More to a Smile Than Lips and Teeth

To that end, Dr. Niedenthal and her colleagues have surveyed a wide range of studies, from brain scans to cultural observations, to build a new scientific model of the smile. They believe they can account not only for the source of smiles, but how people perceive them. In a recent issue of the journal Behavioral and Brain Sciences, they arguethat smiles are not simply the expression of an internal feeling. Smiles in fact are only the most visible part of an intimate melding between two minds.
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But most importantly, Dr. Niedenthal argues, people recognize smiles by mimicking them. When a smiling person locks eyes with another person, the viewer unknowingly mimics a smile as well. In their new paper, Dr. Niedenthal and her colleagues point to a number of studies indicating that this imitation activates many of the same regions of the brain that are active in the smiler.
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Embodying smiles not only lets people recognize smiles, Dr. Niedenthal argues. It also lets them recognize false smiles. When they unconsciously mimic a false smile, they don’t experience the same brain activity as an authentic one. The mismatch lets them know something’s wrong.
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Dr. Niedenthal herself is now testing the predictions of the model with her colleagues. In one study, she and her colleagues are testing the idea that mimicry lets people recognize authentic smiles. They showed pictures of smiling people to a group of students. Some of the smiles were genuine and others were fake. The students could readily tell the difference between them.

Then Dr. Niedenthal and her colleagues asked the students to place a pencil between their lips. This simple action engaged muscles that could otherwise produce a smile. Unable to mimic the faces they saw, the students had a much harder time telling which smiles were real and which were fake.