From a historical point of view, a smile is an integral sign, because a person from all over the world shows such a feeling. There is also a difference between a reflex smile and a smile that mimics the way certain emotions are expressed.
But if we consider the frequency with which smiles appear in our time, then this is a sad fact. The more people are involved in society and immersed in the tense atmosphere of city life, the less they show friendly emotions, smile less and show less interest in other people in terms of their emotional state.
With the help of laughter, the body receives the hormone endorphin, balances blood pressure, improves metabolic processes.
Smiling can also affect your emotional state. It is worth noting that disorders, depressions, neuroses have recently been common. But there is an effective way to help relieve tension, relieve stress - a smile. With it, you want to look at things and situations positively
Scientific studies of the appearance of a smile
In the middle of the 19th century, Charles Darwin was the first to reveal that human facial expressions are a continuation of facial expressions characteristic of great apes: with the help of facial expressions, primates conveyed threat, anxiety, fright, demonstrated peacefulness. According to Darwin, human facial expressions first expressed readiness for attack, movement, defense, and only in the course of human development, facial expressions began to convey information about the inner state of a person, about his desire to establish communication with other people.

