What happens when we smile at people

psychology : The science of smiling

These scenes will not be forgotten for a long time: Tired children, women and men with worn out faces were hugged like close relatives and friends at German train stations after their long journey. Local helpers met the refugees with beaming smiles.

Was that a September fairy tale? Definitely a research case. "When strangers first meet, the presence of a smile reliably predicts that you are familiar and willing to share resources," says Paula Niedenthal of the University of Wisconsin in Madison. The psychologist was able to prove that a country's migration history is decisive for how easy it is for its residents to smile in everyday life.

Niedenthal and her colleagues used indicators for "historical heterogeneity". These figures summarize how many states the ancestors of today's residents came from over the past 500 years. Canada ranks high in this index with a figure of 63. China and Japan have the index number one because of their extremely homogeneous population, Germany is in the middle. The researchers then asked citizens of different nationalities how useful it was to show feelings in public.

A certificate of trustworthiness

In the countries with many immigrants, the prevailing opinion was that one should not keep one's emotions behind the mountain. Especially not with the positive ones. In addition to Canada, New Zealand and the USA excelled through a “culture of smiling”, write the researchers in the journal “PNAS”. In countries where the population was composed homogeneously for centuries, the reactions of others are easy to predict - regardless of the language, says Niedenthal. Minimal facial expressions are enough to understand each other.

If, on the other hand, a country is thrown together more colorfully due to its history, then it was always necessary to express feelings and intentions as unmistakably as possible - with the help of the facial muscles. One of the unspoken rules is to give a smile even to strangers. A certificate of trustworthiness that a person does not lose as easily as his papers.

The friendly facial expression not only has the power to forge and strengthen bonds or to reward someone. He can take on a third task: whoever smiles when and how may reveal hierarchies and cement them. For example, when subordinates dress up their bosses and swallow the anger over the overtime they have been charged with unnoticed. This aspect of the smile, as shown by a survey of 726 people in nine countries, is more important in societies with a homogeneous population and stable hierarchies. In countries with a high heterogeneity index, on the other hand, it is mostly interpreted as a friendly gesture. It is definitely a social lubricant.

Even babies communicate with a smile

Mouth and eye ring muscles are used from an early age by people of all cultures to form the characteristic facial expression of a smile. It begins with newborns' faces, usually in their sleep, twisting into what looks like a smile but isn't yet a smile. "Angel smile" is the popular saying about this magical first approach. By four to eight weeks, babies really start smiling at others. Only then is the brain ready for it.

Probably everything stands and falls with the fact that the nerve cells that network the basal ganglia deep in the brain are coated with a myelin layer, says neurobiologist Lise Eliot from the Chicago Medical School. Only then are these structures below the cerebral cortex, which control every voluntary movement, fully functional.

“The social smile is probably the most universal of all the milestones in human development,” she writes in her book “What's going on inside?”. Even infants who are blind from birth can do this. It is probably also universal that parents melt away as soon as the little toothless mouths open and the corners of the mouth pull upwards slightly thanks to finely tuned muscle contractions.

The timing is right after a short time

As early as a few months, babies have mastered the art of finding the best time to smile. Developmental psychologists and robotics specialists from the University of California in San Diego have proven this in an unusual way: They first observed how infants and their mothers interact with one another.

Then they programmed a small robot with a doll's face so that it “recognized” the facial expressions of its counterpart and mastered different strategies of interaction. If “Diego San” imitated exactly the behavior that the babies copied, he was able to conjure up a particularly large number of counter-smiles on the faces of the test subjects by using his own smile sparingly. Of course, the researchers do not want to claim that even infants consciously use their facial expressions.

The monkey's grin of fear

Lise Eliot considers smile to be the ultimate human greeting. For the innate opportunity for all of us to establish contact with one another. In addition, babies usually start their first speech-based, babbling attempts at “protocommunication” a short time later. So distant harbingers of language.

Do animals smile when they lack language? Marina Davila-Ross of Portsmouth University and her colleagues have found evidence of this in chimpanzees. They analyzed film recordings and saw facial expressions in the great apes - mostly accompanied by laugh-like sounds - that resembled those of smiling people. That is a forerunner of our smile, they suspect. Whether and what feelings are associated with this in chimpanzees is another question.

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