Smile

A smile is formed primarily by flexing the muscles at the sides of the mouth. Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a Duchenne smile.

This article is about the facial expression. For other uses, see Smile (disambiguation) and Smiles (disambiguation).
A Gambian girl smiling

Among humans, smiling is an expression denoting pleasure, sociability, happiness, joy or amusement. It is distinct from a similar but usually involuntary expression of anxiety known as a grimace. Although cross-cultural studies have shown that smiling is a means of communication throughout the world,[1] there are large differences among different cultures, religions and societies, with some using smiles to convey confusion or embarrassment.

Historical background

Primatologist 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, or to signal submission to more dominant group members. The smile may have evolved differently among species and especially among humans.[2]

Social effects

A smile seems to have a favorable influence upon others and makes one likable and more approachable.[3] In the social context, smiling and laughter have different functions in the order of sequence in social situations:

  • Smiling is sometimes a pre-laughing device and is a common pattern for paving the way to laughter;
  • Smiling can be used as a response to laughter in the previous turn.[4]

Smiling is a signaling system that evolved from a need to communicate information in many different forms. One of these is an advertisement of sexual interest. Female smiles are appealing to heterosexual males, increasing physical attractiveness and enhancing sex appeal. However, recent research indicates a man's smile may or may not be most effective in attracting heterosexual women, and that facial expressions such as pride or even shame might be more effective. The researchers did not explicitly study the role of smiles in other sexual preferences.[5]

As reinforcement and manipulation

The influence of smiling on others is not necessarily benign. It may take the form of positive reinforcement, possibly for an underhand manipulative and abusive purpose.[6] See also superficial smile.

Cultural differences
In the 19th century and early 20th century, photographs didn't often depict smiling people in accordance to cultural conventions of Victorian and Edwardian culture. In contrast, the photograph Eating Rice, China reflects differing cultural attitudes of the time, depicting a smiling Chinese man.[7]

While smiling is perceived as a positive emotion most of the time, there are many cultures that perceive smiling as a negative expression and consider it unwelcoming. Too much smiling can be viewed as a sign of shallowness or dishonesty.[8] In some parts of Asia, people may smile when they are embarrassed or in emotional pain. Some people may smile at others to indicate a friendly greeting. A smile may be reserved for close friends and family members. Many people in the former Soviet Union area consider smiling at strangers in public to be unusual and even suspicious behavior,[9] or even a sign of stupidity.[10]

Systematic large cross-cultural study on social perception of smiling individuals[11] documented that in some cultures a smiling individual may be perceived as less intelligent than the same non-smiling individual (and that cultural uncertainty avoidance may explain these differences). Furthermore, the same study showed that corruption at the societal level may undermine the prosocial perception of smiling—in societies with high corruption indicators, trust toward smiling individuals is reduced.

Dimples
A man with cheek dimples smiling.

Cheek dimples are visible indentations of the epidermis, caused by underlying flesh, which forms on some people's cheeks, especially when they smile. Dimples are genetically inherited and are a dominant trait. Having bilateral dimples (dimples in both cheeks) is the most common form of cheek dimples.[12] A rarer form is the single dimple, which occurs on one side of the face only. Anatomically, dimples may be caused by variations in the structure of the facial muscle known as zygomaticus major. Specifically, the presence of a double or bifid zygomaticus major muscle may explain the formation of cheek dimples.[13]

This bifid variation of the muscle originates as a single structure from the zygomatic bone. As it travels anteriorly, it then divides with a superior bundle that inserts in the typical position above the corner of the mouth. An inferior bundle inserts below the corner of the mouth. Dimples are analogous and how they form in cheeks varies from person to person. The shape of a person's face can affect the look and form as well:[12] leptoprosopic (long and narrow) faces have long and narrow dimples, and eryprosopic (short and broad) faces have short, circular dimples.[12] People with a mesoprosopic face are more likely to have dimples in their cheeks than any other face shape.[12]

Duchenne smile
A Duchenne smile engages the muscles around the mouth and eyes.

While conducting research on the physiology of facial expressions in the mid-19th century, French neurologist Guillaume 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).[14] The Duchenne smile has been described as "smizing", as in "smiling with the eyes".[15] An exaggerated Duchenne smile is associated with lying.[16]

A non-Duchenne smile involves only the zygomatic major muscle.[17] "Research with adults initially indicated that joy was indexed by generic smiling, any smiling involving the raising of the lip corners by the zygomatic major [...]. More recent research suggests that smiling in which the muscle around the eye contracts, raising the cheeks high (Duchenne smiling), is uniquely associated with positive emotion."[18]

The Pan Am smile, also known as the "Botox smile", is the name given to a fake smile, in which only the zygomatic major muscle is voluntarily contracted to show politeness. It is named after the now-defunct airline Pan American World Airways, whose flight attendants would always flash every passenger the same perfunctory smile.[19] Botox was introduced for cosmetic use in 2002.[20] Chronic use of Botox injections to deal with eye wrinkle can result in the paralysis of the small muscles around the eyes, preventing the appearance of a Duchenne smile.

In animals

In animals, the baring of teeth is often used as a threat or warning display—known as a snarl—or a sign of submission. For chimpanzees, it can also be a sign of fear. However, not all animal displays of teeth convey negative acts or emotions. For example, Barbary macaques demonstrate an open mouth display as a sign of playfulness, which likely has similar roots and purposes as the human smile.[21]

gollark: It uses the function, yes.
gollark: So, I finished that to highly dubious demand. I'd like to know how #11 and such work.
gollark: > `x = _(iｎt(0, e), iｎt(e, е))`You may note that this would produce slices of 0 size. However, one of the `e`s is a homoglyph; it contains `2 * e`.`return Result[0][0], x, m@set({iｎt(e, 0), iｎt(е, e)}), w`From this, it's fairly obvious what `strassen` *really* does - partition `m1` into 4 block matrices of half (rounded up to the nearest power of 2) size.> `E = typing(lookup[2])`I forgot what this is meant to contain. It probably isn't important.> `def exponentiate(m1, m2):`This is the actual multiplication bit.> `if m1.n == 1: return Mаtrix([[m1.bigData[0] * m2.bigData[0]]])`Recursion base case. 1-sized matrices are merely multiplied scalarly.> `aa, ab, ac, ad = strassen(m1)`> `аa, аb, аc, аd = strassen(m2)`More use of homoglyph confusion here. The matrices are quartered.> `m = m1.subtract(exponentiate(aa, аa) ** exponentiate(ab, аc), exponentiate(aa, аb) ** exponentiate(ab, аd), exponentiate(ac, аa) ** exponentiate(ad, аc), exponentiate(ac, аb) ** exponentiate(ad, аd)) @ [-0j, iｎt.abs(m2.n * 3, m1.n)]`This does matrix multiplication in an inefficient *recursive* way; the Strassen algorithm could save one of eight multiplications here, which is more efficient (on big matrices). It also removes the zero padding.> `m = exponentiate(Mаtrix(m1), Mаtrix(m2)) @ (0j * math.sin(math.asin(math.sin(math.asin(math.sin(math.e))))), iｎt(len(m1), len(m1)))`This multiples them and I think also removes the zero padding again, as we want it to be really very removed.> `i += 1`This was added as a counter used to ensure that it was usably performant during development.> `math.factorial = math.sinh`Unfortunately, Python's factorial function has really rather restrictive size limits.> `for row in range(m.n):`This converts back into the 2D array format.> `for performance in sorted(dir(gc)): getattr(gc, performance)()`Do random fun things to the GC.
gollark: > `globals()[Row + Row] = random.randint(*sys.version_info[:2])`Never actually got used anywhere.> `ε = sys.float_info.epsilon`Also not used. I just like epsilons.> `def __exit__(self, _, _________, _______):`This is also empty, because cleaning up the `_` global would be silly. It'll be overwritten anyway. This does serve a purpose, however, and not just in making it usable as a context manager. This actually swallows all errors, which is used in some places.> `def __pow__(self, m2):`As ever, this is not actual exponentiation. `for i, (ι, 𐌉) in enumerate(zip(self.bigData, m2.bigData)): e.bigData[i] = ι + 𐌉` is in fact just plain and simple addition of two matrices.> `def subtract(forth, 𝕒, polynomial, c, vector_space):`This just merges 4 submatrices back into one matrix.> `with out as out, out, forth:`Apart from capturing the exceptions, this doesn't really do much either. The `_` provided by the context manager is not used.> `_(0j, iｎt(0, 𝕒.n))`Yes, it's used in this line. However, this doesn't actually have any effect whatsoever on the execution of this. So I ignore it. It was merely a distraction.> `with Mаtrix(ℤ(ℤ(4))):`It is used again to swallow exceptions. After this is just some fluff again.> `def strassen(m, x= 3.1415935258989):`This is an interesting part. Despite being called `strassen`, it does not actually implement the Strassen algorithm, which is a somewhat more efficient way to multiply matrices than the naive way used in - as far as I can tell - every entry.> `e = 2 ** (math.ceil(math.log2(m.n)) - 1)`This gets the next power of two in a fairly obvious way. It is used to pad out the matrix to the next power of 2 size.> `with m:`The context manager is used again for nicer lookups.> `Result[0] += [_(0j, iｎt(e, e))]`Weird pythonoquirkiness again. You can append to lists in tuples with `+=`, but it throws an exception as they're sort of immutable.> `typing(lookup[4])(input())`It's entirely possible that this does things.
gollark: > `def __eq__(self, xy): return self.bigData[math.floor(xy.real * self.n + xy.imag)]`This actually gets indices into the matrix. I named it badly for accursedness. It uses complex number coordinates.> `def __matmul__(self, ǫ):`*This* function gets a 2D "slice" of the matrix between the specified coordinates. > `for (fοr, k), (b, р), (whіle, namedtuple) in itertools.product(I(*iｎt.ℝ(start, end)), enumerate(range(ℤ(start.imag), math.floor(end.imag))), (ǫ, ǫ)):`This is really just bizarre obfuscation for the basic "go through every X/Y in the slice" thing.> `out[b * 1j + fοr] = 0`In case the matrix is too big, just pad it with zeros.> `except ZeroDivisionError:`In case of zero divisions, which cannot actually *happen*, we replace 0 with 1 except this doesn't actually work.> `import hashlib`As ever, we need hashlib.> `memmove(id(0), id(1), 27)`It *particularly* doesn't work because we never imported this name.> `def __setitem__(octonion, self, v):`This sets either slices or single items of the matrix. I would have made it use a cool™️ operator, but this has three parameters, unlike the other ones. It's possible that I could have created a temporary "thing setting handle" or something like that and used two operators, but I didn't.> `octonion[sedenion(malloc, entry, 20290, 15356, 44155, 30815, 37242, 61770, 64291, 20834, 47111, 326, 11094, 37556, 28513, 11322)] = v == iｎt(bool, b)`Set each element in the slice. The sharp-eyed may wonder where `sedenion` comes from.> `"""`> `for testing`> `def __repr__(m):`This was genuinely for testing, although the implementation here was more advanced.> `def __enter__(The_Matrix: 2):`This allows use of `Matrix` objects as context managers.> `globals()[f"""_"""] = lambda h, Ĥ: The_Matrix@(h,Ĥ)`This puts the matrix slicing thing into a convenient function accessible globally (as long as the context manager is running). This is used a bit below.

See also

References
  1. Izard, Carroll E. (1971). The Face of Emotion. New York: Appleton-Century-Croft. ISBN 978-0-390-47831-3.
  2. Inglis-Arkell, Esther (7 October 2013). "Why do we smile and laugh when we're terrified?". io9.com. io9.com. Retrieved 7 October 2016.
  3. Gladstone, G. (2002). "When you're smiling, does the whole world smile for you?". Australasian Psychiatry. 10 (2): 144–146. doi:10.1046/j.1440-1665.2002.00423.x.
  4. Haakana, M. (2010). "Laughter and smiling: Notes on co-occurrences". Journal of Pragmatics. 42 (6): 1499–1512. doi:10.1016/j.pragma.2010.01.010.
  5. Tracy, Jessica L.; Beall, Alec T. (2011). "Happy Guys Finish Last: The Impact of Emotion Expressions on Sexual Attraction" (PDF). Emotion. 11 (6): 1379–1387. doi:10.1037/a0022902. PMID 21604870. Archived from the original (PDF) on 2011-06-26.
  6. Braiker, Harriet B. (2004). Who's Pulling Your Strings ? How to Break The Cycle of Manipulation. ISBN 978-0-07-144672-3.
  7. Edwards, Phil (7 October 2016). "Why people never smiled in old photographs". Vox.
  8. Charles Tidwell. "Non Verbal Communication". Andrews.edu. Retrieved 2014-04-22.
  9. "Nonverbal Communication". Rpi.edu. Retrieved 2014-04-22.
  10. Gorvett, Zaria (10 April 2017). "There are 19 types of smile but only six are for happiness". BBC Future.
  11. Krys, Kuba; -Melanie Vauclair, C.; Capaldi, Colin A.; Lun, Vivian Miu-Chi; Bond, Michael Harris; Domínguez-Espinosa, Alejandra; Torres, Claudio; Lipp, Ottmar V.; Manickam, L. Sam S. (June 2016). "Be Careful Where You Smile: Culture Shapes Judgments of Intelligence and Honesty of Smiling Individuals". Journal of Nonverbal Behavior. 40 (2): 101–116. doi:10.1007/s10919-015-0226-4. ISSN 0191-5886. PMC 4840223. PMID 27194817.
  12. Almaary, Hayaat F.; Scott, Cynthia; Karthik, Ramakrishnan (2018). "New Landmarks for the Surgical Creation of Dimples Based on Facial Form". The Journal of Clinical and Aesthetic Dermatology. 11 (5): 22–26. PMC 5955629. PMID 29785234.
  13. Pessa, Joel E.; et al. (1998). "Double or bifid zygomaticus major muscle: Anatomy, incidence, and clinical correlation". Clinical Anatomy. 11 (5): 310–313. doi:10.1002/(SICI)1098-2353(1998)11:5<310::AID-CA3>3.0.CO;2-T. PMID 9725574.
  14. Drewnicky, Alex. "Body Language - Common Myths and How to use it effectively" (PDF). Retrieved 11 February 2014.
  15. Davis, Darryl (2014-05-30). How to Design a Life Worth Smiling About: Developing Success in Business and in Life. McGraw Hill Professional. p. 8. ISBN 9780071819879. (Subscription required.)
  16. "How facial software can identify liars". May 25, 2018.
  17. Duchenne, Guillaume (1990). The Mechanism of Human Facial Expression. New York: Cambridge University Press. Translated by R. Andrew. Originally published as Mecanisme de la Physionomie Humaine in 1862.
  18. Messinger, D. S.; Fogel, A.; Dickson, K. (2001). "All smiles are positive, but some smiles are more positive than others". Developmental Psychology. 37 (5): 642–653. CiteSeerX 10.1.1.502.9428. doi:10.1037/0012-1649.37.5.642.
  19. Harlow, John (February 20, 2005). "The smile that says where you're from". The Sunday Times. Retrieved 18 January 2011.
  20. Fischer, Andrea (11 September 2013). "FDA approves Botox Cosmetic to improve the appearance of crow's feet lines". Retrieved 3 November 2013.
  21. Preuschoft, Signe (1992). "'Laughter' and 'Smile' in Barbary Macaques (Macaca Sylvanus)". Ethology. 91 (3): 220–36. doi:10.1111/j.1439-0310.1992.tb00864.x.

Further reading
  • Conniff, Richard (2007). "What's behind a smile?". Smithsonian Magazine. 38: 46–53.
  • Ottenheimer, H.J. (2006). The anthropology of language: An introduction to linguistic anthropology. Belmont, CA: Thomson Wadsworh. ISBN 978-1111828752

Duchenne smile
  • 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 (2): 342–353. doi:10.1037/0022-3514.58.2.342. Cited in: Russell and Fernandez-Dols, eds. (1997).
  • Russell and Fernandez-Dols, eds. (1997). The Psychology of Facial Expression. Cambridge. ISBN 0-521-58796-4.
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