Miss America 2014 - Nina Davuluri is incredibly beautiful. She also is the first Miss America of Indian ethnicity. Unfortunately, but of no great surprise, she also makes the same mistake that a lot of gorgeous people do, particularly those with perfect teeth - she displays (and dramatically so) the maximum amount of teeth possible - including those on the bottom.
If the smile is sincere (also termed a Duchenne Smile) the lower teeth should almost never be seen. The only exceptions are in the context of a smile mixed with laughter, with a downward angle view (either from a camera, from the point of view of a taller person, etc.) or out of simple fatigue (e.g. holding a posed smile too long).
Although Nina laughs a bit in this video (also out of context and which has other nonverbal ramifications), the vast majority of her "smiles" display her lower teeth. Often we all need to "smile" when we do not feel joy or happiness - and these are termed "social smiles". Some people have higher quality (and more believable) social smiles than others. There is quite a variety of social smiles, and not surprisingly, people tend to default to a particular variety of which they've used for years (the vast majority of times without realizing it).
It is important to emphasize that although Ms. Davuluri's smile is not sincere, it does not indicate that she - or anyone else with a similar display is "insincere as whole person" - but just in that moment. Whether representing herself or her country, Nina Davuluri would have a much higher "Sincerity Quotient" and thus build more rapport if she would smile display a sincere smile.
The mouth component is but one element of a sincere smile. Do you know its other requirements?
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