A smile is a sign of welcome that is known all around the world. It is the one gesture that is instantly recognized everywhere. In addition, smiling is good for you. A smile, even a forced smile, makes you feel better. Smiles release endorphins, seratonin, and natural pain killers, which make you feel happy. As a bonus, a smile reduces stress and boosts your immune system. All of us should smile much more than we do.

Even blind people can hear a smile, as they can detect it in the voices of people who are smiling. A genuine, warm smile tells others that you’re friendly, honest, and easy to get along with. A genuine smile lights up the face and involves the eyes as well as the mouth. A false smile involves the mouth, but doesn’t reach the eyes. An easy way to determine if a smile is genuine is to look for the crinkle of skin (crow’s feet) at the corner of the eyes. If it’s not apparent, the smile is not genuine.

Babies practice their smiles in the womb, up to two months before they’re born. As they’re totally helpless, they need to develop the muscles that create smiles to entice people to look after them.9 Even babies produce genuine and fake smiles. An experiment performed with thirty-five ten-month-old babies showed that they could smile at a stranger without using the muscles around their eyes. However, as soon as each baby’s mother came into view, he or she produced a genuine smile.10

Smiles are generally associated with happiness, but everyone has a variety of smiles that are used for different purposes. The most common of these is the apologetic smile that we use all day long when we accidentally interact with someone else. You’d apologize and give this smile if you accidentally bumped into someone at a train station. If you squeezed into a crowded elevator, you’d probably avoid eye contact, but would smile to effectively apologize to everyone for forcing them to stand closer together. In a busy city, the average person would use this smile dozens of times during the day. Although this all-purpose smile is a smile, it’s not a genuine one.

Another smile that isn’t genuine is the nervous half smile that people use when they’re not feeling confident or sure of themselves. Perhaps you've seen a presenter do that yourself when he has been delivering powerpoint training. Sometimes anxiety means the smile is largely on one side of the face. I know someone who does a nervous half smile at the end of almost every sentence when he’s talking. It’s a sign that he feels uncomfortable, as he is not sure of himself.

Smiles are frequently used to cover up feelings and emotions. Someone who lost an important tennis tournament would smile to cover up his or her feelings while congratulating his opponent.

People who deal with the public smile to make their dealings with others more pleasant. Cabin attendants are a good example of this. However, their smiles are also intended to reassure any passengers who are afraid of flying.

There are many different types of smiles, ranging from a gentle smile with the teeth unexposed to a broad smile created in situations when someone is laughing as well as smiling.

Someone who is smiling to him- or herself gives a gentle smile with the lips closed.

When people meet, the upper incisors are visible when they smile. They also make eye contact with each other.

A broad smile occurs when people are enjoying themselves and are laughing as well as smiling. The upper and lower incisors are visible, and little direct eye contact is made.

An oblong smile occurs when people are being polite, or are pretending to have a good time. It is also used when people are holding back, and are not willing to say what they think. In this smile, the lips stretch into an oblong shape and the mouth remains closed. Consequently, this smile is sometimes known as the tight-lipped smile.

A variation of this occurs when someone grins with the lips firmly closed. This means the person is deliberately holding something back, and concealing what he or she really feels behind the smile. There is also the clamped smile, which occurs when the muscles around the mouth are tensed, creating the impression that the person was going to smile, but managed to hold it back.

Smiles of this sort can be frustrating to others, as it’s impossible to tell if the person is really smiling. People who want to dominate others smile seldom. When they do, they usually use a closed-mouth smile.