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Smile

life science Maturity 11-13 Next article →

A smile is a facial expression made by moving muscles. Most smiles happen when you flex the muscles at the sides of your mouth.

Little kid smiling.
Little kid smiling.

Humans use smiles to show many happy feelings. You might smile when you feel joy, amusement, or sociability. A smile is different from a grimace. A grimace is a facial expression for feeling anxious.

Leonardo da Vinci 043-mod
Leonardo da Vinci 043-mod

Some smiles are more special than others. These involve the muscles around the eyes too.

There are two main ways a smile works. A Duchenne smile uses two different muscle groups. First, the zygomatic major muscle pulls the mouth corners up. Second, the orbicularis oculi muscle pulls the cheeks up. This second part creates small lines called crow's feet.

Smiling girl
Smiling girl

This kind of smile is often called "smizing." This means you are smiling with your eyes. A different kind is the non-Duchenne smile. This only uses the muscle at the mouth. Some people call a fake version a "Pan Am smile."

Scientists have studied these expressions for a long time. A French neurologist named Guillaume Duchenne studied them in the mid-19th century. He identified the two distinct types of smiles. He found how the muscles work together to change a face.

Smiling girl
Smiling girl

Later, researchers found that Duchenne smiles show real positive emotion. Other studies looked at how people see smiles in different cultures. These researchers looked at photos of students and political leaders. They even watched how people smile in everyday life.

Smiling can mean different things in different places. In the U.S. and France, smiles are very common. However, smiles are less common in Japan or China. In some parts of Asia, a smile might show embarrassment. In the former Soviet Union area, smiling at strangers can seem unusual. Some people might even think a smile is a sign of stupidity.

Little kid smiling.
Little kid smiling.

In some places, too much smiling can seem dishonest. This shows that a smile is not the same everywhere.

Smiles have a very old history in nature. A researcher named Signe Preuschoft traces them back 30 million years. They may have started as a "fear grin" in monkeys and apes. These animals show teeth to show they are not a threat.

Knoxville zoo - chimpanzee teeth
Knoxville zoo - chimpanzee teeth

This is a way to signal submission to others. Some animals like Barbary macaques use open mouths to play. Some humans also have dimples when they smile. Dimples come from a special muscle in the cheek. They are a trait you inherit from your parents.

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🖼️ Images & Media (4)
File:Leonardo da Vinci 043-mod.jpg
Leonardo da Vinci 043-mod.jpg
File:Little_kid_smiling..jpg
Little_kid_smiling..jpg
File:Smiling girl.jpg
Smiling girl.jpg
File:Knoxville zoo - chimpanzee teeth.jpg
Knoxville zoo - chimpanzee teeth.jpg
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