Smile

A smile is a facial expression 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". Smiles performed without the eye contraction can be perceived as "fake".

Among humans, smiling is an expression denoting pleasure, sociability, happiness, 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, there are large differences between different cultures, 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. The smile may have evolved differently among species and especially among humans. Apart from Biology as an academic discipline that interprets the smile, those who study kinesics and psychology such as Freitas-Magalhaes view the smile as an affect display that can communicate feelings such as love, happiness, pride, contempt, and embarrassment.

Usain Bolt

Usain St. Leo Bolt, OJ, CD (/ˈjuːseɪn/; born 21 August 1986) is a Jamaican sprinter. Regarded as the fastest person ever timed, he is the first man to hold both the 100 metres and 200 metres world records since fully automatic time measurements became mandatory in 1977. Along with his teammates, he also set the world record in the 4×100 metres relay. He is the reigning Olympic champion in these three events, and the first man since Leonidas of Rhodes to win six Olympic gold medals in sprinting, and an eleven-time World champion. He was the first to achieve the "double double" of winning 100 m and 200 m titles at consecutive Olympics (2008 and 2012), and topped this through the first "double triple" (including 4×100 m relays).

Although gaining worldwide popularity for a sprint double victory at the Beijing Games, Bolt has had more victories as a 200 m runner. While he had not won any significant 100 m title prior to the 2008 Olympics, he had won numerous crowns in the 200 m event at the youth, junior and senior levels. Further, at the 2013 World Championships in Moscow, Bolt completed a hat-trick of 200 m world titles by winning his third straight gold in the event. His 2009 record breaking margin for 100 m, from 9.69 seconds (his own previous world record) to 9.58, is the highest since the start of fully automatic time measurements.