A Duchenne smile is when the cheek raises and forms a wrinkle around the eyes.

Many researchers think that Duchenne smiles are usually hard to make when you are pretending to smile.

Although there are many different types of smiles, researchers are interested in the duchenne smile because it is done with the eyes.

Specifically, he looked at the lips to see if students smiled with a Duchenne smile, which is an involuntary and genuine grin.

Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a "Duchenne smile".

They more often make a genuine smile (known scientifically as a Duchenne smile, when two different facial muscles fire).

The Duchenne smile: emotional expression and brain psysiology II.

The Duchenne smile was named after the French physician Guillaume Duchenne.

Sincere and involuntary Duchenne smile: contraction of zygomatic major and inferior part of orbicularis oculi.

In “Emotions Revealed,” Ekman provides a graphic photo-illustration of the difference between the Duchenne smile, the real smile and the social smile.

In B, which shows real enjoyment with a Duchenne smile, the cheeks are higher, the contour of the cheeks has changed, and the eyebrows have moved down slightly.

Only the Duchenne smile evoked heightened activity in regions of the brain, particularly the left anterior region of the cortex, which previous research had found were centers for happy emotions.

Dr. Davidson, who did the work with Dr. Ekman, used computerized brain-wave measures to assess brain activity while volunteers tried the Duchenne smile and other grins.

Chronic use of Botox injections to deal with eye wrinkle can result in the paralysis of the small muscles around the eyes, preventing the appearance of a Duchenne smile.

That’s the crucial difference between what I call a Duchenne smile, the true smile of enjoyment, named after the French neurologist who first made this discovery in 1862, and the forced smile, the social smile.

Smiling, on the other hand, is easily recognized as an expression of happiness, but even here there is a distinction between cheek-raising or Duchenne smiles and non-emotional smiles, which are thought to be used mainly as social signals.

A Duchenne smile involves contraction of both the zygomatic major muscle (which raises the corners of the mouth) and the orbicularis oculi muscle (which raises the cheeks and forms crow's feet around the eyes).

By blowing up images from player cards, researchers assessed player smiles—categorizing them as "no smile," "partial smile" and what is known as a "Duchenne smile," or the authentic, spontaneous expression of happiness named for a 19th century French neurologist.

But there was another brain change typical of spontaneous pleasure - increased activity in the left prefrontal cortex - which did not occur with the Duchenne smile, said Dr. Richard Davidson, a psychophysiologist at the University of Wisconsin.

"The key markers of the Duchenne smile that readily distinguish it from all others are the crow's feet wrinkles around the eyes and a subtle drop in the eye cover fold so that the skin above the eye moves down slightly toward the eyeball," said Dr. Ekman.

Subtle Mood Lift Even though the deliberate Duchenne smile did not evoke all the brain changes that usually occur during the spontaneous one, Dr. Davidson said that it may mean that the facial maneuver can produce some of the subtler effects of a good mood apart from happiness itself.

They continue that, if, as previous research suggests, the emotion conveyed in expressions is truly indicative of contentment, "individuals whose underlying emotional disposition is reflected in voluntary or involuntary Duchenne smiles may be basically happier than those with less intense smiles, and hence more predisposed to benefit from the effects of positive emotionality."

This puts the face into a pattern called the "Duchenne smile," after Guillaume Benjamin Amand Duchenne, a French neurologist who in the 1860's was the first to map the movements of the more than 100 muscles of the face; he used electric shocks to stimulate each muscle in a patient who felt no pain.