 🙁 as sad, while the Japanese found it in the eyes and ^_^ as happy and ;_; how tearful. The variation may reflect an American tendency to express emotions and a Japanese tendency to repress them; After all, as Duchenne well knew, the mouth is easier to manipulate into a smile than the eyes (see photos opposite). A back-up study published earlier this year found that Japanese participants emphasized the top half of a face when determining its trustworthiness, while Americans focused on the bottom half.

The presence of the people around us can also influence our smile. An experiment conducted by Robert Kraut and published in a 1979 issue of the Journal of Personality and Social Psychology reported that bowlers smiled more often when looking at their friends in the box than when watching the bowling alley. Of course, people smile to themselves, but many believe that the social context pulls our lips more than pure, isolated emotion. Alan Fridlund of the University of California, Santa Barbara found that people smile more when imagining other people around them than when they are alone, even when their general levels of happiness remain the same.

Meaning altruism and attraction.

It stands to reason that if our smiles are affected by social settings, it is likely that smiling has a social purpose. One of those functions, according to recent findings, could be to indicate altruism. To test this notion, a team of researchers led by British behaviorist Marc Mehu observed the smiles of test subjects who were instructed to share part of the license plate with a friend. When people were involved in this sharing activity, they showed more Duchenne smiles than in a neutral setting. Perhaps people emit genuine smiles to "reliably announce altruistic intentions," Mehu and his colleagues concluded in a 2007 issue of Evolution and Human Behavior.

It makes sense that the Duchenne smile heralds a cooperative nature. After all, one person's commitment has obvious social value, and a real smile is hard to fake. The ability to identify a truly clustered individual would be especially useful for people vulnerable to social exclusion. With this in mind, a group of researchers from Miami University in Ohio recently asked test subjects to rate different smiles as real or fake. Prior to the assignment, some were prepared for expulsion through a writing assignment in which they had to write about a time when they were rejected. Compared with a control group and others primed for inclusion, excluded participants showed better ability to distinguish Duchenne smiles from fake ones, the authors reported in Psychological Science in 2008.

People not only gain useful information from a smile, but also use this knowledge to guide their own behavior. In a follow-up experiment published in the Journal of Experimental Social Psychology in 2010, the same researchers found that people who were primed for exclusion showed a greater preference for working with people who displayed a genuine Duchenne smile than those who did. a cheap smile . "Duchenne smiles are a sign of collaboration, of altruism," says Michael Bernstein, now at Penn State Abington, lead author of both papers. "Smiling without Duchenne isn't necessarily a bad thing, it doesn't mean you're threatening, but it's not a good sign. [Social outcasts] should look for the best sign, and the Duchenne smile offers an even better sign."

Another function of smiling (and one that is supported by anecdotal evidence) is that it increases our attractiveness. One of the most famous figures in American literature, F. Scott Fitzgerald's Jay Gatsby, had an irresistible smile that was "guaranteed to give exactly the impression of you that you hoped to give in your prime." Science, for its part, has identified part of the reason behind the allure of big smiles. A recent fMRI study found that seeing attractive faces activates the brain's orbitofrontal cortex, a region involved in processing sensory rewards. While this was true for all pretty cups, activity in this region was even stronger when the face in focus was smiling. "The presence of a smile can provide an important cue about whether or not a reward is obtainable," the researchers write in Neuropsychology (2003). Although some might argue that when the brain sees a smile, it has already thought about the reward obtained.

references

Abel E. and Kruger M. (2010) Predict the intensity of smiles in photographs
Longevidade, Psychological Science, 21, 542-544.
Bernstein M.J., Young, S.G., Brown CM, Sacco D.F. e Lehmteiche,
Hm. (1998) Adaptive Responses to Social Social Exclusion
Bounce improves detection of real and fake smiles,
Psychological Science, 19, 10, 981-983.
Bernstein MJ, Sacco D.F., Brown, C.M. Young, S. G. y Claypool,
Hm. (2010). A penchant for genuine smiles after socializing.
Exclusion. Journal of Experimental Social Psychology, 46,
196–199.
Cohn, J. F. and Tronick E. Z. (1983) Response of three-month-old infants
for simulated maternal depression, child development, 54,
185-193.
Darwin, C. (1872) The expression of emotions in man and animals,
London: J. Murray.
Duchenne G.B., (1990) The mechanism of human facial expression, trans.
RA Cuthbertson, Cambridge University Press.
Ekman, P. (1985) Telling Lies: Clues to Deceive the Market,
Politics and Marriage, Norton: New York.
Ekman, P., Davidson, R. J., Friesen, W. V. (1990) A Duquesa
Smiling: Emotional Expression and Brain Physiology II, Journal of
Personality and Social Psychology, 58, 342-353.
Ekman, P. Wallace V. Freisen, O'Sullivan M. (1988) Smiling when you lie,
Journal of Personality and Social Psychology, 54, 414–420.
Fredrickson, B. L. & Levenson, R. W. (1998) Velocity of positive emotions
recovery from the cardiovascular consequences of negative emotions,
Cognition and Emotion, 12, 191-220.
Fridlund, AJ, Sabini J.P., Hedlund, L.E. Behold, YES, Shenker, J.I.
and Knauer, M. J. (1990) Audience effects on lonely faces during
Images: Seeing People in Your Mind, Journal of Nonverbal
Behavior, 14, 113-137.
Harker L. und Keltner D., (2001) Expressions of positive emotion in
College yearbook photos for women and their relationship with
Personality and life plans in adulthood. Diary of
Personality and Social Psychology, 80, 112-124.
Hertenstein, M. J., Hänsel, C. A., Butts A. M., Hile S. N. (2009) Sorriso
The intensity in the photographs predicts divorce later in life. motivation
and emotions 33, 2, 99-105.
Keltner D. and Bonanno, G (1997) A study of laughter and
Dissociation: Clear correlates of laughter and smiling during
Mourning, Journal of Personality and Social Psychology, 73,
687–702.
Herb RE, Johnston RE. (1979) Social and emotional messages from
Smiles: an ethological approach, Journal of Personality and
Social Psychology, 37, 9, 1539-1553.
LaFrance M., Pike, MA, Paluck, E.L. (2003) The conditional smile:
A meta-analysis of gender differences in smiling, psychological
Bulletin, 129, 305–334.
Landis, C. (1924) Studies of Emotional Response II General Behavior
and facial expression, Journal of Comparative Psychology, 4, 5.
Livingstone, MS (2000) Is it hot? It is real? Or just to save space.
Frequency? Science, 290, 1299.
Mehua, M., Grammerb K., y Dunbara, R.I.M., (2007) Sorri quando
Partilha, Evolution and Human Behavior, 28, 415–422.
O'Doherty, J., Winston, J., Critchley, H. Perrett, D., Burt, D. M.,
e Dolan RJ, (2003) Beauty in a smile: the role of medial
orbitofrontal cortex on facial attractiveness. neuropsychology, 41,
147–155.
Ozone H., et al. (2010) What's in a smile? cultural differences
Effects of smiling on reliability reviews, letters in
Evolutionary Behavioral Sciences, 1, 15–18.
Yuki, M., Maddux, W.W., Masuda, T. (2007) Are the windows to the
Is the soul the same in the East and the West? Cultural differences in use
Eyes and mouth as signals to recognize emotions in Japan and
United States, Journal of Experimental Social Psychology, 43,
303–311.